Nutrient couplings between on-site sewage disposal systems, groundwaters, and nearshore surface waters of the Florida Keys

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We performed a one-year study to determine the effects of on-site sewage disposal systems (OSDS, septic tanks) on the nutrient relations of limestone groundwaters and nearshore surface waters of the Florida Keys. Monitor wells were installed on canal residences with OSDS and a control site in the Key Deer National Wildlife Refuge on Big Pine Key. Groundwater and surface water samples were collected monthly during 1987 and analyzed for concentrations of dissolved inorganic nitrogen (DIN = NOf3/sup- + NOf2/sup- + NH4/su+), soluble reactive phosphate (SRP), temperature and salinity. Significant nutrient enrichment (up to 5000-fold) occurred in groundwaters contiguous to OSDS; DIN was enriched an average of 400-fold and SRP some 70-fold compared to control groundwaters. Ammonium was the dominant nitrogenous species and its concentration ranged from a low of 0.77 μM in control wells to 2.75 mM in OSDS-enriched groundwaters. Concentrations of nitrate plus nitrite were also highly enriched and ranged from 0.05 μM in control wells to 2.89 mM in enriched groundwaters. Relative to DIN, concentrations of SRP were low and ranged from 30 nM in control wells to 107 μM in enriched groundwaters. N : P ratios of enriched groundwaters were consistently > 100 and increased with increasing distance from the OSDS, suggesting significant, but incomplete, adsorption of SRP by subsurface flow through carbonate substrata. Nutrient concentrations of groundwaters also varied seasonally and were approximately two-fold higher during the winter (DIN = 1035 μM; SRP = 10.3 μM) compared to summer (DIN = 470 μM; SRP = 4.0 μM). In contrast, surface water nutrient concentrations were two-fold higher during the summer (DIN = 5.0 μM; SRP = 0.50 μM) compared to winter (DIN = 2.5 μM; SRP = 0.15 μM). Direct measurement of subsurface groundwater flow rate indicated that tides and increased groundwater recharge enhanced flow some two-fold and six-fold, respectively. Accordingly, the observed seasonal coupling of OSDS-derived nutrients from groundwaters to surface waters is maximum during summer because of seasonally maximum tides and increased hydraulic head during the summer wet season. The yearly average benthic flux of anthropogenic DIN into contiguous canal surface waters is 55 mmol m-2 day-1, a value some five-fold greater than the highest rate of benthic N-fixation measured in carbonate-rich tropical marine waters.

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... One anthropogenic driver of degradation to aquatic environments is poorly treated human waste. For example, in some environments onsite sewage treatment and disposal systems (septic systems) can be a significant source of nutrient and bacterial pollution via subsurface transport of contaminated groundwater to nearby waterbodies (Lapointe et al., 1990;Lipp et al., 2001;Lapointe et al., 2017;Brewton et al., 2022). In the United States, 20 % of homes (26.1 million) currently rely on septic systems to treat domestic waste (USEPA, 2008). ...
... The positive correlation of NH 4 + with enterococci, E. coli, and HF183, suggests a human waste source, such as septic systems. Septic systems in areas with high water tables and porous sandy soils, such as Lee County, facilitate the rapid transport of NH 4 + enriched groundwater to surface water (LeBlanc, 1985;Ptacek, 1998), especially in locations with high densities of septic systems and/or high water tables (Lapointe et al., 1990(Lapointe et al., , 2012(Lapointe et al., , 2017Herren et al., 2021;Brewton et al., 2022). As many primary producers preferentially uptake NH 4 + over other N sources (Blomqvist et al., 1994;Beversdorf et al., 2015), these inputs can play a critical role in the development of HABs. ...
... Nutrient loading from human waste transported through groundwater can result in stoichiometric shifts because of adsorption of SRP, which can elevate N:P (Lapointe et al., 1990). The highest DIN:SRP were observed in urban drainage ditches and canals, while lower DIN:SRP were observed in estuarine canals located directly on the Caloosahatchee River Estuary. ...
The coastal communities of Lee County, Florida, USA have grown rapidly since the 1970s. In this county, drainage ditches, canals, creeks, and the Caloosahatchee River Estuary often have high concentrations of nutrients and bacteria limiting their designated uses. Septic systems have previously been identified as a major pollution source in some areas of Lee County; therefore, this study sought to identify the extent of this issue throughout the county. To accomplish this, surface water samples were collected at 25 drainage ditch, creek, or canal sites suspected of human waste contamination from septic systems in various drainage basins throughout Lee County during January 2020-January 2021. Water samples were analyzed for nutrients, dual stable nitrate isotopes (δ15N-NO3-, δ18O-NO3-), fecal indicator bacteria (enterococci, Escherichia coli), a molecular tracer of human waste (HF183), and chemical tracers of human waste (the artificial sweetener sucralose, pharmaceuticals). Particulate organic matter (POM) and macrophytes were also collected and analyzed for stable carbon (δ13C) and nitrogen (δ15N) isotopes, as well as elemental composition (C:N:P). To broaden the assessment of stable isotope values and C:N:P, archived macrophyte samples from 2019 were also included in analyses. Ammonium concentrations were high (> 4.3 μM) in 55 % of samples. Fecal bacteria were high in 66 % of samples. HF183 was detected in 50 % of samples and positively correlated with enterococci (r = 0.32). Sucralose concentrations were high (> 380 ng/L) in 54 % of samples, while carbamazepine was detected in 40 % of samples. Human waste N sources were indicated by δ15N > 3.00 ‰ at 44 % of sites by δ15N-NO3-, 68 % of sites by POM, and at 100 % of sites where macrophyte samples were collected. This large-scale study provides evidence of widespread human waste pollution throughout Lee County and can help guide infrastructure improvements to promote sustainable development. These findings should be applicable to urbanized regions globally that are experiencing declines in water quality and harmful algal blooms due to development with inadequate infrastructure.
... Despite these poor conditions, Florida's coastal communities often contain high densities of septic systems (Flanagan et al., 2020) that can account for >50% of domestic waste disposal (Herren et al., 2021). As such, evidence of nutrient and bacterial pollution from septic system effluent contamination has been observed throughout the state (Lapointe et al., 1990;Lapointe and Krupa, 1995;Paul et al., 1995;Arnade, 1999;Corbett et al., 2000;Lipp et al., 2001;Bacchus and Barile, 2005;Lapointe and Bedford, 2007;Meeroff et al., 2008;Lapointe et al., 2017;Barile, 2018;Herren et al., 2021). Thus, source identification of nutrient and microbial pollution in Florida's coastal areas is necessary to determine the associated human health and environmental risks, as well as for the development of mitigation strategies. ...
... Groundwater NH 4 + concentrations were particularly high in the central drainage and Powell Creek basins, while NO x concentrations were at background levels (Fig. 4). These drainage basins had the highest water tables (Fig. 3), which would likely suppress coupled nitrification-denitrification (Lapointe et al., 1990;Mallin, 2013). Conversely, in Hancock Creek where water tables were deeper, groundwater NO x concentrations were highest and NH 4 + concentrations were lower, indicating that some nitrification was occurring. ...
... The various significant correlations of HF183, carbamazepine, and acetaminophen with surface water NH 4 + , NO x , and TN concentrations help to connect this N loading to effluent from septic systems (Fig. S12). Conversely, surface water P concentrations were not variable between watersheds and may not be as affected by septic system effluent loading because some of these additional P inputs are likely adsorbed by sediments (Lapointe et al., 1990;Weiskel and Howes, 1992). The study region has P-rich phosphorus deposits in the Bone Valley Formation, which provide for natural elevation of P concentrations (Odum, 1953). ...
As human population growth has expanded in Southwest Florida, water quality has become degraded with an increased occurrence of harmful algal blooms (HABs). Red tide (Karenia brevis) originating offshore, intensifies in nearshore waters along Florida's Gulf Coast, and blue-green algae (Microcystis spp.) originating in Lake Okeechobee is discharged into the Caloosahatchee River. These HABs could be enhanced by anthropogenic nitrogen (N) and phosphorus (P) from adjacent watersheds. North Fort Myers is a heavily developed, low-lying city on the Caloosahatchee River Estuary serviced by septic systems with documented nutrient and bacterial pollution. To identify sources of pollution within North Fort Myers and determine connections with downstream HABs, this multiyear (2017–2020) study examined septic system- groundwater- surface water couplings through the analysis of water table depth, nutrients (N, P), fecal indicator bacteria (FIB), molecular markers (HF183, GFD, Gull2), chemical tracers (sucralose, pharmaceuticals, herbicides, pesticides), stable isotopes of groundwater (δ¹⁵N-NH4, δ¹⁵N-NO3) and particulate organic matter (POM; δ¹⁵N, δ¹³C), and POM elemental composition (C:N:P). POM samples were also collected during K. brevis and Microcystis spp. HAB events. Most (>80%) water table depth measurements were too shallow to support septic system functioning (<1.07 m). High concentrations of NH4⁺ and NOx, up to 1094 μM and 482 μM respectively, were found in groundwater and surface waters. δ¹⁵N values of groundwater (+4.7‰) were similar to septic effluent (+4.9‰), POM (+4.7‰), and downstream HABs (+4.8 to 6.9‰), indicating a human waste N source. In surface waters, FIB were elevated and HF183 was detected, while in groundwater and surface waters sucralose, carbamazepine, primidone, and acetaminophen were detected. These data suggest that groundwater and surface water in North Fort Myers are coupled and contaminated by septic system effluent, which is negatively affecting water quality and contributing to the maintenance and intensification of downstream HABs.
... Groundwater had significantly higher dissolved nutrient concentrations, nutrient ratios, and more enriched δ 15 N-NO 3 − than surface waters (all > +3‰), indicating septic system-enriched groundwater as a nutrient source to adjacent surface waters. This has implications for nutrient loading and eutrophication, as submarine groundwater discharge (SGD) is a primary mechanism for nutrient and microbial transport to coastal waters (Brezonik, 1972;Bicki et al., 1984;Lapointe et al., 1990;Valiela et al., 1992;Weiskel and Howes, 1992;NRC, 1993). Porous, sandy sediments lack the organic carbon compounds needed for microbial nitrification/denitrification of dissolved NH 4 + from septic effluent, which explains why NH 4 + , rather than NO 3 − , is the dominant form of reactive nitrogen in groundwater during this study. ...
... Thus, these sediments have been designated as "poor" for septic systems because they do not adequately remove N (Wettstein et al., 1986). Conversely, groundwater P tends to be scavenged by sediments, leading to much higher DIN:SRP and TDN:TDP in groundwater than surface water (Lapointe et al., 1990;Weiskel and Howes, 1992). However, over time soils can become P-saturated, reducing their adsorption capability and P-leaching may increase (Lusk et al., 2017). ...
... As such, high concentrations of both N and P were found in residential groundwaters in this study as well as in previous studies of septic systems in similar environments (Lapointe and Krupa, 1995a,b;Corbett et al., 2002;Belanger et al., 2007;Lapointe et al., 2017). Further increased groundwater flow results from rapid infiltration of rainwater into drainfields and the groundwater table below (Lapointe et al., 1990). Groundwater transport rates as high as 0.4 m/day have been recorded on Florida barrier islands (Corbett et al., 2000) and can range from 0.35 m/d in sandy soils (Harden et al., 2003) to 79 m/d in porous limestone (Dillon et al., 1999). ...
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Effluent from septic systems can pollute groundwater and surface waters in coastal watersheds. These effects are unknown for the highly urbanized central Indian River Lagoon (CIRL), Florida, where septic systems represent > 50% of wastewater disposal. To better understand these impacts, water quality was assessed along both canals and a tributary that drain into the CIRL. Dissolved nutrient concentrations were higher near septic systems than in natural areas. δ¹⁵N values of groundwater (+7.2‰), surface water (+5.5‰), and macrophytes (+9.7‰) were within the range for wastewater (>+3‰), as were surface water concentrations of the artificial sweetener sucralose (100 to 1700 ng/L) and fecal indicator bacteria density. These results indicate that septic systems are promoting eutrophication in the CIRL by contributing nutrient pollution to surface water via groundwater. This study demonstrates the need to reduce reliance on septic systems in urbanized coastal communities to improve water quality and subsequently mitigate harmful algal blooms.
... In this region, it has been identified that a strong low-salinity signal into the surface Caribbean water mass was due to the considerable freshwater input from the SGDs (Carrillo et al. 2016). Characterizing the contribution of SGDs is important, since SGDs are significant sources of nutrients from groundwater and wastewater to coastal ecosystems (Lapointe et al. 1990;Paytan et al. 2006;Mutchler et al. 2010;Hernández-Terrones et al. 2015;Young et al. 2018). ...
... To Maya, low-tourism development region (Mahahual-Xahuayxol). A1 Akumal Bay, T1 Tulum beach, S1 Shambala, CH1 Chávez, M1-3 Mahahual beaches, X1 Xahuayxol, T2 Tankah, C1 Xcacel cenote, C2 Manatí cenote, C3 Encantado cenote. The bold arrow marks the following regions: Holbox fracture zone-Xel-Ha zone and evaporite zone; the dotted arrow shows the groundwater flow in each zone: northeast and southeast (b) ammonification (Lapointe et al. 1990). On the other hand, nitrate concentration normally was not detected (De la Lanza-Espino et al. 2006), although during this study, the concentration was between below the detection limit and 1.6 μM, probably due to the nitrification processes. ...
... By contrast, due to the properties of the carbonate rocks, the SRP content of groundwater is relatively low; CaCO 3 adsorbs the phosphate molecules, which limits their availability in the environment (Lapointe et al. 1990 The environmental effects generated by tourist activities along the coasts of the Mexican Caribbean have been used to classify tourist destinations (Fig. 7): the northern zone (Cancún), as a highly developed tourist area; Akumal and Tulum in the Riviera Maya, as an area with intermediate development; and the Mahahual localities (Costa Maya), as sites of low-level development (Sánchez et al. 2013;. ...
Water quality in the Mexican Caribbean is affected by increases in tourism infrastructure and poor wastewater treatment. Additionally, karst geomorphology facilitates the infiltration of organic matter to subterranean water and coastal fresh water that originates from submarine groundwater discharges (SGDs), altering the environment. The tourism infrastructure grows at different rates along the Caribbean coast, characterizing zones with diverse levels of tourism impact. The aim of this work was to measure nutrient concentrations in superficial coastal water and fresh water to evaluate the water quality through different zones along a gradient from intermediate- (Riviera Maya) to low-tourism (Costa Maya) development regions. Furthermore, this study aimed to compare the measured nutrient concentrations with the Mexican ecological criteria of water quality 001/89 (CECCA-001/89), detect possible contributions by SGDs, and determine whether the nitrogen (N) sources are anthropogenic using stable nitrogen isotopes in the seagrass Thalassia testudinum. According to the results, nutrient concentrations (ammonium, nitrate, nitrite, and orthophosphate) differed significantly between the Riviera Maya and Costa Maya (P = 0.0001). Sites such as Shambala, Chávez, Tankah, Mahahual 2, Tulum, Akumal, and Xahuayxol exceeded the upper levels set by the CE-CCA-001/89. Tankah, Shambala, and Chávez were influenced by SGDs. The nitrogen isotope ratio in Akumal and Tulum coast water shows that they are under N loading derived to the sewage percentage of δ15N in Akumal, Tulum, and Mahahual, showing that these sites suffer N loading due to sewage. Our study recommends continuous monitoring and coastal characterization to detect SGD and to regulate, treat, and dispose of sewage.
... Recognition of the paramount importance of water quality to the health of coral reefs in the Florida Keys led to its designation as an "Area of Critical State Concern" by the Florida Legislature in 1974 (Table 1). Following the first reports of coral reef decline off Key Largo in the 1970s (Dustan 1977;Dustan and Halas 1987) and the role of septic systems in contributing to nearshore eutrophication (Lapointe et al. 1990), nutrient pollution became a primary issue in the Florida Keys. In 1988, 50 coral reef experts met at a National Oceanic and Atmospheric Administration (NOAA)-sponsored workshop in Key Largo, Florida and ranked various problems affecting the coral reefs of the Florida Keys; the primary conclusion was "excessive amounts of nutrients invading the Florida Reef Tract from the Keys and from Florida Bay are a serious and widespread problem" (NOAA 1988; Table 1). ...
... The WQPP was the first of its kind for a United States marine sanctuary (NOAA 1996;Kruczynski and McManus 2002). Florida (1974), Public Law 92-532 1980 Interim Action Plan and structural modifications begin to increase water deliveries to Everglades National Park and Shark River Slough Light and Dineen (1994) 1981 Looe Key National Marine Sanctuary (LKNMS) designated at Looe Key reef 46 Federal Register 946 1981 Discolored water, algal blooms, and seagrass die-off reported by fishermen in western Florida Bay DeMaria (1996) 1982 Heavy rainfall and water managers implementation of the "rainfall plan" increase freshwater deliveries through Shark River Slough Cane (1983), Light and Dineen (1994), Rudnick et al. (1999Rudnick et al. ( ) 1983 Long-spined sea urchin Diadema antillarum die-off in the Florida Keys and Caribbean region Lessios et al. (1984) 1987 Mass mortality of turtlegrass Thalassia testudinum begins in Florida Bay Robblee et al. (1991), Hall et al. (2016Hall et al. ( ) 1987 First mass coral bleaching event observed in the Florida Keys Jaap (1988), Causey (2008) Lapointe et al. (1990), Lapointe and Clark (1992) 1990 Nitrogen enrichment linked to seagrass die-off in Florida Bay Duarte (1990Duarte ( ) 1991 Freshwater deliveries increased to Florida Bay and the Florida Keys through Shark River Slough and Taylor Slough Rudnick et al. (1999), Brand (2002), Lapointe et al. (2002Lapointe et al. ( ) 1991 Cyanobacterial bloom and sponge mortality in Florida Bay Butler et al. (1995Butler et al. ( ) 1992 Algal blooms spread from Florida Bay to offshore bank reefs of the Florida Keys Lapointe et al. (1994), Lapointe and Matzie (1996), Lapointe et al. (2002 Congressional testimony on coral reef loss and eutrophication in the Florida Keys ...
... The residential population of the Florida Keys increased from 68,730 in 1984 to 74,044 in 2014, and tourism (overnight stays, not including day trippers) also increased in this period, reaching 3.6 million in 2014. Several studies have demonstrated the couplings between nutrient enrichment from local sewage pollution in the Florida Keys (septic systems result in high N:P ratios of ~ 100:1 in groundwaters; Lapointe et al. 1990) and algal blooms and hypoxia (Lapointe and Clark 1992;Lapointe et al. 2004), including the offshore LKSPA (Lapointe and Matzie 1996). Ward-Paige et al. (2005) reported increased growth of the fecal bioindicator and boring sponge Cliona delitrix, which has caused bioerosion of reef frameworks over broad areas of the FKNMS. ...
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Increased loadings of nitrogen (N) from fertilizers, top soil, sewage, and atmospheric deposition are important drivers of eutrophication in coastal waters globally. Monitoring seawater and macroalgae can reveal long-term changes in N and phosphorus (P) availability and N:P stoichiometry that are critical to understanding the global crisis of coral reef decline. Analysis of a unique 3-decade data set for Looe Key reef, located offshore the lower Florida Keys, showed increased dissolved inorganic nitrogen (DIN), chlorophyll a, DIN:soluble reactive phosphorus (SRP) ratios, as well as higher tissue C:P and N:P ratios in macroalgae during the early 1990s. These data, combined with remote sensing and nutrient monitoring between the Everglades and Looe Key, indicated that the significant DIN enrichment between 1991 and 1995 at Looe Key coincided with increased Everglades runoff, which drains agricultural and urban areas extending north to Orlando, Florida. This resulted in increased P limitation of reef primary producers that can cause metabolic stress in stony corals. Outbreaks of stony coral disease, bleaching, and mortality between 1995 and 2000 followed DIN enrichment, algal blooms, and increased DIN:SRP ratios, suggesting that eutrophication interacted with other factors causing coral reef decline at Looe Key. Although water temperatures at Looe Key exceeded the 30.5 °C bleaching threshold repeatedly over the 3-decade study, the three mass bleaching events occurred only when DIN:SRP ratios increased following heavy rainfall and increased Everglades runoff. These results suggest that Everglades discharges, in conjunction with local nutrient sources, contributed to DIN enrichment, eutrophication, and increased N:P ratios at Looe Key, exacerbating P limitation, coral stress and decline. Improved management of water quality at the local and regional levels could moderate N inputs and maintain more balanced N:P stoichiometry, thereby reducing the risk of coral bleaching, disease, and mortality under the current level of temperature stress.
... In this region, it has been identified that a strong low-salinity signal into the surface Caribbean water mass was due to the considerable freshwater input from the SGDs ( Carrillo et al. 2016). Characterizing the contribution of SGDs is important, since SGDs are significant sources of nutrients from groundwater and wastewater to coastal ecosystems ( Lapointe et al. 1990;Paytan et al. 2006;Mutchler et al. 2010;Hernández-Terrones et al. 2015;Young et al. 2018). ...
... Author's personal copy (b) ammonification ( Lapointe et al. 1990). On the other hand, nitrate concentration normally was not detected (De la Lanza- Espino et al. 2006), although during this study, the concentra- tion was between below the detection limit and 1.6 μM, prob- ably due to the nitrification processes. ...
... The presence of ammonium in groundwater and coastal waters may be due to several factors: the reduction of nitrate to ammonium, lessened ammonium oxidation dur- ing its transport by groundwater ( Hernández-Terrones et al. 2015), or recent pollution (Table 3). By contrast, due to the properties of the carbonate rocks, the SRP content of groundwater is relatively low; CaCO 3 adsorbs the phosphate molecules, which limits their availabil- ity in the environment ( Lapointe et al. 1990 ...
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Water quality in the Mexican Caribbean is affected by increases in tourism infrastructure and poor wastewater treatment. Additionally, karst geomorphology facilitates the infiltration of organic matter to subterranean water and coastal fresh water that originates from submarine groundwater discharges (SGDs), altering the environment. The tourism infrastructure grows at different rates along the Caribbean coast, characterizing zones with diverse levels of tourism impact. The aim of this work was to measure nutrient concentrations in superficial coastal water and fresh water to evaluate the water quality through different zones along a gradient from intermediate- (Riviera Maya) to low-tourism (Costa Maya) development regions. Furthermore, this study aimed to compare the measured nutrient concentrations with the Mexican ecological criteria of water quality 001/89 (CE-CCA-001/89), detect possible contributions by SGDs, and determine whether the nitrogen (N) sources are anthropogenic using stable nitrogen isotopes in the seagrass Thalassia testudinum. According to the results, nutrient concentrations (ammonium, nitrate, nitrite, and orthophosphate) differed significantly between the Riviera Maya and Costa Maya (P = 0.0001). Sites such as Shambala, Chávez, Tankah, Mahahual 2, Tulum, Akumal, and Xahuayxol exceeded the upper levels set by the CE-CCA-001/89. Tankah, Shambala, and Chávez were influenced by SGDs. The nitrogen isotope ratio in Akumal and Tulum coast water shows that they are under N loading derived to the sewage percentage of δ15N in Akumal, Tulum, and Mahahual, showing that these sites suffer N loading due to sewage. Our study recommends continuous monitoring and coastal characterization to detect SGD and to regulate, treat, and dispose of sewage.
... With > 50% of the world's population living within coastal areas, sewage pollution has become a growing global problem that is largely unrecognized. Untreated sewage from cesspools and septic tanks is a concern for human and environmental health in rural areas (Lapointe et al., 1990;Paul et al., 2000;Whittier and El-Kadi, 2014). Sewage pollution is a complex environmental problem because it is a cocktail containing elevated and potentially hazardous levels of pathogens, hydrocarbons, nutrients, toxins, organic and inorganic compounds, and endocrine disruptors (Wear and Vega Thurber, 2015). ...
... Nutrient concentrations are also commonly used to assess water quality. It has been shown that nutrient concentrations are significantly higher nearshore with known sewage pollution (Lapointe et al., 1990;Nelson et al., 2015). However, measuring nutrients at the shoreline alone as a sewage indicator is not informative enough for management actions because of their numerous non-sewage watershed sources. ...
... concentrations received a medium weight (weight = 2) as HDOH uses this FIB to assess marine recreational water safety specifically for sewage pollution, but not the highest weight because concentrations fluctuate over short time scales (min to h) and have other sources, like soils, in tropical areas (Hardina and Fujioka, 1991;Byappanahalli and Fujioka, 1998;Byappanahalli and Fujioka, 2004). Nutrient concentrations received the lowest weight (weight = 1) since sewage pollution is known to increase them, but nutrients can also come from other sources within the watershed and concentrations can vary over short time scales (Lapointe et al., 1990;David et al., 2013;Nelson et al., 2015). The equation for calculating the overall sewage pollution score for each station was: (C. ...
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Sewage pollution is contributing to the global decline of coral reefs. Identifying locations where it is entering waters near reefs is therefore a management priority. Our study documented shoreline sewage pollution hotspots in a coastal community with a fringing coral reef (Puakō, Hawai'i) using dye tracer studies, sewage indicator measurements, and a pollution scoring tool. Sewage reached shoreline waters within 9 h to 3 d. Fecal indicator bacteria concentrations were high and variable, and δ 15 N macroalgal values were indicative of sewage at many stations. Shoreline nutrient concentrations were two times higher than those in upland groundwater. Pollution hotspots were identified with a scoring tool using three sewage indicators. It confirmed known locations of sewage pollution from dye tracer studies. Our study highlights the need for a multi-indicator approach and scoring tool to identify sewage pollution hotspots. This approach will be useful for other coastal communities grappling with sewage pollution.
... While not without risk, when properly treated and applied this method of recycling waste material has been deemed safe for both humans and the environment (AMS, 2011). There has also been an increasing interest in Florida to understand the often overlooked role of on-site sewage disposal systems (OSTDS; septic systems and shallow injection wells) in enrichment and microbial contamination of shallow groundwaters and adjacent surface waters via submarine groundwater discharge (SGD; Lapointe et al., 1990Lapointe et al., , 2012Lapointe and Krupa, 1995a,b;Paul et al., 1995a,b;Griffin et al., 1999;Tarnowski, 2014). In addition to SGD, SLE water quality is also affected by tidal creeks and primary canals (C-44, C-23, and C-24; Fig. 2) and, in turn, the sediments that can sequester incoming N and P from these sources (Howes et al., 2008;Havens et al., 2016). ...
... These livestock waste values depend on if the effluent is nitrified, or not, as values can be much lower. Nitrogen in OSTDS effluent is primarily in the form of ammonium (Bicki et al., 1984;Lapointe et al., 1990;Valiela et al., 1997) with d 15 N values of +4 À 5 o / oo (Lapointe and Krupa, 1995a,b;Hinkle et al., 2008;Katz et al., 2010), but through ammonia volatilization and microbial processing values can become more enriched (i.e. treated wastewater). ...
... In addition to stable isotope analyses, measurement of C:N:P content in macroalgae and phytoplankton provides a measure of nutrient quantity and stoichiometry that is useful in assessing the relative importance of N-versus P-limitation (Atkinson and Smith, 1983;Lapointe et al., 1992). This is particularly appropriate for assessing OSTDS groundwater-borne sewage pollution that can deliver nutrient pollution at high N:P ratios as a result of selective adsorption of P onto soil particles (Bicki et al., 1984;Lapointe et al., 1990;Weiskel and Howes, 1992). In dense residential communities relying primarily on OSTDS, high cumulative P inputs to groundwater can supersaturate the soil and reduce its ability to selectively adsorb P (Bicki et al., 1984). ...
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Nutrient enrichment is a significant global-scale driver of change in coastal waters, contributing to an array of problems in coastal ecosystems. The St. Lucie Estuary (SLE) in southeast Florida has received national attention as a result of its poor water quality (elevated nutrient concentrations and fecal bacteria counts), recurring toxic Microcystis aeruginosa blooms, and its proximity to the northern boundary of tropical coral species in the United States. The SLE has an artificially large watershed comprised of a network of drainage canals, one of which (C-44) is used to lower the water level in Lake Okeechobee. Public attention has primarily been directed at nutrient inputs originating from the lake, but recent concern over the importance of local watershed impacts prompted a one-year watershed study designed to investigate the interactions between on-site sewage treatment and disposal systems (OSTDS or septic systems), groundwaters, and surface waters in the SLE and nearshore reefs. Results provided multiple lines of evidence of OSTDS contamination of the SLE and its watershed: 1) dissolved nutrients in groundwaters and surface waters were most concentrated adjacent to two older (pre-1978) residential communities and the primary canals, and 2) sucralose was present in groundwater at residential sites (up to 32.0 mg/L) and adjacent surface waters (up to 5.5 mg/L), and 3) d 15 N values in surface water (+7.5 o / oo), macroalgae (+4.4 o / oo) and phytoplankton (+5.0 o / oo) were within the published range (>+3 o / oo) for sewage N and similar to values in OSTDS-contaminated groundwaters. Measured d 15 N values in M. aeruginosa became increasingly enriched during transport from the C-44 canal (5.8 o / oo) into the mid-estuary (8.0 o / oo), indicating uptake and growth on sewage N sources within the urbanized estuary. Consequently, there is a need to reduce N and P loading, as well as fecal loading, from the SLE watershed via septic-to-sewer conversion projects and to minimize the frequency and intensity of the releases from Lake Okeechobee to the SLE via additional water storage north of the lake. These enhancements would improve water quality in both the SLE and Lake Okeechobee, reduce the occurrence of toxic harmful algal blooms in the linked systems, and improve overall ecosystem health in the SLE and downstream reefs.
... In the case of PO 3− 4 , phosphorus precipitates with calcium carbonates and is adsorbed on iron and manganese oxides; therefore, it may be unlikely that non-anthropogenic sources of phosphorus can significantly influence the availability of PO 3− 4 through submarine groundwater discharge (Santos et al. 2021). Nevertheless, near human settlements, PO 3− 4 concentration of groundwater was higher than that of surface waters in the Florida Keys, Florida, USA (Lapointe et al. 1990). Indeed, phosphorus flux through submarine groundwater discharge is expected to contribute to the phosphorus budget in coastal waters (Lapointe et al. 1990;Slomp and Van Cappellen 2004;Sadat-Noori et al. 2016). ...
... Nevertheless, near human settlements, PO 3− 4 concentration of groundwater was higher than that of surface waters in the Florida Keys, Florida, USA (Lapointe et al. 1990). Indeed, phosphorus flux through submarine groundwater discharge is expected to contribute to the phosphorus budget in coastal waters (Lapointe et al. 1990;Slomp and Van Cappellen 2004;Sadat-Noori et al. 2016). Congruent with NH + 4 , we similarly hypothesize that the relatively high magnitudes of V max and low values of V max /K s observed for C. okamuranus may also enable this alga to opportunistically absorb PO 3− 4 when made available through submarine ground water discharge. ...
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The uptake kinetics of NO3-, NH4+, and PO43- were investigated for the brown alga Cladosiphon okamuranus, which is a major cultivated species in the Ryukyu Islands, Japan. Macroscopic sporophytes from individuals obtained at four different localities were used for the experiment. Uptake rates of NH4+ and PO43- in specimens from all localities increased with elevated substrate concentration, which were analyzed assuming Michaelis–Menten kinetics. In all samples from the four localities, NO3- uptake rates increased until about 20 μM and then gradually decreased as the substrate concentration increased, which followed single-enzyme Michaelis–Menten kinetics with substrate inhibition. The Vmax/Ks ratio (a measure of adaptation to low nutrient concentrations) was different among all samples. Uptake rates of NO3- and PO43- varied with temperature in samples at three localities, however the NH4+ uptake rate was invariant with temperature. There were differences in the nutrient uptake kinetics of macroscopic sporophytes of C. okamuranus among nutrients. Uptake rates for NH4+ exceeded NO3-. The relatively higher uptake rates for NH4+ may indicate an adaptive property for efficient absorption of transient NH4+ supply from groundwater discharge in the subtropical Ryukyu Islands under low nitrate conditions.
... This is evidenced by below detection concentrations of NH 3 . The maximum groundwater NH 3 concentration observed in this study during the fully operational phase (0.035 mg/L) is in stark contrast to the higher concentrations of groundwater NH 3 that have been observed in other parts of Florida near septic systems, including the Florida Keys (up to 38.5 mg/L) (Lapointe et al. 1990), Jupiter (up to 17.9 mg/L) (Lapointe & Krupa 1995), Martin County (up to 50 mg/L) (Lapointe et al. 2017), and North Fort Myers (up to 15.3 mg/L) (Brewton et al. 2022). The decreased NH 3 loading has significant environmental implications as many HABs preferentially uptake these forms of N (Glibert et al. 2016;Kramer et al. 2018;Hampel et al. 2019). ...
... By the last sampling date of the fully operational phase (June 30, 2021), which averaged 12.2 mg/L, groundwater NO x concentrations were 5.9 mg/L. Similar to NH 3 , high groundwater NO x concentrations downgradient of septic systems have been observed in other locations in Florida, such as in Tampa (up to 56 mg/L) (Bicki et al. 1984), the Florida Keys (up to 38.5 mg/L) (Lapointe et al. 1990), and Jupiter (up to 21.5 mg/L) (Lapointe & Krupa 1995). While the DWTU in this study generally performed better at TP removal than what has been observed downgradient from septic systems, to meet regulatory requirements and attain levels that are protective of the environmental and human health, some improvement could be achieved through additional chemical filters or advanced performance absorption beds (e.g., using 'Bold & Gold'). ...
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Wastewater management is a critical issue globally. In Florida, the importance of this issue is heightened by the proximity to sensitive ecosystems. Distributed wastewater treatment units (DWTU) are a recent, state-approved alternative to septic system conversions to centralized sewer infrastructure. In this study, the performance of a DWTU was tested at a new residence in Lake Hamilton, FL. A monitoring well was installed downgradient of the DWTU absorption field to establish baseline groundwater conditions prior to occupation of the residence. The residence was occupied, after which groundwater, DWTU influent, and effluent samples were collected. Many effluent parameters significantly decreased compared to influent, including ammonia (NH3; 97%), total Kjeldahl nitrogen (TKN; 95%), total nitrogen (TN; 88%), the TN:TP ratio (84%), fecal coliforms (92%), carbonaceous biochemical oxygen demand (CBOD; 96%), and total suspended solids (TSS; 96%). In the groundwater, nutrient concentrations initially increased compared to the baseline data, but eventually decreased, demonstrating that the DWTU was effective at improving quality of wastewater effluent. These systems could be especially effective in sensitive areas where advanced wastewater treatment has been mandated or is needed. HIGHLIGHTS A distributed wastewater treatment unit was installed and studied at a residence in Florida.; The distributed wastewater treatment unit significantly improved water quality of the residential wastewater effluent.; 97% of ammonia, 88% of TN, and 92% of fecal coliforms were removed from effluent.; Downgradient groundwater quality was better protected from wastewater contamination.;
... I also purchased a KV Associates heat-pulsing groundwater flowmeter to quantify lateral groundwater flow and effects of tidal pump-ing and rainfall on nutrient transport ( Figure 4A). The research showed a high degree of DIN enrichment and relatively less enrichment of soluble reactive phosphorus (SRP) in groundwaters due to adsorption of P onto the limestone substrata (Lapointe et al. 1990). Ebbing tides resulted in accelerated groundwater discharge, and rainfall caused transient surge flow of groundwaters into adjacent surface waters. ...
... My findings of nutrient pollution from septic systems were not well received by some of the public, nor by the new officials and scientists supported by the FKNMS program. A senior seagrass biologist from the University of Virginia who was involved in developing the FKNMS Management Plan disputed the conclusions of my peer-reviewed research that had been published in the journals Biogeochemistry (Lapointe et al. 1990) and Estuaries (Lapointe and Clark 1992). At a tumultuous Sanctuary Advisory Council (SAC) Meeting in August 1992 led by SAC Chairman George Barley (co-founder of the Everglades Foundation), Jay Zieman stated that the evidence for septic impacts were "poorly filtered white papers" and conclusions were nothing more than an "allegation." ...
... Several studies describe the transport of nutrients via groundwater towards the ocean in tropical karstic regions as in northwest Yucatan (Mexico) (Hanshaw and Back, 1980;Herrera-Silveira, 1998;Young et al., 2008;Null et al., 2014), Bermuda (Lapointe and O'Connell, 1989;Simmons and Lyons, 1994), Barbados (Lewis, 1987) and Guam (Redding et al., 2013), while some studies investigated their temporal variability (Lewis, 1987;Lapointe et al., 1990;ArandaCirerol et al., 2006;Tapia González et al., 2008). Southeast Asia belongs to one of the regions with the strongest human modifications in the coastal zone (Elvidge et al., 1997) where significant groundwater nutrient fluxes to the coastal zone were observed in Bangkok, Manila and Jepara (Burnett et al., 2007;Taniguchi et al., 2008;Adyasari et al., 2018). ...
... Especially nitrate fluxes were high during the wet season, which might be due to nitrogen leaching from a surface source like fertilizers, animal waste and general urban waste, which can also be observed in other karstic areas (Guo and Jiang, 2009). During wet season high groundwater nitrogen fluxes towards the coastal ocean were for example also observed in Florida Keys (Lapointe et al., 1990) and in Bermudas, possibly due to the use of fertilizers in the hinterland (Lewis, 1987). In Gunung Kidul major crops such as rice, corn and soy are mainly fertilized during wet season from October until March when water availability is high (Katam, 2017). ...
... La contaminación de las aguas subterráneas es una consecuencia de las actividades humanas que puede ser la amenaza más discreta para los ecosistemas costeros (Lapointe et al. 1990). En regiones kársticas como Florida y la Península de Yucatán, el agua puede infiltrarse rápidamente hacia los mantos acuíferos y a las complejas redes de ríos subterráneos cuyos destinos son poco claros. ...
... En regiones kársticas como Florida y la Península de Yucatán, el agua puede infiltrarse rápidamente hacia los mantos acuíferos y a las complejas redes de ríos subterráneos cuyos destinos son poco claros. Éstos generalmente desembocan en el manglar cerca de la costa o dentro de la laguna costera en forma de "Ojos de agua" (Fig. 1), por ende el riesgo que conlleva la contaminación de los cuerpos de agua subterráneos es alto y el peligro que representa la liberación de estas aguas a la costa es aún mayor (Lapointe et al. 1990). (Haynes et al. 2007;Kaczmarsky et al. 2005). ...
... During each sampling event, triplicate (n = 3) seawater samples were collected ~0.25 m below the surface into 0.25 L high-density polyethylene (HDPE) bottles and submerged ice in a cooler until returned to the Harbor Branch Oceanographic Institute at Florida Atlantic University (HBOI-FAU) laboratory for processing. Sites adjacent to canals, tributaries, and inlets (NIRL4, CIRL1, CIRL2, CIRL3, CIRL4, SIRL2, and SIRL5 in Fig. 1) were sampled during an ebbing tide to account for tidal pumping of groundwater (Lapointe et al., 1990). The seawater samples were filtered through 0.7 μm GF/F filters and frozen at − 20 • C until analysis, while filters were retained and frozen for estimation of chlorophyll a concentrations. ...
In Florida's Indian River Lagoon (IRL), anthropogenic eutrophication has resulted in harmful algal blooms and catastrophic seagrass losses. Hoping to improve water quality, policy makers enacted fertilizer bans, assuming that this would reduce the nitrogen (N) load. To assess the effectiveness of these bans, seawater and macroalgal samples were collected at 20 sites "pre" and ~ five-years "post" bans and analyzed to determine concentrations of dissolved nutrients and stable nitrogen isotope values (δ15N). Higher concentrations of ammonium and nitrate were observed post-ban and macroalgal δ15N values increased. A comparison of nutrient concentrations and δ15N between brown tide (Aureoumbra lagunensis) blooms indicated that the post-ban bloom was more strongly N-enriched with higher δ15N values than the pre-ban bloom, which had depleted values in the range of fertilizers. These data indicate a primary role of human waste influence in the IRL, suggesting that current management actions have been insufficient at mitigating eutrophication.
... In the first case, the wastewater plants apply only primary treatments which only guarantees just a ~15 % reduction in nitrogen and ~20 % reduction in phosphorus (Stanners and Bourdeau, 1995;Grizzetti and Bouraoui, 2006). In the second case, pit latrines concentrate and export extreme amounts of nutrients into groundwater, estimated by Lapointe et al. (1990) to be above 2000 μM for DIN. The combination of large daily water consumption and wastewater production with poor sewage treatment has resulted in large and continuous emissions of wastewater discharges with its almost intact fertilizing power into the groundwater and marine environments. ...
Insufficient attention to the large volumes of wastewater produced by expansive tourism and urban development in the north of the Mexican Caribbean has increased concerns on the ecological and economic sustainability of this important tourist destination, which is currently threatened by massive arrivals of pelagic Sargassum. Comparing environmental descriptions for sites exposed to contrasting anthropogenic pressure and before and during massive Sargassum tides, uncovered significant shifts in the environmental conditions in the last 20 years, from oligotrophic to mesotrophic-eutrophic conditions. The most significant changes were observed in the north, for habitats exposed to high anthropogenic pressure. Accordingly, the severe threat that massive Sargassum beaching currently represents for the survival of Caribbean coral reefs cannot be considered the only driver of reef eutrophication in the Mexican Caribbean, as the habitat degradation documented here has an important contribution from anthropogenic fertilization.
... Moreover, anthropogenic pressures such as coastal development, and tourism have had and continue to have an immense impact on the nearshore water quality of the area. This, in combination with a history of leaching from cesspits since 1940's until advanced wastewater treatment installation in 2017, has contributed to poor water quality with the accumulation of nutrients in the nearshore environs (Lapointe et al., 1990;Paul et al., 1997;Montenero et al., 2020). A central component of Florida Keys coastal development is the presence of over 500 dredged residential canals and marinas; these exacerbate the accumulation of nutrients through a variety of processes (Montenero et al., 2020). ...
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Introduction Coral species are negatively impacted by anthropogenic stressors worldwide. Nearshore coastal ecosystems provide an excellent study system for the investigation of the impacts of local land-based stressors such as nutrients on coral assemblages due to their proximity to land based sources of pollution. The nearshore environs of the Florida Keys are an intensively developed and intensively managed system; Florida Keys waters have been characterized by chronic eutrophication since 1999. Benthic communities are known to change or “shift” under chronic eutrophication. Objectives This research examines the patterns of occurrence in stony corals correlating to detailed nearshore water quality measurements. The questions addressed are a) What are the coral assemblages within 500 meters of the shoreline, and which species are resilient to these environs? b) How does water quality impact coral occurrence? Methods This study examined the immediate nearshore (0-500m) areas of 13 sites using a randomized blocked experimental design for both water quality and benthic sampling. Water quality parameters measured included chlorophyll-a, nitrates + nitrites (NOx), total nitrogen, total Kjeldahl nitrogen, total phosphorus, Salinity, pH, temperature, and dissolved oxygen. Benthic surveys documented stony coral occurrence using belt transects with point intercept measurements. Results Stony coral species occurrence was limited at most of the study sites. Siderastrea radians and Porites divaricata were the two common species that appear to have a higher tolerance to eutrophic conditions under these shallow water conditions. Of the 13 study sites, 2 sites had no coral species occurring; this analysis was based on the comparison between sites with and without stony coral species. Water column Chlorophyll-a, pH, dissolved oxygen saturation, temperature, NOx, N:P ratio, total nitrogen and total phosphorus were found to be significantly different between the sites with and without corals. Further multivariate analysis showed a clear clustering of the two groups. Conclusion The low overall diversity and the higher occurrences of stress tolerant species provide evidence of the effects of coastal eutrophication on the coastal Florida Keys ecosystem. Our data suggest that more conservative water quality thresholds should be posed to improve nearshore biodiversity and ecological functioning of coastal systems.
... These legacy nutrients may be remobilized and slowly released to the environment at the scale of decades (Tesoriero, Duff, Saad, Spahr, & Wolock, 2013). The entirety of the Florida Keys is influenced by legacy nutrients in the groundwater resultant from the impact of cesspits and septic tanks which were in use for decades prior to region-wide institution of advanced wastewater treatment (Lapointe, O'Connell, & Garrett, 1990), which obscures the effect of canals as point sources of legacy nutrients. ...
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The waters of the Florida Keys are naturally oligotrophic, however, discharge from the Everglades, anthropogenic changes to the coastline, and groundwater runoff from the carbonate islands contribute excess nutrients to the ecosystem. Eutrophication is acknowledged as a major threat to coastal ecosystems and successful efforts have been made to reduce direct anthropogenic nutrient pollution. The main driver of eutrophication is nutrient input; this study focuses on the nitrogen and phosphorous content of the water column. Eutrophication is also driven by hydrologic exchange, as the main method of transport of anthropogenic nutrients into the system is groundwater runoff. Chemical responses in the water column are indicated by reductions in dissolved oxygen saturation and pH. Benthic response to eutrophication is measured in this study by quantification of submerged aquatic vegetation (SAV) using Braun-Blanquet cover abundance (BBCA) surveys. The Florida Keys Residential Canal Project (2019-2021) was a rigorous water quality sampling project that included SAV surveys within thirteen study areas located across the Keys. The sampling strategy of the project was designed to capture ecological information across a range of shorelines with varying anthropogenic disturbances with quarterly water quality sampling and semiannual SAV surveys. The water quality feature space is reduced by principal component analysis and ordinated by uniform manifold approximation and projection. Gaussian mixed modeling identifies two clusters of points based on water quality characteristics. The clusters reflect opposing eutrophic states, with one cluster representing relatively good water quality and the other representing relatively poor conditions. Linear discriminant analysis is presented as a method by which the multi-dimensional eutrophic state of the water column can be expressed with a single metric. SAV data is summarized by calculating the mean BBCA score as well as transforming that data into relative taxon composition for each transect. The presence of the taxa is used as input for functional clustering of redundant components of systems to model the abundance of the functional groups found in the surveys. The redundant taxa generated by each model is aggregated into an adjacency matrix for the generation of a taxon network. The network structure is determined by maximizing the modularity of the minimum spanning tree of the network overall possible partitions to generate eight functionally redundant SAV taxon motifs. SAV communities are delineated by projecting bootstrap aggregated pairwise Goodman-Kruskal γ coefficient matrix between transects and identifying clusters with the density-based spatial clustering of applications with noise algorithm. A Thalassia testudinum dominated community, a mixed SAV community, and two macroalgae-dominated communities are recognized. Water quality parameters as a function of distance from the shore to show verify that the 500 m “halo zone” used to define the border between local and regional influences on the water column is sufficient. Residential canals can have two significantly different patterns of influence on the adjacent waters relative to the waters outside state parks: nutrient pollution and impacted water quality can proliferate from the canal mouth to the extent of the study area at moderate levels, or the zone immediately influenced by the canal mouth is highly impacted but recovers to state park equivalent levels of impact at the 500m boundary. Finally, the ecological relationship between measured water quality parameters and SAV abundance is examined using redundancy analysis (RDA). pH is identified as a strong indicator of the eutrophic state of the water column. The seagrass-dominated community stands out as occupying a separate space within the RDA results, with dynamics among the macroalgae taxa being primarily driven by nitrogen availability. Seagrasses drive a high variability in dissolved oxygen saturation resultant of variation in light availability. A macroalgal gradient exists that aligns with the degree of eutrophic stress imposed on the water column in the form of dissolved oxygen reduction and acidification with increased stratification of the water column. This gradient is representative of a qualitative succession that is observed across the study areas as a response to, or recovery from, eutrophication.
... The seasonal high-water table has been associated with elevated N and P concentrations through the inhibition of P binding to soils and the release of ammonium to groundwater without nitrification (Bicki andBrown, 1990, Lapointe et al., 2017;Buszka andReeves, 2021, Herren et al., 2021). Enriched groundwater can also be a significant source of nutrients to adjacent surface waters via submarine groundwater discharge transport (Bicki and Brown, 1990;Lapointe et al., 1990;Meeroff et al., 2008;Pujari et al., 2012). ...
Water quality impairment linked to household septic systems presents a significant challenge for environmental management professionals given the costs and complexity of encouraging residents to convert to sewer systems. Septic-to-sewer conversion programs may be more effective if they employ innovative techniques such as social marketing to accelerate engagement, but there is a lack of the necessary formative audience research available on which to promote sanitation-related technologies and behaviors using these types of strategies. We used Diffusion of Innovations theory as a lens through which to view support for septic-to-sewer conversion programs, considering perceptions of relative advantage, compatibility, complexity, and observability as factors (i.e., barriers, motivators) in the decision to convert to sewer. We collected data from 518 septic system owners in the state of Florida, USA. Four out of ten respondents indicated there were septic-to-sewer conversion plans in place in their community, and most of these individuals reported the plans were voluntary rather than mandatory. Residents with plans in place had more favorable perceptions than those without such plans and were largely supportive of septic-to-sewer conversion programs. Ordinal regression revealed compatibility and observability were significant predictors of residents' support for septic-to-sewer conversion. When conversion project status variables were added to the final ordinal model, compatibility remained a significant predictor, and completed conversion status also predicted support. Environmental management professionals should consider using characteristics of compatibility and observability to bolster engagement in septic-to-sewer conversion programs, and consider integrating the influences of other communities with completed conversion programs.
... In another study in the Florida Keys, Lapointe et al. (1990) reported a 400-fold increase in inorganic N (ammonium, nitrate, and nitrite) concentrations in groundwater beneath septic systems as compared to groundwater under a control area (no septic systems). These authors also noted that season of the year controlled the fate of septic tank-derived N. ...
In the United States, about 4,800 water bodies are impaired due to excess nitrogen (N), and septic systems are recognized as one source of N pollution. This 6-page fact sheet describes the behavior and transport of N from a conventional septic system and the summarizes the sources of N in sewage, the forms and behavior of N in septic tanks and drain fields, and the fate and transport of N in groundwater. Written by Gurpal Toor, Mary Lusk, and Tom Obreza, and published by the UF Department of Soil and Water Science, June 2011. SL348/SS550: Onsite Sewage Treatment and Disposal Systems: Nitrogen (
... Akumal are impacted by nutrients from anthropic sources, including faulty septic tanks, untreated wastewater spills, water-treatment plant overloading, and untreated wastewater injection in the area (Hernández-Terrones et al., 2015). This implies an interaction between the high levels of nitrogen found in Akumal coastal waters (Hernández-Terrones et al., 2011Naranjo-García, 2015;Mata Lara et al., 2016), the low level of phosphorus related to the karstic relief trap (Lapointe et al., 1990;Hernández-Terrones et al., 2015) and the imbalance of coral symbiosis (D'Angelo and Wiedenmann, 2014;Rädecker et al., 2015). Furthermore, Akumal Reef has been identified as highly susceptible to diseases outbreaks (Steneck and Lang, 2003;Ruiz-Moreno et al., 2012) and our results show how disease prevalence increases and persists over the decades. ...
Interactions between multiple stressors (climate change, pollution, and overfishing) can erode ecological thresholds and trigger a phase shift from a coral-dominated reef state to less desired benthic states. Akumal Reef located in the North of the Mexican Caribbean is an important case study to quantify the ecological changes of coral reefs affected by multiple stressors. Here we used both field data (benthic cover, coral condition, fish biomass), together with satellite data of the main stressors (degree heating weeks, chlorophyll a, and urban area), to (i) reconstruct the timeline of stressors that have affected Akumal Reef from 1995 to 2019; (ii) describe the changes in coral reef components (benthic cover, bleaching, coral diseases, and fish biomass) in this period; and (iii) propose a model integrating coral benthic changes and the significant stressors influencing those changes through time while taking into account stressors interactions and partial effects. Our results show that between 1995 and 2019, hard coral cover suffered an average absolute loss of 84%. This loss contrasted with an average absolute gain in total algae cover of 74% and was negatively associated with an increase of 290% in the urban area. During the study period, there has been no signal of positive recovery in hard coral cover, and increasingly available space has been occupied alternatively by filamentous algae or macroalgae after acute stressor events, such as bleaching or disease, which are more frequent, and persistent in the last decade. Our integrative model highlights interactions between urban area, maximum degree heating weeks, and chlorophyll a as main drivers of hard coral decrease, as well as interactions between urban area and precipitation, related to total algae increase. Akumal Reef degradation trend must be rapidly addressed by implementing management tools integrated into a comprehensive coastal planning model, which must reduce pollution and overfishing, allowing the recovery of its structure and function, and providing persistence of ecosystem services in a context of global changes and ecological ‘surprises’.
... Continuous urban, suburban, rural housing and commercial development alters groundwater quality through wastewater and landscape runoff and is of growing concern, especially where groundwater directly discharges to coastal waters (Knee et al. 2010). In many coastal areas, OSDS associated with development are considered one of the major sources of nutrient contamination (e.g., Lapointe et al. 1990;Harris 1995;Reay 2004). The majority of these OSDS are cesspools, where wastewater effluent is not treated before entering the groundwater system . ...
Fresh groundwater is a critical resource supporting coastal ecosystems that rely on low-salinity, nutrient-rich groundwater discharge. This resource, however, is subject to contamination from point- and nonpoint-sources such as on-site sewage disposal systems (OSDS) and urban developments. Thus, the significance of flow and transport processes near the coastline due to density effects and water circulation in a complex hydrogeologic system was investigated. A three-dimensional, density-dependent groundwater model was developed for the Keauhou basal aquifer (Hawai‘i Island, USA), where hydraulic head, salinity, nutrient concentrations, and submarine spring flux rates were used as calibration variables to best constrain parameters and produce a comprehensive aquifer management tool. In contrast, a freshwater-only model failed to properly simulate nutrient transport, despite the reasonable success in calibrating hydraulic head measurements. An unrealistic value for hydraulic conductivity was necessary for freshwater-only calibration, proving that hydraulic conductivity is a process-based variable (i.e., depends on model conceptualization and the simulated processes). The density-dependent model was applied to assess relative contaminant source contributions, and to evaluate aquifer response concerning water levels and quality due to changing environmental conditions. Nutrients detected in the aquifer are primarily sourced from OSDS, which was supported by a nitrogen isotope mixing model. Additionally, effects of sea-level rise emphasized the complexity of the study site and the importance of model boundaries. While the model is developed and applied for West Hawai‘i, the adapted approaches and procedures and research findings are applicable to other coastal aquifers.
... However, these tourist service providers may not equip their facilities with the wastewater treatment that protects the underground and surface water from anthropogenic pollution. Studies showed that contaminants from the septic tank transferred to the surrounded coastal zones increased the nutrients concentration as well as the presence of human enterobacteria in the nearby environment (Lapointe et al 1990;Paul et al 1995). ...
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The increase of anthropogenic land-based activities in the Pemuteran village, a tourist spot in the northern part of Bali Island, threatened the health of its coral reefs. Therefore, this study aimed to assess the impact of anthropogenic activities in the coral reef by using two indicator bacteria (Enterococci and Vibrio). Study sites were chosen based on human activities whereas coral genus was selected following the three most abundant genera in each site. The mucus of coral fragments and the water column overlying the reefs were sampled. These samples were both tested for the presence of Vibrio in TCBS nutrient at 37°C for 24 hours and Enterococci in Slanetz and Bartley nutrient at 41°C for 24 hours. Results showed that the abundance of Enterococci in the mucus of all coral genera were relatively similar, whereas its abundances in seawater were significantly higher than those in mucus. In contrast to Vibrio, the abundances in mucus in all coral genera were significantly higher than those in seawater. Despite the likely relativeness to the natural characteristics of both indicator bacteria, the extremely high concentration of total organic carbon and nitrate in the water column, particularly nitrate, significantly enhance the abundance of Enterococci. The high level of nutrients was detected in the site which has the highest human activities, milkfish culture and marine recreational spot. The abundant of Vibrio may reveal the cause of the high prevalence of coral diseases in this area, whereas Enterococci indicate that anthropogenic pollution has reached its coral reef ecosystem.
... Numerous studies in karst coastal environments have shown that nutrients in water discharges are higher near urban settlements (Lapointe and Clark, 1992;Lapointe et al., 2004;Álvarez-Góngora and Herrera-Silveira, 2006;Hernández-Terrones et al., 2011). The high NH 4 + concentrations in the water column at the PJ site evidence anthropogenic N inputs as the presence of this nutrient has been related to recent contamination sources (Lapointe et al., 1990;Camacho-Cruz et al., 2019). In addition, the δ 15 N values recorded in T. testudinum nearshore (10 m from the coast) in both seasons (cold-front season, 7.58‰; dry season, 7.35‰) were the highest recorded in our study area and may indicate a large input of wastewater from the continent. ...
We measured dissolved inorganic nitrogen (DIN = NH 4 + + NO x [= NO 3 − + NO 2 − ]), soluble reactive phosphorous (SRP), and ecological indicators (chlorophyll-a concentration, coverage of submerged aquatic vegetation, and %N, C:N and δ 15 N values in the seagrass Thalassia testudinum) to evaluate the effects of nutrient enrichment at three shallow coastal sites on the northern part of the Mexican Caribbean (Puerto Morelos, Puerto Juárez, and Isla Blanca) in two contrasting (cold-front or dry) seasons of the year. High nutrient concentrations prevailed in both seasons but were significantly higher during the cold-front season, probably as a result of sediment resuspension and groundwater discharges. The highest δ 15 N values were recorded in Puerto Juárez in both seasons (cold-front, 7.58‰; dry, 7.35‰). The highest macroalgae coverage and NH 4 + concentration were also recorded in this site. These results, together with the high correlation between δ 15 N and NH 4 + (r = 0.94) and DIN (r = 0.88) concentrations , suggest wastewater contamination in Puerto Juárez due to the influence of the city of Cancún. In contrast, the lowest mean δ 15 N (−1.35‰) and nutrient enrichment effects (i.e., highest coverage of T. testudinum and lowest macroalgae coverage) were observed in Isla Blanca, a site with no urban settlements. The low δ 15 N values recorded along the Puerto Morelos coastal transect suggest that a significant fraction of the nitrogen assimilated by T. testudinum may come from either exudates or the decomposition of drifting Sargassum stranded in the coast, as the δ 15 N values recorded in Sargassum (−0.64‰) were similar to those found in the seagrass (−0.83‰). The correlation between the DIN:SRP ratio and chlorophyll-a concentration in the study area may indicate N-limitation of phytoplankton growth, despite the high DIN concentrations. Beyond the differences observed between sites-which may indicate site-specific, long-term nutrient inputs-the indicators examined evidence environmental deterioration of the study area, likely due to a shift in the nutrient regime (away from oligotrophic), particularly in Puerto Juárez, the site with the heaviest load of urban and tourism activities.
... Importantly, the dataset that Julian used in these analyses was biased low and not fully representative of Looe Key water quality because these data represented only surface samples due to exclusion of the bottom samples (Julian 2020). This is of particular concern as the bulk of human wastewater generated in the Florida Keys is disposed of in either shallow or deep groundwaters through the use of cesspits, septic systems, shallow injection wells (Class V), and deep injection wells (Class I), all of which can enter coastal waters through submarine groundwater discharge at the benthic boundary layer (Simmons 1992;Shinn et al. 1994;Lapointe et al. 1990Lapointe et al. , 2004. Using only surface water data would also not capture more dense, hypersaline, nutrient enriched bottom waters discharging from Florida Bay to the offshore reefs. ...
The comment by Julian (2020) criticizes aspects of our paper, “Nitrogen enrichment, altered stoichiometry, and coral reef decline at Looe Key, Florida Keys, USA.” The comment begins by misrepresenting our extensive literature review, while providing no justification for the claim of a “skewed reading.” Julian’s critique focused on methods of data handling, statistics, and spatial awareness, which we demonstrate in every case to be either irrelevant or incorrect. We provide additional supporting data that refute these claims. For example, Julian criticized the removal of data points below the method detection limits (MDLs), but when these points are included, the results do not change. Further, Julian criticized our removal of outliers, but so few points were excluded that it did not change the results of the statistical analyses. Julian also misinterpreted the methods of our correlation and stepwise regression analyses but did not dispute the Kruskal–Wallis tests of our 30-year dataset that revealed significant decadal changes. Julian’s closing paragraph is replete with misinformation and demonstrates a lack of understanding as to how increased freshwater flows associated with Everglades Restoration have led to a worsening of algal blooms and coral decline in the Florida Keys National Marine Sanctuary (FKNMS). This comment represents a smokescreen to confuse the scientific community about the physical connectivity of the Everglades basin and the FKNMS. Past water management policies based on politics, not sound science, have caused irreparable and ongoing environmental damage to sensitive coral reef communities in the FKNMS.
... Depth profiles of mean percent cover of a) total coral and b) Dictyosphaeria cavernosa averaged over fifteen survey sites in Kāne'oheBay censused in 1971, 1983, and 1990. Source: Hunter and Evans, 1995 Bulletin of Marine Science. ...
Technical Report
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Cesspools are widely used as a sewage disposal method across the Hawaiian Islands. However, cesspools lack adequate treatment of waste to protect the surrounding environment from dangerous pathogens and nutrients. Each day, approximately 88,000 cesspools across Hawai‘i release nearly 55 million gallons of sewage into the ground, much of it reaching groundwater. This report assembled a comprehensive list and analysis of research studies pertaining to the status of wastewater pollution —with an emphasis on cesspools— and associated impacts on water resources, nearshore ecosystems, and human health. Many of the studies discussed within this white paper provided valid scientific evidence to support the creation of a long-range statewide cesspool conversion plan. Knowledge gaps in areas such as hydraulic/hydrologic modeling and technological methods were identified, with additional limitations in identifying and tracking specific wastewater sources. Many of these limitations, however, can be overcome. For example, limitations in identifying particular sources of wastewater pollution using %N and δ15N can be supplemented with available land-use information and source tracking information to clarify concentration and isotopic data of nitrogen. Resource management presents many challenges, including the recognition of diverse societal views and values. To overcome discrepancies in available data and varying societal values, the use of transparent, adaptable framework methods such as “structured decision making” offers approaches for problem-solving. Such frameworks are consistent with a holistic management approach to onsite wastewater management that incorporates the natural and social sciences to identify and address barriers as a method to reduce negative impacts.
... Water samples were collected for analysis of dissolved nutrient concentrations in three seasons: the 2013 wet season, the 2015 dry season, and the 2015 wet season. Sampling sites adjacent to canals, tributaries, and inlets (e.g., NIRL4, CIRL1, CIRL2, CIRL3, CIRL4, SIRL2, and SIRL5 in Fig. 1) were sampled during an ebbing tide to account for tidal pumping of groundwater (Lapointe et al., 1990). At all sites, seawater samples were collected in triplicate 0.25 m below the surface into acid-washed 500 ml high-density polyethylene (HDPE) bottles and covered with ice in a dark cooler until returned to the Harbor Branch Oceanographic Institute at Florida Atlantic University (HBOI-FAU) laboratory for processing. ...
Historically, extensive seagrass meadows were common throughout the Indian River Lagoon (IRL) in east-central Florida, USA. Between 2011 and 2017, widespread catastrophic seagrass losses (~95%) occurred in the IRL following unprecedented harmful algal blooms (HABs), including persistent brown tides (Aureoumbra lagunensis). Little is known about how dissolved nutrients and chlorophyll a are related to light limitation or how biochemical factors, such as the elemental composition (C:N:P) and stable isotope signatures (δ13C, δ15N), of seagrasses within the IRL relate to coverage. Accordingly, we conducted a survey from 2013 to 2015 at 20 sites to better understand these relationships. Results showed a negative correlation between DIN and salinity, indicating freshwater inputs as a DIN source. Seawater N:P ratios and chlorophyll a concentrations were higher in the urbanized, poorly-flushed northern IRL segments. Kd values were higher in the wet season and often exceeded seagrass light requirements (0.8 m-1) for restoration, demonstrating light limitation. Species distribution varied by location. Halodule wrightii was ubiquitous, whereas Syringodium filiforme was not found in the northernmost segments. Thalassia testudinum was only present in the two southernmost segments that had the lowest TDN and highest light availability (Kd). Blade %N and %P also frequently exceeded critical values of 1.8% and 0.2%, respectively, especially in the northern segments. Further, δ15N was positively correlated with ammonium, suggesting wastewater as a major N source. The δ13C values indicated a trend of increasing light limitation from south to north, which helps explain the recent catastrophic loss of seagrasses in the northern IRL. Overall, elemental composition reflected high N-availability and seagrass species distributions were relatable to spatial trends in N and light limitation. For effective restoration, resource managers must reduce N-loading to the IRL to diminish HABs and increase light availability. Regular biochemical monitoring of seagrass tissue should also be implemented during restoration efforts.
... In the Mexican Caribbean, continental waters enter the ocean mainly through Submarine Groundwater Discharges (SGD), which represent an important pathway for nutrients and other contaminants that can potentially affect coral reefs (Burnett et al., 2006;Paytan et al., 2006). In karstic regions, the risk of groundwater pollution is high (Lapointe, O'Connell, and Garrett, 1990) because of the rapid recharge and channelized flow pathways through fractures and cave systems (Null et al., 2014). Nutrients promote the growth of macroalgae, which compete with corals for space, reducing their recruitment, growth, fecundity, and survival through various mechanisms (Chadwick and Morrow, 2011;Suchley and Alvarez-Filip, 2018). ...
INTRODUCTION The physical structure of a coral reef has profound effects on nearshore hydrodynamics which in turn affects ecosystem functioning and, ultimately, its associated biodiversity. Structurally complex habitats facilitate the coexistence of species through niche partitioning and the provision of shelters from predators and environmental stressors (Warfe and Barmuta, 2006; Willis, Winemiller, and Lopez-Fernandez, 2005). Therefore, the loss of architectural complexity can cause reduction in biodiversity, and thus, compromise habitat productivity (Beukers and Jones, 1997). Qualitatively, roughness or rugosity is a measure of a surface's departure from one that is geometrically smooth, which is a parameter that has been used to quantify topographic complexity of coral reefs (Hearn, 2011). Turbulence induced by the coral colonies affects the rate of particle entrainment in the water column. In consequence, food acquisition for several reef species depends on the dispersion processes and how near-bed flow dynamics exchange mass between the reef and the surrounding ocean. As the coral reef grows and becomes rougher, the assemblages of benthic organisms that can be supported by it increase in terms of density and species richness (Falter, Atkinson, and Coimbra, 2005; Monismith, 2007; Reidenbach et al., 2006). Loss of roughness also has important implications for coastal protection, since large amounts of wave energy are dissipated by reef crests due their high rugosity (Lowe et al., 2005; Rogers et al., 2016). In the Caribbean, coral degradation has occurred for the last 40 years (Alvarez-Filip et al., 2009), through a combination of human (e.g., overfishing, sedimentation, eutrophication) and natural disturbances (Gardner et al., 2003; Hughes, 1994; Hughes et al., 2005; Suchley and Alvarez-Filip, 2018). Natural disturbances may be physical (e.g., hurricanes) or biological (e.g., diseases). The effects of hurricanes on coral reefs have been widely studied and include the mechanical stress produced by storm surges and blows suffered by coral fragments (Woodley et al., 1981); and the abrasive effect of sediment that is easily resuspended and transported during a storm (Hubbard and Pockock, 1972). It has been observed that the recovery of coral reefs from the impact of a hurricane can take decades, or sometimes it would not happen at all. For example, in Puerto Morelos, Mexico, the coral reef community showed no recovery of hard corals 15 years after Hurricane Gilbert (Rodríguez-Martínez et al., 2010). Therefore, hurricanes have a prominent role in controlling the configuration and composition of fringing reefs in the tropical Western-Atlantic (Blanchon et al., 2017; Perry, 2001). Disturbances tend to synchronize, and single causes for reef degradation are rarely the case. For example, in the Caribbean apart from hurricane effects, this ecosystem has been strongly impacted by the white-band disease, and by a reduction of herbivores such as the black sea urchin (Diadema antillarium) due to overfishing (Alvarez-Filip et al., 2009; Gardner et al., 2003; Hughes, 1994). In the past, many studies have indicated overfishing of herbivorous fish as the key factor for the widespread dominance of macroalgae in coral reef environments, but recent studies suggest that watershed pollutants can now be identified as the main inducers of coral phase shifts, which represents a change in paradigm for coral reef science (Arias-González et al., 2017; Suchley, McField, and Alvarez-Filip, 2016). In the Mexican Caribbean, continental waters enter the ocean mainly through Submarine Groundwater Discharges (SGD), which represent an important pathway for nutrients and other contaminants that can potentially affect coral reefs (Burnett et al., 2006; Paytan et al., 2006). In karstic regions, the risk of groundwater pollution is high (Lapointe, O'Connell, and Garrett, 1990) because of the rapid recharge and channelized flow pathways through fractures and cave systems (Null et al., 2014). Nutrients promote the growth of macroalgae, which compete with corals for space, reducing their recruitment, growth, fecundity, and survival through various mechanisms (Chadwick and Morrow, 2011; Suchley and Alvarez-Filip, 2018). Therefore, there is a need to better understand how anthropogenic activity and groundwater delivery are linked to land use and pollutant transport in areas with karst geology, since the impact to local coastal ecosystems can have serious detrimental consequences (Null et al., 2014). The aim of this investigation is to study the link between macroalgae cover and roughness in a reef lagoon that has a spatially varying influence of SGD close to the reefs. The negative relationship between macroalgae cover and reef roughness in regions of high SGD influence would be supporting the idea that phase shifts (from coral to macroalgae dominance in benthic cover) are being intensified by poor water quality in the region.
... The makaha allowed for a limited exchange of water between the fishpond and the surrounding ocean resulting in longer residence time and brackish water conditions that favored the food species raised there (Kikuchi, 1976). The retention of water behind semi porous walls, along with the inputs of nutrient-rich groundwater, makes these ponds sensitive to eutrophication or other contamination from polluted groundwater (Valiela et al., 1990;Nixon et al., 2007;Lapointe et al., 1990). ...
... Leaking septic tanks have been previously identified as significant non-point sources of sewage pollution adversely impacting adjacent coral reef systems (Lewis, 1987;Bonkosky et al., 2009;Méndez-Lázaro et al., 2012;Díaz-Ortega and Hernández-Delgado, 2014). There is evidence that coastal groundwater and surface waters throughout developed urban areas are characterized by increasing elevated concentrations of N and P through time (Lewis, 1987;Lapointe et al., 1990). However, impacts of leaking septic tanks on coastal coral reefs and recreational beaches have still been poorly addressed. ...
The impact of fecal contamination of coastal waters and coral reefs is a major cause of concern in marine reserves in Puerto Rico. The measurement of the association between septic tank frequency in watersheds of creeks draining into these reserves and coastal water quality and coral reef condition is of importance in configuring pollution control policy. Fecal coliforms and enterococci assays were used to measure the density of fecal contaminants across the Tres Palmas Marine Reserve (TPMR) in Rincon, Puerto Rico. Inshore waters are intermittent creeks, receiving fecal pollution only from faulty septic tanks. Fecal indicators measurements showed higher densities near the southernmost creek mouth emptying into TPMR, a finding consistent with a larger amount of dwellings with septic tanks within this watershed (Vista Azul creek). A Septic Weight Index was constructed to analyze sewage impact from all watersheds draining into the marine reserve. Linear Regression analyses showed a significant association between these non-point source fecal pollution sources and both coastal water quality and impact on some parameters measuring the condition of Acropora palmata coral reef colonies.
... A third potential stressor is the salinity of the water available to Florida Keys trees, which is affected not only by distance to water table and source (rainfall or tides), but also by bedrock geology [14]. In the easternmost (Upper) Keys, even the water closest to the surface is brackish, because the coralline limestone that forms these islands is extremely permeable, allowing groundwater to mix freely with surrounding seawater [15]. In the lower Florida Keys, where a less permeable oolitic limestone overlies the coralline rock formation, a freshwater lens operating under Ghyben-Herzberg dynamics comprises the groundwater surface in some island interiors [16]. ...
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Tree species in coastal forests may exhibit specialization or plasticity in coping with drought through changes in their stomatal morphology or activity, allowing for a balance between gas exchange and water loss in a periodically stressful environment. To examine these responses, we sought to answer two primary research questions: a) how is variation in B. simaruba’s stomatal traits partitioned across hierarchical levels, i.e., site, tree, and leaf; and b) is variation in stomatal traits an integrated response to physiological stress expressed across the habitat gradient of Florida Keys forests? At eight sites distributed throughout the Keys, five leaves were collected from three mature trees for stomatal analysis. Leaf carbon stable isotope ratio (δ13C) was determined to infer the changes in water use efficiency caused by physiological stress experienced by each tree. The results showed that substantial proportions of the total variance in three traits (stomatal density, stomatal size, and δ13C) were observed at all levels, suggesting that processes operating at each scale are important in determining trait values. A significant negative correlation between stomatal density and size across scales was observed. Path model analysis showed that environmental variables, distance to ground water and ground water salinity, affect leaf δ13C indirectly, via its effects on stomatal traits, not directly to leaf δ13C. Therefore, the combination of small and densely distributed stomata seems to represent a strategy that allows B. simaruba to conserve water under conditions of physiological drought induced by either higher ground water salinity or flooding stress at very low elevation.
... Nutrient enrichment from both point and nonpoint sources of agriculture and other urban activities are recognized as major sources of nitrogen and phosphorus to aquatic ecosystems (Terrio, 1995;Carpenter et al., 1998). Furthermore, seepage from on-site sewage facilities (OSSFs) is recognized as a significant and increasingly important source of nutrients and other down the drain contaminants to surface waters (Schaider et al., 2017;Lapointe et al., 1990). Within the Dickinson Bayou watershed, there is approximately 5000 OSSFs, which represents a microcosm of sub-watersheds in the Houston-Galveston region in which over 300,000 OSSFs systems are located (Morrison, 2014). ...
In the rapidly urbanizing watersheds and estuaries flowing to the Gulf of Mexico in Texas, USA, instream flows are increasingly influenced by point source and nonpoint source discharges. Spatial and temporal tidal influences on water quality, especially for contaminants of emerging concern (CECs), is poorly understood in estuaries and coastal systems. We selected Dickinson Bayou, an urban estuary in Galveston County, Texas, for study because it has historically impaired water quality, receives point source discharge from one major wastewater treatment plant (WWTP), while also being influenced by high densities of onsite sewage facilities upstream in the watershed. We explored the occurrence and potential hazards of aquatic contaminants, including nutrients, indicator bacteria for pathogens, and CECs, in relation to this point source discharge, across seasons and at high and low tides. Aquatic contaminants and associated hazards varied significantly in relation to the WWTP discharge, and were influenced by onsite systems. In fact, spatiotemporal water quality varied by class of contaminants (e.g., nutrients, indicator bacteria, CECs), which indicates that traditional surface water monitoring activities should account for such environmental complexity. This study provides a diagnostic approach for future studies of emerging water quality challenges across gradients of rapidly urbanizing coastal bays and estuaries.
... • Data Set S1 Lapointe et al., 1999;Lapointe & Clark, 1992;Wiegner et al., 2016). However, there is limited data available describing temporal site-specific patterns of groundwater nutrient discharge and how these may have changed as a result of anthropogenic activity. ...
Anthropogenic activity on tropical islands has been linked with nitrogen (N) contamination of groundwater and subsequent coral reef health decline. However, identifying the temporal patterns of groundwater N contamination has proven difficult because of an absence of long-term records. Here we use δ¹⁵N in coral skeleton organic material (CS-δ¹⁵N) to reconstruct historical patterns of groundwater N discharge to a coral reef system at Rarotonga in the Cook Islands in the South Pacific. Analysis of coral skeletal material dating back to 1880 CE clearly shows that the δ¹⁵N of N available in the reef environment around Rarotonga increased between 1980 and 2000. We propose that rapid agricultural development in the Cook Islands between 1960 and 1985 increased aquifer N concentrations leading to the elevated δ¹⁵N of groundwater NO3⁻. The discharge of this groundwater N appears to have continued for at least 15 years after the cessation of the agricultural boom. This has important implications for the management of groundwater contamination on low-lying tropical islands.
... Although point-source sewage pollution has long been recognized as a cause of HABs (Sawyer, 1965;Hagan, 1969;Smith et al., 1981;Lapointe et al., 2005a;Teichberg et al., 2010), non-point-source inputs of sewage, such as from septic tanks, shallow injection wells, fertilizers, and nutrientenriched submarine groundwater discharges, can also increase nutrient loading, eutrophication, and the development of macroalgal blooms (Johannes and Hearn, 1985;Lapointe and O'Connell, 1989;Lapointe et al., 1990;Valiela et al., 1990Valiela et al., , 1997Lapointe, 1997;Teichberg et al., 2010). In addition, siliciclastic environments tend toward stronger N-limitation of macroalgal blooms (Hanisak, 1979;Nixon and Pilson, 1983;Lapointe et al., 1992), compared to carbonate-rich waters that tend more toward stronger P-limitation due to adsorption of P in sediments (Lapointe et al., 1992;McGlathery et al., 1994;Lapointe, 1997). ...
Macroalgae are a natural, common feature of inland waters as well as estuaries, coastal waters, and oceanic waters particularly the Gulf of Mexico, North Atlantic Ocean, and Caribbean Sea where pelagic Sargassum is distributed. As the causes and effects of macroalgal blooms are similar in many ways to those associated with harmful phytoplankton species, scientists use the term harmful algal bloom (HAB) to describe this diverse array of bloom phenomena. Many studies have addressed the importance of nutrient loading to the development of macroalgal HAB. Unlike toxic phytoplankton blooms, macroalgal blooms usually lack direct chemical toxicity, but typically have a broader range of distribution and ecological impacts. Because of the negative environmental and economic impacts that are often associated with harmful macroalgal blooms, government agencies and private stakeholders have increasingly sought various strategies for management and mitigation, although the main historic approaches, physical removal and herbicide treatment, remain common.
... Mangrove forests are vulnerable habitats, which endure a multitude of anthropogenic stresses and continue to decline worldwide (Duke et al., 2007;Valiela, Bowen, & York, 2001). Sewage discharge in particular can reduce water quality, generate anoxic conditions, and increase water-column pathogens, and thus impact these habitats (Lapointe & Clark, 1992;Lapointe, O'Connell, & Garrett, 1990). ...
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Mangroves are of great ecological and socioeconomic importance, yet they are under threat from urban development on the southern Pacific coast of Costa Rica. To test for possible nutrient‐related impacts, we compared water‐column nutrient concentrations, C and N stable isotope values and other environmental variables between mangroves with known sewage loading (three ‘nutrient loaded’ locations) and those without such loading (three ‘reference’ locations). Instantaneous nutrient concentrations were low at all locations, Secchi depth was greater at reference locations, and chlorophyll concentrations were higher at nutrient loaded mangroves. Suspended matter did not vary between reference and nutrient loaded mangroves, and nor did bivalve and algal δ¹³C and δ¹⁵N values. Enrichment of δ¹⁵N and δ¹³C of red mangrove leaves at the nutrient loaded locations is attributed to pulsed inputs of materials that were not detected in the instantaneous nutrient data. We provide evidence of isotopic enrichment at nutrient loaded locations from mangrove material and recommend that adequate waste water treatment be carried out on all anthropogenic discharges into this vulnerable marine system.
... In addition, nearshore patch reefs of the Florida reef tract are exposed to fluctuations in temperature and salinity and to greater variability in turbidity and light attenuation [31,32]. Their proximity to land also potentially exposes these reefs to more direct anthropogenic effects such as terrestrial runoff, pollution [33][34][35], and fishing, boating and diving [31]. Despite this, prior to the 2010 cold-water event, patch reefs demonstrated the highest coral cover, highest growth rates and lowest incidences of partial mortality on the reef tract and hence had been identified as resilient to a variety of acute and chronic stressors [32]. ...
... This result clearly reflects that the seawater N/P ratios were the result of the mixing between riverine inputs (low N/P ratios) and SGD (high N/P ratios). Since the N/P ratio is often used to evaluate the potential limitations of primary production, high N/P ratios in the groundwater could force the primary production conditions to change from N-limitation to P-limitation; thus, affecting the ecology (Lapointe et al., 1990;Slomp & Van Cappellen, 2004;Su et al., 2011) and changing the microalgal community composition Su et al., 2011) of the coastal waters. Thus, we suggest that the high nutrient levels and N/P ratios in the SGD around the Maowei Sea likely exceed the limits that would allow for environmental self-purification. ...
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Submarine groundwater discharge (SGD) has been recognized as an important pathway for nutrients into estuaries, coasts, and the adjacent seas. In this study, 222Rn was used to estimate the SGD‐associated nutrient fluxes into an aquaculture area in a typical tropical bay (Maowei Sea, China). The SGD into the Maowei Sea during June 2016 was estimated to be 0.36 ± 0.33 m d−1 and was associated with SGD‐derived dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved silicon (DSi) fluxes (mol d−1) of (4.5 ± 5.5) × 106, (5.3 ± 9.1) × 104, and (9.4 ± 9.3) × 106, respectively. The SGD‐derived nutrients (i.e., DIN, DIP, and DSi) were more than 1.9, 0.9, and 3.6 times the amounts in the local river input and served as dominant sources in the nutrient budgets in the Maowei Sea. Moreover, the N/P ratios in the SGD around the Maowei Sea were high (mean: 64), and these ratios likely exceeded the environmental self‐purification capacity, thereby enhancing the biomass and changing the phytoplankton community structure. Therefore, SGD processes with derived nutrients may affect the biogeochemical cycles and marine ecological environment in the Maowei Sea. Furthermore, the N/P ratios (∼67) in oysters are very close to those in the SGD in the Maowei Sea; this coincidence suggests that the high N/P ratios in the SGD are likely to be one of the most important sources that support oyster aquaculture, which might weaken the burden of water eutrophication in the Maowei Sea. SGD is the dominant source of nutrients to the Maowei Sea The SGD‐derived nutrients are higher in the Maowei Sea than those estimated in other similar studies SGD‐derived nutrients could support high‐quantity aquaculture (oyster) in the Maowei Sea
... December 2016) may be attributed to a wash-out of nitrogen from a surface source which accumulated in the soil and in sinkholes during the dry season like fertilizers, animal waste and general village waste, which can also be observed in other karstic areas (Guo and Jiang 2009). During wet season high groundwater nutrient fluxes towards the coastal ocean were for example also 25 observed in Florida Keys (Lapointe et al. 1990) and in Bermudas, possibly due to the use of fertilizers in the hinterland (Lewis 1987). In Gunung Kidul major crops such as rice, corn and soy are mainly fertilized during rainy season during the first two weeks of November and the first two weeks of March, when water availability is high (Katam 2017). ...
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In tropical karstic regions, knowledge about the timing and quantity of land–ocean groundwater nutrient fluxes is important, as those nutrients may affect coastal ecosystems and contaminate coastal springs. High aquifer permeability of the karst, combined with high recharge and discharge during heavy rain events, leads to a close connectivity between groundwater in the hinterland and the coastal zone. The alteration between drier periods and heavy rain events can lead to a high temporal variability of groundwater discharge associated nutrient fluxes from the hinterland towards the coast. We studied the timing of land-ocean groundwater nutrient fluxes in the tropical karstic region of Gunung Kidul (southern Java Indonesia) from November 2015 until December 2016. Satellite infrared imagery revealed two major areas of direct submarine and coastal groundwater discharge. δ¹⁸O and δD signatures, nutrient concentrations, combined with precipitation and groundwater discharge data, indicate a rapid groundwater recharge and transport from the catchment area towards the coastal ocean. Measured groundwater discharge rates varied from less than 1 m³/s up to 16.6 m³/s and were dominantly controlled by recharge in the hinterland and surface infiltration during the rainy season. Nitrate fluxes ranged from 5 × 103 to 139 × 103 mol/day and DSi fluxes from 50 × 103 to 310 × 103 mol/day. High nitrate concentrations coinciding with phases of high discharge lead to particularly high nitrate fluxes. This counter intuitive temporal connection might be due to fertilization during the onset of the wet season and the retention of nutrients from untreated sewage in the soil and in sinkholes during dryer periods, which are then washed into the aquifer during heavy rain events. In the tropical karstic region of southern Java, extraordinarily high land-ocean nutrient fluxes occur therefore during the onset of periods with high discharge, which makes coastal water and coastal springs prone to contamination during this time, while flood recession and dry periods are characterized by lower nutrient fluxes. In tropical karstic regions the timing of land–ocean groundwater nutrient fluxes is thus highly variable, which may lead to ecological implications. High nutrient fluxes during certain times of the year may explain the sudden occurrence of harmful algae blooms in coastal environments and have to be considered in coastal groundwater management.
... The naming of the phenomenon varies depending on the community background of the describing scientists. The term "submarine groundwater discharge" was mentioned first in the 1970′s (Zektzer et al., 1973;Johannes, 1980) and early on adopted by scientists of the marine community (Simmons and Netherton, 1987;Cuet et al., 1988;Lapointe et al., 1990). Others, focusing on karstic environments with their conduits called the discharging water "submarine springs" (Kohout, 1966;Stefanon, 1972;Fleury et al., 2007), or "vrulja" (after a spring in Croatia) (Bögli, 1980;Sekulic and Vertacnik, 1996). ...
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Terrestrial groundwater discharging directly into the sea (“fresh submarine groundwater discharge”, fresh SGD) is increasingly recognized as nutrient and pollutant pathway from land to coastal oceans. However, its active use by coastal populations and its role for coastal societies is nearly entirely neglected. Here we present examples from a variety of places and from all available sources around the world to highlight that fresh submarine groundwater discharge is widely valued as a water resource for drinking, hygiene, agriculture, fishing, tourism, culture, or ship navigation. In Peru, fresh SGD is used for drinking, on Tahiti for bathing, in Greece for irrigation, in Bali for blessing, and already Alexander von Humboldt noted the danger for smaller vessels from a submarine spring off Cuba, but at which Manatees gathered and were hunted by fishermen. These are just a few of the presented examples, which document the complex value fresh submarine groundwater discharge has for coastal communities. Because global change will strongly affect this water resource we should assess and understand that value, before the phenomenon will disappear at many locations due to terrestrial groundwater extraction or sea level increase.
... Due to their proximity to coastlines, coral reefs are subject to a myriad of anthropogenic impacts and are one of the most reduced and endangered ecosystems in the world (Hughes, 1994;Pandolfi et al., 2003;Buddemeier et al., 2011); many of these problems are tied to increased coastal development. Many studies have assessed pollution effects on coral reef systems (e.g., Lapointe et al., 1990;Costa Jr. et al., 2000;Sheppard et al., 2009;Melbourne-Thomas et al., 2011;Fabricius et al., 2012;Comeau et al., 2013;Kuffner et al., 2015). Sewage is of spe-cial interest because organic matter, dissolved nutrients, toxins, and pathogens can be transported by groundwater and runoff into coastal waters. ...
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Pollution from untreated human sewage is one of several environmental concerns in the coastal waters of Belize. This study utilized distributions of fecal sterols and foraminiferal assemblages to determine if human sewage is affecting the coral reef system off the coast of Caye Caulker, Belize. A total of 125 sediment samples were collected from which fe-cal sterol concentrations (coprostanol, cholestanol and cholesterol) and diagnostic stanol ratios, sediment texture (% mud), and foraminiferal ecological indices, including species richness , density, and diversity, and the FORAM Index (FI), were assessed. Elevated concentrations of coprostanol were primarily found inshore, with 20 samples exceeding 100 ng/g. The two stanol ratios , evaluated together, confirmed presence of human sewage at 17 sites. Foraminiferal assemblages were dominated by Quinqueloculina, Trochulina, Archaias and Asterigerina. Predominance of sand-sized sediments and the prevalence of Trochulina rosea and Asterigerina carinata reflected the active hydrodynamic regime, particularly on the eastern side of the caye. While the FI values overall indicated that water quality is conducive to reef growth and recovery, data from 37 samples indicated that the area is experiencing environmental change, especially on the southwestern side. Significant positive correlations were found between coprostanol and both foraminiferal density and diversity, while coprostanol and FI were negatively correlated. These results indicate that human sewage is inducing nutrification, which may be promoting reported increases in macroalgal abundances throughout Belize, though the active wave and current regimes are limiting the impacts on the eastern, Caribbean-facing side of Caye Caulker.
... For example, methemoglobinemia (blue baby syndrome) in infants can occur due to the consumption of water exceeding U.S. EPA drinking water standard of 10 mg L −1 of nitrate (NO 3 )-N (Knobeloch et al., 2000). Further, excess N transport from the shallow groundwater to nearby surface waters can cause algal blooms, hypoxia, and eutrophication (Beal et al., 2005;Lapointe et al., 1990;Lapointe et al., 2015;Withers et al., 2011). Therefore, appropriate drainfield design should be used to reduce N loading from septic systems to groundwater. ...
Appropriate drainfield design in septic systems can be an effective tool to optimize nitrogen (N) removal and protect public and environmental health. Our objective was to investigate how the conventional drainfield designs affect N transformations in septic systems. We investigated the N treatment efficiency of two in-situ drainfield designs (6.1 m long and 0.61 m wide), which were constructed by (1) adding 30.5 cm sand on top of natural soil (referred to as drip dispersal) and (2) adding 30.5 cm gravel layer on top of 30.5 cm of sand and natural soil (referred to as gravel trench). A drip line was placed on top of the sand layer (in drip dispersal) or gravel layer (in gravel trench) to disperse 120 L of effluent before adding another 15.3 cm of sand layer and planting St. Augustine grass. Suction cup lysimeters, installed at 30.5, 61.0, and 106.7 cm depth below the drip lines of both drainfields, were used to collect soil-water samples over 64 events (May 2012–December 2013). Mean total N concentration was 66 mg L −1 in the effluent, which significantly (p < 0.05) decreased by 49% in the drip dispersal and 21% in the gravel trench systems. Most of the effluent N was nitrified within 30.5–106.7 cm depth of drainfields. Significantly (p < 0.05) greater NO x –N in the gravel trench (45.6 ± 1.3 mg L −1) than drip dispersal (28 ± 3.1 mg L −1) was attributed to the presence of additional 30.5 cm gravel layer that caused greater oxygen diffusion resulting in lower gaseous N loss via coupled nitrification-denitrification. Total organic N was not significantly different between the effluent (7.3 mg L −1 ; n = 61) and drainfields (5.5–6.4 mg L −1 ; n = 192) suggesting that organic N forms remained mobile in the drainfields. We conclude that the drip dispersal was more effective at attenuating NO x –N than gravel trench due to the greater gaseous N loss and should be preferred in areas with shallow groundwater (< 1 m deep) to protect groundwater N contamination.
... 43, Wieden mann et al. 2013;60, Ezzat et al. 2015), and much higher than the Redfield ratio. Such imbalances in N:P ratios are also found in natural settings where groundwater discharges onto coral reefs (D'Elia et al. 1981, Lapointe et al. 1990, Umezawa et al. 2002, Tanaka et al. 2011a Fig. 5. Summary of the effects of nutrient enrichment on Montipora digitata and Porites cylindrica. The description of effects (↑: increase, ↓: decrease, →: no effect) is based on the effects found after 9 wk of the culture experiment. ...
To study the effects of nutrient availability on scleractinian corals, fragments of Monti - pora digitata and Porites cylindrica were cultured in nutrient-enriched seawater (nitrate: 1.4 to 1.9 μmol l⁻¹ and phosphate: 0.1 μmol l⁻¹) for 2 mo under laboratory conditions. For both coral species, the chlorophyll a concentration of the endosymbiotic algae increased significantly in both nitrogen only (+N) and nitrogen plus phosphorus (+NP) treatments compared to the control. Endosymbiont carbon (C) content of M. digitata increased only under +NP conditions, indicating that phosphorus (P) was limiting the production of endosymbiont cells. Host C and nitrogen (N) contents were not affected by nutrient enrichment for both coral species, suggesting that the moderate nutrient enrichment did not contribute considerably to the production of host tissue. C stable isotope ratios (δ¹³C) of the endosymbionts and host gradually decreased during the experiment, and even more so in the +N treatment. This suggests that the coral host preferentially catabolized δ¹³Cenriched organic matter, such as storage lipids, and that this catabolism was enhanced when the N:P ratio of available nutrients was not balanced. Finally, the skeletal δ¹³C was also positively correlated with the host and endosymbiont δ¹³C values, which implies that the δ¹³C of host tissue was at least partially affecting the skeletal δ¹³C. Overall, moderate nutrient enrichment should not have a negative effect on coral metabolism provided that the N:P ratio of available nutrients is balanced.
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Groundwater is widely spread both on land and under seas and oceans. Today, hydrogeologists and oceanologists recognize the potentially significant contribution of submarine groundwater discharge to coastal areas. The term submarine groundwater discharge (SGD) is commonly used to describe sources below sea level. It should be noted that submarine waters also include the sources located within tidal (littoral) zones, although they get underwater only during high tides. Observation of submarine discharge showed its significant impact on the ecological condition of coastal structures. Along with the percolation of underground water along most of the world’s coastlines, a significant amount of fresh water and substances dissolved in it is spread across large areas. However, the role of such a phenomenon as submarine discharge for coastal communities is practically not considered. The article gives examples from many literary sources, highlighting the importance of submarine discharge sources for local population in their everyday activities for many centuries. This is a source of drinking water, hygienic product, water for agriculture, fishing, shipping, culture, and tourism. In many parts of the world, there are sources of submarine discharge, which have a unique shape and are considered important only because of their exceptional nature and the habitat of freshwater organisms. These examples confirm the uniqueness of such a phenomenon of live activity of coastal communities. As a result, there is a necessity for a comprehensive approach to the study of submarine discharge, which is relevant not only from the point of view of changes in coastal environment but also from the point of view of the global circulation of water and substances on Earth.
This book chapter includes the study of submarine groundwater discharge (SGD) across various coastlines and related nutrient fluxes to the coastal oceans. SGD represents an essential pathway of materials like carbon, nitrate, phosphate, silicate, and trace metals between land and sea. Global DOC and DIC Fluxes through SGD studied across different mangrove climatic zones indicate that the area of tropics accounted for 71% and 81% of DIC and DOC fluxes, respectively. Subtropics contributes 29% and 19% respectively, while the contribution of temperate region is even less than 1% for both the parameters. An increase of about 38% in SGD nitrogen input between 1950 and 2000 has been observed in global coastal water and is estimated to increase by 22% between 2000 and 2050. The rise in nitrogen is not followed by an equivalent increase in phosphate and silicate, suggesting that nitrogen is the primary nutrient affected by SGD. The increase in nitrogen is mainly due to the anthropogenic contamination of the certain aquifer, which in turn modify the Redfield ratio where the N/P ratio exceeds the river system revealing that human activities can change N-limited coastal primary production to P-limited one. The Indian coastline is mainly composed of red, yellow, and alluvial soils, which are poor in nutrients. Hence Indian farmers use excessive fertilizers to obtain a better yield. Which plays a significant role in controlling nutrient dynamics in groundwater. SGD-derived trace metals are also equal to or higher than the river fluxes and contribute approximately 10% of total trace elements to the oceans.
The influx of fresh groundwater and re-circulated sea water into coastal ecosystem occurs through the submarine groundwater discharge (SGD). Measurement of salinity, radium tracers (²²⁴Ra, and ²²⁶Ra isotopes) and nutrients in estuarine water, coastal surface water and groundwater during December 2019 estimated the SGD and associated nutrient fluxes near the Karameniyar estuary (Gulf of Mannar) and surroundings of the Manapad region at southern part of Tamil Nadu state in India. The presence of excessive radium tracers revealed that the SGD was contributing to Ra desorption from the sediments and enrichment in the coastal waters. We estimated SGD of approximately 0.03–0.59 m³ m⁻² d⁻¹ for the Manapad region and relatively more homogeneous but comparatively less values in the Karameniyar estuary (0.03–0.34 m³ m⁻² d⁻¹). Higher average values of dissolved inorganic nitrogen (DIN; 43.62 μmol L⁻¹) and soluble reactive phosphate (SRP; 1.848 μmol L⁻¹) suggested greater influence of SGD on the overall coastal water nutrient budget. This study also indicated simultaneous occurrence of fresh and saline SGD in this region.
Intoxications of captive bottlenose dolphins (Tursiops truncatus) in the Florida Keys have been linked to observed interactions with marine macrophytic algal and cyanobacterial communities within enclosures. Taxonomic characterization of these communities coupled, in turn, to available observational data collected during intoxication events point to a contribution of filamentous cyanobacterial assemblages comprised of members of the polyphyletic genus, Lyngbya sensu lato. To identify toxic metabolites possibly relevant to these intoxications, chemical screening for known neurotoxins from cyanobacteria, as well as other regionally relevant harmful algal bloom (HAB) taxa, was combined with toxicity testing, and subsequent bioassay-guided fractionation, employing early life stages (i.e., embryos and larvae) of zebrafish (Danio rerio) as a well-established aquatic vertebrate toxicological model. Chemical analyses did not detect (within analytical limits) any of the known algal or cyanobacterial neurotoxins. Toxicity testing, alongside bioassay-guided fractionation, however, identified several chemical fractions with a range of potentially relevant bioactivities in both zebrafish embryos and post-hatch larvae including, in particular, behavioral (e.g., aberrant swimming) and physiological (e.g., altered heart rate) endpoints indicative of possible neurotoxicity, and subsequent chemical characterization of fractions suggested a contribution of the previously identified bioactive metabolite, eudesmacarbonate, in the observed toxicity. Comparative toxicological assessment with PbTx-2, as a positive control for neurotoxicity in the zebrafish model, further supported neurotoxic activity of cyanobacterial metabolites potentially relevant, in turn, to a contribution of these metabolites to dolphin intoxications. These findings suggest, in general, that marine zoological facilities may be affected by regional HABs, and assessments of potentially toxigenic algae and cyanobacteria should be included in management strategies in these facilities.
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Bonefish (Albula vulpes) support a world-renowned fishery in South Florida, USA. However, fishing guides and anglers have been reporting significant declines in bonefish angling quality over that past three decades. In the absence of any long-term bonefish stock and ecosystem assessments, the cause of this decline in the fishery is unclear. Here we summarize our current knowledge of bonefish ecology in Florida and discuss potential causes of fishery decline. Reductions and alterations in freshwater flows from the Everglades have caused major changes in bonefish habitat, including acute (anoxic conditions) and chronic (changes in benthic flora and fauna) effects in Florida Bay and Biscayne Bay. Various pollutants from agricultural and urban runoff may also be impacting bonefish population(s) directly and/or indirectly throughout their range. Efforts to locate juvenile A. vulpes in Florida have been largely unsuccessful to date, suggesting abundances may be low, and/or juveniles have unknown habitat requirements in Florida. Further, bonefish larvae may be sourced from adult individuals outside of Florida in areas such as Cuba or Mexico, in which case bonefish conservation in other regions is highly relevant to the Florida population. Extreme weather events may have also contributed to the decline; an extreme cold spell in 2010 caused significant bonefish mortality and coincided with documented declines in the fishery. The fishery may also be impacting the population. We outline research needs and potential approaches to better understand the causes of the bonefish decline in Florida and restore populations of this ecologically and socioeconomically important species.
Submarine fresh groundwater discharging from discrete zones such as conduits overlain by thick sediment remains poorly documented and understood despite common anecdotal accounts of it. We analyzed this phenomenon by a suite of variable-density, variably-saturated groundwater flow simulations guided by field studies. The field observations included point flux and salinity measurements using seepage meters spread across the intertidal and the subtidal zones. The discretely measured seepage fluxes in the subtidal region were as high and the salinity was as fresh as those from the intertidal zone. Both fluxes and salinities varied with tides. Two-dimensional simulations of the idealized beach-ocean vertical section with discrete freshwater springs at the base showed the development of seawater recirculation cells along the edge of freshwater discharge plumes emanating from the outlets, causing mixing. Brackish water discharges at the sediment-water interface above where the plume mixes with the recirculating seawater. Sensitivity analyses showed that stronger terrestrial fresh groundwater flow increases the freshwater plume size but does not affect the mixing zone width. Tidal oscillations and a dynamic fresh groundwater flow widened the mixing zones and increased porewater flux across the sediment-water interface. Sediment thickness had a minor effect on the width of both the freshwater plume and its surrounding mixing zone. The subtidal freshwater plume and mixing zone likely represent a unique but potentially ubiquitous setting which hosts dramatic ecological and chemical gradients. Their local biogeochemical niche and coastal scale ecosystem impacts will need to be considered in investigations of coastlines.
In order to assess the microbial water quality in canal waters throughout the Florida Keys, a survey was conducted to determine the concentration of microbial fecal indicators and the presence of human pathogenic microorganisms. A total of 19 sites, including 17 canal sites and 2 nearshore water sites, were assayed for total coliforms, fecal coliforms, Escherichia coli , Clostridium perfringens , enterococci, coliphages, F-specific (F ⁺ ) RNA coliphages, Giardia lamblia , Cryptosporidium parvum , and human enteric viruses (polioviruses, coxsackie A and B viruses, echoviruses, hepatitis A viruses, Norwalk viruses, and small round-structured viruses). Numbers of coliforms ranged from <1 to 1,410, E. coli organisms from <1 to 130, Clostridium spp. from <1 to 520, and enterococci from <1 to 800 CFU/100 ml of sample. Two sites were positive for coliphages, but no F ⁺ phages were identified. The sites were ranked according to microbial water quality and compared to various water quality standards and guidelines. Seventy-nine percent of the sites were positive for the presence of enteroviruses by reverse transcriptase PCR (polioviruses, coxsackie A and B viruses, and echoviruses). Sixty-three percent of the sites were positive for the presence of hepatitis A viruses. Ten percent of the sites were positive for the presence of Norwalk viruses. Ninety-five percent of the sites were positive for at least one of the virus groups. These results indicate that the canals and nearshore waters throughout the Florida Keys are being impacted by human fecal material carrying human enteric viruses through current wastewater treatment strategies such as septic tanks. Exposure to canal waters through recreation and work may be contributing to human health risks.
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The freshwater aquifer at Discovery Bay, Jamaica, produces subterranean springs and seeps near the reef at the mouth and along the southern and western shorelines of the bay. A strong inverse correlation exists between salinity and N concentration. Undiluted spring-water typically contains 80 μg at N per liter or more, primarily as nitrate, but is essentially devoid of P. Input from the springs is enough to reduce the salinity by one to several parts per thousand near these sites and appears to produce a significant enrichment of nitrogen to the bay.
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Despite the recent advances in seagrass ecology over the last ten years, there are still numerous aspects of the ecological and biological interactions that occur in seagrass ecosystems that remain poorly understood. We have attempted, here, to place into perspective one interrelationship that could have important implications in the production and vigor of seagrasses. This is the relationship between epiphytic fouling by macroalgae and periphyton and the grazers which consume them as a food source while leaving the leaves intact. Our approach to this review was first to describe the relationships between macroalgae, periphyton and the seagrass host in terms of physical benefits, biochemical interactions, factors which reduce fouling on the host, and the effects of epiphytism on seagrass photosynthesis. We then examined the importance of epiphytes as a food source for those herbivores found in seagrass beds, and looked at the consequences of this grazing and removal of epiphytes for the seagrass host. Based on the potential impact of epiphytes on seagrass and grazers on epiphytes, we developed a hypothetical model that describes the effect of increasing epiphytic fouling on seagrass production in the presence and absence of grazers. From this model, we have made predictions on the direction of seagrass decline with diminishing light along depth and estuarine gradients. Lastly, we touched briefly on the problem of eutrophication and how it affects the balance of these interrelationships, and the management options to insure the health and survival of seagrass habitats in the face of increasing stress by man on these critically important ecosystems.
The most obvious symptom of eutrophication in this estuarine system is a green alga, Cladophora, which was sparse in 1966 but now accumulates and rots on the shores. The work is part of a continuing study designed to assess the relationships between nutrient input and the growth of Cladophora and phytoplankton. The system consists of two shallow basins, interconnected and linked to the ocean by a narrow channel. It is fed by three rivers; 90 percent of river flow occurs during four winter months. Phytoplankton and water nutrient levels are low in summer, but high during and after an input of river nutrients in winter. Nitrogen:phosphorus ratios, regression analyses, and nutrient limitation assays suggest that nitrogen is potentially limiting in summer and autumn, phosphorus in winter and spring. The Harvey typically supports higher phytoplankton levels than the Peel. Diatom populations may be replaced by blue-greens in summer in the Harvey. Cladophora forms detached spheres of branched filaments and is only prominent in the Peel. Changes in biomass and growth of confined populations in the field, together with laboratory experiments, show that growth occurs when temperatures and light intensities are high, not in winter when water column nutrient levels are high. Water from between the algal spheres has increased levels of phosphorus compared with the water column above, emphasising the possible importance of nutrient release from decaying material below. It is suggested that phytoplankton are important in trapping water-column nutrients during and after river nutrient input, and that subsequent Cladophora and phytoplankton growth depends on nutrient recycling.
Of the major nutrient cycles in natural waters, the nitrogen cycle is perhaps the most interesting, the most complex and the least understood from a quantitative point of view. The geocycle of nitrogen is largely a biochemical phenomenon; in natural waters it is almost entirely so. Thus the nitrogen cycle, like the carbon and phosphorus cycles, is inextricably related to aquatic organic productivity. Although many elements and compounds are required for biosynthesis, nitrogen and phosphorus have long been considered to be the principal limiting nutrients for primary production; evidence lately obtained suggests that carbon may also limit production in some situations. The recent concern over cultural eutrophication has stimulated much new research in the following areas: the chemistry and biochemistry of nutrients in aquatic systems, the quantification of the sources and sinks of nutrients, and the dynamics of nutrient uptake and release. In this review, the author discusses these subjects with respect to the cycle of nitrogen in natural waters.
With sewage diversion, the biomass of both plankton and benthos decreased rapidly. Benthic biological composition has not yet returned to presewage conditions, partly because some key organisms are long-lived and partly because the bay substratum has been perturbed by both the sewage and other human influences.-from Authors
Authigenic minerals form in three types of environment: 1) oxic (containing measurable dissolved O2), 2) anoxic-sulphidic (containing measurable dissolved H2S), and 3) anoxic-non sulphidic (containing neither O2 nor H2S). Few authigenic minerals form in oxic environments; anoxic-sulphidic environments are characterized by pyrite formation; anoxic-nonsulphidic conditions are characteristic of fine-grained, freshwater lake and swamp sediments.A.C.B.
Observations over a period of nearly 20 years confirm the fact that the salt-water front in the Biscayne aquifer along the coast of the Miami area, Florida, is dynamically stable at a position seaward of that computed according to the Ghyben-Herzberg principle. During periods of heavy recharge the fresh-water head is high enough to cause the fresh water, the salt water, and the zone of diffusion between them to move seaward. In addition to this bodily movement of the system, there is a seaward flow of diluted salt water in the zone of diffusion. When the fresh-water head is low, salt water in the lower part of the aquifer intrudes inland, but some of the diluted sea water in the zone of diffusion continues to flow seaward. Cross sections showing equipotential lines in terms of equivalent fresh-water head show that the sea water flows inland, becoming progressively diluted with fresh water, to a line along which there is no horizontal component of flow, after which it moves upward and returns to the sea. The cyclic flow acts as a deterrent to the encroachment of sea water because of return to the sea of a part of the inland flow. Introduction. The basic premise of the Ghyben-Herzberg principle is that the position of the interface between fresh water and salt water incoastal aquifer will be governed by a hydrostatic equilibrium between fresh water and the more dense sea water. Hubbert (1940, pp. 924-926) showed, however, that because fresh water was known to flow seaward, the position of the interface would be governed by a dynamic equilibrium between flowing fresh water and static salt water. This concept is shown in Figure i where the depth to a point on the interface (z) would be equal to the head of fresh water (h) with reference to sea level at the point on the interface multiplied by the ratio of the tween the densities of sea water (p,) and fresh water. Observations over a period of nearly 20 years indicate that the salt front in the Biscayne aquifer of the Miami, Florida, area is dynami- cally stabilized seaward of the theoretical posi- tion given by either concept (Fig. 2). Recent studies indicate that the lack of agreement re- sults from the fact that two assumptions in- herent in the above developments are not ful-
The geology of Bermuda can be described as a sequence of Pleistocene, aeolian limestones displaying a full range of diagenetic grades. In the study area, containing the Central Lens, the two major rock bodies are of the Belmont and Paget Groups. They form adjacent parallel aquifers of greatly contrasting permeability. The older Belmont Limestone having undergone greater solutional alteration is the more permeable. The long-term averages of eight years of data indicate that under steady-state conditions the Central Lens configuration supports the Ghyben—Herzberg theory. On a yearly average basis, however, the degree of disequilibrium is substantial. The water table is shown to be far more responsive to variations in recharge than is the interface and possible causes for this are discussed. On less than a yearly average basis the water-table levels are dominated by the influence of sea level, which cannot be readily removed, and, therefore, presents a major obstacle to short-term studies. Demonstration of a relatively stable lens thickness, below sea level, allows a less cautious approach to management of pumping rates than previously taken. A maximum permissible thinning of the lens is considered as 45% in fresh areas and 60% in brackish areas. Under these conditions it is calculated from Henry's equation that ˜ 75% of recharge could be abstracted.
ABST33ACT Seawater diluted with secondcary-treated sewage effluent provides excellent enrichment for the maintenance of mixed natural populations of marine phytoplankton in continuous culture. Treated effluent, sampled over 1 year, was consistent in the ratios of plant nutrients and similar in its properties of plant growth stimulation and level of toxicity. The hetero- geneous continuous culture system produced large quantities of plant carbon with the concomitant removal of nitrogen and phosphorus from sewage effluent. The plant species that grew in the continuous cultures were common to the typical coastal phytoplankton and the selection and elimination of sDecies was gradual considering the chemical com- plexity of the sewage effluent enrichment.
Rates of groundwater discharge onto coral reefs at Barbados, West Indies, were measured with seepage meters and miniature piezometers. Seepage flux varied spatially, was correlated with water depth, and was about twice as high during the wet season as during the dry. Groundwater nitrogen concentrations were correlated with salinity but phosphate concentrations were not. Nitrate content of the discharge was much higher than was phosphate content. Measured fluxes were consistent with groundwater discharge estimates from aquifer models, but a large data set would be required to make accurate predictions of areal groundwater discharge and nutrient loading.
Abundant macroalgae of southern Florida Bay were assayed for nitrogen (N) and phosphorus (P) limitation of productivity by enrichment effects on in situ growth rate, tissue C:N:P molar ratios, and capacity of alkaline phosphatase. Growth of two frondose rhodophytes, Gracilaria tikvahiae and Laurencia poitei, was stimulated primarily by P (although N was also limiting during winter) as was growth of two frondose phaeophytes, Sargassum polyceratium and Sargassum pteropleuron. Tissue C:P and N:P ratios of the unenriched rhodophytes were elevated, ranging from 1,080 to 1,939 and 75 to 147, respectively; C:P and N:P ratios of the unenriched phaeophytes were lower, ranging from 550 to 1,307 and 23 to 25, respectively. These tissue ratios support the primary P limitation suggested by the growth assays and suggest that phylogenetic differences may exist in storage and utilization of N and P compounds relative to C. Levels of dissolved inorganic nutrients (NH4+, NO3-, and PO43-) in seawater during these studies also suggest that P, relative to N, was most limiting during summer months when NO3- and NH4+ were seasonally elevated and seawater N:P ratios were >30:1. Assays for alkaline phosphatase activity in phylogenetically diverse forms of Florida Bay macro algae indicated broadly different capacities of this exoenzyme, with the highest rates observed for Dictyota divaricata and L. poitei and the lowest rates for G. tikvahiae. Considering that D. divaricata and L. poitei had the greatest observed capacity for this enzyme and that these and related species are particularly abundant in southern Florida Bay, utilization of dissolved organic phosphate pools appears to be ecologically important to sustaining productivity of indigenous frondose macroalgae in P-limited Florida Bay.
Contamination of groundwater is a pervasive and serious problem in many developed coastal areas1–3, but potential interactions of groundwaters with, and their impact on, adjoining coastal waters have generally not been considered. Although submarine ground-water discharge could be an important source of nitrogen to coastal marine environments4, there has been no direct evidence for this. Recently, subsurface discharge has been shown to account for about 10–20% of the freshwater input to Great South Bay, New York5. The upper aquifer is the presumed source of this discharge and, because it is heavily contaminated with nitrate6, we suggest that groundwater is an important source of nitrate to the bay. Our determinations of the interstitial nutrient chemistry of freshly collected cores from nearshore sediments support this hypothesis. Although highly variable in time, cores taken after substantial rainfall showed increasing nitrate concentrations and decreasing salinities with depth. We conclude that submarine groundwater discharge is indeed a source of nitrate which should be considered in estimates of nitrogen influx to coastal marine ecosystems.
A relatively uncomplicated automated method for the determination of ammonium in sea water as indophenol blue has been compared at sea with the more complicated rubazoic acid method. The results from the two methods were in good agreement; a correlation coefficient of 0·96 was calculated from the data. A brief description of the indophenol blue method is given.
The relative effects of NH 4+(N) and PO 43-(P) on growth rate, photosynthetic capacity (Pmax), and levels of chemical constituents of the red macroalga Gracilaria tikvahiae McLachlan were assayed during winter and summer, 1983 in inshore waters of the Florida Keys by using in-situ cage cultures. During winter, both N and P enrichment enhanced growth over that of ambient seawater; however, P rather than N accounted for more (60%) of the increased winter growth. During summer, P, but not N, enhanced growth over ambient seawater and accounted for 80% of increased growth. Similarly, Pmax was enhanced by both P and N during winter (but mostly by P) and only by P during summer. Elevated C:P, C:N and N:P ratios of G. tikvahiae tissue during winter, but only C:P and N:P ratios during summer, support the pattern of winter N and P limitation and summer P-limitation. This seasonal pattern of N vs P limited growth of G. tikvahiae appears to be a response to seasonally variable dissolved inorganic N (twofold greater concentrations of NH 4+and NO 3-during summer compared to winter) and constantly low to undetectable concentrations of PO 43-. Mean C:P and N:P ratios of G. tikvahiae tissue during the study were 1 818 and 124, respectively, values among the highest reported for macroalgae.
Theoretical diffusive flux rates for dissolved reactive phosphate (DRP) were determined for sediments in a small area of the Indian River, Florida for the period March–May 1982. Flux rates from the sediment varied from 29 to 70 × 10−6g per m2 per day in seagrass associated sediments to 3–25 × 10−6g per m2 per day for an area devoid of seagrass. Simultaneous measurements of groundwater seepage velocities indicated greater velocities in seagrass associated sediments (1.03 × 10−6m per sec) than an area devoid of grass (0.77 × 10−6m per sec). Measured seepage flux accounted for more than 99% of the combined estimated diffusive and seepage flux of DRP for nearshore seagrass sediments. Also noted was an apparent direct relationship between tidal height, DRP and seepage velocity in nearshore sediments (25 m from shore) which further demonstrates the importance of hydrogeologic variables to these areas.
Chemical reactions that occur in landfills are analogous to those reactions that occur in marine sediments. Lateral zonation of C, N, S, O, H, Fe and Mn species in landfills is similar to the vertical zonation of these species in marine sediments and results from the following reaction sequence: (1) oxidation of C, N and S species in the presence of dissolved free oxygen to HCO3−, NO3− and SO2−4; (2) after consumption of molecular oxygen, then NO3− is reduced, and Fe and Mn are solubilized; (3) SO2−4 is reduced to sulfide; and (4) organic compounds become the source of oxygen, and CH4 and NH4+ are formed as fermentation products. In a landfill in Delaware the oxidation potential increases downgradient and the redox zones in the reducing plume are characterized by: CH4, NH4+, Fe2+. Mn2+, HCO3− and NO3−. Lack of SO2−4 at that landfill eliminates the sulfide zone. Although it has not been observed at landfills, mineral alteration should result in precipitation of pyrite and/or siderite downgradient. Controls on the pH of leachate are the relative rates of production of HCO3−, NH4+ and CH4. Production of methane by fermentation at landfills results in 13C isotope fractionation and the accumulation of isotopically heavy σCO2 (+10 to +18‰ PDB). Isotope measurements may be useful to determine the extent of CO2 reduction in landfills and extent of dilution downgradient. The boundaries of reaction zones in stressed aquifers are determined by head distribution and flow velocity. Thus, if the groundwater flow is rapid relative to reaction rates, redox zones will develop downgradient. Where groundwater flow velocities are low the zones will overlap to the extent that they may be indeterminate.
The green alga Cladophora prolifera (Chlorophyta, Cladophorales) has formed widespread blooms in Bermuda's inshore waters during the past 20 years, but, to date, no conclusive evidence links these blooms to nutrient enrichment. This study assessed the nutrient-dependance of productivity of Cladophora collected from Harrington Sound, a confined P-limited marine system where Cladophora first became abundant. Both N- and P-enrichment decreased the doubling time of Cladophora, which ranged from 14 days (with N and P enrichment) to 100 days (without enrichment). Nutrient enrichment also enhanced the light-saturated photosynthetic capacity (i.e. Pmax) of Cladophora, which ranged from 0·50 mg C g dry wt−1 h−1 (without enrichment) to 1·0 mg C g dry wt−1 h−1 (with enrichment). Tissue C:N, C:P and N:P ratios of unenriched Cladophora were elevated—25, 942, and 49, respectively—levels that suggest limitation by both N and P but primary limitation by P. Pore-waters under Cladophora mats had reduced salinities, elevated concentrations of NH4, and high N:P ratios (N:P of 85), suggesting that N-rich groundwater seepage enriches Cladophora mats. The alkaline phosphatase capacity of Cladophora was high compared to other macroalgae in Harrington Sound, and its capacity was enhanced by N-enrichment and suppressed by P-enrichment. Because the productivity of Cladophora is nutrient-limited in shallow waters of Harrington Sound, enhanced growth and increased biomass of Cladophora result from cumulative seepage of N-rich groundwaters coupled with efficient utilization and recycling of dissolved organo-phosphorus compounds.
A single solution reagent is described for the determination of phosphorus in sea water. It consists of an acidified solution of ammonium molybdate containing ascorbic acid and a small amount of antimony. This reagent reacts rapidly with phosphate ion yielding a blue-purple compound which contains antimony and phosphorus in a 1:1 atomic ratio. The complex is very stable and obeys Beer's law up to a phosphate concentration of at least 2 μg/ml.The sensitivity of the procedure is comparable with that of the stannous chloride method. The salt error is less than 1 %.RésuméUne méthode spectrophotométrique est décrite pour le dosage du phosphate dans l'eau de mer, an moyen de molybdate d'ammonium, en présence d'acide ascorbique et d'antimoinc. Il se forme rapidement un composé violet bleu, renfermant antimoine et phosphore dans un rapport atomique de 1:1.ZusammenfassungBeschreibung einer Methode zur Bestimmung von Phosphat in Mecrwasser mit Hilfe von Ammoniummolybdat in Gegenwart von Ascorbinsäure und Antimon. Der gebildete blau-violette Komplex wird spektrophotometrisch gemessen.
Kaneohe Bay, Hawaii, received increasing amounts of sewage from the 1950s through 1977. Most sewage was diverted from the bay in 1977 and early 1978. This investigation, begun in January 1976 and continued through August 1979, described the bay over that period, with particular reference to the responses of the ecosystem to sewage diversion. The sewage was a nutritional subsidy. All of the inorganic nitrogen and most of the inorganic phosphorus introduced into the ecosystem were taken up biologically before being advected from the bay. The major uptake was by phytoplankton, and the internal water-column cycle between dissolved nutrients, phytoplankton, zooplankton, microheterotrophs, and detritus supported a rate of productivity far exceeding the rate of nutrient loading. These water-column particles were partly washed out of the ecosystem and partly sedimented and became available to the benthos. The primary benthic response to nutrient loading was a large buildup of detritivorous heterotrophic biomass. Cycling of nutrients among heterotrophs, autotrophs, detritus, and inorganic nutrients was important. With sewage diversion, the biomass of both plankton and benthos decreased rapidly. Benthic biological composition has not yet returned to presewage conditions, partly because some key organisms are long-lived and partly because the bay substratum has been perturbed by both the sewage and other human influences.
Algal reef flats at Enewetak Atoll, Marshall Islands, fix atmospheric nitrogen at rates comparable to those in managed agriculture. The dominant nitrogen fixer appears to be the blue-green alga Calothrix crustacea. Since this nutrient enrichment contributes to the high productivity of adjacent coral reefs and undoubtedly to atoll lagoons, it is recommended that the algal reef flats receive increased conservation priority.
The Bermuda Marine Environment, Vol. III. The final report of the Bermuda Inshore Waters Investigations
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