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Drift rhodophyte blooms emerge in Lee County, Florida, USA: Evidence of escalating coastal eutrophication

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Drift rhodophyte blooms emerge in Lee County, Florida, USA: Evidence of escalating coastal eutrophication

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Macroalgal blooms have increased globally in recent decades as a result of increased nutrient enrichment and eutrophication of coastal waters. In Lee County, Florida, this problem reached a critical stage in 2003/2004 when massive rhodophyte blooms washed ashore, making beaches unsuitable for recreation and requiring an expensive removal program. To better understand the ecology of these blooms, water quality and macroalgae sampling was conducted in August 2004, prior to hurricane Charley, and again in late October following several months of large freshwater discharges from the Caloosahatchee River. During both samplings, water and macroalgae were collected along a gradient extending from the Caloosahatchee River to natural and artificial reefs up to 26 km from shore.

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... 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. ...
... Lee County, FL, is bisected by the Caloosahatchee River and Estuary, which historically was low in nutrients (Odum et al., 1955). However, the area has become highly developed since the 1950s (Fig. S1) and surface water in the Caloosahatchee River Estuary is now nutrient laden (Lapointe and Bedford, 2007;Vargo et al., 2008). Thus, some segments of the Caloosahatchee River Estuary are classified as impaired under Section 303(d) of the United States Clean Water Act of 1972 for nutrients, fecal coliforms, DO, and chlorophyll, while HABs are a recurring issue (see Fig. S2). ...
... Thus, some segments of the Caloosahatchee River Estuary are classified as impaired under Section 303(d) of the United States Clean Water Act of 1972 for nutrients, fecal coliforms, DO, and chlorophyll, while HABs are a recurring issue (see Fig. S2). For example, "red tide" blooms of the dinoflagellate Karenia brevis have become increasingly abundant, especially in nearshore environments (Brand and Compton, 2007), and have long been linked to nutrient enrichment from riverine inputs and estuarine flux (Slobodkin, 1953;Odum et al., 1955;Doig and Martin, 1974;Vargo et al., 2008;Yentsch et al., 2008;Medina et al., 2020;Medina et al., 2022), particularly during high flow years (Lapointe and Bedford, 2007;Heil et al., 2014). Additionally, beginning in 2003 red drift macroalgal HABs developed off the Lee County coast (Fig. S2) and were associated with increasing nutrient contributions from human waste, as well as rainfall and agricultural fertilizers (Lapointe and Bedford, 2007). ...
Article
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.
... Algal blooms are the cause of large-scale damage and disruption to coastal operators [1], including power generation plants whose water intakes can get blocked, or mechanically damaged [2]. In France, 3.6 million francs were spent on the removal of 90,000 m 3 of microalgae "green tides" in 1992, while in Lee County (USA) a total of $260,500 was spent in 2003/2004 to address problems caused by Rhodophyta blooms, and in Australia $160,000 are spent every year removing around 13,000 m 3 of macroalgae [1]. ...
... Algal blooms are the cause of large-scale damage and disruption to coastal operators [1], including power generation plants whose water intakes can get blocked, or mechanically damaged [2]. In France, 3.6 million francs were spent on the removal of 90,000 m 3 of microalgae "green tides" in 1992, while in Lee County (USA) a total of $260,500 was spent in 2003/2004 to address problems caused by Rhodophyta blooms, and in Australia $160,000 are spent every year removing around 13,000 m 3 of macroalgae [1]. Microalgal blooms are well known for their propensity to generate 'red tides' as well as their strong links to harmful algal blooms (HABs) [3][4][5]. ...
... This transition from being sessile, to being mobile, plays a key role in the generation of damaging blooms. MABs also have an impact on indigenous species, nuclear power stations and fish farms [1,14], particularly when amassing to sizes over 0.50 km 2 [14]. Assuming a macroalgae mass of 1 kg m −2 , this would suggest a bloom mass of around 560 tons. ...
Article
Full-text available
Macroalgae blooms (MABs) are a global natural hazard that are likely to increase in occurrence with climate change and increased agricultural runoff. MABs can cause major issues for indigenous species, fish farms, nuclear power stations, and tourism activities. This project focuses on the impacts of MABs on the operations of a British nuclear power station. However, the outputs and findings are also of relevance to other coastal operators with similar problems. Through the provision of an early-warning detection system for MABs, it should be possible to minimize the damaging effects and possibly avoid them altogether. Current methods based on satellite imagery cannot be used to detect low-density mobile vegetation at various water depths. This work is the first step towards providing a system that can warn a coastal operator 6-8 h prior to a marine ingress event. A fundamental component of such a warning system is the spectral reflectance properties of the problematic macroalgae species. This is necessary to optimize the detection capability for the problematic macroalgae in the marine environment. We measured the reflectance signatures of eight species of macroalgae that we sampled in the vicinity of the power station. Only wavelengths below 900 nm (700 nm for similarity percentage (SIMPER)) were analyzed, building on current methodologies. We then derived 1st derivative spectra of these eight sampled species. A multifaceted univariate and multivariate approach was used to visualize the spectral reflectance, and an analysis of similarities (ANOSIM) provided a species-level discrimination rate of 85% for all possible pairwise comparisons. A SIMPER analysis was used to detect wavebands that consistently contributed to the simultaneous discrimination of all eight sampled macroalgae species to both a group level (535-570 nm), and to a species level (570-590 nm). Sampling locations were confirmed using a fixed-wing unmanned aerial vehicle (UAV), with the collected imagery being used to produce a single orthographic image via standard photogrammetric processes. The waveband found to contribute consistently to group-level discrimination has previously been found to be associated with photosynthetic pigmentation, whereas the species-level discriminatory waveband did not share this association. This suggests that the photosynthetic pigments were not spectrally diverse enough to successfully distinguish all eight species. We suggest that future work should investigate a Charge-Coupled Device (CCD)-based sensor using the wavebands highlighted above. This should facilitate the development of a regional-scale early-warning MAB detection system using UAVs, and help inform optimum sensor filter selection.
... The increased nutrients fuel the growth of opportunistic macroalgae and phytoplankton until light reduction has compromised submerged aquatic vegetation (SAV) growth, like seagrasses (Burkholder et al., 2007;Lapointe et al., 2004;Morris and Virnstein, 2004;Smith et al., 1999). High biomass macroalgae accumulations that result from excess nutrients are considered harmful algal blooms (HABs; Lapointe and Bedford, 2007), which can provide major nutrient sinks during bloom formation and sources of recycled nutrients after decomposition, eventually affecting phytoplankton blooms. Unlike phytoplankton HABs, macroalgal HABs are usually non-toxic, but can cause major ecosystem impacts such as habitat destruction, oxygen depletion, and nutrient/biogeochemical cycling alterations (Lapointe and Bedford, 2007;Lapointe et al., 1994;McGlathery, 2001;Valiela et al., 1997), thereby reducing biodiversity (Burkholder et al., 2007;Howarth et al., 2000;McGlathery, 2001). ...
... High biomass macroalgae accumulations that result from excess nutrients are considered harmful algal blooms (HABs; Lapointe and Bedford, 2007), which can provide major nutrient sinks during bloom formation and sources of recycled nutrients after decomposition, eventually affecting phytoplankton blooms. Unlike phytoplankton HABs, macroalgal HABs are usually non-toxic, but can cause major ecosystem impacts such as habitat destruction, oxygen depletion, and nutrient/biogeochemical cycling alterations (Lapointe and Bedford, 2007;Lapointe et al., 1994;McGlathery, 2001;Valiela et al., 1997), thereby reducing biodiversity (Burkholder et al., 2007;Howarth et al., 2000;McGlathery, 2001). ...
... The rhodophytes, H. musciformis and G. tikvahiae have been common bloom-formers in the IRL for decades (Benz et al., 1979). Massive drift rhodophyte blooms which were composed mainly of H. musciformis, Hypnea spinella, and some G. tikvahiae, developed in Lee County in 2003 and 2004 following nutrient-rich discharges from Lake Okeechobee (Lapointe and Bedford, 2007). The chlorophyte U. lactuca and non-native H. musciformis have also become problematic in shallow coastal waters impacted by sewage pollution Maui, Hawai'i (Dailer et al., 2012). ...
... F.A.C; Parmer et al., 2008). These TDN values were considerably higher than the TDN values measured in October 2004, following the 2004 hurricanes, along the Caloosahatchee River at the Franklin Lock (70.9 mM), which also receives Lake Okeechobee discharges conveyed to the west coast of Florida (Lapointe and Bedford, 2007). Similarly, the average TDP concentrations for the Middle Estuary in June and November were 11.4 and 9.3 mM, respectively, values more than threefold higher than the proposed 2.61 mM TP target for this estuary (62-304.705 ...
... F.A.C; Parmer et al., 2008). These TDP concentrations for the SLE are also proportionally higher than the corresponding TDP concentrations measured in the Caloosahatchee River at the Franklin Lock in October 2004, which averaged ,2.0 mM (Lapointe and Bedford, 2007). The corresponding stoichiometry of the TDN : TDP ratio in the C-44 discharges was relatively low in June 2005, averaging ,11, considerably lower than the value of 35 at the Franklin Lock in October 2004 (Lapointe and Bedford, 2007). ...
... These TDP concentrations for the SLE are also proportionally higher than the corresponding TDP concentrations measured in the Caloosahatchee River at the Franklin Lock in October 2004, which averaged ,2.0 mM (Lapointe and Bedford, 2007). The corresponding stoichiometry of the TDN : TDP ratio in the C-44 discharges was relatively low in June 2005, averaging ,11, considerably lower than the value of 35 at the Franklin Lock in October 2004 (Lapointe and Bedford, 2007). Even though the TDN and TDP concentrations were several-fold lower throughout the SLE in March 2006 than they were in June and November 2005, all sites still remained above the proposed targets for TDN and TDP, with the exception of TDP at the Peck's Lake reference site. ...
Article
Lapointe, B.E.; Herren, L.W., and Bedford, B.J., 2012. Effects of hurricanes, land use, and water management on nutrient and microbial pollution: St. Lucie Estuary, southeast Florida. Multiple hurricanes impacted southeast Florida during 2004 and 2005, producing record rainfall and large-scale stormwater runoff into the urbanized St. Lucie Estuary (SLE). To assess effects on water quality, field samples were taken in June and November 2005 and March 2006 along the SLE's three main segments: the South Fork, connected via the C-44 canal to Lake Okeechobee; the North Fork, which receives residential and agricultural runoff from the C-23 and C-24 canals; and the Middle Estuary, which flows into the Indian River Lagoon and Atlantic Ocean. Salinities were <1‰ throughout the normally brackish estuary during the 2005 samplings, but returned to near-normal levels by March 2006 in all but the South Fork. Low salinities in 2005 correlated with low dissolved oxygen, high turbidity, elevated nitrogen and phosphorus concentrations, and high fecal and total coliform counts. Highest turbidity (84.4 NTU), nitrate (37.9 μM), and total dissolved nitrogen (130.8 μM) concentrations occurred in the South Fork, whereas the highest ammonium (15.4 μM), soluble reactive phosphorus (10.5 μM), and total dissolved phosphorus (13.8 μM) concentrations occurred in the North Fork. High fecal and total coliform counts occurred in tidal creeks adjacent to dense residential areas that rely on septic tanks for on-site sewage disposal. The data suggest that increased stormwater retention, minimization of freshwater releases from Lake Okeechobee, and enhanced treatment of both stormwater and sewage are needed to mitigate future stormwater-driven water quality perturbations in the SLE.
... 30 years, and a greater focus on the consequences of accumulations of macroalgal biomass, usually cast onto beaches or within coastal embayments (e.g. Raffaelli et al. 1998;Taylor 1999;Vahteri et al. 2000;Lapointe & Bedford 2007;Sugimoto et al. 2007;Teichberg et al. 2010;Lyons et al. 2014). ...
... Species of Gracilaria are reported in macroalgal blooms from around the world (e.g. Lapointe & Bedford 2007;Thornber et al. 2008;Piñón-Gimate et al. 2009;Kennish et al. 2011;Newton & Thornber 2012), with both native and non-native species (e.g. Gracilaria vermiculophylla (Ohmi) Papenf.) ...
... Several species belonging to the Solieriaceae have been reported to grow in nuisance quantities in other parts of the world (e.g. Perrone & Cecere 1994;Lapointe & Bedford 2007). Petrocelli et al. (2013) summarised the history of both Agardhiella subulata (C.Agardh) Kraft & M.J.Wynne (initially misidentified as Solieria chordalis) and Solieria filiformis (Kutz.) ...
Article
When large volumes of macroalgae wash up on beaches, accumulate in coastal areas or within confined bays, there can be significant local impacts. Blooms of macroalgae are being reported throughout the world with increasing frequency in estuarine and coastal areas in both temperate and tropical regions. This review examines examples of nuisance accumulations of macroalgae in New Zealand, the geographic and seasonal distribution of nuisance algal records, available data on impacts on coastal communities, including impacts on human activities, and considers some of the factors that may lead to excessive growth, as well as attempts to ameliorate the associated problems.
... To our knowledge, there have been no additional studies of macroalgal communities near Sanibel Island since the 1960s. A more recent study linking river flows to beach stranding events (Lapointe and Bedford 2007) suggested that more research on the distribution and abundance of macroalgae was needed. ...
... Most of these species are branching red algae (Division Rhodophyta), with 12 species of brown algae (Division Phaeophyta), 14 total species of green algae (Division Chlorophyta), and 1 common cyanobacteria (Division Cyanophyta). For comparison, during this study or in previous studies (Dawes 2004;Lapointe and Bedford 2007), a total of 20 macroalgal species were collected and identified during stranding events from 2003 to 2005. Most of the common stranding species were branching red algae; however, there were brown and green algae collected. ...
... In other parts of the Gulf of Mexico, nutrient loading and coastal development can have large impacts on the shelf (Rabalais et al. 1994). A period of high flows and frequent hurricanes from 2003 to 2006 coincided with several large-scale macroalgal stranding events on the beaches of Sanibel, FL (Dawes 2004;Lapointe and Bedford 2007). While inshore effects of high flow have been shown to negatively affect oysters (Volety et al. 2009), seagrass , and water quality (Booth et al. 2016;, the far-field effects on the shelf were thought to be minimal. ...
Article
Large accumulations of stranded macroalgae on the beaches of Sanibel Island from 2004 to 2007 were unusual and thought to be driven by high rainfall and river flows stemming from a high frequency of hurricanes. The southwest Florida shelf was thought to be isolated from far-field effects such as high river flows and urbanization but field- and laboratory-based studies suggest that nitrogen enrichment, fragmentation, and species composition of macroalgal communities on the shelf and in the estuary contribute to beach stranding events. Macroalgae were sampled using a belt transect method to determine species distribution and abundance. Macroalgae were abundant (1) in the lower estuary with abundant seagrass and (2) on limestone outcroppings in the Gulf of Mexico. An MDS analysis of the quadrat samples indicated two distinct macroalgal community types, a “Sound” assemblage around Pine Island Sound and a “Gulf” assemblage, associated with a live bottom and patch reef in the Gulf of Mexico. Peak abundances for the two community types differed with the Gulf having peak abundances from July to November, while peak abundances in the Sound occurred from January to July. Sound macroalgal tissue had significantly enriched δ¹⁵N compared to Gulf tissue when all species were combined and in five of six species collected at both locations suggesting that stable isotope analysis could be useful in combination with species composition in determining the source of macroalgae during stranding events. In addition, a laboratory study was conducted on four species that were sampled and frequently collected as a result of stranding events. Laboratory growth experiments demonstrated the potential for three of four common species (Solieria filiformis, Gracilaria tikvahiae, Agardhiella subulata) to fragment and grow significantly more under elevated nitrate conditions.
... Multiple studies indicate that wastewater is a significant source of dissolved nutrients and fecal indicator bacteria (FIB) to the IRL and its tributaries (Lapointe and Krupa, 1995a,b;Lapointe et al., 2012Lapointe et al., , 2015Lapointe et al., , 2017Barile, 2018). Highly enriched stable N isotope (δ 15 N) values in IRL macroalgae (δ 15 N > +6.30‰; Lapointe et al., 2015;Barile, 2018) parallel values observed in macroalgae collected from the sewageimpacted waters of Boston Harbor and Cape Cod, MA (France et al., 1998;McClelland and Valiela, 1998), Southeast FL (Barile, 2004;Lapointe et al., 2005), Southwest FL (Lapointe and Bedford, 2007), and tributaries to the southern IRL including the Loxahatchee River (Lapointe and Krupa, 1995a,b) and the St. Lucie Estuary (Lapointe et al., 2017). Except for emergency situations, sewage discharges (outfalls) into surface waters of the IRL have been eliminated through the IRL Act of 1990 (NEP, 2008). ...
... Florida has both unsuitable soil types and high groundwater tables that combined can result in septic system effluent continuously flowing into groundwater, contaminating it with high levels of nutrients and FIB (Bicki et al., 1984;Bicki and Brown, 1990;Woodward-Clyde Consultants, 1994). This contamination ultimately discharges into surface waters (i.e., canals, tributaries, and estuaries) contributing to water quality degradation and HABs (Lapointe and Bedford, 2007;Lapointe et al., 2012Lapointe et al., , 2017. The generally higher NH 4 + (~30 μM) than NO 3 − observed in residential groundwater in this study is indicative of limited nitrification of septic system effluent (Withers et al., 2014) that constrains N removal in soils by denitrification of NO 3 − . ...
Article
Full-text available
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.
... Extensive hurricane runoff from north of Lake Okeechobee, the Peace River, Myakka River, and Caloosahatchee basin mixed in a buoyant, stratified plume that extended some 70 km offshore in October 2004. Our 2004 study, which involved sampling before and after the 2004 hurricanes, showed significantly increased DIN concentrations and lowered N:P ratio in the stratified plume water to 26 km offshore (Lapointe and Bedford 2007). This buoyant plume phenomenon has long been considered a prerequisite for Florida red tide (Slobodkin 1953) and has been used worldwide to model the initiation of various red tide phenomena. ...
... > +6.0‰, similar to macroalgae values on inshore reefs and within the range of sewage N(Lapointe and Bedford 2007). ...
... Nutrient enrichment generally results in increased primary production of algae, including phytoplankton, benthic macroalgae and algal turfs, as overall biodiversity is reduced (Bell et al., 2014;D'Angelo and Wiedenmann, 2014;Duarte, 1995;Foster and Schiel, 2010;Prouty et al., 2017;Tewfik et al., 2007). Unlike some phytoplankton blooms, such as toxic "red tides", macroalgal blooms generally lack direct chemical toxicity but can still result in harmful environmental effects including changes in habitat, oxygen depletion, production of hydrogen sulfide, alteration of biogeochemical cycles, increased grazing, and die-off of seagrasses and coral reefs (Anderson, 2007;ECOHAB, 1995;Lapointe and Bedford, 2007;McGlathery, 1995). Nutrients from a variety of sources including large river systems (Mississippi, Amazon, Orinoco, Congo) in the Atlantic basin have contributed to increasing macroalgal blooms, most notably the "golden tides" of Sargassum spp. ...
... The opposite trend of enriched macroalgal δ 15 N values in nearshore urbanized areas to more depleted values in offshore waters has been widely reported for sewage-stressed coral reefs in the Caribbean region, including southeast Florida , Florida Keys , Tobago , Jamaica and the Bahamas ( Barile and Lapointe, 2005). The more enriched δ 15 N values > +3‰ in the nearshore macroalgae reflect the more processed N from sewage, manure effluent and animal processing waste whereas values < +3‰ reflect more depleted N sources such as N 2 fixation (0‰), atmospheric deposition (− 3.0 to +1.0‰), and synthetic fertilizers (0 to +3‰) (Lapointe and Bedford, 2007). While we were unable to evaluate the details of the pattern of freshwater discharge and flow from the Belize River and Haulover Creek into the nearshore and broader BBR lagoon, a number of approaches (hydrodynamic modelling, remote sensing) have recently been used to assess freshwater flows and associated impacts of land-based pollution on coral reef systems elsewhere (Alvarez-Romero et al., 2013;Wolff et al., 2018). ...
Article
Macroalgal blooms are increasing on the Belize Barrier Reef (BBR) as scleractinian coral cover declines. Although some have attributed this to reduced grazing, the role of land-based nutrient pollution has not been assessed. Nutrient enrichment was quantified through macroalgal tissue analysis from Belize City to the offshore fore reef and at several central BBR lagoon sites. These recent data were compared to baseline data from the 1980s. Significant nearshore-to-offshore gradients of %N, %P and δ¹³C in macroalgae all indicated land-based sources of these nutrients. Macroalgal δ¹⁵N values were generally enriched in nearshore waters where values matched those reported for human sewage. Notably, the N:P ratios of recent macroalgae measurements were elevated at all sites, more than two-fold higher than values from the 1980s (~30: 1 to 70:1). These results support the hypothesis that nitrogen enrichment from land-based sources has increased phosphorus limitation driving macroalgal blooms and coral stress on the BBR.
... Measurement of stable carbon and nitrogen isotopes (d 13 C, d 15 N) in macroalgal tissue have been widely used to discriminate among natural (upwelling, N-fixation) and anthropogenic (sewage, fertilizers) nutrient sources (Risk et al., 2008). Because natural N-fixation source values are close to 0% (Heaton, 1986;France et al., 1998), atmospheric N typically ranges from À3% to +1% (Paerl and Fogel, 1994) and synthetic fertilizer N ranges from À2% to +2% (Bateman and Kelly, 2007); these N sources are all depleted relative to enriched values of +3% to +19% for human sewage (Heaton, 1986;Costanzo et al., 2001; (France et al., 1998), Childs River, Cape Cod, MA (McClelland andValiela, 1998), Narrangansett Bay, RI (Thornber et al., 2008), Sarasota Bay, FL (Lapointe, 2013), Moreton Bay, Australia (Costanzo et al., 2001), and nearshore reefs off urban areas of east-central Florida (Barile, 2004), southeast Florida (Lapointe et al., 2005a), southwest Florida (Lapointe and Bedford, 2007), Jamaica (Lapointe et al., 2011), and Tobago (Lapointe et al., 2010; Table 1). In addition, measurement of C:N:P contents of macroalgae provides a measure of nutrient quantity and stoichiometry that is useful in assessing the relative importance of N vs. P-limitation (Atkinson and Smith, 1983;Lapointe et al., 1992). ...
... During the 2005 discharges from Lake Okeechobee to the Caloosahatchee River on Florida's west coast, similarly enriched d 15 N values of +11.5% were measured in M. aeruginosa in the Caloosahatchee estuary and + 7.83% in red tides -Karenia brevisin coastal waters off Sanibel Island (Yentsch et al., 2008). Like the SLE, the Caloosahatchee River receives considerable sewage N inputs from OSTDS, but also municipal surface water sewage outfalls (Lapointe and Bedford, 2007). In comparison, the d 15 N value of $+3.5% we measured in the superbloom in ML is at the low end of the wastewater N range, and could reflect minimal transformation/fractionation of sewage effluent as well as additional fertilizer and top soil N contributions that would have more depleted d 15 N values, such as those reported for macroalgal blooms in western Florida Bay ($+2%; . ...
... In addition, direct measurements in seawater do not reveal the bioavailable concentrations (Orlandi et al., 2014;Dailer et al., 2010;Barr, 2007). The use of stable nitrogen isotopes ( 15 N/ 14 N expressed as d 15 N) in biotic and abiotic samples is one way to investigate nutrient sources directly (Lamb et al., 2012;Costanzo et al., 2001), but biotic samples may be better because they can record long-term environmental changes (Lapointe and Bedford, 2007). Benthic macroalgae have already been shown to be reliable indicators of the effect of anthropogenic nutrient loads in aquatic ecosystems. ...
... Macroalgal d 15 N generally accurately reflects N inputs from terrestrial sources because fractionation is negligible during uptake and assimilation (Ochoa-Izaguirre and Soto-Jimenez, 2015;Orlandi et al., 2014;Dudley et al., 2010;Deutsch and Voss, 2006;Cohen and Fong, 2005;Naldi and Wheeler, 2002). The measurement of d 15 N in macroalgae has consequently become a widely used tool to study N pollution (Barr et al., 2013;Dailer et al., 2010;Lapointe and Bedford, 2007;Costanzo et al., 2001Costanzo et al., , 2005Savage and Elmgren, 2004;Lapointe et al., 2004;Gartner et al., 2002) in particular for tracing aquaculture wastes (Carballeira et al., 2013;Garcia-Sanz et al., 2011;Costanzo et al., 2003;Jones et al., 2001). The range of d 15 N values in algal tissue makes it possible not only to trace anthropogenic sources of N but also to distinguish between natural and anthropogenic N sources, the latter include fertilizer, sewage and manure (Carballeira et al., 2013(Carballeira et al., , 2014Dailer et al., 2012;Garcia-Sanz et al., 2011;Risk et al., 2009). ...
Article
Full-text available
A fine-scale survey of δ(15)N, δ(13)C, tissue-N in seaweeds was conducted using samples from 17 sampling points at two sites (Grandcamp-Maisy (GM), Courseulles/Mer (COU)) along the French coast of the English Channel in 2012 and 2013. Partial triadic analysis was performed on the parameter data sets and revealed the functioning of three areas: one estuary (EstA) and two rocky areas (GM(∗), COU(∗)). In contrast to oceanic and anthropogenic reference points similar temporal dynamics characterized δ(15)N signatures and N contents at GM(∗) and COU(∗). Nutrient dynamics were similar: the N-concentrations in seawater originated from the River Seine and local coastal rivers while P-concentrations mainly from these local rivers. δ(15)N at GM(∗) were linked to turbidity suggesting inputs of autochthonous organic matter from large-scale summer seaweed beachings made up of a mixture of Rhodophyta, Phaeophyta and Chlorophyta species. This study highlights the coupling between seaweed beachings and nitrogen sources of intertidal macroalgae. Copyright © 2015 Elsevier Ltd. All rights reserved.
... Thomas and Rumbold (2006 and references therein) reviewed a number of water quality assessments for the Estero Bay watershed and, despite differences in methodology, data sets, and basin boundaries, there was agreement among the various assessments that excess nutrients and suspended solids are a recurring problem in Estero Bay tributaries. Lapointe and Bedford (2007) recorded high ammonium levels in the Imperial River that may have been associated with sewage outfall in land-based runoff. Schmid et al. (2006b) observed evidence of cultural eutrophication (extensive phytoplankton bloom, supersaturated dissolved oxygen followed by anoxia, and fish kill) in the upper reaches of Ten-Mile Canal which flows into Mullock Creek. ...
... Red algae and filamentous green algae occur in low salinity waters typical of high freshwater discharges to estuaries (Carter et al., 1973;Biber and Irlandi, 2006) and these algae respond to anthropogenic nutrient enrichment with enhanced growth and increased biomass (Valiela et al., 1997;McGlathery, 2001;Österling and Pihl, 2001;Lapointe and Bedford, 2007). ...
Technical Report
Full-text available
The objectives of the current study were (1) to perform comprehensive mapping of benthic habitat distributions in Estero Bay, (2) to analyze benthic habitat compositions relative to the entry points of the bay’s major tributaries, (3) to analyze aggregations of decapod crustacean inhabiting oyster reefs relative to salinity patterns in each tributary, (4) to analyze the morphometrics of turtle grass in the bay as indicators of water quality, and (5) to visually survey the estuarine system for listed species of marine reptiles during sampling efforts.
... The increased nutrients fuel the growth of opportunistic macroalgae and phytoplankton (Lapointe et al., 2004;Morris and Virnstein, 2004). High biomass macroalgae accumulations are usually non-toxic; however, they can cause major ecosystem disruption, such as habitat destruction, oxygen depletion and alterations in nutrient/biogeochemical cycling (McGlathery, 2001;Valiela et al., 1997;Lapointe and Bedford, 2007). ...
... Globally, many studies use stable nitrogen isotope ratios (δ 15 N) as a tool to discriminate between natural and anthropogenic nitrogen sources that could support excessive macroalgal growth (e.g., Costanzo et al., 2001;Umezawa et al., 2002;Gartner et al., 2002;Savage and Elmgren, 2004;Bacchus et al., 2014). The δ 15 N in macroalgae can be used to assess land-based nutrient enrichment in coastal waters by "fingerprinting" the source of nitrogen because several sources have δ 15 N signatures that are between known ranges (Heaton, 1986;Lapointe and Bedford, 2007). Some macroalgae can reflect the N isotopic signatures of their source with little fractionation, making these species potential indicators of anthropogenic nutrient inputs (Savage and Elmgren, 2004;Deutsch and Voss, 2006;Thornber et al., 2008;Bristow et al., 2013;Viana and Bode, 2015). ...
... In tropical and subtropical marine ecosystems, the most direct effect of nutrient enrichment is increased algal abundance. Blooms of opportunistic algae have been linked to increases in nutrient loading to coastal waters of O'ahu (Smith et al., 1981), Maui Sun, 1996), Bermuda (Lapointe and O'Connell, 1989;McGlathery, 1992), Jamaica (D'Elia et al., 1981;Lapointe, 1997), Florida (Lapointe, 1997;Lapointe et al., 2005a;Lapointe and Bedford, 2007), The Bahamas (Lapointe et al., 2004), Brazil (Costa et al., 2008), Martinique (Littler et al., 1992), Reunion Island (Naim, 1993), China (Liu et al., 2013) and Australia's Great Barrier Reef (Bell, 1992). In oligotrophic waters, growth and reproduction of macroalgae are often limited by nutrients (Lapointe, 1997;Larned, 1998). ...
... Blooms of opportunistic algae have been linked to increased coastal nutrient concentrations in Hawaiʻi Smith et al., 1981;Sun, 1996), Florida (Lapointe, 1997;Lapointe et al., 2005a;Lapointe and Bedford, 2007), Bermuda (Lapointe and O'Connell, 1989;McGlathery, 1992), Jamaica (Lapointe, 1997), The Bahamas (Lapointe et al., 2004), Brazil (Costa et al., 2008), Martinique (Littler et al., 1992), Reunion Island (Naim, 1993), China (Liu et al., 2013), and Australia's Great Barrier Reef (Bell, 1992). The most obvious and direct impacts of macroalgae on corals are observed when algal species overgrow and physically disturb corals while competing for light, nutrients, and space (Hughes, 1989;Hunter and Evans, 1995;Lirman, 2001;Martinez et al., 2012;Smith et al., 2004a;Smith et al., 2005;Smith et al., 1981). ...
Thesis
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Submarine groundwater discharge (SGD) is a ubiquitous process that delivers significant amounts of nutrients and other solutes to coastal ecosystems worldwide. Although the quality and quantity of SGD has been characterized at many sites, the biological implications of this process remain poorly understood. The objective of this work was to compare the physiological response of macroalgae and benthic community structure across gradients of SGD and nutrient loading in Hawai‘i. Common marine algae were collected and/or deployed at several sites on O‘ahu, and Maui. Selection of sites was informed by adjacent land use, known locations of wastewater injection wells, and previous estimates of environmental risk due to onsite sewage disposal systems (OSDS). For deployed samples, initial values of algal tissue nitrogen (N) parameters were determined after pretreatment in low nutrient conditions. At all locations, algal tissue nitrogen (N) parameters (δ15N, N %, and C:N) were compared with the N parameters (δ15N and N concentration) of coastal groundwater , marine surface water, or groundwater simulations. Algal tissue N was highest (> 2 %) in samples located nearshore at sites adjacent to coastal aquifers enriched with anthropogenic sources of N. The lowest tissue N values (< 1 %) were found offshore or at relatively unimpacted sites. In general, the δ15N values of algal tissues and water samples were highest (9 - 18 ‰) at sites adjacent to high-volume wastewater injection wells and high densities of OSDS; lowest values (< 4 ‰) were observed in samples adjacent to sugarcane fields. Benthic diversity was greatest in locations with low anthropogenic impact. In contrast, highly impacted locations were dominated by opportunistic species. This work advances the use and interpretation of algal bioassays by highlighting the importance of onshore-offshore trends, and deviations from initial N parameter values, for the detection of N source and relative N availability. Wastewater was detectable and a major source of N at many locations. These results support recent studies that indicate SGD is a significant transport pathway for anthropogenic pollutants with important biogeochemical implications. Minimizing contaminant loads to coastal aquifers will reduce pollutant delivery to nearshore reefs in areas with SGD flux.
... Compared to the atmospheric N 2 , the organic N sources show a greater 15 N: 14 N ratio, whereas the inorganic N sources have a lower 15 N: 14 N ratio (Orlandi et al. 2017;Sulzman 2007). This difference in N isotopic composition is translated in a different isotopic signature (δ 15 N) of the organic and inorganic N sources: δ 15 N ≥ 6‰ for wastewaters and manure (Dailer et al. 2010;Risk et al. 2009;Titlyanov et al. 2011) and − 3‰ ≤ δ 15 N ≤ + 3‰ for the industrial fertilizers (Dailer et al. 2010;Lapointe and Bedford 2007;Wang et al. 2016). ...
... These high values, which were associated with high dissolved nitrogen levels in seawaters, indicated respectively a moderate and a high organic origin of the N inputs suggesting the need of wastewater collection and treatment systems. East of this area, δ 15 N values indicated "non-impacted" conditions, according to current literature classification (Dailer et al. 2010;Fiorentino et al. 2017;Lapointe and Bedford 2007;Risk et al. 2009;Titlyanov et al. 2011;Wang et al. 2016). In particular, the values found in Sisangan are consistent with the location of the site near the Sisangan National Park, where human activities are strongly regulated. ...
Article
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The Caspian Sea hosts areas of high ecological value as well as industrial, leisure, and agricultural activities that dump into the water body different kinds of pollutants. In this complex context, a proper description of the origin and potential sources of pollution is necessary to address management and mitigation actions aimed at preserving the quality of the water resource and the integrity of the ecosystems. Here, we aimed at detecting sources of both nitrogen inputs, by N stable isotope analysis of macroalgae, and metals in macroalgae and sediments in two highly anthropized coastal stretches at the Iranian side of the Caspian Sea. Sampling was done near the mouth of rivers and canals draining agricultural and urbanized areas. In the westernmost waters, facing a port city, low macroalgal δ¹⁵N signatures indicated industrial fertilizers as the principal source of pollution. By contrast, in the central coastal waters, facing touristic areas, the high macroalgal δ¹⁵N indicated N inputs from wastewaters. Here the lowest dissolved oxygen concentrations in waters were associated with excess dissolved inorganic nitrogen. Metal concentrations varied largely in the study areas and were lower in macroalgae than in sediments. Localized peaks of Pb and Zn in sediments were observed in the central coastal sites as probable byproducts of mining activity transported downstream. By contrast, Cr and Ni concentrations were high in all sampling sites, thus potentially representing hazardous elements for marine biota. Overall, macroalgal δ¹⁵N coupled with metal analysis in macroalgae and sediments was useful for identifying the main sources of pollution in these highly anthropized coastal areas. This double approach in comprehensive monitoring programs could thus effectively inform stakeholders on major environmental threats, allowing targeted management measures.
... Pensacola Beach-near the western end of Santa Rosa Island (SRI), a 55-mile-long barrier island in northwest Florida-is known for its sugar-white sands and clear emerald waters; however, there are complex natural processes at work that are not always pleasing to the senses. Sargassum is a common type of brown macroalgae found intermingled in the Gulf of Mexico (Lapointe and Bedford 2007;Gower and King 2011). Once the Sargassum (and other mats of dead plant and other organic material) washes up onto the shore it is characterized as beach wrack. ...
... Animals, especially birds and sea turtles, foraging in or passing though the wrack could ingest plastic and other garbage, or become entangled in fishing line, nets, or ropes (Gheskiere et al. 2006;Defeo et al. 2009). Economic losses have also been associated with extensive wrack accumulations through loss of tourism and expensive beach cleanup costs (Lapointe and Bedford 2007). ...
Article
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The yearly influx of Sargassum onto the beaches of northwest Florida is considered a nuisance to some and a necessity to others. In Pensacola Beach, the Santa Rosa Island Authority rakes the wrack with mechanical beach cleaners to improve the aesthetic quality for beachgoers. The purpose of this study was three-fold: to evaluate the local faunal use of Sargassum wrack, to gauge public perception of Sargassum on the beach, and to test whether public perception of the beauty of the beach, the necessity of raking, and the likelihood of visiting could be influenced by a simple educational sign. A two-part methodology consisted of 1) systematic observation of faunal use, and 2) interviews of 200 beachgoers via a detailed pre-post/post only public use survey. Results showed that 11 of the 22 species of shorebirds documented, including two uncommon migrants, were observed using Sargassum wrack to forage, rest, and hide. Public survey results demonstrated that although beachgoers generally considered themselves to be “ecofriendly”, their perceptions of Sargassum wrack can be positively influenced through environmental education such as informative signage on the beach. In conclusion, Sargassum wrack provides valuable additional habitat to shorebirds and other critters, and that leaving the beach wrack to naturally become part of the ecosystem would not deter most beachgoers (70%) from visiting Pensacola Beach. This research contributes valuable information to coastal managers and other stakeholders for improved ecosystem protection and management.
... septics, reclaimed, atmospheric, etc.) were not directly assessed. Instead, results of the isotopic analysis for the SPOM samples were compared to previously reported isotopic signatures in the region(Demers, 2008;Lapointe and Bedford, 2007;Greenwood et al., 2008;Malkin, 2010;Lapointe et al. 2016; Yang and Toor, Table studies (Demers, 2008;Lapointe and Bedford, 2007;Greenwood et al., 2008;Malkin, 2010;Lapointe et al. 2016; Yang and Toor, 2016), values above 3‰ represent potential wastewater/septic signatures rather than fertilizer or atmospheric. Regarding d(Figure 3-25) which agreed with previous studies(Malkin, 2010). ...
... septics, reclaimed, atmospheric, etc.) were not directly assessed. Instead, results of the isotopic analysis for the SPOM samples were compared to previously reported isotopic signatures in the region(Demers, 2008;Lapointe and Bedford, 2007;Greenwood et al., 2008;Malkin, 2010;Lapointe et al. 2016; Yang and Toor, Table studies (Demers, 2008;Lapointe and Bedford, 2007;Greenwood et al., 2008;Malkin, 2010;Lapointe et al. 2016; Yang and Toor, 2016), values above 3‰ represent potential wastewater/septic signatures rather than fertilizer or atmospheric. Regarding d(Figure 3-25) which agreed with previous studies(Malkin, 2010). ...
Technical Report
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A follow-up study to the 2016 tidal creeks report focusing on indicator development and nutrient dynamics along the creek salinity gradient
... In marine ecosystems, a large number of biotic and abiotic indicators are used as tracers of continental nitrogen inputs by isotopic analysis Marine Pollution Bulletin 110 (2016) 470-483 (Gartner et al., 2002;Lamb et al., 2012;Ochoa-Izaguirre and Soto-Jimenez, 2015;Pinon-Gimate et al., 2009;Raimonet et al., 2013;Savage and Elmgren, 2004). Contrary to abiotic indicators the measurement of the isotopic signature δ 15 N in biotic samples has the advantage of providing information on the bioavailable nitrogen fraction associated with the risk of eutrophication (Lapointe and Bedford, 2007). In addition, benthic macroalgae have been proven as reliable indicators of anthropogenic nutrient loads because (1) they absorb nutrients directly in the water column and accumulate them in their tissue, (2) they can reflect the temporal integration of the δ 15 N sources during either short periods (few days) or longer periods (several weeks) (Deutsch and Voss, 2006;Gartner et al., 2002), (3) the fractionation during uptake and assimilation is considered to be negligible at usual concentrations of dissolved inorganic nitrogen (DIN) in seawater (Cohen and Fong, 2005;Deutsch and Voss, 2006;Dudley et al., 2010;Naldi and Wheeler, 2002;Swart et al., 2014), (4) the measurement of δ 15 N can integrate spatial and temporal variabilities of δ 15 N-DIN sources (Gartner et al., 2002;Savage and Elmgren, 2004) and (5) the variation of δ 15 N values is higher in macroalgae than in other organisms (Riera et al., 2000), ranging from 0.2 to 50.1‰ (Dailer et al., 2010) which enables better discrimination of N sources. ...
... In addition, benthic macroalgae have been proven as reliable indicators of anthropogenic nutrient loads because (1) they absorb nutrients directly in the water column and accumulate them in their tissue, (2) they can reflect the temporal integration of the δ 15 N sources during either short periods (few days) or longer periods (several weeks) (Deutsch and Voss, 2006;Gartner et al., 2002), (3) the fractionation during uptake and assimilation is considered to be negligible at usual concentrations of dissolved inorganic nitrogen (DIN) in seawater (Cohen and Fong, 2005;Deutsch and Voss, 2006;Dudley et al., 2010;Naldi and Wheeler, 2002;Swart et al., 2014), (4) the measurement of δ 15 N can integrate spatial and temporal variabilities of δ 15 N-DIN sources (Gartner et al., 2002;Savage and Elmgren, 2004) and (5) the variation of δ 15 N values is higher in macroalgae than in other organisms (Riera et al., 2000), ranging from 0.2 to 50.1‰ (Dailer et al., 2010) which enables better discrimination of N sources. Algal δ 15 N values have been used globally to detect sources of anthropogenic N in coastal systems (Barr et al., 2013;Costanzo et al., 2001Costanzo et al., , 2005Dailer et al., 2010;Gartner et al., 2002;Lapointe and Bedford, 2007;Lapointe et al., 2004;Lemesle et al., 2015;Savage and Elmgren, 2004) and in particular to trace aquaculture wastes (Carballeira et al., 2013;Costanzo et al., 2003;Garcia-Sanz et al., 2011;Jones et al., 2001). Several macroalgae species belonging to different phyla were used for monitoring δ 15 N isotopic signatures in algal tissue, but generally either only one species or a mixture of species (see review Dailer et al., 2012) Therefore few studies have been carried out in order to compare the individual δ 15 N isotopic signature of marine macroalgal species collected in the same location and time for tracking N pollution in the marine environment (Carballeira et al., 2013;Deutsch and Voss, 2006;Gartner et al., 2002;Ochoa-Izaguirre and Soto-Jimenez, 2015;Orlandi et al., 2014;Raimonet et al., 2013;Viana et al., 2011). ...
Article
δ15N of annual (Ulva sp., Porphyra sp.) and perennial intertidal seaweed species (Chondrus crispus, Fucus sp.) collected on 17 sampling points along the French coast of the English Channel in 2012 and 2013 were assessed on their suitability as bioindicators of N pollution in coastal areas. A sine function applied for δ15N time series data showed for all the species the same seasonal trend with lowest δ15N values in April and highest in summer but with no significant interspecific differences of amplitude (α) and phase angle (ϕ). This model provides a useful tool for monitoring the inter-annual changes of N pollution. An interspecific variability of δ15N values was observed, probably due to their tolerance to emersion. An in vitro study for comparing the kinetic acquisition of the isotopic signal and N uptake mechanisms of each species underlined the influence of algal physiology on the δ15N interspecific variability.
... Additionally, nutrient loadings speed up the deterioration of marine ecosystems (Viana and Bode, 2015). High accumulation or blooms of seaweeds can cause ecosystem disturbance, such as oxygen depletion, habitat loss, and nutrient cycling (Lapointe and Bedford, 2007;Varekamp et al., 2014;Wu et al., 2018). Moreover, algal blooms can cause negative economic impacts on commercial fisheries, and recreational and tourist industries (Liu et al., 2009;Teichberg et al., 2012). ...
... However, the combined use of both d 15 N and d 18 O to identify the nitrate sources in macroalgae is rather limited (Alstyne, 2016;Endo et al., 2018). Recently, the use of isotopic signature in particularly macroalgae has become more popular to identify nitrogen sources in shallow coastal ecosystems (Lapointe and Bedford, 2007;Piñ on-Gimate et al., 2009;Wang et al., 2016;Rossi et al., 2018). Macroalgae specific nitrogen isotope signature (d 15 N) has been used as a potential indicator to differentiate natural and anthropogenic nitrogen sources (Piñ on-Gimate et al., 2009;Viana and Bode, 2015;Alstyne, 2016). ...
... There is a decreasing gradient of nitrogen and phosphorus from Lake Okeechobee to the Gulf of Mexico, suggesting that Lake Okeechobee is a major source of nutrients to the coastal waters through a combination of conservative (dilution with Gulf waters) and non-conservative (algal/plant uptake) processes. Algal tissues near the mouth of the Caloosahatchee Estuary demonstrated elevated δN15 ratios, suggesting that nutrients in stormwater runoff are being assimilated into macroalgal biomass (Lapointe and Bedford, 2007;Milbrandt et al., 2010). ...
... Any crops considered for the southeast must be specifically evaluated for its impacts on water quality because nutrient runoff from agriculture poses increasing threats to drinking water, recreational areas, and natural springs in these regions. This can be seen with the eutrophication conditions experienced in the Gulf of Mexico around the Mississippi River delta ( Rabalais et al. 1996) as well as in Florida ( Brand et al. 2010;Lapointe and Bedford 2007), for example. The issue of water quality for the southeast is particularly critical in the north central regions of Florida. ...
Article
Sesame (Sesamum indicum L.) yield response to nitrogen (N) application has been well documented, but the temporal dynamics of N accumulation and partitioning by sesame are poorly understood. Such knowledge is needed to better inform fertilization decisions and improve N use efficiency (NUE). The objective of this study was to characterize N and biomass accumulation, partitioning, and remobilization among diverse sesame cultivars grown in the humid southeastern USA. A two-year field study was conducted at the University of Florida Plant Science Research and Education Unit in Citra, Florida in 2013 and 2014. Four commercially available cultivars (S30, S32, S36, and S39) with variable maturity and branching characteristics were sampled at multiple growth stages and divided into vegetative (stalks plus leaves), reproductive (capsules plus seed), and root (only S30 and S36) components to determine biomass and N accumulation. Medium-maturing cultivars (S30 and S32) reached peak aboveground biomass accumulation at late-bloom stage and accumulated ∼5100 kg biomass ha−1 by dry down, while peak aboveground biomass accumulation for late-maturing cultivars (S36 and S39) was reached at physiological maturity and amounted to 8242–8739 kg biomass ha−1 at dry down. Cultivars reached peak N accumulation at mid-bloom (S30), late-bloom (S32 and S39), and physiological maturity (S36). Total N accumulated by cultivars ranged from70 to 99 kg N ha−1 in aboveground biomass, of which 33–60% was taken up during the reproductive growth phase. It was also estimated that 31–66% of aboveground vegetative N was remobilized to capsules and seed during reproductive growth. Root N accumulation peaked at mid-bloom stage, at which point S30 and S36 had accumulated approximately 4 kg N ha−1. Removal of N with harvested seed amounted to 29–49 kg N ha−1, with S36 removing more total N with harvest than both medium-maturing cultivars. This pattern of N accumulation suggests that plant available N has the potential to impact sesame reproductive nutrient allocation, but additional research is needed to determine if the impact of the timing of N fertilization differs among more diverse sesame maturity classes.
... Chapman (2013) argued that since most people will never learn about algae as part of their education, awareness of them would probably arise from bad direct or indirect experiences leading to everlasting negative perceptions towards them. For example, large accumulations of cast-up marine algae on beaches can impair surfers and swimmers by blocking access to the water, they can cause the presence of "nuisance" animals like crows and gulls harassing beachgoers, and can result in substantial economic losses for tourism and expensive clean-ups (Lapointe & Bedford, 2007;Williams et al., 2008). Phenomena like algal blooms and beach-cast green tides may be covered by the local and international media exclusively for their problematic effects on people and wildlife while ignoring the human roots of these phenomena (Guyomarc'h & Le Foll, 2011). ...
Article
Marine algae offer numerous extrinsic and intrinsic ecosystem services. Human impacts and climate change, however, have contributed to disrupting or compromising their ecology and distribution. Continuing research and monitoring of marine algae are pivotal but require public support. This study investigated public knowledge of and attitude towards marine algae and support for their research and monitoring. The focus was coastal users, a diversified group of interest for research into the perceptions of marine algae. The study was carried out in the Conero Riviera (Adriatic Sea, Italy), a location where coastal users come into contact with several types of marine algae. Semi-structured interviews were conducted in 2020 with 202 randomly selected scuba divers, beach and promenade visitors in the Riviera. Data analysis was thematic and statistical. Participants possessed basic knowledge of marine algae, which was more sophisticated among scuba divers. Coastal users ascribed both extrinsic and intrinsic values to marine algae. Most participants recognised the importance of protecting and managing marine algae while supported research and monitoring, prioritising types of marine algae which provide specific extrinsic and intrinsic ecosystem services. Based on the results, strategies of outreach, communication and engagement are suggested for the study location and types of coastal users. This study contributed to the growing body of research on Ocean Literacy, confirming the importance of investigating perceptions of marine resources to steer research, management and outreach strategies.
... The USA is a developed/industrialized country; it is responsible for a substantial part of publications when compared to developing countries (Meneghini et al., 2006). For instance, the USA has invested more than $20 million to mitigate the impact of eutrophication in aquatic ecosystems, mainly in areas with a potential for tourism (Lapointe & Bedford, 2007). ...
Article
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As plantas medicinais são utilizadas pelo homem desde o início da história e atualmente empregadas como recursos na medicina alternativa por grande parte da população mundial. Esse uso deve-se à facilidade de acesso às plantas em relação aos medicamentos alopáticos. O objetivo deste trabalho foi, primariamente, desenvolver uma análise cienciométrica sobre as tendências dos estudos com plantas medicinais no Brasil, investigando se o número de trabalhos cresceu ao longo dos anos. Além disso, foi identificamos as principais plantas que são estudadas pelo seu principio medicinal no Brasil. Para a pesquisa foi empregada a base de dados Scielo, com artigos de 1995 a 2011, utilizando a palavra “Planta Medicinal” como palavra-chave. Foram avaliados 329 artigos, mas somente 265 foram compatíveis à pesquisa. Artigos que não foram desenvolvidos no Brasil; que não utilizaram o termo planta medicinal; ou não citaram plantas foram excluídos das análises. Em cada artigo selecionado foram coletadas as seguintes informações: título do artigo, quantidade de autores, instituições responsáveis pelo estudo, local das instituições, ano de publicação, tipo de estudo (ex.: farmacológico, agropecuário e ecológico) e as plantas que foram estudadas. Por meio de análises desses dados foi possível verificar as tendências dos estudos com plantas medicinais no Brasil. Conforme esperado, a maior parte dos artigos avaliados estão voltados para a Farmacologia, com aplicação em diversas áreas da saúde e em segundo lugar a Agropecuária, devido ao interesse em desenvolver produtos a partir de plantas para o controle de pragas. Entretanto, verificou-se o emprego em outras áreas, como a Bioquímica, Botânica, Ecologia, Genética/Molecular e Educação que apesar de serem menos frequentes, são essenciais, pois os estudos com plantas medicinais requerem profissionais de múltiplas áreas. Além da investigação da medicina popular é necessários considerar aspectos como o isolamento, purificação, caracterização dos princípios ativos, investigação farmacológica de extratos, constituintes químicos e transformações químicas. Dentre as plantas que tiveram maior destaque nos estudos está a Hortelã (Mentha piperita L), muito utilizada pela população devido a suas ações: vermífuga, antibacteriana e anti-inflamatória.
... In the case of Garopaba bloom, the main species recorded, i.e., A. uruguayense, also shows a simple morphology with branched uniseriate filaments. Bloom formation of H. musciformis in Florida, USA has been recorded in areas where there is enrichment in organic matter (Lapointe and Bedford 2007). Dailer et al. (2012) have shown that H. musciformis is an opportunistic macroalga that can physiologically respond to excess nutrients in a similar way as Ulva spp. in areas near the coast of Maui affected by anthropogenic enrichment of nutrients. ...
Article
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Blooms of macroalgae have grown over the planet in recent decades as a possible result of eutrophication of coastal waters. Visually, a bloom forming can be identified by dominant presence of an organism at the expense of others. In mid-January 2014, a forming bloom of red algae was detected on the beach of Garopaba, Santa Catarina State, Brazil. This aroused the interest of tourists and locals as well as the scientific community. Thus, the objective of this study was to characterize and quantify the photosynthetic floating organisms contributing to this phenomenon. In addition, we qualitatively compared algal composition of the bloom to those deposited in the post-beach area and the adjacent rocky shore community. Five sampling points in random patches of floating material were defined. At each point, five replicates were taken with a cube of 32,768 cm(3), resulting in a total of 25 samples. Samples were collected in the inner area enclosed by a PVC quadrate of about 900 cm(2) from the shore and the specimens found in post-beach zone ( wrack). Twenty-four taxa of macroalgae were found in the bloom, with Aglaothamnion uruguayense as the dominance one. Ten taxa were found on shore. Only four taxa were found in the post-beach area. The biomass estimated for A. uruguayense in the floating material was 8.35 tons with an estimated area of 52,770 m(2). It is possible that this huge biomass value of the bloom is related to the local nutrient intake, and our results reinforce the necessity of coastal integrative management initiatives.
... Impacts on water quality through nitrogen recovery potential Any crops considered for the southeast must be specifically evaluated for its impacts on water quality because nutrient runoff from agriculture poses increasing threats to drinking water, recreational areas, and natural springs in these regions. This can be seen with the eutrophication conditions experienced in the Gulf of Mexico around the Mississippi River delta (Rabalais et al. 1996) as well as in Florida (Brand et al. 2010;Lapointe and Bedford 2007), for example. The issue of water quality for the southeast is particularly critical in the north central regions of Florida. ...
Article
Sesame is a new crop for the southeastern USA, most recently being considered for this region because of frequent drought events in the historical farming area of the crop, that is, Texas and Oklahoma, and for overall expansion of its domestic production. Although sesame was introduced in the USA in the 19th century, its commercial cultivation was not possible before the 1990s with the release of non-dehiscent cultivars. The southeastern USA has been considered promising because of its greater annual precipitation as compared with the southwestern USA. In addition, sesame has some highly valuable agronomic characteristics that could make the crop a beneficial addition to crop rotations in the southeast. These crop characteristics include the following: nematode resistance potential, drought tolerance, nitrogen recovery ability, rotational suitability with the predominant agronomic crops in the region, and capacity to attract a wide variety of pollinators. Since very little United States-based literature is available on the crop, the objective of this review is to provide: 1) a sesame history in the USA; 2) a description of the botanical characteristics of the crop that make it suitable for mechanized production in the USA; and 3) an overview of the principal sesame production methods of interest for the southeastern USA.
... Other studies have reported a reduction in oxygen production following changes in salinity in U. lactuca (Lartigue et al. 2003) and a decrease in growth and increase in antioxidant production from salinity stress in U. prolifera (Luo and Liu 2011). Higher nitrogen delivered as a pulse from atmospheric deposition significantly increased U. compressa growth rates, matching findings from other studies showing that a release from N limitation can enhance macroalgal growth (Lapointe and Bedford 2007;Teichberg et al. 2010). ...
Article
Global climate change has led to increased sea surface temperatures and altered precipitation patterns worldwide. Concurrently, macroalgal blooms in coastal systems have been increasing in frequency and severity globally and are successful due to their fast growth rates and broad environmental tolerances. Here, we examine the responses of the bloom-forming green algae Ulva compressa and U. lacinulata to individual and interactive effects of increased temperature and rain (divided into salinity and nitrogen effects). We assessed these impacts on the growth, photosynthetic efficiency, and tissue carbon and nitrogen content of both species. We found that temperatures ranging from 15–27 °C had no significant effect on the growth rate of either U. compressa or U. lacinulata, although both species tended to have lower growth rates after exposure to 27 °C for 3 weeks. High nitrogen, defined as a pulse of 60 µM NO3 and 20 µM NH4, enhanced the growth rate of U. compressa but not U. lacinulata and did not impact the photosynthetic efficiency of either species, although the C:N ratio revealed significant N limitation in both species. Lastly, we found the effects of temperature and rain (via added nitrogen) were not additive. Our results suggest that direct deposition of nitrogen via rain will enhance the growth of U. compressa, while increased temperatures likely will not. Together, our findings indicate that the prevalence of macroalgal blooms in coastal systems will likely increase under global climate change.
... In the absence of grazing, the growth and productivity of some -but not all -groups of macroalgae are nutrient-limited, and increase with minute increases in dissolved inorganic nutrients and particulate organic matter (Littler and Littler 2007). Macroalgae can be dominant around point sources of nutrients (Smith et al. 1981;Lapointe et al. 2004,Lapointe andBedford 2007). On the Great Barrier Reef, total macroalgal cover increases several-fold along gradients of declining water clarity and increasing nutrients (van Woesik et al. 1999;Fabricius and De'ath 2004;Fabricius et al. 2005b). ...
... Many species of macroalgae respond to increasing nutrient supply by increasing their biomass (Lapointe et al., 1994;Morand and Briand, 1996;Valiela et al., 1997). Early reports of drift algae accumulations of Gracilaria and Ulva spp. in Tampa Bay from the 1960's to the early 1980's were attributed to eutrophication within the Bay (Humm, 1973;Guist and Humm, 1976;Avery, 1997 County beaches in southwest Florida began to experience large Rhodophyte blooms which washed ashore on beaches in large quantities which was attributed to local increases in nutrient inputs (Lapointe and Bedford, 2007). While not directly toxic, these mats resulted in a variety of environmental problems including dissolved oxygen depletion, displaced species, habitat destruction, increases in arsenic and fecal coliform counts, changes in biogeochemical cycling and seagrass and coral dieoffs (Lapointe et al., 1994(Lapointe et al., , 2020McGlathery, 1995;Valiela et al., 1997;Board and National Research Council, 2000). ...
... Macroalgal blooms are occurring in greater size and frequency around the world, especially in areas experiencing increased eutrophication (Charlier et al., 2007;Hu et al., 2010;Kamer et al., 2001;Lapointe and Bedford, 2007, 2011Smith et al., 2005;Ye et al., 2011). These blooms can have a variety of effects on coastal communities. ...
... The USA is a developed/industrialized country; it is responsible for a substantial part of publications when compared to developing countries (Meneghini et al., 2006). For instance, the USA has invested more than $20 million to mitigate the impact of eutrophication in aquatic ecosystems, mainly in areas with a potential for tourism (Lapointe & Bedford, 2007). ...
Article
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Aim: Reveal the direction for future studies about eutrophication, or even reveal the preoccupation among the scientific community about this environmental problem. With a systematic synthesis of eutrophication studies, scientists may be able to understand the state of the literature on aquatic ecosystems around the world. This study intends to identify the main factors used to control algal blooms and the eutrophication process, the countries and environments which have more research about this theme or even identify the articles’ subjects in different periods (e.g.: Experimental, theoretic, monitoring, conservation). Methods We analyzed all studies published in the Thomson ISI Web of Science on both eutrophication and phytoplankton between 2001 and 2016. Results During the period analyzed, we observed an increase in concern about this subject. Authors from institutions in the USA and China wrote most of the studies. The most important geographic and socioeconomic aspects to determine the publication number were total area and HDI respectively. However, the main determinant for the publication about this subject was international collaboration. Some of the most actual themes in ecology and conservation (e.g.: functional groups, climate change, experiment, perdition models, regional scales, invasive species) were addressed in the studies analysed. Invasive species such as Tilapia and Cylindrospermopsis raciborskii were the most cited species on these keywords. Conclusion Despite the current issues addressed in the studies on phytoplankton and eutrophication, some subjects, such as climate change or spatial pattern, were only common in years more recent. Even though studies focusing in functional diversity are highly relevant for conservation, they were not common in any year studied. The major determinant factor related to the increasing in eutrophication knowledge was the international collaboration
... It is also capable of optimizing organically-derived nutrients such as urea and amino acids (e.g., Wilson, 1966;Baden and Mende, 1979;Vargo and Shanley, 1985;Shimizu and Wrensford, 1993;Steidinger et al., 1998;Gomperts, 2002). Some possible nutrient sources include Trichodesmium nitrogen fixation, zooplankton excretion, anthropogenic nutrients, benthic nutrient fluxes, nutrients from decaying fish, submarine water discharge (SGD), atmospheric deposition and mixotrophic consumption of picoplankton (e.g., Hu et al., 2006;Mulholland et al., 2006;Lapointe and Bedford, 2007;Lester et al., 2008;Vargo et al., 2008;Yentsch et al., 2008;Glibert et al., 2009;Uhlenbrock, 2009;Dixon et al., 2014;Killberg-Thoreson et al., 2014;Mulholland et al., 2014). ...
... Another large HAB resulted in the largest fish farm mortality ever recorded and a loss of USD $800 million [339]. Increased frequency of respiratory ailments, aerosolized toxins, noxious gas, dead fish, proliferation of biting sand fleas from decaying piles of macroalgae, and discolored waters drive tourists away from beaches, change recreational habits, and thus reduce income from tourism in coastal communities [393][394][395][396]. ...
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Background: Pollution – unwanted waste released to air, water, and land by human activity – is the largest environmental cause of disease in the world today. It is responsible for an estimated nine million premature deaths per year, enormous economic losses, erosion of human capital, and degradation of ecosystems. Ocean pollution is an important, but insufficiently recognized and inadequately controlled component of global pollution. It poses serious threats to human health and well-being. The nature and magnitude of these impacts are only beginning to be understood. Goals: (1) Broadly examine the known and potential impacts of ocean pollution on human health. (2) Inform policy makers, government leaders, international organizations, civil society, and the global public of these threats. (3) Propose priorities for interventions to control and prevent pollution of the seas and safeguard human health. Methods: Topic-focused reviews that examine the effects of ocean pollution on human health, identify gaps in knowledge, project future trends, and offer evidence-based guidance for effective intervention. Environmental Findings: Pollution of the oceans is widespread, worsening, and in most countries poorly controlled. It is a complex mixture of toxic metals, plastics, manufactured chemicals, petroleum, urban and industrial wastes, pesticides, fertilizers, pharmaceutical chemicals, agricultural runoff, and sewage. More than 80% arises from land-based sources. It reaches the oceans through rivers, runoff, atmospheric deposition and direct discharges. It is often heaviest near the coasts and most highly concentrated along the coasts of low- and middle-income countries. Plastic is a rapidly increasing and highly visible component of ocean pollution, and an estimated 10 million metric tons of plastic waste enter the seas each year. Mercury is the metal pollutant of greatest concern in the oceans; it is released from two main sources – coal combustion and small-scale gold mining. Global spread of industrialized agriculture with increasing use of chemical fertilizer leads to extension of Harmful Algal Blooms (HABs) to previously unaffected regions. Chemical pollutants are ubiquitous and contaminate seas and marine organisms from the high Arctic to the abyssal depths. Ecosystem Findings: Ocean pollution has multiple negative impacts on marine ecosystems, and these impacts are exacerbated by global climate change. Petroleum-based pollutants reduce photosynthesis in marine microorganisms that generate oxygen. Increasing absorption of carbon dioxide into the seas causes ocean acidification, which destroys coral reefs, impairs shellfish development, dissolves calcium-containing microorganisms at the base of the marine food web, and increases the toxicity of some pollutants. Plastic pollution threatens marine mammals, fish, and seabirds and accumulates in large mid-ocean gyres. It breaks down into microplastic and nanoplastic particles containing multiple manufactured chemicals that can enter the tissues of marine organisms, including species consumed by humans. Industrial releases, runoff, and sewage increase frequency and severity of HABs, bacterial pollution, and anti-microbial resistance. Pollution and sea surface warming are triggering poleward migration of dangerous pathogens such as the Vibrio species. Industrial discharges, pharmaceutical wastes, pesticides, and sewage contribute to global declines in fish stocks. Human Health Findings: Methylmercury and PCBs are the ocean pollutants whose human health effects are best understood. Exposures of infants in utero to these pollutants through maternal consumption of contaminated seafood can damage developing brains, reduce IQ and increase children’s risks for autism, ADHD and learning disorders. Adult exposures to methylmercury increase risks for cardiovascular disease and dementia. Manufactured chemicals – phthalates, bisphenol A, flame retardants, and perfluorinated chemicals, many of them released into the seas from plastic waste – can disrupt endocrine signaling, reduce male fertility, damage the nervous system, and increase risk of cancer. HABs produce potent toxins that accumulate in fish and shellfish. When ingested, these toxins can cause severe neurological impairment and rapid death. HAB toxins can also become airborne and cause respiratory disease. Pathogenic marine bacteria cause gastrointestinal diseases and deep wound infections. With climate change and increasing pollution, risk is high that Vibrio infections, including cholera, will increase in frequency and extend to new areas. All of the health impacts of ocean pollution fall disproportionately on vulnerable populations in the Global South – environmental injustice on a planetary scale. Conclusions: Ocean pollution is a global problem. It arises from multiple sources and crosses national boundaries. It is the consequence of reckless, shortsighted, and unsustainable exploitation of the earth’s resources. It endangers marine ecosystems. It impedes the production of atmospheric oxygen. Its threats to human health are great and growing, but still incompletely understood. Its economic costs are only beginning to be counted. Ocean pollution can be prevented. Like all forms of pollution, ocean pollution can be controlled by deploying data-driven strategies based on law, policy, technology, and enforcement that target priority pollution sources. Many countries have used these tools to control air and water pollution and are now applying them to ocean pollution. Successes achieved to date demonstrate that broader control is feasible. Heavily polluted harbors have been cleaned, estuaries rejuvenated, and coral reefs restored. Prevention of ocean pollution creates many benefits. It boosts economies, increases tourism, helps restore fisheries, and improves human health and well-being. It advances the Sustainable Development Goals (SDG). These benefits will last for centuries. Recommendations: World leaders who recognize the gravity of ocean pollution, acknowledge its growing dangers, engage civil society and the global public, and take bold, evidence-based action to stop pollution at source will be critical to preventing ocean pollution and safeguarding human health. Prevention of pollution from land-based sources is key. Eliminating coal combustion and banning all uses of mercury will reduce mercury pollution. Bans on single-use plastic and better management of plastic waste reduce plastic pollution. Bans on persistent organic pollutants (POPs) have reduced pollution by PCBs and DDT. Control of industrial discharges, treatment of sewage, and reduced applications of fertilizers have mitigated coastal pollution and are reducing frequency of HABs. National, regional and international marine pollution control programs that are adequately funded and backed by strong enforcement have been shown to be effective. Robust monitoring is essential to track progress. Further interventions that hold great promise include wide-scale transition to renewable fuels; transition to a circular economy that creates little waste and focuses on equity rather than on endless growth; embracing the principles of green chemistry; and building scientific capacity in all countries. Designation of Marine Protected Areas (MPAs) will safeguard critical ecosystems, protect vulnerable fish stocks, and enhance human health and well-being. Creation of MPAs is an important manifestation of national and international commitment to protecting the health of the seas.
... Early reports of drift algae accumulations of Gracilaria and Ulva spp. in Tampa Bay from the 1960's to the early 1980's were attributed to eutrophication within the Bay (Humm, 1973;Guist and Humm, 1976;Avery, 1997). In 2003-2004 County beaches in southwest Florida began to experience large Rhodophyte blooms which washed ashore on beaches in large quantities which was attributed to local increases in nutrient inputs (Lapointe and Bedford, 2007). While not directly toxic, these mats resulted in a variety of environmental problems including dissolved oxygen depletion, displaced species, habitat destruction, increases in arsenic and fecal coliform counts, changes in biogeochemical cycling and seagrass and coral dieoffs (Lapointe et al., 1994(Lapointe et al., , 2020McGlathery, 1995;Valiela et al., 1997;Board and National Research Council, 2000). ...
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Harmful Algal Blooms (HABs) pose unique risks to the citizens, stakeholders, visitors, environment and economy of the state of Florida. Florida has been historically subjected to reoccurring blooms of the toxic marine dinoflagellate Karenia brevis (C. C. Davis) G. Hansen & Moestrup since at least first contact with explorers in the 1500’s. However, ongoing immigration of more than 100,000 people year –1 into the state, elevated population densities in coastal areas with attendant rapid, often unregulated development, coastal eutrophication, and climate change impacts (e.g., increasing hurricane severity, increases in water temperature, ocean acidification and sea level rise) has likely increased the occurrence of other HABs, both freshwater and marine, within the state as well as the number of people impacted by these blooms. Currently, over 75 freshwater, estuarine, coastal and marine HAB species are routinely monitored by state agencies. While only blooms of K. brevis , the dinoflagellate Pyrodinium bahamense (Böhm) Steidinger, Tester, and Taylor and the diatom Pseudo-nitzschia spp. have resulted in closure of commercial shellfish beds, other HAB species, including freshwater and marine cyanobacteria, pose either imminent or unknown risks to human, environmental and economic health. HAB related human health risks can be classified into those related to consumption of contaminated shellfish and finfish, consumption of or contact with bloom or toxin contaminated water or exposure to aerosolized HAB toxins. While acute human illnesses resulting from consumption of brevetoxin-, saxitoxin-, and domoic acid-contaminated commercial shellfish have been minimized by effective monitoring and regulation, illnesses due to unregulated toxin exposures, e.g., ciguatoxins and cyanotoxins, are not well documented or understood. Aerosolized HAB toxins potentially impact the largest number of people within Florida. While short-term (days to weeks) impacts of aerosolized brevetoxin exposure are well documented (e.g., decreased respiratory function for at-risk subgroups such as asthmatics), little is known of longer term (>1 month) impacts of exposure or the risks posed by aerosolized cyanotoxin [e.g., microcystin, β- N -methylamino- L -alanine (BMAA)] exposure. Environmental risks of K. brevis blooms are the best studied of Florida HABs and include acute exposure impacts such as significant dies-offs of fish, marine mammals, seabirds and turtles, as well as negative impacts on larval and juvenile stages of many biota. When K. brevis blooms are present, brevetoxins can be found throughout the water column and are widespread in both pelagic and benthic biota. The presence of brevetoxins in living tissue of both fish and marine mammals suggests that food web transfer of these toxins is occurring, resulting in toxin transport beyond the spatial and temporal range of the bloom such that impacts of these toxins may occur in areas not regularly subjected to blooms. Climate change impacts, including temperature effects on cell metabolism, shifting ocean circulation patterns and changes in HAB species range and bloom duration, may exacerbate these dynamics. Secondary HAB related environmental impacts are also possible due to hypoxia and anoxia resulting from elevated bloom biomass and/or the decomposition of HAB related mortalities. Economic risks related to HABs in Florida are diverse and impact multiple stakeholder groups. Direct costs related to human health impacts (e.g., increased hospital visits) as well as recreational and commercial fisheries can be significant, especially with wide-spread sustained HABs. Recreational and tourism-based industries which sustain a significant portion of Florida’s economy are especially vulnerable to both direct (e.g., declines in coastal hotel occupancy rates and restaurant and recreational users) and indirect (e.g., negative publicity impacts, associated job losses) impacts from HABs. While risks related to K. brevis blooms are established, Florida also remains susceptible to future HABs due to large scale freshwater management practices, degrading water quality, potential transport of HABs between freshwater and marine systems and the state’s vulnerability to climate change impacts.
... Coastal industries regularly battle with the 'marine ingress problem' (Purcell, 2005;Flynn and Chapra, 2014). Marine ingress predominantly forms as large aggregations of jellyfish and submerged aquatic vegetation (Lapointe and Bedford, 2007;Kim et al., 2012), although other less conspicuous forms do exist as well (Maclsaac, 1996). Coastal industries such as desalination plants and nuclear power stations often require large volumes of water to operate; water intakes at these coastal locations can get clogged during marine ingress events, resulting in reduced productivity (Kim et al., 2012). ...
Article
From the shutting down of coastal tourism industries, the mass destruction of aquaculture, to the clogging of power station water intakes, marine ingress events have the potential to cause widespread disruption along our coastlines. To gain the ability to respond to such events, efforts are being made to advance the understanding of bloom events which predominantly present as large aggregations of jellyfish, or detached aquatic macroalgaes in the water column. This paper investigates the optimal flight search patterns with a focus on marine ingress bloom detection from unmanned aircraft systems (UAS). The detection performance of four flight search patterns are examined against five different bloom shapes. Monte-Carlo simulations are deployed to assess probable performance of flight search pattern against variable bloom shapes. A total of 50,000 simulated flights were conducted, offering a maximum of 500 million marine ingress objects for possible detection. A two phased flight approach is proposed, with first phase flights conducted as area search strategies, and second phase flights as datum searches for scenarios where some information of possible bloom location is available. Parallel sweep was found to be the best performing generalist flight search pattern, closely followed by the phase two search pattern expanding square. Crossing barrier was found to be competitive but appeared to lend itself towards specific detection scenarios with sector search being a consistently poor performing flight search pattern. This paper also investigates the comparative performance of visual line of sight (VLOS), extended visual line of sight (EVLOS), and beyond visual line of sight (BVLOS) operations. Increase of total survey area was found to increase bloom detection frequency, with BVLOS operations the highest performer successfully increasing bloom detection by a factor of 3.7. This paper exhibits the first assessment of flight search patterns within the context of drone-based detection of marine ingress bloom events. This should facilitate the development of an early warning detection system that can provide reliable warning to coastal industries prior to a marine ingress event occurring.
... Interest in A. clathratum and other seaweed species has risen recently due to its immunomodulatory and antioxidant activities [4][5][6]. However, increasing masses of seaweed waste have been reported worldwide due to climate change and eutrophication by fertilizer runoff [7,8]. A large amount of seaweed wastes are deposited on the shores of Korea peninsula [9], and A. clathratum mass in particular has accumulated on the northeast coast of Korea causing serious environmental problems. ...
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Agarum clathratum, a brown macroalgae species, has recently become a serious environmental problem on the coasts of Korea. In an effort to solve this problem, fungal diversity associated with decaying A. clathratum was investigated and related β-glucosidase and endoglucanase activities were described. A total of 233 fungal strains were isolated from A. clathratum at 15 sites and identified 89 species based on morphology and a multigene analysis using the internal transcribed spacer region (ITS) and protein-coding genes including actin (act), β-tubulin (benA), calmodulin (CaM), and translation elongation factor (tef1). Acremonium, Corollospora, and Penicillium were the dominant genera, and Acremonium fuci and Corollospora gracilis were the dominant species. Fifty-one species exhibited cellulase activity, with A. fuci, Alfaria terrestris, Hypoxylon perforatum, P. madriti, and Pleosporales sp. Five showing the highest enzyme activities. Further enzyme quantification confirmed that these species had higher cellulase activity than P. crysogenum, a fungal species described in previous studies. This study lays the groundwork for bioremediation using fungi to remove decaying seaweed from populated areas and provides important background for potential industrial applications of environmentally friendly processes.
... In addition to land use land cover changes, the population along the southwest coast of Florida has increased 10-40-fold during the past half century. There have also been significant increases in the past few decades in nutrient and chlorophyll concentrations (Turner et al. 2006) and in macroalgal abundance in these coastal waters (Lapointe and Bedford 2007). ...
Article
The appearance of Karenia brevis red tides in the Gulf of Mexico have been studied widely in terms of its negative effects on marine life at various trophic levels. In this study, the long-term spatial and temporal patterns of Karenia brevis were analyzed along the western shelf of the Florida peninsula, where they were found to be primarily clustered. A variety of geospatial techniques were used to reveal the location dynamics of the presence of the algae. The spatial patterns of the blooms exhibited a predominantly northwest to southeast orientation along Florida’s western shelf. At the decadal scale, the spatial mean centers of the dinoflagellate were clustered along the western shelf from Tampa Bay to just south of the Caloosahatchee River Basin. In order to analyze the change in the spatial concentrations of Karenia brevis, we utilized Emerging Hot Spots Analysis. The results indicated the concentration of the bloom’s hotspots to be sporadic, meaning variable hotspots over the years, though not statistically significant. However, the results of Hot Spots Cold Spots analysis at the individual annual scale revealed the location of statistically significant hotspots along the western shelf with variable locations. In addition, we conducted all of the geospatial analysis at different depth categories. The results demonstrated substantial differences in the spatial and temporal patterns between the shallow (less than 6.831 m) and deep (greater than 6.831 m) depths. For instance, the shallow depth presence points were clustered in the Tampa Bay area, while the deep presence points were found in smaller clusters further north along Florida’s west coast. These results imply that underlying physical or biological factors are responsible for annual changes in bloom prevalence, such as the presence and origination of upwelling in the region. The presence of less frequent deep-ocean upwelling shifts nutrient acquisition in favor of faster growing phytoplankton like diatoms over slow growing dinoflagellates such as Karenia brevis, which require wind-driven upwelling to bolster blooms.
... Macroalgae (seaweeds) also cause significant problems. Over the past several decades, blooms of macroalgae have been increasing along many of the world's coastlines (e.g., Lapointe and Bedford, 2007;Keesing et al., 2011;Wang et al., 2019). These have a broad range of ecological effects and can affect human health as well through the production of H 2 S as the biomass washed onto shorelines decays. ...
Article
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Harmful algal blooms (HABs) are diverse phenomena involving multiple. species and classes of algae that occupy a broad range of habitats from lakes to oceans and produce a multiplicity of toxins or bioactive compounds that impact many different resources. Here, a review of the status of this complex array of marine HAB problems in the U.S. is presented, providing historical information and trends as well as future perspectives. The study relies on thirty years (1990–2019) of data in HAEDAT - the IOC-ICES-PICES Harmful Algal Event database, but also includes many other reports. At a qualitative level, the U.S. national HAB problem is far more extensive than was the case decades ago, with more toxic species and toxins to monitor, as well as a larger range of impacted resources and areas affected. Quantitatively, no significant trend is seen for paralytic shellfish toxin (PST) events over the study interval, though there is clear evidence of the expansion of the problem into new regions and the emergence of a species that produces PSTs in Florida – Pyrodinium bahamense. Amnesic shellfish toxin (AST) events have significantly increased in the U.S., with an overall pattern of frequent outbreaks on the West Coast, emerging, recurring outbreaks on the East Coast, and sporadic incidents in the Gulf of Mexico. Despite the long historical record of neurotoxic shellfish toxin (NST) events, no significant trend is observed over the past 30 years. The recent emergence of diarrhetic shellfish toxins (DSTs) in the U.S. began along the Gulf Coast in 2008 and expanded to the West and East Coasts, though no significant trend through time is seen since then. Ciguatoxin (CTX) events caused by Gambierdiscus dinoflagellates have long impacted tropical and subtropical locations in the U.S., but due to a lack of monitoring programs as well as under-reporting of illnesses, data on these events are not available for time series analysis. Geographic expansion of Gambierdiscus into temperate and non-endemic areas (e.g., northern Gulf of Mexico) is apparent, and fostered by ocean warming. HAB-related marine wildlife morbidity and mortality events appear to be increasing, with statistically significant increasing trends observed in marine mammal poisonings caused by ASTs along the coast of California and NSTs in Florida. Since their first occurrence in 1985 in New York, brown tides resulting from high-density blooms of Aureococcus have spread south to Delaware, Maryland, and Virginia, while those caused by Aureoumbra have spread from the Gulf Coast to the east coast of Florida. Blooms of Margalefidinium polykrikoides occurred in four locations in the U.S. from 1921–2001 but have appeared in more than 15 U.S. estuaries since then, with ocean warming implicated as a causative factor. Numerous blooms of toxic cyanobacteria have been documented in all 50 U.S. states and the transport of cyanotoxins from freshwater systems into marine coastal waters is a recently identified and potentially significant threat to public and ecosystem health. Taken together, there is a significant increasing trend in all HAB events in HAEDAT over the 30-year study interval. Part of this observed HAB expansion simply reflects a better realization of the true or historic scale of the problem, long obscured by inadequate monitoring. Other contributing factors include the dispersion of species to new areas, the discovery of new HAB poisoning syndromes or impacts, and the stimulatory effects of human activities like nutrient pollution, aquaculture expansion, and ocean warming, among others. One result of this multifaceted expansion is that many regions of the U.S. now face a daunting diversity of species and toxins, representing a significant and growing challenge to resource managers and public health officials in terms of toxins, regions, and time intervals to monitor, and necessitating new approaches to monitoring and management. Mobilization of funding and resources for research, monitoring and management of HABs requires accurate information on the scale and nature of the national problem. HAEDAT and other databases can be of great value in this regard but efforts are needed to expand and sustain the collection of data regionally and nationally.
... Macroalgal blooms are widely reported and are increasing in size and frequency around the world, especially in areas experiencing increased eutrophication (Charlier et al. 2007;Burke et al. 2011;Hu et al. 2010;Kamer et al. 2001;Lapointe and Bedford 2007Smith et al. 2005; van Hees and Van Alstyne 2013; Ye et al. 2011;Charlier et al. 2007), which is regarded as the general cause of most green-tide events in oceanic ecosystems worldwide Liu et al. 2009;Morand and Merceron 2005). Excessive growth of macroalgae is a response to a given biotope, to a supply, probably an oversupply, of nutrients of natural or anthropogenic origin; if anthropogenic, this may be the result of an environmental disturbance (Morand and Merceron 2005). ...
Article
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An increase in the human population has caused eutrophication in shore water due to the release of nitrogen and phosphorus. Green tides caused by the proliferation of green macroalgae are an important direct consequence of eutrophication worldwide. We studied the nutrient uptake rate (NUR) and the expression of nutrient transporter genes in the green alga Ulva linza, an alga which forms green tides almost every summer in the Yellow Sea, and identified 6 nutrient transporter genes which contributed to the uptake of ammonium, nitrate, and phosphorus. Two environmental conditions, temperature and nutrient concentration, were found to significantly influence the NUR and gene expression of nutrient transporters. The optimum concentrations for uptake of ammonium, nitrate, and phosphorus were 1398.7, 710.4, and 230.7 μmol L−1 respectively, while the optimum temperature was 15 °C. Six nutrient transporter genes (amt1, amt2, and amt3 for ammonium uptake, nit for nitrate uptake, hapt, and lapt for phosphorus) were found to have an optimal working environment in terms of temperature and nutrient concentration, respectively.
... During bloom decomposition, macroinvertebrate abundance declines (Cummins et al. 2004) and dissolved organic nitrogen is re leased into the water column (Tyler et al. 2001), which can fuel further primary production (reviewed by Raffaelli et al. 1998). Macroalgal blooms are also costly to clean up (Atkins et al. 1993, Lapointe & Bedford 2007. ...
Article
ABSTRACT: Macroalgal blooms have increased in frequency worldwide due to anthropogenic activities. Algal blooms can disrupt recreational activities, interfere with fisheries, and deplete oxygen during decomposition. Narragansett Bay has experienced macroalgal blooms dominated by blade-forming Ulva for over a century. Evidence from other systems has suggested that Ulva can negatively impact other organisms. The first objective of this study was to determine whether bloom-forming U. compressa and U. rigida inhibit the growth of co-occurring macroalgae—Gracilaria vermiculophylla, Cystoclonium purpureum, and Chondrus crispus—during co-culture via laboratory-based assays. We found that U. compressa and U. rigida significantly inhibited the growth of all 3 macroalgae. We were able to verify the negative effects of U. compressa, but not U. rigida, on the growth of G. vermiculophylla in flow-through seawater tanks. Our second objective was to determine if Ulva exudate decreased the survival of eastern oyster larvae in laboratory challenge experiments. We documented a significant negative effect of Ulva exudate on oyster survival, which depended on both the Ulva species and the nutrient condition. The strongest effect on oyster larval survival was seen in larvae exposed to nutrient-replete Ulva compressa exudate, which had <30% relative survival after 1 wk. Our results indicate that bloom-forming Ulva has the potential to inhibit co-occurring macroalgae and cause oyster larval mortality.
... Another large HAB resulted in the largest fish farm mortality ever recorded and a loss of USD $800 million [339]. Increased frequency of respiratory ailments, aerosolized toxins, noxious gas, dead fish, proliferation of biting sand fleas from decaying piles of macroalgae, and discolored waters drive tourists away from beaches, change recreational habits, and thus reduce income from tourism in coastal communities [393][394][395][396]. ...
Article
Full-text available
Background: Pollution – unwanted waste released to air, water, and land by human activity – is the largest environmental cause of disease in the world today. It is responsible for an estimated nine million premature deaths per year, enormous economic losses, erosion of human capital, and degradation of ecosystems. Ocean pollution is an important, but insufficiently recognized and inadequately controlled component of global pollution. It poses serious threats to human health and well-being. The nature and magnitude of these impacts are only beginning to be understood. Goals: (1) Broadly examine the known and potential impacts of ocean pollution on human health. (2) Inform policy makers, government leaders, international organizations, civil society, and the global public of these threats. (3) Propose priorities for interventions to control and prevent pollution of the seas and safeguard human health. Methods: Topic-focused reviews that examine the effects of ocean pollution on human health, identify gaps in knowledge, project future trends, and offer evidence-based guidance for effective intervention. Environmental Findings: Pollution of the oceans is widespread, worsening, and in most countries poorly controlled. It is a complex mixture of toxic metals, plastics, manufactured chemicals, petroleum, urban and industrial wastes, pesticides, fertilizers, pharmaceutical chemicals, agricultural runoff, and sewage. More than 80% arises from land-based sources. It reaches the oceans through rivers, runoff, atmospheric deposition and direct discharges. It is often heaviest near the coasts and most highly concentrated along the coasts of low- and middle-income countries. Plastic is a rapidly increasing and highly visible component of ocean pollution, and an estimated 10 million metric tons of plastic waste enter the seas each year. Mercury is the metal pollutant of greatest concern in the oceans; it is released from two main sources – coal combustion and small-scale gold mining. Global spread of industrialized agriculture with increasing use of chemical fertilizer leads to extension of Harmful Algal Blooms (HABs) to previously unaffected regions. Chemical pollutants are ubiquitous and contaminate seas and marine organisms from the high Arctic to the abyssal depths. Ecosystem Findings: Ocean pollution has multiple negative impacts on marine ecosystems, and these impacts are exacerbated by global climate change. Petroleum-based pollutants reduce photosynthesis in marine microorganisms that generate oxygen. Increasing absorption of carbon dioxide into the seas causes ocean acidification, which destroys coral reefs, impairs shellfish development, dissolves calcium-containing microorganisms at the base of the marine food web, and increases the toxicity of some pollutants. Plastic pollution threatens marine mammals, fish, and seabirds and accumulates in large mid-ocean gyres. It breaks down into microplastic and nanoplastic particles containing multiple manufactured chemicals that can enter the tissues of marine organisms, including species consumed by humans. Industrial releases, runoff, and sewage increase frequency and severity of HABs, bacterial pollution, and anti-microbial resistance. Pollution and sea surface warming are triggering poleward migration of dangerous pathogens such as the Vibrio species. Industrial discharges, pharmaceutical wastes, pesticides, and sewage contribute to global declines in fish stocks. Human Health Findings: Methylmercury and PCBs are the ocean pollutants whose human health effects are best understood. Exposures of infants in utero to these pollutants through maternal consumption of contaminated seafood can damage developing brains, reduce IQ and increase children’s risks for autism, ADHD and learning disorders. Adult exposures to methylmercury increase risks for cardiovascular disease and dementia. Manufactured chemicals – phthalates, bisphenol A, flame retardants, and perfluorinated chemicals, many of them released into the seas from plastic waste – can disrupt endocrine signaling, reduce male fertility, damage the nervous system, and increase risk of cancer. HABs produce potent toxins that accumulate in fish and shellfish. When ingested, these toxins can cause severe neurological impairment and rapid death. HAB toxins can also become airborne and cause respiratory disease. Pathogenic marine bacteria cause gastrointestinal diseases and deep wound infections. With climate change and increasing pollution, risk is high that Vibrio infections, including cholera, will increase in frequency and extend to new areas. All of the health impacts of ocean pollution fall disproportionately on vulnerable populations in the Global South – environmental injustice on a planetary scale. Conclusions: Ocean pollution is a global problem. It arises from multiple sources and crosses national boundaries. It is the consequence of reckless, shortsighted, and unsustainable exploitation of the earth’s resources. It endangers marine ecosystems. It impedes the production of atmospheric oxygen. Its threats to human health are great and growing, but still incompletely understood. Its economic costs are only beginning to be counted. Ocean pollution can be prevented. Like all forms of pollution, ocean pollution can be controlled by deploying data-driven strategies based on law, policy, technology, and enforcement that target priority pollution sources. Many countries have used these tools to control air and water pollution and are now applying them to ocean pollution. Successes achieved to date demonstrate that broader control is feasible. Heavily polluted harbors have been cleaned, estuaries rejuvenated, and coral reefs restored. Prevention of ocean pollution creates many benefits. It boosts economies, increases tourism, helps restore fisheries, and improves human health and well-being. It advances the Sustainable Development Goals (SDG). These benefits will last for centuries. Recommendations: World leaders who recognize the gravity of ocean pollution, acknowledge its growing dangers, engage civil society and the global public, and take bold, evidence-based action to stop pollution at source will be critical to preventing ocean pollution and safeguarding human health. Prevention of pollution from land-based sources is key. Eliminating coal combustion and banning all uses of mercury will reduce mercury pollution. Bans on single-use plastic and better management of plastic waste reduce plastic pollution. Bans on persistent organic pollutants (POPs) have reduced pollution by PCBs and DDT. Control of industrial discharges, treatment of sewage, and reduced applications of fertilizers have mitigated coastal pollution and are reducing frequency of HABs. National, regional and international marine pollution control programs that are adequately funded and backed by strong enforcement have been shown to be effective. Robust monitoring is essential to track progress. Further interventions that hold great promise include wide-scale transition to renewable fuels; transition to a circular economy that creates little waste and focuses on equity rather than on endless growth; embracing the principles of green chemistry; and building scientific capacity in all countries. Designation of Marine Protected Areas (MPAs) will safeguard critical ecosystems, protect vulnerable fish stocks, and enhance human health and well-being. Creation of MPAs is an important manifestation of national and international commitment to protecting the health of the seas.
... Another large HAB resulted in the largest fish farm mortality ever recorded and a loss of USD $800 million [339]. Increased frequency of respiratory ailments, aerosolized toxins, noxious gas, dead fish, proliferation of biting sand fleas from decaying piles of macroalgae, and discolored waters drive tourists away from beaches, change recreational habits, and thus reduce income from tourism in coastal communities [393][394][395][396]. ...
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Chapter
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We examined whether delta(15)N levels of marine biota with different nutrient uptake characteristics can be used to trace the dispersal of sewage effluent in highly mixed, nitrogen-limited waters, and whether they can reveal the dispersal of sewage over different timescales. We hypothesised that macroalgal species with fast uptake rates would display a spatial pattern in 615 N levels reflecting recent sewage dispersal while those with slower rates would provide a signal integrated over a longer time period. Filter-feeding sponges and ascidians were also sampled to see if they reflected patterns in the dispersal of sewage particulate organic matter (POM). A laboratory experiment was performed to test whether the 515 N level of 3 macroalgal species (Ulva australis, Vidalia sp, and Ecklonia radiata) and 2 filter-feeding species (Clathria sp. and Pyura australis) was altered after cultivation in sewage nitrogen. We then sampled each organism along transects radiating away from the outlet of a wastewater treatment plant north of Perth, Western Australia, to determine spatial patterns in delta(15)N. U. australis and Vidalia sp. developed higher isotopic signatures when exposed to low concentrations of sewage nitrogen (1:500 dilution in seawater) for 7 d in the laboratory, U, australis and Vidalia sp. showed an increase of 1.7 and 1.4parts per thousand in treatments respectively. In the field, macroalgae sampled north and south of the sewage outlet generally had higher delta(15)N levels than those sampled west of the outlet and at the reference site, and algae within 500 m of the outfall tended to have lower values than at 1000 m or more from the outfall, These trends are consistent with our current knowledge of plume dynamics: a predominantly northerly drift of effluent as a buoyant plume that tends not to be fully mixed in the water column for the first 500 m. The results confirmed that the delta(15)N signature of macroalgae could be used to trace sewage disposed in well-mixed waters. The strength of the spatial trends varied between algae, with E. radiata, the species with the lowest nutrient uptake rates and affinity, having the least spatial variability. We interpret this as reflecting a wider regional dispersal of sewage in the longer time frame, but a strong northerly drift in the short term, which was reflected in the delta(15)N values of the species with the fastest nitrogen uptake rates. The results were consistent with our hypothesis and are suggestive of a relationship between algal functional form and isotopic signatures that can be applied to determine the dispersal of sewage over different timescales. The delta(15)N values of benthic filter feeders did not provide strong evidence to suggest that they can be used to represent the dispersal of sewage POM, but trends found in the field experiment for Clathria sp. warrant further investigation.
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We examined spatial trends in ratios of stable isotopes of nitrogen (delta N-15), carbon (delta C-13), and sulfur (delta S-34) in riparian food webs leading to a riparian, insectivorous bird species, the tree swallow (Tachycineta bicolor), on rivers receiving pulp-mill effluent and municipal sewage and compared them with ratios of these isotopes in components of the effluents themselves. The study was conducted on two rivers in western Canada at sites upstream and downstream from sewage and pulp mill effluent sources. Municipal sewage contained materials with delta N-15 or delta C-13 values that were distinct from background conditions in the receiving environment. Pulp-mill effluent contained materials with delta S-34 values that were distinct from those at upstream sites on the rivers. At both locations, effluent-derived nitrogen and sulfur were observed in algae and suspended sediments at sites downstream from the effluent sources. This was also observed in adult aquatic insects, the one exception bring that uptake of effluent-derived nitrogen was detected isotopically at only one location. Tree swallows' use of sewage-derived nitrogen was evident only at one location, while use of pulp-mill-derived sulfur was evident only at the other location. Our study demonstrates the usefulness and limitations of measuring stable isotopes for tracing the movement of nutrients derived from sewage and pulp-mill effluent in freshwater ecosystems and, further, indicates that such tracing may be extended to riparian species feeding on aquatic prey.
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Excessive human-derived nutrient availability has been implicated as a primary driver in the decline of the water quality and biota of coastal ecosystems. In 2003, seven sites along an urbanized section (∼100 km) of the Atlantic littoral coastline in east-central Florida were assessed for the bio-availability of the primary nutrients nitrogen and phosphorus. Ratios of dissolved inorganic nitrogen (DIN = nitrate + nitrite + ammonium) to soluble reactive phosphorus (SRP) in 74 beach water samples averaged 8:1, indicating strong water column nitrogen-limitation. DIN concentrations ranged from 0.69 to 8.11 µM with a grand mean of 2.10 µM, a value two-fold above the reported threshold value of ∼1 µM that saturates growth of Florida red tide, Karenia brevis and macroalgae species utilized in this study, such as Ulva lactuca. The majority (mean = 56%) of this DIN was in the form of ammonium, even during a peak upwelling event in June and August, suggesting the importance of anthropogenic land-based nitrogen as the primary N source. Macroalgae from subtidal sabellariid worm reefs were assessed for δ15N. At all study sites, macroalgal tissue mean δ15N values ranged from +8.7 to +9.9‰, values similar to those in macroalgae from sewage-polluted coastal areas, such as Boston Harbor. Many of the abundant macroalgae collected on these reefs, including Ulva lactuca, Chaetomorpha linum, Gracilaria tikvihae, and Caulerpa prolifera, are known sewage indicator species in other eutrophic coastal water bodies receiving excessive anthropogenic nutrient loads. These results suggest the need for improved nutrient removal in wastewater treatment facilities that discharge nearly 100 million liters of secondary-treated sewage effluent/day into the highly transmissive silica-sand barrier island of Brevard and Indian River Counties in east-central Florida.
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1] A Karenia brevis Harmful Algal Bloom affected coastal waters shallower than 50 m off west-central Florida from January 2005 through January 2006, showing a sustained anomaly of $1 mg chlorophyll m À3 over an area of up to 67,500 km 2 . Red tides occur in the same area (approximately 26– 29°N, 82– 83°W) almost every year, but the intense 2005 bloom led to a widespread hypoxic zone (dissolved oxygen <2 mg L À1) that caused mortalities of benthic communities, fish, turtles, birds, and marine mammals. Runoff alone provided insufficient nitrogen to support this bloom. We pose the hypothesis that submarine groundwater discharge (SGD) provides the missing nutrients, and indeed can trigger and support the recurrent red tides off west-central Florida. SGD inputs of dissolved inorganic nitrogen (DIN) in Tampa Bay alone are $35% of that discharged by all central Florida rivers draining west combined. We propose that the unusual number of hurricanes in 2004 resulted in high runoff, and in higher than normal SGD emerging along the west Florida coast throughout 2005, initiating and fueling the persistent HAB. This mechanism may also explain recurrent red tides in other coastal regions of the Gulf of Mexico.
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The sources and distribution of nutrients in the Charlotte Harbor estuarine system were evaluated using nutrient dilution curve models. Except for ammonia, nutrient concentrations were highest and most variable in the rivers, and generally decreased with increasing salinity. Observed and theoretical dilution curves for phosphorus were generally in close agreement, which suggests conservative behavior. Phosphorus concentrations sagged below a straight line because phosphorus-rich water from the upper Peace River basin was diluted by tributaries in the lower basin. The concentrations of dissolved silica appeared to be conservative on some occasions. On other occasions, dissolved silica appeared to be removed at low salimties or released at higher salinities. Concentrations of ammonia were highly variable along the salinity gradient, presumably because of variations in ammonia regeneration and uptake. Concentrations of nitrite plus nitrate were well below conservative dilution curves, probably due to phy-toplankton uptake. At salinities greater than 20%, nitrite plus nitrate concentrations were usually at or below the detection limit and may limit phytoplankton productivity. Projected increased nitrogen loadings from urban development in the basin would favor undesirable increases in phytoplankton and benthic algal growth in waters where sufficient light is available.
Chapter
The use of radioisotopes and rare stable isotopes in field investigations of plankton nutrition both in lakes and the ocean is now widely practiced. The introduction of the 14C technique to measure phytoplankton photosynthesis (1) revolutionized the study of aquatic primary productivity. The use of 32P in plankton studies has received less attention (2,3,4), and more recently 15N has proven to be a useful tool (5,6). The literature of the last two decades which includes various applications of these isotopes in studies of aquatic biology is heavily burdened by discussions of problems in experimental design and data interpretation (7,8,9,10). In general the application of such techniques to aquatic biology has progressed more slowly than in other fields of study, and ecologists have been criticized (11) for their naive and often erroneous use of isotopes in studies of transfer processes within aquatic ecosystems. Recently, innovative applications of isotope tracer studies to
Chapter
Study of natural variation in 15N can provide information on biogeochemical, physical, physiological and biochemical investigations. Following considerations of measurement, isotope effects and fractionation, comments are made on 15N in the atmospheric, terrestrial, freshwater, estuarine and marine compartments; sources; and food chain dynamics. -P.J.Jarvis
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Pollution of the hydrosphere and atmosphere by compounds of nitrogen is a serious problem. This paper reviews the manner in which studies of natural abundance 15N/14N ratios may be employed in investigating the sources and mechanisms of pollution.Cultivation-induced mineralization of soil nitrogen, fertilizer, and animal or sewage wastes are the three main sources of nitrate pollution in the hydrosphere. In many cases these sources produce nitrate with distinguishable 15N/14N ratios, and on this basic isotopic data for nitrate have been successfully used for identifying the source of pollution in a wide variety of ground- and surface water environments. Distinction between continentally- and marine-derived organic nitrogen in ecologically sensitive coastal waters also appears possible. These differences in 15N/14N ratios, however, are largely the result of kinetic isotope fractionation associated with bacterially-mediated reactions. The unpredictable magnitude of this type of fractionation tends to restrict the use of nitrogen isotope data in the hydrosphere to semi-quantitative interpretations.Observations of the isotopic fractionation between nitrogen compounds in the atmosphere may provide valuable information on whether their physico-chemical reactions are controlled by kinetic or by equilibrium processes. The possibility of using 15N/14N data for distinguishing between anthropogenic and natural sources of NOx gases, potentially a very important application, is as yet unproven.
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We measured the C/N ratio and δ15 N values of two brown macroalgae— Padina spp. and Dictyota sp., which are distributed over all the subtropical fringing reefs of the Ryukyu Islands, Japan—to evaluate the feasibility of these algae as indicators of the terrestrial nitrogen load to the reef. The correlations between the distance from the shoreline and algal C/N ratio and surrounding NO concentrations were not clear, although their average values among the 2 3 reefs seemed to indicate differences in nitrogen loadings from the land. The δ15 N values of these algae, on the other hand, linearly or curvilinearly decreased from 18‰ to 12‰ with increasing distance from the shoreline, indicating the difference in nitrogen sources available to macroalgae. The slope of the decline among eight study areas had different characters, which seemed to depend on the residence time of reef seawater and the fluxes of terrestrial nitrogen. Using δ15 N values of brown algae as an indicator, we confirmed that primary producers, such as macroalgae on the reefs, assimilated land-derived nitrogen and successfully evaluated time-integrated effects of terrestrial ni- trogen on coral reef algae, which had been missed by conventional monitoring of the water column nutrients.
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We reconstructed water quality changes for 1800 to 2000 in Charlotte Harbor (Florida), a shallow subtropical estuary, by using a suite of biological and geochemical proxies in dated sediments collected in the region of a present day, midsummer hypoxic zone. The declining freshwater loading into the estuary from 1931 to the 1980s is not the probable causal agent encouraging the appearance or expansion of a hypoxia zone (measuring up to 90 km 2 in summer). Rather, the reconstructed trends in nitrogen loading indicate increased phytoplankton production has likely caused a decline in bottom water oxygen concentrations. Sedimentary biogenic silica (BSi), carbon, nitrogen, and phosphorus concentrations increased concurrently with known or inferred changes in nutrient loadings. There were direct relationships between phytoplankton pigments and BSi, heavier d 34 S with increased carbon load- ing, and sequestration of P, Al, and Fe as carbon loading increased. The results from the sediment analyses and the results from mixing models using C : N ratios and d 13 C suggest an estuarine system that is responsive to increased carbon loading from the nitrogen-limited phytoplankton community and whose sediments are becoming increasingly anoxic as a result. The present nitrogen loading is about three times above that prior to the 1800s, suggesting that without management intervention the anticipated doubling of the watershed's population from 1990 to 2020 will greatly increase the nitrogen loading to this estuary and will lead to much higher amounts of phytoplankton biomass and accumulation and exacerbate hypoxic conditions.
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During the past two decades coral reefs in the greater Caribbean area have been altered by phase shifts away from corals and toward macroalgae or algal turfs. This study tested the hypothesis that because the phase shift on reefs in Jamaica and southeast Florida involved frondose macroalgae, bottom-up control via nutrient enrichment must be a causal factor. The approach was multifaceted and included measurement of near-bottom nutrient concen- trations, salinity, nutrient enrichment bioassays, alkaline phosphatase assays, tissue C : N : P ratios, and tissue 15N : 14N (6"N) ratios. In both locations, concentrations of dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP) exceeded nutrient thresholds (- 1 .O PM DIN, 0.1 PM SRP) noted to sustain macroalgal blooms on Caribbean coral reefs. High seawater DIN : SRP ratios, alkaline phosphatase activity, and tissue C : P and N : P ratios of macroalgae on the carbonate-rich Jamaican reef suggested SRP limitation of productivity compared to lower values of these variables on siliciclastic reefs in Florida that suggested DIN limitation. This pattern was corroborated experimentally when SRP enrichment increased P,,,, (photosynthetic capacity at light saturation) of the chlorophyte Chaetomorpha Zinum in Jamaica compared to DIN enrichment that increased (x (the photosynthetic efficiency under low irradiance) of the deeper growing chlorophyte Codium isthmocladum in southeast Florida. Increased DIN concentrations were associated with reduced salinity on both reefs, indicating submarine groundwatcr discharge was a significant source of DIN. Elevated S15N values of C. isthmocladum tissue further pointed to wastewater DIN as a source of nitrogen contributing to the blooms in southeast Florida.
Article
Nutrient and grazing levels were manipulated in a 10 wk field experiment at 2 sites in a subtropical lagoon in Bermuda to evaluate their relative effects on the abundance and growth of the dominant seagrass and macroalgae. One site was eutrophic, the other mesotrophic to oligotrophic. Nutrients were added to the sediment-water interface using slow-release fertilizer, and the dominant herbivores in the system, the purple sea urchin Lytechinus variegatus and herbivorous fishes (primarily the resident parrotfish Sparisoma radians), were partitioned using roofless cages. Nutrient enrichment caused an increase in the percent cover of the filamentous, mat-forming macroalga Spyridea hypnoides. This response is consistent with the dominance of this macroalga in the eutrophic portion of the bay and with previous work showing that this species has rapid nutrient uptake and growth potentials, enabling it to take advantage of elevated nutrient concentrations in the water column. Enrichment also caused a decline in both the percent cover and aboveground biomass of the dominant seagrass Thalassia testudinum at the eutrophic site but not at the mesotrophic site. Estimates of productivity and grazing losses during the experiment indicated that the decline was primarily a result of enhanced grazing by herbivorous fishes and not of either increased urchin grazing or reduced seagrass growth from shading. Nutrient enrichment caused an increase in the nitrogen content of the seagrass, particularly at the eutrophic site. Fertilization may have been less effective at the mesotrophic site due to the dilution of fertilizer nutrients in greater current flow. Herbivorous fishes preferentially chose the high-nitrogen epiphyte-covered T. testudinum at both sites, but particularly selected the higher-nitrogen seagrass at the eutrophic site. Intense grazing on this nitrogen-enriched T. testudinum was responsible for the creation and maintenance of small-scale (<1 m(2)) patches in aboveground biomass in the seagrass meadow, an occurrence also observed naturally in places at the eutrophic site.
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Excessive growth of seaweeds is a response of the biocenose, in a particular biotope, to a supply of nutrients. This supply may be natural or of anthropogenic origin. In the latter case, excessive growths and drifts of algae are consequences of the disturbance in the environment. Such growths are becoming increasingly widespread as the result of the progressive eutrophication of coastal waters, and now occur in at least twenty five countries worldwide. For example, particularly significant accumulations of seaweed are observed annually in Italy (1 000 000 t fresh weight). France (100 000-200 000 t), and Australia (100 000-600 000 t). The densities range from 0.2 to 400 kg m-2 the thickness of the mats from 2 to 100cm. The first part of the present review describes the worldwide phenomenon and includes information on the localities affected and the density, biomass, annual production and harvesting time of the excessive algal growths. The second part tries to analyse the phenomenon and the problems posed by seaweed decay. Lagoons, bays and shallow estuaries near industrial, agricultural and urban areas are most affected by these increases in algal growth. In temperate waters, excessive growth of macroalgae is generally observed during the summer, while in tropical waters, it occurs during the winter. At first, the development of opportunist and tolerant seaweeds acts as a purifying system. Then, when the seaweed is stranded or the environmental conditions become unfavourable, the plants die and decompose. At this stage, a large biomass can become troublesome. In summary, the impact on the environment is as follows: an increase in the herbivore population, competition or toxicity towards flora and fauna, alteration of the sediment, recycling of nutrients and pollutants in the ecosystem, nuisance for local residents and reduction of tourism. Cast weed is sometimes collected from the beaches and dumped inland, but this method of disposal merely constitutes a transfer of pollution. Consequently, different ways of treatment were developed, including composting and methanisation.
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Macroalgal blooms arc produced by nutrient enrichment of estuaries in which the sea floor lies within the photic zone. We review fcaturcs of macroalgal blooms pointed out in recent literature and summarize work done in the Waquoit Bay Land Margin Ecosystems Research project which suggests that nutrient loads, water residcncc times, presence of fringing salt marshes, and grazing affect macroalgal blooms. Increases in nitrogen supply raise macroalgal N uptake rates, N contents of tissues, photosynthesis-irradiance curves and P,,,.,, and accelerate growth of fronds. The resulting increase in macroalgal biomass is the macroalgal bloom, which can displace other estuarine producers, Fringing marshes and brief water residence impair the intensity of macroalgal blooms. Grazing pressure may control blooms of palatable macroalgac, but only at lower N loading rates. Macroalgal blooms end when growth of the phytoplankton attenuates irradiation reaching the bottom. In cstuarics with brief water rcsidencc times, phytoplankton may not have enough time to grow and shade macrophytcs. High phytoplankton division rates achieved at high nutrient concentrations may compensate for the brief time to divide before cells arc transported out of the estuary. Increased N loads and associated macroalgal blooms pervasively and fundamentally alter estuarinc ecosystems. Macroalgae intercept nutrients regenerated from sediments and thus uncoupIe biogeochemical sedimentary cycles from those in the water column. Macroalgae take up so much N that water quality seen:? high even where N loads are high. Macroalgal C moves more readily through microbial and consumer food webs than C derived from seagrasscs that were replaced by macroalgae. Macroalgae dominate 0, profiles of the water columns of shallow estuaries and thus alter the biogeochemistry of the sediments. Marc frequent hypoxia and habitat changes associated with macroalgal blooms also changes the abundance of bcnthic fauna in affected estuaries. Approaches to rcmediation of the many pervasive cffccts of macroalgal blooms riced to include interception of nutrients at their watcrshcd sources and perhaps removal by harvest of macroalgae or by increased flushing. Al- though we have much knowledge of macroalgal dynamics, all such management initiatives will require additional information.
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We report analyses of the nitrogen isotropic composition of nitrate in the eastern Indian and Pacific sectors of the Southern Ocean. In this paper, we focus on the subsurface data as well as data from the deep waters of other ocean basins. Nitrate delta15N is relatively invariant in much of the abyssal ocean (i.e., below 2.5 km), with a value of 4.8+/-0.20/00 observed in Lower Circumpolar Deep Water, North Atlantic Deep Water, and central Pacific deep water. The isotopic invariance of deep ocean nitrate stems fundamentally from the completeness of nitrate utilization in most of the global surface ocean, the Southern Ocean surface being an important exception. In the Subantarctic Zone (north of the Polar Frontal Zone) the nitrate delta15N of Upper Circumpolar Deep Water is ~0.70/00 greater than that of Lower Circumpolar Deep Water. This isotopic enrichment appears to result from denitrification in the low-latitude water masses with which Upper Circumpolar Deep Water communicates. The isotopic enrichment of Upper Circumpolar Deep Water is diminished in the Antarctic, probably because of the remineralization of sinking organic N, which has a low delta15N in the Antarctic. Relative to the other water masses of the Southern Ocean, the Subantarctic thermocline has a very low nitrate delta15N for its nitrate concentration because of exchange with the low-latitude thermocline, where this isotopic signature appears to originate. This signature of the low-latitude thermocline has two probable causes: (1) mixing with