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Map of the Indian River lagoon system. Included are labels for the 5 subsections of the IRL system: Mosquito Lagoon, Banana River Lagoon, Northern, Central and Southern Indian River Lagoon. Sample site locations denoted as (+).
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Abstract
The Indian River Lagoon (IRL) system, a poorly flushed 240km long estuary in east-central Florida (USA), previously received 200 MLD of point source municipal wastewater that was largely mitigated by the mid-1990’s. Since then, non-point source loads, including septic tank effluent, have become more important. Seventy sites were sampled fo...
Citations
... Computational equation employed in the QUAL 2Kw model includes Michaelis-Menten equations (nutrient analysis), the half-saturation, Smith's function, and Steele's equations (for determining the impact of light penetration in the waterbody) (Chapra & Pelletier, 2003;Kannel et al., 2011;Wool & Fitzpatrick, 2014;Mbuh et al., 2018;Shemeera, 2018). QUAL 2Kw solver has a potential capability of simulating the desired parameters of the river under investigation following a one-dimensional, steady flow fluid dynamic variability to capture the competitive impact of macrophytic interaction with the water quality parameters (Barile, 2018). ...
An accurate investigation of bio-physical and chemical parameters as proxy of in situ water quality conditions in the Himalayan region is highly challenging owing to cumbersome, strenuous, and physically exhausting sampling exercises at high altitude locations. The upper stretches of Yamuna River in the Himachal Pradesh are typical examples of such sampling locations that have rarely been examined in the past studies. A widely accepted and recognized QUAL 2Kw model is applied for estimating the water quality parameters on the upper segment of the Yamuna River from Paonta Sahib to Cullackpur. These water quality indicators mainly included electric conductivity, pH, dissolved oxygen, temperature, carbonaceous biological oxygen demand (CBOD), inorganic suspended solids, total nitrogen, total phosphorus, and alkalinity, which were systematically investigated for predicting the spatio-temporal trends during the year 2018. A total of 12 distantly located river sites were identified for sample collection and data validation using QUAL 2Kw model. The present investigation attempts to reveal long-term degraded impact of untreated wastewater and biased agricultural practices on the water quality conditions over the upper stretches of Yamuna River. The QUAL 2Kw-derived values for selected variables were inter-compared with in situ values, and any deviation from measured values was ascertained based on meaningful statistical measures. The lower error of RMSE, MRE, and BIAS, corresponding to < 15%, ± 10%., ± 20%, and ~ 1 slope evidently indicated better matchup of values, wherein, higher slope correlation coefficient (R²) of ~ 90% indicated the robust performance of the QUAL 2Kw algorithm in accurately predicting the chosen variables. A comparative assessment of QUAL 2Kw and WASP has been performed to justify aptness of water quality model in scenarios of lean flow.
... 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. ...
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.
... Seagrass coverage in the IRL was documented as increasing or stable through 2006 (Virnstein et al., 2007;Morris et al., 2016Morris et al., , 2018Morris et al., , 2021Indian River Lagoon National Estuary Program, 2020). However, in early 2011, a harmful algal bloom (HAB) was detected in the IRL that extended from early spring through late fall, causing a widespread seagrass die-off (Barlie, 2018;Lapointe et al., 2015Lapointe et al., , 2020Morris et al. 2016Morris et al. , 2018Morris et al. , 2021. This HAB proliferated in the lagoon as a result of anthropogenic nutrient inputs, which caused depleted oxygen levels (Kamerosky et al., 2015;Lapointe et al., 2015Lapointe et al., , 2020Sneed et al., 2017;Barlie, 2018). ...
... However, in early 2011, a harmful algal bloom (HAB) was detected in the IRL that extended from early spring through late fall, causing a widespread seagrass die-off (Barlie, 2018;Lapointe et al., 2015Lapointe et al., , 2020Morris et al. 2016Morris et al. , 2018Morris et al. , 2021. This HAB proliferated in the lagoon as a result of anthropogenic nutrient inputs, which caused depleted oxygen levels (Kamerosky et al., 2015;Lapointe et al., 2015Lapointe et al., , 2020Sneed et al., 2017;Barlie, 2018). An increase in turbidity and low light conditions further contributed to a decline in the abundance and extent of seagrass beds in the lagoon (Phlips et al., 2015;Morris et al., 2016Morris et al., , 2018Morris et al., , 2021. ...
Investigating the long-term fluctuations of the feeding ecology of megaherbivores such as sirenians is important, as any changes could be indicative of shifts in resource availability. The Indian River Lagoon (IRL), eastern Florida, USA, is a critical habitat for the Florida manatee (Trichechus manatus latirostris). However, the IRL has experienced a substantial decline in seagrass in 2011 due to the persistence of several harmful algal blooms. Using microhistological analysis, we examined the diet of manatees over a discontinuous sampling period spanning over 40 years using stomach contents collected from carcasses recovered in the IRL. Samples collected between 2013-2015 (post-seagrass die-off, n = 90) were compared to archived stomach samples collected between 1977-1989 (pre-seagrass die-off, n = 103). Samples analyzed from 1977-1989 contained primarily seagrasses (61.7%), followed by algae (28.4%) and vascular plants (1.7%). In contrast, stomach samples from the post-seagrass die-off primarily contained algae (49.5%), followed by seagrasses (34%) and vascular plants (2.7%). Between 1977-1989 and 2013–2015, manatees in the IRL experienced a 44.9% decline in seagrass consumption, and a 74.3% increase in algal consumption. This dietary shift was not influenced by body length, a proxy of age, or sex. Our results indicate that the dietary shift experienced by manatees is due to the decline of available seagrass forage in the IRL, and highlight the dietary plasticity of manatees in the face of changes in resource availability. However, the individual health and population-level consequences of this dietary shift are unknown. An increase in mortality due to undetermined causes in this region since 2012 can be associated with deteriorating body conditions of manatees in the IRL, possibly resulting from a lack of seagrass diet. Future research could further investigate behavioral changes affecting manatees in relation to seagrass decline in the IRL, including the energetic costs of this dietary change.
... A shift of manatees to a predominantly macroalgal diet could have resulted in the inadvertent ingestion of toxic or pathogenic compounds. There is a diverse macroalgal population in the IRL, with Gracilaria tikvahiae, Hypnea musciformis, Acanthophora spicifera, Chaetomorpha sp., Ulva lactuca, and Codium decorticatum the major components of the drift algae that sometimes form high-biomass blooms under eutrophic conditions (Virnstein and Carbonara, 1985;Littler et al., 2008;Whitehouse and Lapointe, 2015;Barile, 2018). Qualitative gutcontent analysis of manatee carcasses examined during the UME revealed diverse macroalgae and seagrasses, paralleling the known availability of these forage items in the IRL following the major seagrass die-off of Thalassia testudinum, Halodule wrightii, and Syringodium filiforme triggered by superbloom events in 2012 (Morris et al., 2018). ...
The Indian River Lagoon (IRL) on Florida’s east coast is a biologically diverse estuary and an important habitat to the threatened Florida manatee (Trichechus manatus latirostris). An unusual mortality event (UME) was declared by the Working Group on Marine Mammal Unusual Mortality Events in 2013 after a marked increase in manatee deaths in the IRL of an unknown cause. This UME followed a dramatic reduction of seagrass coverage in the IRL due to chronic non-toxic phytoplankton blooms, with a resultant ecosystem shift to mixed macroalgal dominance. At least 199 manatee deaths fitting the UME case definition were documented in and adjacent to the IRL during 2012–2019; mortality was highest in 2013, when 111 of these deaths were documented. The case definition included carcasses in good nutritional condition, with multiorgan congestion or wet lungs consistent with drowning without trauma. The gastrointestinal compartments of manatee carcasses were filled with diverse macroalga species, and the contents were notably more fluid than usual. Gross intestinal findings included blebbing to segmental thickening of the wall. Microscopic lesions were primarily intestinal, including necrosis, edema, hemorrhage, mucosa-associated lymphoid changes, and inflammation, sometimes associated with Gram-positive bacterial rods. A multidisciplinary approach of environmental and carcass sampling found no causative evidence through tests for micro- and macroalgal biotoxins, trace metals, general toxin screening, or vitreum biochemistry. Microbiological, cytological, immunohistochemical, and molecular analyses of Clostridiales from intestinal samples identified Clostridioides difficile toxin A, toxins A/B and toxin A gene; Paeniclostridium sordellii lethal gene (and other potential virulence factors from a sequenced strain); and Clostridium perfringens alpha and epsilon toxin genes. The results from this 8 year-long investigation are indicative that the cause of death in this manatee UME was associated with clostridial infection, initiated by a shift to a predominantly macroalgal diet.
... Urban and agricultural development and other associated anthropogenic activities lead to increasing water demands as well as stormwater, wastewater, and agricultural runoff to inland and coastal aquatic systems. In Florida, coastal development has been ongoing since 1912 when the Florida East Coast Railway linked to the Florida Keys, and has been characterized by both recent and historical marine and freshwater eutrophication (Brezonik et al., 1969;Lapointe and Clark, 1992;Havens and James, 2005;Turner et al., 2006;Barile, 2018;Lapointe et al., 2019Lapointe et al., , 2020). An additional anthropogenic activity in Florida is the management of freshwater flows by both state and federal levels. ...
... This species is resilient in hypersaline conditions (Buskey et al., 1998;Liu and Buskey, 2000) and outcompetes phytoplankton under conditions of reduced N, especially dissolved organic N, low P (Kang et al., 2015) and high N:P ratios . The IRL is hypereutrophic (Bricker et al., 2007), with nutrient inputs shifting from pointsource dominance in the 1980's to non-point source inputs such as sewage enriched in reduced N forms (Virnstein and Carbonara, 1985;Barile and LaPointe, 1999;Barile, 2018). This species has been shown to preferentially take up NH 4 + and urea in the IRL where the bloom was characterized by lower δ 15 N stable isotope values, suggesting support by regenerated N compounds (Kang et al., 2015). ...
... In 2009, estimates found that the IRL was worth $3.7 billion dollars in ecosystem services and revenue, with a large part of these services coming from the (historic) 72,400 acres of seagrass in the lagoon, estimated at $2 billion annually (USEPA, 2009). "Superblooms" of toxic algae (caused by poor water quality) subsequently covered tens of thousands of acres, destroying up to 95% of seagrass in the lagoon, and precipitating a phase shift of the environment into a "toxic phytoplankton-dominated system" (Barile, 2018;Lapointe et al., 2020). The seagrass and its associated communities have yet to recover (Barile, 2018;Lapointe et al., 2020). ...
... "Superblooms" of toxic algae (caused by poor water quality) subsequently covered tens of thousands of acres, destroying up to 95% of seagrass in the lagoon, and precipitating a phase shift of the environment into a "toxic phytoplankton-dominated system" (Barile, 2018;Lapointe et al., 2020). The seagrass and its associated communities have yet to recover (Barile, 2018;Lapointe et al., 2020). While algae and bare sediment have largely replaced seagrass and macroalgae in this area, there is a functioning seagrass bed directly across the study site, indicating that seagrass establishment was possible. ...
While attention in coastal ecosystem restoration has increased over the last two decades, the success rate of efforts remains relatively low. To increase success rates, physical restoration techniques often utilize supporting or protective materials to provide a stable surface for transplantation, and in some cases reduce herbivory and hydrodynamic disturbances. In this study, we evaluated the effectiveness of traditional (staples, burlap) and novel (BESE- elements, a biodegradable potato starch lattice) physical restoration techniques on the growth of transplanted Halodule wrightii seagrass. A first experiment revealed that seagrass planted in both two-stacked BESE structure without planting holes and four-stacked BESE with holes had significantly higher shoot count and blade length than four-stacked BESE without holes, with the latter design losing all seagrass shortly after deployment as shoots could not float through the structure. In a second experiment, the BESE lattice treatment (four-stacked with holes) had three times the shoot count and equal to greater blade length compared to traditional methods of physical restoration (staples and burlap), likely due to BESE providing some protection from hydrodynamic activity. However, disturbances, possibly including herbivory and hydrodynamic activity (culminating with Hurricane Irma), prevented long term study, illustrating the importance of stochastic abiotic factors in seagrass planting success. Overall our study demonstrates the effectiveness of using BESE lattice designs and similar physical techniques in the restoration of seagrass beds.
... However, to our knowledge there have been no additional studies on the faunal associates of C. prolifera in this region. Since 2011, there has been a drastic reduction (58%) in seagrass cover throughout much of the IRL associated with declining water quality (Phlips et al. 2015, Barile 2018, Sayemuzzaman et al. 2018, Lapointe et. al. 2020, and C. prolifera is the only attached macrophyte remaining in many locations (Morris et al. 2021. ...
The abundance and species composition of the macrofauna inhabiting adjacent beds of the seagrass Halodule wrightii and the attached macroalga Caulerpa prolifera were compared seasonally from eight sites sampled within the Indian River Lagoon, Florida during 1987–1988. At each site, sampling employed a benthic corer, an epifaunal sampler, a dipnet, and fish traps to examine utilization patterns of different components of the fauna. Abundance of animals in both habitats was both high and similar. Epifaunal invertebrate densities averaged over 16,000 m−2 from H. wrightii and over 20,300 m−2 from C. prolifera . Despite a few species-compositional differences, there was no consistent difference in either the abundance or number of species of the macrofauna of C. prolifera versus H. wrightii for any sampling method except fish traps. Fish were significantly more abundant, but not more species rich, in H. wrightii . We conclude that C. prolifera offers habitat for many small invertebrates comparable to that of seagrass, making C. prolifera beds a valuable biological resource. While C. prolifera habitat may not support all the ecosystem services of seagrass beds and is not currently protected in Florida, it as a potential vegetated habitat refugium and may warrant management and protection practices similar to those for seagrass beds.
... This "2011 superbloom" lasted 7 months and is thought to have contributed to the loss of over 40% of established seagrass beds in the area (SJRWMD, 2012;Lapointe et al., 2015;Phlips et al., 2015). Since then, high concentrations of other nanophytoplankton taxa (∼2-10 µm diameter) have been reported nearly annually and sometimes coincidentally or sequentially with other HABs, presenting new challenges to management, conservation, monitoring, and restoration efforts in the IRL (FWC-FWRI HAB Monitoring Database; Gobler and Sunda, 2012;Kang et al., 2015;Barile, 2018). Specifically, in 2012, the first documented brown tide caused by the nanophytoplankton Aureoumbra lagunensis further affected the northern IRL system with maximum recorded biomass of ∼200 µg L −1 chlorophyll-a surpassing values measured during the 2011 superbloom event. ...
... There is also one direct but limited connection between the Banana River Lagoon and the Atlantic Ocean through the Port Canaveral Navigational Lock. As a result, water circulation in the Banana River Lagoon is low and influenced by winds, the water residence time is long, and the water quality is poor due to excess nutrients (Barile, 2018). Estimates to exchange 50% of this subbasin water volume range from ∼70 to 156 d (Steward et al., 2005;Reyier et al., 2008), and this poorly flushed environment may contribute to the persistence and recurrence of blooms (Phlips et al., 2002). ...
The Indian River Lagoon (IRL), located on the east coast of Florida, is a complex estuarine ecosystem that is negatively affected by recurring harmful algal blooms (HABs) from distinct taxonomic/functional groups. Enhanced monitoring was established to facilitate rapid quantification of three recurrent bloom taxa, Aureoumbra lagunensis, Pyrodinium bahamense, and Pseudo-nitzschia spp., and included corroborating techniques to improve the identification of small-celled nanoplankton (<10 µm in diameter). Identification and enumeration of these target taxa were conducted during 2015-2020 using a combination of light microscopy and species-specific approaches, specifically immunofluorescence flow cytometry as well as a newly developed qPCR assay for A. lagunensis presented here for the first time. An annual bloom index (ABI) was established for each taxon based on occurrence and abundance data. Blooms of A. lagunensis (>2 × 10 8 cells L −1) were observed in all 6 years sampled and across multiple seasons. In contrast, abundance of P. bahamense, largely driven by the annual temperature cycle that moderates life cycle transitions and growth, displayed a strong seasonal pattern with blooms (10 5-10 7 cells L −1) generally developing in early summer and subsiding in autumn. However, P. bahamense bloom development was delayed and abundance was significantly lower in years and locations with sustained A. lagunensis blooms. Pseudo-nitzschia spp. were broadly distributed with sporadic bloom concentrations (reaching 10 7 cells L −1), but with minimal concentrations of the toxin domoic acid detected (<0.02 µg L −1). In summer 2020, multiple monitoring tools characterized a novel nano-cyanobacterium bloom (reaching 10 9 cells L −1) Frontiers in Marine Science | www.frontiersin.org 1 November 2021 | Volume 8 | Article 769877 Lopez et al. HAB Variability in the IRL that coincided with a decline in A. lagunensis and persisted into autumn. Statistical and time-series analyses of this spatiotemporally intensive dataset highlight prominent patterns in variability for some taxa, but also identify challenges of characterizing mechanisms underlying more episodic yet persistent events. Nevertheless, the intersect of temperature and salinity as environmental proxies proved to be informative in delineating niche partitioning, not only in the case of taxa with long-standing data sets but also for seemingly unprecedented blooms of novel nanoplanktonic taxa.
... A recurrence of brown tide in the spring of 2016 (Phlips et al., 2019;Schaefer et al., 2019) allowed us to investigate the effects of an ongoing bloom event. While most intense in the BR (Lapointe et al., 2017;Barile, 2018), all basins of the northern IRL were affected by the 2016 bloom (Schaefer et al., 2019). The responses of the communities to the bloom were complex, and significant variability among seasons and years that occurs regularly within these communities likely contributed to the differences detected in pre-bloom and bloom samples. ...
Understanding the structure and function of infaunal communities is useful in determining the biodiversity and ecosystem function of shallow estuaries. We conducted a survey of infaunal communities within three separate water basins [Mosquito Lagoon (ML), Indian River (IR), and Banana River (BR)] in the larger Northern Indian River Lagoon, FL, United States to establish a database of infaunal community structure and function. Twenty-seven sites were sampled quarterly from 2014 to 2016. Analysis of all samples determined that basin, season, and sediment composition were the primary drivers of macrobenthic community composition. Diversity was highest in the ML, and lower in spring compared to other seasons. The occurrence of a brown tide (Aureoumbra lagunensis) in 2016 allowed a comparison of winter and spring communities before (2015) and during (2016) a bloom event. Community composition and diversity at the BR sites were the most affected by the bloom event with the lowest diversity and abundances during the bloom. Diversity in the IR was also lower during the bloom, while the ML was unaffected by the bloom. Species of all feeding groups were affected by the bloom, with lower abundances found in all groups. In addition, to determine the overall trophic diversity of infaunal communities, we collected infaunal organisms from two of the quarterly sampled sites for isotope analyses. Values of δ13C and δ15N from infaunal tissue were compared to those of potential food sources at each site. Substantial interspecific variation in isotope values of infaunal organisms within a site suggests the presence of diverse nutritional modes that include suspension and deposit feeding and predation. Together, these data suggest that infaunal communities contribute to benthic pelagic coupling and nutrient cycling within the estuarine communities, but the overall function of these communities may be tightly linked to their species composition.
... 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). ...
... 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). ...
... Similar wastewater contamination from septic systems was observed in the St. Lucie Estuary (Lapointe et al., 2017) and this study confirms that those issues were not specific to that area, but rather likely representative of conditions along the entire 150 km expanse of the IRL, including its canals and tributaries. This research also supports previous findings that wastewater from poorly sited septic systems is promoting eutrophication in the IRL (Lapointe et al., 2012(Lapointe et al., , 2015(Lapointe et al., , 2017Barile, 2018), as well as contributing to expansive seagrass losses (Lapointe et al., 2020) and ongoing Florida manatee mortalities by starvation. Given the recent unprecedented HABs and catastrophic seagrass losses observed in this estuary (Lapointe et al., 2015;Phlips et al., 2015;Barile, 2018;Morris et al., 2018;Lapointe et al., 2020;Morris et al., 2021) identification of specific nutrient sources contributing to this issue is essential. ...
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.
