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Tidal and Nontidal Flushing of Florida's Indian River Lagoon
Abstract
The flushing of Florida’s Indian River Lagoon is investigated as a response to tidal and low-frequency lagoon-shelf exchanges
in the presence of freshwater gains and losses. A one-dimensional computer model uses the continuity equation to convert water-level
variations into both advective transport within the lagoon and lagoon-shelf exchanges. The model also incorporates transport
by longitudinal diffusion. Flushing is quantified by calculating the 50% renewal time, R50, for each of 16 segments. R50 is calculated for tidal exchanges enhanced by 0–30 cm nontidal fluctuations in coastal sea level, then for a range of rainfall
rates. In both series of simulations, results suggest that in the northern sub-basin, R50 increases dramatically with distance from the inlet due to relatively weak tidal and nontidal exchanges. A 50% renewal occurs
in about one tidal cycle just inside Sebastian Inlet; at the northern end of the northern sub-basin, R50 is over 230 d, and only coastal sea-level variations on the order of 30 cm and/or dry season rainfall rates decrease R50 to less than 1 yr. R50 is 1 wk or less throughout the central and southern sub-basins, where lagoon-shelf exchanges occur through two inlets. Simulations
involving seasonal variations in precipitation and evaporation indicate that maximum and minimum rates of freshwater input
lead minimum and maximum salinities by time periods on the order of 2–3 wk for the lagoon as a whole and in the northern sub-basin.
The central and southern sub-basins respond in 1–2 wk.
... Previous studies indicated that the northern IRL region has a long water residence time. Using a box model that divided the lagoon (excluding Banana River and Mosquito Lagoon) into 16 connected segments (boxes), Smith (1993) showed that water exchanges between segments in the IRL are mainly due to tidal and wind-driven transport. He further computed the flushing time of the lagoon and concluded that the 50% renewal time (aka water residence time) is less than 1-2 weeks in central and southern IRL and ~ 230 days in the NIRL. ...
... In addition, these studies did not examine the specifics of local connectivity between sub-basins or how exactly waters in different areas within each sub-basin (e.g., nearshore, central basin) are being renewed. Smith (1993) briefly examined the influence of sea level by increasing sea level by 30 cm. Yet his model did not include coastal ocean specifically and therefore the influence of coastal oceans on the water residence time in the lagoon has been largely unknown. ...
... It is well known that the water residence time in the IRL has a N-S gradient with increasing residence time toward the north (Smith 1993;Sheng and Kim 2009). Our result by seeding the entire lagoon with an inert tracer shows a residence time increasing from about 2 weeks in the southern IRL to about 150 days north of Sebastian Inlet through Melbourne (Fig. 7a). ...
The northern Indian River Lagoon (IRL) has been experiencing severe water quality degradation and phytoplankton blooms in the last decade or so. Two important factors for maintaining high water quality in estuaries are the water residence time and connectivity. Here we used a newly developed high-resolution hydrodynamic model to investigate both factors in this area. Two types of numerical experiments have been carried out: (1) tracer dilution experiments in which an inert tracer was released from selected sub-basins and tracked for 3 months, and (2) particle experiments in which a number of neutrally buoyant particles were released from selected areas and tracked for 1 month. The results indicate that surface winds may drive complex yet coherent residual circulation, including semi-enclosed re-circulation cells, within each subbasin, with the patterns mainly depending on the directions of prevailing winds. These patterns may promote retention of waters and transport barriers within sub-basins, leading to long water residence time with limited connectivity between sub-basins, and spatial heterogeneity of water properties such as salinity, nutrients, organic matter, and dissolved oxygen. Despite their transient nature (weekly to monthly), these dynamic features and associated processes may also significantly affect the development of phytoplankton blooms and marine habitats in this region. On the other hand, water throughout the lagoon was strongly influenced by the water level in the coastal oceans, especially the frontal position of the Gulf Stream. This suggests that water exchanges through the inlets, albeit limited, are important to the water quality and phytoplankton blooms in the lagoon.
... The Indian River Lagoon is part of a transgressive barrier island-lagoonal coastal system (e.g., Kraft and Chrzastowski, 1985) surrounded by Pleistocene beach ridges to the west on mainland Florida, as well as to the east on the bounding barrier island (Figure 1). The lagoon is microtidal with tidal amplitudes generally <10 cm and has a mean depth of 1.5 m (Smith, 1993). Consequently, the shallow depth and wind-driven waves typically ensure that the Indian River Lagoon water column is well-mixed (Smith, 1987(Smith, , 1993Martin et al., 2007). ...
... The lagoon is microtidal with tidal amplitudes generally <10 cm and has a mean depth of 1.5 m (Smith, 1993). Consequently, the shallow depth and wind-driven waves typically ensure that the Indian River Lagoon water column is well-mixed (Smith, 1987(Smith, , 1993Martin et al., 2007). Exchange of Indian River Lagoon waters with the Atlantic Ocean occurs via three inlets (i.e., Sebastian, Ft. ...
... The closest of these inlets (i.e., Sebastian Inlet) is about 33 km southeast of the study site. The residence time of lagoon water near the study site is estimated to be 18 days, on average, based on computer modeling using waterlevel variation measurements; however, residence times can be as high as a year in the northern reaches of the lagoon (Smith, 1993). Inputs of freshwater to the Indian River Lagoon within the study site include two small rivers (i.e., Eau Gallie River and Crane Creek; Figure 1), urban storm runoff, direct rainfall, and SGD . ...
Rare earth elements (REE) and Nd isotope compositions of surface and groundwaters from the Indian River Lagoon in Florida were measured to investigate the influence of submarine groundwater discharge (SGD) on these parameters in coastal waters. The Nd flux of the terrestrial component of SGD is around 0.7±0.03 μmol Nd/day per m of shoreline across the nearshore seepage face of the subterranean estuary. This translates to a terrestrial SGD Nd flux of 4±0.2 mmol/day for the entire 5,880 m long shoreline of the studied portion of the lagoon. The Nd flux from bioirrigation across the nearshore seepage face is 1±0.05 μmol Nd/day per m of shoreline, or 6±0.3 mmol/day for the entire shoreline. The combination of these two SGD fluxes is the same as the local, effective river water flux of Nd to the lagoon of 12.7±5.3 mmol/day. Using a similar approach, the marine-sourced SGD flux of Nd is 31.4±1.6 μmol Nd/day per m of shoreline, or 184±9.2 mmol/day for the investigated portion of the lagoon, which is 45 times higher than the terrestrial SGD Nd flux. Terrestrial-sourced SGD has an εNd(0) value of −5±0.42, which is similar to carbonate rocks (i.e., Ocala Limestone) from the Upper Floridan Aquifer (−5.6), but more radiogenic than the recirculated marine SGD, for which εNd(0) is −7±0.24. Marine SGD has a Nd isotope composition that is identical to the εNd(0) of Fe(III) oxide/oxyhydroxide coated sands of the surficial aquifer (−7.15±0.24 and −6.98±0.36). These secondary Fe(III) oxides/oxyhydroxides formed during subaerial weathering when sea level was substantially lower during the last glacial maximum. Subsequent flooding of these surficial sands by rising sea level followed by reductive dissolution of the Fe(III) oxide/oxyhydroxide coatings can explain the Nd isotope composition of the marine SGD component. Surficial waters of the Indian River Lagoon have an εNd(0) of −6.47±0.32, and are a mixture of terrestrial and marine SGD components, as well as the local rivers (−8.63 and −8.14). Nonetheless, the chief Nd source is marine SGD that has reacted with Fe(III) oxide/oxyhydroxide coatings on the surficial aquifer sands of the subterranean estuary.
... The Banana River (BR) (202 km 2 ) and the Mosquito Lagoon (ML) (140 km 2 ) included each sub-basin in its entirety (Fig 1). The Indian River basin was divided into two sub-basins: the northern Indian River (NIR) (378 km 2 , previously defined as north of Eau Gallie Causeway [55], with little tidal and non-tidal flushing [56]), and the southern Indian River (SIR) (182 km 2 ) which consisted of three previously defined basins [55] and includes three of the four inlets (Fig 1). Due to a lack of tidal flushing, the BR and NIR have decreased water quality compared to the majority of ML and SIR [56][57][58], and were the common epicenter of prior IRL UMEs [37,59]. ...
... The Indian River basin was divided into two sub-basins: the northern Indian River (NIR) (378 km 2 , previously defined as north of Eau Gallie Causeway [55], with little tidal and non-tidal flushing [56]), and the southern Indian River (SIR) (182 km 2 ) which consisted of three previously defined basins [55] and includes three of the four inlets (Fig 1). Due to a lack of tidal flushing, the BR and NIR have decreased water quality compared to the majority of ML and SIR [56][57][58], and were the common epicenter of prior IRL UMEs [37,59]. By portioning the lagoon, we were able to compare our results with previous abundance studies [21,23] and with community estimates peripheral to the basins [60]. ...
... Differences in dorsal fin marking rates between populations may be influenced by ecosystems [98]. Since extensive portions of the IRL are relatively isolated [56] in contrast to more open bays [2,13,90,91], heterogeneity between regions (e.g., anthropogenic activities, conspecific interactions) could contribute to differences in marked ratios. Furthermore, in other study regions, rates of dorsal fin marking have a sex-bias, with significantly higher rates of dorsal fin nicks in males [99]. ...
Common bottlenose dolphins (Tursiops truncatus truncatus) inhabiting the Indian River Lagoon (IRL) estuarine system along the east coast of Florida are impacted by anthropogenic activities and have had multiple unexplained mortality events. Given this, managers need precise estimates of demographic and abundance parameters. Mark-recapture photo-identification boat-based surveys following a Robust Design were used to estimate abundance, adult survival, and temporary emigration for the IRL estuarine system stock of bottlenose dolphins. Models allowed for temporary emigration and included a parameter (time since first capture) to assess evidence for transient individuals. Surveys (n = 135) were conducted along predetermined contour and transect lines throughout the entire IRL (2016-2017). The best fitting model allowed survival to differ for residents and transients and to vary by primary period, detection to vary by secondary session, and did not include temporary emigration. Dolphin abundance was estimated from 981 (95% CI: 882-1,090) in winter to 1,078 (95% CI: 968-1,201) in summer with a mean of 1,032 (95% CI: 969-1,098). Model averaged seasonal survival rate for marked residents was 0.85-1.00. Capture probability was 0.20 to 0.42 during secondary sessions and the transient rate was estimated as 0.06 to 0.07. This study is the first Robust Design mark-recapture survey to estimate abundance for IRL dolphins and provides population estimates to improve future survey design, as well as an example of data simulation to validate and optimize sampling design. Transients likely included individuals with home ranges extending north of the IRL requiring further assessment of stock delineation. Results were similar to prior abundance estimates from line-transect aerial surveys suggesting population stability over the last decade. These results will enable managers to evaluate the impact of fisheries-related takes and provide baseline demographic parameters for the IRL dolphin population which contends with anthropogenic impacts and repeated mortality events.
... With increased urbanization, the lagoon has experienced increased pollution from nonpoint sources such as septic tanks and wastewater drainage (Browne et al., 2011). In addition, Mosquito Lagoon is an enclosed and poorly drained estuary with negligible tidal flushing (Smith, 1993;Lapointe et al., 2015). Mosquito Lagoon is instead impacted more by non-tidal flushing mechanisms including local wind forcing and rainfall or extreme weather events (Smith, 1993). ...
... In addition, Mosquito Lagoon is an enclosed and poorly drained estuary with negligible tidal flushing (Smith, 1993;Lapointe et al., 2015). Mosquito Lagoon is instead impacted more by non-tidal flushing mechanisms including local wind forcing and rainfall or extreme weather events (Smith, 1993). It has been estimated that 50% renewal of water takes between 200 and 300 days in Mosquito Lagoon, compared to about a week in the southern lagoon or one tidal cycle near inlets (Smith, 2016). ...
... Li et al., 2015;Li et al., 2016;van Cauwenberghe and Janssen, 2014). This may be due to extensive urbanization, intensive recreational use, weather, and limited flushing in Mosquito Lagoon (Lapointe et al., 2015;Smith, 1993;Smith, 2016). To better understand the global microplastics, we need to continue to increase the number of studies, such as ours, in various habitats and geographies. ...
This study determined the quantity and diversity of microplastics in water and soft tissues of eastern oysters (Crassostrea virginica) and Atlantic mud crabs (Panopeus herbstii) in Mosquito Lagoon, a shallow, microtidal estuary along the east coast of central Florida. One-liter water samples had an average of 23.1 microplastic pieces (n = 15). Crabs (n = 90) had an average of 4.2 pieces in tissues/individual plus an average of 20.3 pieces/individual temporarily entangled in exposed surfaces and released within 5 days in tanks. Adult oysters (n = 90) had an average of 16.5 microplastic pieces/individual. Fibers, mostly royal/dark blue in color, dominated our collections. When compared per gram of tissue, crabs had two orders of magnitude more microplastic pieces than oysters. Our numbers were higher than previous studies on invertebrate microplastics; this is potentially the result of extensive urbanization, limited flushing, and intensive recreational usage of Mosquito Lagoon.
... Salinity in this segment exhibits a broad range and strongly depends on local precipitation and freshwater runoff. Low-frequency water level variations play a more significant role than tidal forcings, making coastal sea level a key factor in this segment [12,13]. ...
... Eng. 2024, 12, 775 ...
This study investigates the effects of the gulf stream (GS) on sea-level oscillations across various time scales and assesses the performance of a coastal and estuarine model nested within a global model in simulating these variations. It aims to improve boundary conditions to simulate sea-level oscillations more accurately by considering the influence of GS flow. An inverse correlation is observed between observed sea-level oscillation and GS flow, which becomes more pronounced over longer time scales. Using Delft3D, a high-resolution coastal and estuarine model is developed to simulate circulation dynamics in the central Indian River Lagoon (IRL), FL, and adjacent coastal areas on the Florida east coast. The model is nested into the HYCOM (Hybrid Coordinate Ocean Model), and meteorological forcings are derived from the NARR (North American Regional Reanalysis) model. The model demonstrates satisfactory performance across key parameters, including tide, salinity, water temperature, and currents. However, there remains a noticeable difference between the modeled and observed data. To address this, the model is executed with modified flow boundary conditions at eastern boundary nodes, integrating HYCOM tide, and observing low-frequency sea-level variations. The implementation of the new boundary conditions results in an improved simulation of sea-level oscillations. This study presents the conceptual framework and detailed methodologies employed in the creation of a high-resolution model tailored for estuarine and coastal areas nested into global models capable of satisfactorily simulating sea-level oscillations even when the global model does not represent GS effects.
... Areas of the lagoon system sampled during our study have a subtropical climate and are poorly flushed with no inlets to the ocean along a 140-km stretch, including the entire area chosen for this study (Figure 1). Calculated renewal times for water in our study area range from~100−300 days (Smith, 1993;Rosario-Llantin and Zarillo, 2021). Human development and addition of causeways over the past century have subdivided the estuary and further restricted circulation (Indian River Lagoon National Estuary Program [IRLNEP], 2007). ...
... These parameters are consistent with other fine-grained lagoonal and coastal sediments wherein advection is not a significant component of total fluxes (Schultz and Ruppel, 2002;Charbonnier et al., 2023). Furthermore, tidal ranges in our study area were <1-5 cm (Smith, 1993) and bioturbation was minimal in these organism-poor sediments (Fuller et al., 2021). ...
Nutrient fluxes from fine-grained, organic-rich sediments in estuaries can hasten the onset and progression of eutrophication and harmful algal blooms. Targeted efforts to manage degraded sediments and improve estuarine water quality require a better understanding of physicochemical controls and the relative importance of benthic fluxes. Toward that end, we determined fluxes from organic-rich, high porosity sediments deposited during the past 5-6 decades along 60 km of the Indian River Lagoon, a barrier island lagoon in Florida, USA. Highly bioavailable ammonium and phosphate were the predominant chemical forms of interstitial nitrogen and phosphorus in these highly-reducing sediments. Median fluxes of ammonium and phosphate were 320 µmol m⁻² h⁻¹ and 11 µmol m⁻² h⁻¹, respectively. Fluxes were 3-10 times greater when sediment temperatures were >28°C and interstitial sulfide concentrations were >1 mM. Temperature-compensated fluxes of ammonium and phosphate were significantly correlated with sediment organic matter content; total organic carbon averaged 5.3 ± 2.4% and the maximum was 12.4% for the sediments studied. Fine-scale physical probing, plus lidar data, showed that these organic-rich sediments covered <10% of our study area; however, fluxes from these sediments were estimated to supply 20-40% of internal + external annual loads of nitrogen and phosphorus. Furthermore, 60% of nitrogen and phosphorus fluxes from sediments in the northern Indian River Lagoon came from just 22% of the total surface area. Lagoon segments with high benthic fluxes overlapped in part with areas prone to harmful algal blooms. Effective strategies to manage degraded sediments in the Indian River Lagoon depend on knowing the relative magnitude of internal loading of nutrients as well as appropriate techniques to mitigate sediment fluxes.
... There are a few major freshwater inputs to the IRL in this region, including Turkey Creek, Crane Creek, and the Eau Gallie River with additional surface water flow into the IRL from smaller creeks, outfalls, and drainage ditches, as well as diffuse stormwater runoff (Trefry & Fox, 2021). This region of the IRL is the furthest distance to an ocean inlet, though minimal water exchange occurs with the Atlantic Ocean when the Canaveral Lock is opened at Port Canaveral; thus, this region has high water residence times (Smith, 1993;Phlips et al., 2021) with an estimated 50 % water exchange rate of 107 days in the NIRL and 156 days in the BR (Steward et al., 2005). Water movement is also restricted and compartmentalized by eight causeways across this section of the lagoon (Bilskie et al., 2019). ...
... Physical forces in the study area likely contribute to the observed changes in benthic cover. For example, long water residence times in the NIRL and BR, as well as restricted circulation (Smith, 1993;Bilskie et al., 2019;Jiang, 2023), limit the flushing of nutrients and other contaminants from the system. Thus, as the system became saturated with N and P (Lapointe et al., 2015, resilience decreased. ...
... In Mosquito Lagoon, annual salinity ranges from 22.6 to 45.2 ppt [39,40]. Tidal amplitudes range between 1 cm and 1 m, and water levels vary based on season with the highest water levels occurring in the fall months [41,42]. Water temperatures in Mosquito Lagoon range from 4 to 33 • C [39,40]. ...
... Dead reefs may reach 1 m above the mean high water [13,45], allowing them to be exposed and available for bird use even during high tide and the high-water season. Mosquito Lagoon experiences a high-water season in the fall months due to rainfall levels and wind speed/direction [42]. During this 3-5-month period (depending on the year), live and restored oyster reefs may remain submerged even during low tide [56]. ...
In order to mitigate the degradation of eastern oyster (Crassostrea virginica) reefs in Mosquito Lagoon (ML) along the east coast of central Florida, oyster reef restoration efforts have been in place for over 14 years. These restored reefs are successful in terms of universal oyster metrics (i.e., density, shell height, reef height) and are similar to natural reefs. However, little is known about the impact of this restoration on bird populations. ML provides a habitat for many bird species, including several listed as “threatened” by the Florida Fish and Wildlife Conservation Commission. Many of these birds rely on oyster reefs for foraging and loafing habitats. As benthic invertebrates serve as an important food source for coastal birds, we monitored the abundances and diversity of these organisms on live, restored, and dead reefs. We collected sediment samples from the reef sites pre-restoration, and one month, six months, one year, two years, and three years post-restoration. We counted benthic invertebrates present in the sediment samples, and sorted them by taxa (polychaetes, amphipods, isopods, gastropods, bivalves, decapods). Benthic invertebrate abundances on restored reefs became similar to live reefs over time (species composition, density), indicating that the prey base on restored reefs was similar to that of live reefs within 6 months. A second objective of this study was to determine if restored oyster reefs reach the same abundances, foraging behaviors, and diversity of bird species on natural, live reefs. We conducted monthly bird surveys to assess bird utilization of live, restored, and dead reefs. After three years, the abundances, behaviors, and assemblages of birds on restored reefs were similar to live reefs.
... Ponce de Leon Inlet is at the extreme northern end of Mosquito Lagoon; the lock at Port Canaveral intermittently connects the ocean to the Banana River Lagoon; the next connection is 140 km to the south at Sebastian Inlet; and Fort Pierce, St. Lucie, and Jupiter inlets are all found in the remaining portion of the lagoon. The three southern inlets increase oceanic exchange in that region (Smith, 1993). In contrast, the lack of inlets in the northern portion of the system leads to residence times that can exceed 1 year and weak tidal forcing, with tidal amplitudes being less than 10 cm. ...
... In contrast, the lack of inlets in the northern portion of the system leads to residence times that can exceed 1 year and weak tidal forcing, with tidal amplitudes being less than 10 cm. In fact, seasonal winds and oceanic forcing driven by changes in the Gulf Stream cause larger variations by raising water levels 5-30 cm throughout the IRL (Smith, 1993(Smith, , 2001Woodward-Clyde Consultants, 1994). ...
Seagrass is a major structural habitat in the Indian River Lagoon. Maps documented locations and areal extents of beds periodically since the 1940s, and surveys of fixed transects yielded changes in percent cover and depths at the end of the canopy since 1994. Areal extent increased by ∼7,000 ha from 1994 to 2009, mean percent cover within beds decreased from ∼40 to 20%, and mean percent cover standardized to maximum transect length remained near 20%. Thus, conditions supported a consistent biomass because cover decreased as areal extent increased. Between 2011 and 2019, ∼19,000 ha or ∼58% of seagrasses were lost, with offshore ends of canopies moving shoreward and shallower, and standardized mean percent cover decreased to ∼4%. These changes coincided with blooms of phytoplankton, and ≤ 27% of incident subsurface irradiance at 0.9 m was stressful. Decreases in mean percent cover per month of stress became larger when initial mean cover per transect was < 20%, which suggested that the ratio of aboveground to belowground tissues in the expanded and sparser beds led to respiratory demand that was not met by photosynthesis. Despite intermittent improvements in light penetration, widespread recovery of seagrasses has not occurred potentially due to detrimental feedbacks. For example, loss of seagrass exposed sediments to waves, and the resulting disturbance may have hampered recruitment of new shoots. The same decreases also made 58–88% of the carbon, nitrogen, and phosphorus in seagrass tissue available to other primary producers. These nutrients did not enhance growth of epiphytes, whose biomass decreased by ∼42%, but they apparently fueled blooms of phytoplankton, with mean chlorophyll-a concentrations increasing by > 900%. Such intense blooms increased shading and loss of seagrasses. Fortunately, data showed that patches of seagrasses at depths of 0.5–0.9 m persisted for 22–24 years, which suggested that this depth zone could hold the key to recovery. Nevertheless, optimistic estimates predict recovery could take 12–17 years. Such a long-term, widespread loss of a key structural habitat may generate multiple adverse effects in the system, and mitigating such effects may entail planting seagrasses to accelerate recovery.
... This research was conducted to assess the efficacy of using BESE materials to restore intertidal C. virginica reefs within Mosquito Lagoon (ML), the northernmost estuary within the Indian River Lagoon (IRL) system, which stretches 251 km along the Atlantic coast of Florida, USA. Characterized as a hotspot for biodiversity and a critical component of the regional economy [34], ML is a shallow (1.7 m average depth) microtidal coastal lagoon with a long water residence time (mean water half-life~76 days), salinities of 22.6 to 45.2 ppt, and subtropical water temperatures (typically exceeding 20 • C from March to November, with lows of 0 and 15 • C in winter [35,36]. Areal coverage of natural intertidal C. virginica reefs within ML declined 24% between 1943 and 2009 [3], primarily in popular boating areas due to boat wakes dislodging live oyster clusters and depositing shells above the intertidal zone where survival plus natural recolonization are not possible [4]. ...
... Monitoring data did suggest a larger regional-scale difference in oyster recruitment within ML, with N reefs (both live and restored) recruiting at higher rates than S reefs and having greater shell heights at some time points. This regional effect within the study ecosystem has been noted previously [20] and is believed to be a consequence of closer proximity to the ocean inlet in the north, promoting higher tidal amplitudes, greater water exchange, and more nutrient availability [36,40]. ...
Oyster reef restoration efforts increasingly consider not only oyster recruitment, but also the recovery of ecological functions and the prevention of deploying harmful plastics. This study investigated the efficacy of a biodegradable plastic-alternative, BESE-elements®, in supporting oyster reef restoration in east-central Florida (USA) with consideration for how this material also influences biogeochemistry. Four experiments (two laboratory, two field-based) were conducted to evaluate the ability of BESE to serve as a microbial substrate, release nutrients, support oyster recruitment and the development of sediment biogeochemical properties on restored reefs, and degrade under field conditions. The results indicated BESE is as successful as traditional plastic in supporting initial reef development. In the lab, BESE accelerated short-term (10-day) sediment respiration rates 14-fold and released dissolved organic carbon, soluble reactive phosphorus, and nitrate to the surface water (71,156, 1980, and 87% increase, respectively) relative to without BESE, but these effects did not translate into measurable changes in reef sediment nutrient pools under field conditions. BESE lost 7–12% mass in the first year, resulting in a half-life of 4.4–6.7 years. Restoration practitioners should evaluate the biogeochemical properties of biodegradable materials prior to large-scale deployment and consider the fate of the restoration effort once the material degrades.
... Pyrodinium bahamense blooms have been reported in the Northern IRL (NIRL) and are expected to continue increasing due to tropicalization and land-use changes (Phlips et al., 2006;Schaefer et al., 2019). The NIRL has long water residence times (> 100 d) due to limited flushing with the Atlantic Ocean (Kang et al., 2015;Phlips et al., 2015;Smith, 1993), which provides favorable conditions for persistent blooms (Steward and Green, 2007;Steward et al., 2006). In 2017, there was a major P. bahamense bloom reported in the NIRL and Banana River Lagoon (BRL), where saxitoxin concentrations were recorded above limits for recreational waters set by other states (Schaefer et al., 2019). ...
... Similar to M. aeruginosa, these nutrient ratios can influence the growth and production of toxin for P. bahamense Phlips et al., 2006). Saxitoxin was present mostly in the NIRL, where water residence times are longer (> 100 d) than the SIRL (Lapointe et al., 2015;Smith, 1993), thus influencing dissolved nutrient concentrations and bloom dynamics. Higher and more variable DIN:SRP values were observed in the NIRL, potentially explaining why DIN:SRP values were associated with saxitoxin concentrations. ...
Harmful algal blooms that can produce toxins are common in the Indian River Lagoon (IRL), which covers ~250 km of Florida's east coast. The current study assessed the dynamics of microcystins and saxitoxin in six segments of the IRL: Banana River Lagoon (BRL), Mosquito Lagoon (ML), Northern IRL (NIRL), Central IRL (CIRL), Southern IRL (SIRL), and the St. Lucie Estuary (SLE). Surface water samples (n = 40) collected during the 2018 wet and 2019 dry season were analyzed to determine associations between toxins and temperature, salinity, pH, oxygen saturation, concentrations of dissolved nutrients and chlorophyll-a, presence of biosynthetic genes for toxins, relative abundance of planktonic species, and composition of the microbial community. The potential toxicity of samples was assessed using multiple mammalian cell lines. Enzyme-Linked Immunosorbent Assays were used to determine concentrations of microcystins and saxitoxin. Overall, the microcystins concentration ranged between 0.01-85.70 µg/L, and saxitoxin concentrations ranged between 0.01-2.43 µg/L across the IRL. Microcystins concentrations were 65% below the limit of quantification (0.05 µg/L), and saxitoxin concentrations were 85% below the limit of detection (0.02 µg/L). Microcystins concentrations were higher in the SLE, while saxitoxin was elevated in the NIRL and BRL. Cytotoxicity related to the presence of microcystins was seen in the SLE during the wet season. No significant patterns between cytotoxicity and saxitoxin were identified. Dissolved nutrients were identified as the most highly related parameters, explaining 53% of microcystin and 47% of saxitoxin variability. Multivariate models suggested cyanobacteria, flagellates, ciliates, and diatoms as the subset of microorganisms whose abundances were maximally correlated with saxitoxin and microcystins concentrations. Lastly, biosynthetic genes for microcystins were detected in the SLE and for saxitoxin in the BRL and NIRL. These results highlight the synergistic roles environmental and biological parameters play in influencing the dynamics of toxin production by harmful algae in the IRL.
... The Indian River Lagoon (IRL) is a shallow lagoon that stretches for 251 km along the Atlantic coast of Central Florida (Dybas 2002). The low-profile reefs of C. virginica for this study are located in the northernmost portion of the IRL known as Mosquito Lagoon, which is microtidal and low in energy and averages 1.7 m deep (Smith 1993). The subtropical climate allows water temperatures to generally exceed 20°C from March to November and fall between 10 and 15°C in winter months; long water residence times result in salinities that range from 22.6 to 45.2 ppt (Phlips et al. 2015). ...
... In Mosquito Lagoon, the north-to-south gradient of study reefs is thought to be a significant contributor to individual reef differences (Chambers et al. 2018). Northern sites are closer to the ocean inlet and experience greater tidal amplitude (Smith 1993), which may contribute to greater reef heights and oyster densities on these reefs (K. Kibler and L.J. Walters, personal communication). ...
By filtering large volumes of water and releasing nutrient-rich biodeposits (feces and pseudofeces), oysters can locally enhance sediment biogeochemical cycling. An active Crassostrea virginica restoration program in Mosquito Lagoon, FL (USA), was leveraged to assess the immediate (first-year) effects of restoration on sediment nutrients. Measurements included extractable and total carbon, nitrogen, and phosphorus on dead, natural, and restored reefs using a before-after-control-impact design. To investigate an observed "age-nutrient paradox" in sediment nutrient concentrations, a laboratory experiment compared feeding rates and biodeposit nutrient content between juvenile and older oysters. The field study documented a 136% increase in ammonium, 78% increase in total nitrogen, 46% increase in total phosphorus, and 75% increase in organic matter concentrations 12 months post-restoration, with extractable nutrients responding more rapidly to restoration than total nutrients. Sediment nutrient increases were positively correlated with oyster density, shell length, and reef height. Moreover, the laboratory study indicated juvenile oysters had higher rates of chlorophyll-a removal and ammonium efflux and produced biodeposits with higher concentrations of dissolved organic carbon, nitrate, and ammonium than older oysters. Overall, this study documented increases in sediment nutrients on intertidal reefs within the first year of restoration, which may be explained by a greater filtration rate and more nutrient-enriched biodeposits contributed by young oysters as compared to older oysters. Sediment total nitrogen and ammonium content may be the most robust monitoring metrics for documenting the ecosystem service of enhanced biogeochemical cycling on restored oyster reefs.
... This however, was not used to directly determine any REE proxies for studying the monsoon changes. Since La/Yb N was used by Thompson et al. (2013) [11], and Takahashi and Noriki (2007) [6] in the estuaries of several major rivers around the world and in Tokyo Bay, respectively, it was deduced to have the potential to be the REE proxy in Sungai Balok for the determination of the monsoon due to rainfall seasonality [12]. The terrigenous detritus also contains lithogenic sources including organic and inorganic components through the weathering in estuarine environments. ...
... This may have been caused by active river discharge transportation from the upper stream after incorporation of heavy rainfall and sources from groundwater discharge [12]. ...
... This however, was not used to directly determine any REE proxies for studying the monsoon changes. Since La/Yb N was used by Thompson et al. (2013) [11], and Takahashi and Noriki (2007) [6] in the estuaries of several major rivers around the world and in Tokyo Bay, respectively, it was deduced to have the potential to be the REE proxy in Sungai Balok for the determination of the monsoon due to rainfall seasonality [12]. The terrigenous detritus also contains lithogenic sources including organic and inorganic components through the weathering in estuarine environments. ...
... This may have been caused by active river discharge transportation from the upper stream after incorporation of heavy rainfall and sources from groundwater discharge [12]. ...
... All six tropical seagrass species known from the western hemisphere (Halophila decipiens, Halophila engelmannii, Halodule wrightii, Ruppia maritima, Syringodium filiforme, and Thalassia testudinum), as well as the endogenous, federally threatened Halophila johnsonii, are found in the IRL and help support the high biodiversity and fisheries found within (Dawes et al., 1995). Long residence times and limited flushing of the system (Briel et al., 1973;Smith, 1993;Phlips et al., 2015), combined with the sensitivity of seagrasses to nutrient enrichment, eutrophication, and light limitation (Lapointe et al., 1994;Steward et al., 2005;Tewfik et al., 2005;Burkholder et al., 2007), has made water quality a key concern for scientists and managers attempting to protect the biodiversity and marine resources of the IRL. ...
... The northern and central regions of the IRL are particularly susceptible to eutrophication because of the high degree of urbanization and lower flushing rates that increase the residence time of water in these segments (Smith, 1993;Bricker et al., 2008; , 2015). The high residence times of these segments and relatively efficient recycling of N, results in buildup of high TDN concentrations, TDN:TDP ratios, and tendency towards P-limitation (Lapointe et al., 2015). ...
Historically, extensive seagrass meadows were common throughout the Indian River Lagoon (IRL) in east-central Florida, USA. Between 2011 and 2017, widespread catastrophic seagrass losses (~95%) occurred in the IRL following unprecedented harmful algal blooms (HABs), including persistent brown tides (Aureoumbra lagunensis). Little is known about how dissolved nutrients and chlorophyll a are related to light limitation or how biochemical factors, such as the elemental composition (C:N:P) and stable isotope signatures (δ13C, δ15N), of seagrasses within the IRL relate to coverage. Accordingly, we conducted a survey from 2013 to 2015 at 20 sites to better understand these relationships. Results showed a negative correlation between DIN and salinity, indicating freshwater inputs as a DIN source. Seawater N:P ratios and chlorophyll a concentrations were higher in the urbanized, poorly-flushed northern IRL segments. Kd values were higher in the wet season and often exceeded seagrass light requirements (0.8 m-1) for restoration, demonstrating light limitation. Species distribution varied by location. Halodule wrightii was ubiquitous, whereas Syringodium filiforme was not found in the northernmost segments. Thalassia testudinum was only present in the two southernmost segments that had the lowest TDN and highest light availability (Kd). Blade %N and %P also frequently exceeded critical values of 1.8% and 0.2%, respectively, especially in the northern segments. Further, δ15N was positively correlated with ammonium, suggesting wastewater as a major N source. The δ13C values indicated a trend of increasing light limitation from south to north, which helps explain the recent catastrophic loss of seagrasses in the northern IRL. Overall, elemental composition reflected high N-availability and seagrass species distributions were relatable to spatial trends in N and light limitation. For effective restoration, resource managers must reduce N-loading to the IRL to diminish HABs and increase light availability. Regular biochemical monitoring of seagrass tissue should also be implemented during restoration efforts.
... The northern section of the IRL, including Mosquito Lagoon and Banana River, are considered "negative estuaries", and experience stagnant water, limited connectivity, and long pollution residence times [93,94]. Water movement models of the northern IRL estimate renewal times of >230 days, compared to ≤7 days throughout the central and southern IRL [95]. Our results showed more MP/L being added at the north and central control and stormwater sites compared to the south (GLM: all p < 0.0001). ...
Stormwater outfalls are frequently listed as sources of microplastic (MP) contamination into aquatic systems. To date, few studies have been undertaken to determine if stormwater outfalls are MP hotspots in estuaries. This study compared the surface waters adjacent to and at least one kilometer away from stormwater outfalls of a subtropical estuarine system: the Indian River Lagoon (IRL) on the east coast of Florida, USA. Citizen scientists collected water samples monthly for 12 months from stormwater outfalls (n = 24) and control sites (n = 6). Overall, 958 MPs were identified from 1800 L of water, with the most found in the fall months during hurricane season. Stormwater outfalls (mean: 0.53 MP/L) were found to discharge smaller MPs (GLM: p = 0.0008) in significantly higher amounts compared to control sites (GLM: p = 0.02), documenting stormwater as a point-source pollutant in this system. Two types of stormwater outfalls drained into the IRL—closed culverts and open drainage channels—with no difference in MP abundances between the two (GLM: p = 0.60). Microfibers dominated collections (89%). Using ATR-FTIR for polymer identification, 80% of the materials found were plastic; polypropylene (29%), polyethylene (18%), and polyethylene terephthalate (18%) were the most abundant polymers found.
... The Indian River Lagoon system is a series of estuaries spanning 251 km along the east coast of central Florida [40]. Mosquito Lagoon, the northernmost estuary in the system, is characterized by shallow waters (average: 1.5 m) and extended water retention times ( Figure 1) [52,53]. It is connected to the ocean at its northern end (Ponce de Leon Inlet) and has no significant freshwater inputs besides rainwater. ...
Intertidal reefs of Crassostrea virginica (eastern oyster) provide ecologically valuable habitat in estuaries along the Atlantic coast of North America. In Mosquito Lagoon, a shallow-water estuary on the east coast of central Florida, USA, historical aerial imagery was used to document a 24% decline in the live C. virginica reef area between 1943 and 2009. Using 2021 imagery, every living and dead reef in the same region was manually digitized to identify changes during the intervening 12 years. Positive impacts of C. virginica reef restoration that took place between 2007 and 2021 were also digitized to quantify long-term restoration impact. Natural, live C. virginica reef coverage throughout the system was found to have decreased by 50.6% between 2009 and 2021 and, thus, 62.6% between 1943 and 2021. This was attributed to reef fragmentation, reef footprint loss, boating activity, and mangrove expansion. Of the 2542 live reefs identified using 2009 imagery, 219 reefs fragmented, 988 reefs no longer had an identifiable footprint, and 598 reefs contained visible mangroves with non-continuous canopies. Conservatively, 63.6% of directly restored reef area was classified as living reef in 2021, and 74.5% of restoration projects were more than 50% live reef. Dead reef area decreased by 57.9% throughout the system. Understanding changes in C. virginica reef acreage, reef numbers, and mangrove expansion is essential for resource management, restoration practices, and tracking climate change impacts on publicly protected estuaries.
... Except for areas near the inlets, circulation and exchange are driven mainly by wind [66]. The resulting month-long to year-long residence times in most of the system means that nutrients accumulate, which can cause blooms of phytoplankton [25,[66][67][68][69][70]. The restricted circulation and limited mixing also facilitate the accumulation of fine-grained organic-rich sediments, commonly called muck, which have accumulated on top of the natural sand and shell since the watershed was developed [7]. ...
To yield environmental benefits, fine sediments with~10% organic matter, termed muck, were dredged from a tributary to the Indian River Lagoon. Key changes were documented by sampling amphipods, sediments, and the water column near the bottom before dredging, and approximately one month and one year after dredging. Overall, muck yielded the fewest taxa, muck or sediments in creeks that were dredged yielded a moderate number of taxa, and undisturbed sediments in the lagoon yielded the highest number of taxa. Amphipods did not appear in areas with muck until one month and one year after dredging. In contrast, amphipods in sediments that were not muck decreased after dredging. Increases in the occurrence of amphipods paralleled increases in concentrations of dissolved oxygen and decreases in the water, silt/clay, and organic content of sediments. Overall, results indicated that conditions for amphipods were improved by removing muck, and that dredging sandier sediment led to decreased taxonomic richness and numbers of amphipods, which resembled the effects of navigational dredging. Thus, this study suggested that managers should consider the type of sediment to be dredged when permitting projects.
... Lagoonal waters holding limited heat capacity are subject to intense seasonal variations in heat fluxes, which can induce buoyancy-driven circulation (Herdman et al. 2015;Zhan et al. 2021). Winds over coastal lagoons have both local and far-field effects, with the main response to the latter being low-frequency water level variations, which generate pressure-induced hydraulic gradients and associated lagoon water infilling/discharge (Smith 1993;Tamborski et al. 2019). In addition, waves breaking on the fore reef may generate cross-reef flows (Lentz et al. 2016(Lentz et al. , 2017, whereas this effect is significant only for lagoons with ...
Coastal lagoons are biodiversity hotspots that support neighboring ecosystems and various services. They can exhibit distinct biophysical characteristics compared to the adjacent open sea and act paradoxically as autonomous ecosystems. Using remotely sensed observations and state‐of‐the‐art numerical simulations, the role of water column hydrodynamics in shaping the seasonal succession of phytoplankton biomass was investigated for a non‐estuarine coastal lagoon situated in the northeastern Red Sea. Observations reveal that seasonal phytoplankton blooms inside the lagoon occur during a distinctively different period compared to the adjacent open sea. We provide evidence that this striking difference is due to the contrasting hydrodynamic conditions between inside and outside the lagoon, through their effects on stratification that regulate nutrient availability and hence favorable conditions to sustain rapid phytoplankton growth. The proposed mechanism may offer new insights into understanding the biophysical dynamics of non‐estuarine coastal lagoons in other tropical regions of the global oceans.
... Water at 1.5 m from station 8 (upstream of Highway US 1) had a salinity of 27, the same as the surface water at station 31 in the IRL. Tides in this segment of the IRL are ,5 cm and flow through the creek is controlled mainly by runoff and wind-driven circulation (Smith 1993). ...
Release of copper (Cu) from antifouling paints on marine vessels continues to be a global pollution concern. Estimates of the total amount of Cu released from antifouling paints are fairly well constrained; however, less is known about the dispersal of this dissolved Cu. To help improve our understanding of the fate of Cu releases from antifouling paints, a study was carried out in Crane Creek and the adjacent Indian River Lagoon, FL. Dissolved Cu released from antifouling paints accounted for .90% of the total dissolved Cu input to the creek. The maximum concentration of dissolved Cu in the creek, 2.2 mg/L, was ,16% above the U.S. EPA chronic value of 1.9 mg/L. Potential adverse impacts from Cu were likely reduced by uptake of dissolved Cu on suspended particles. Mass balance calculations for Cu showed that about one-third of the dissolved, anthropogenic Cu released from antifouling paint was transported from the creek into the adjacent lagoon. About two-thirds of the anthropogenic Cu was independently shown to be deposited in creek sediments. Copper values for creek sediments were as high as 201 mg/g, well above an effects range-low of 70 mg/g.
... Since 2012, 'super blooms' of the brown tide pelagophyte Aureoumbra lagunensis have occurred in the IRL, a narrow, shallow, poorly flushed (Smith, 1993) 240 km long estuary on Florida's east coast (Gobler et al., 2013;Kang et al., 2015;Lapointe et al., 2015Lapointe et al., , 2017Judice et al., 2020). Although not toxic, these blooms are an example of an ecosystem disruption algal bloom (EDAB, Sunda et al., 2006;Gobler and Sunda, 2012), or an algal bloom which significantly alters or degrades ecosystem function. ...
... Fish communities in Mosquito Lagoon have been well documented since the 1990s, with 87 taxa captured in recent studies [74,75]. Mosquito Lagoon is a shallow microtidal system with wind-driven currents [37,76,77]. Boat wakes are a major source of intertidal oyster reef degradation in Mosquito Lagoon [37,77]. ...
Eastern oysters (Crassostrea virginica) are critical foundation species in estuarine waters, but due to a combination of natural and anthropogenic pressures, oyster abundance has declined. Restoring oyster reefs and monitoring restoration success often focuses on oyster metrics, but relatively infrequently, responses of higher trophic level species and the production of related ecosystem services are accounted for. To address this, we compare the response of a resident reef fish guild (gobies, blennies, toadfish) to standard metrics of oyster restoration success. Using lift nets and seines, natural and restored reefs were monitored over a two-year period within Mosquito Lagoon, Florida, USA. Standard metrics are indicative of restoration success; live oyster density and reef thickness increased in restored reefs after 12 and 24 months. Combined, live oyster density and reef thickness were the best predictors of annual resident reef fish abundance compared to water quality metrics. These results suggest that the benefits of restoring oyster reef habitat are conferred to broader components of the food web, with benefits accruing to reef resident fishes that are a key trophic linkage between lower trophic level foundation species and higher trophic level predators inhabiting coastal ecosystems.
... Time of day and weather conditions (cloud cover, wind direction and speed, and air temperature) as well as presence of H 2 S based on smell were noted. Sites ranged in depth from 0.5 to 3.5 m, depth was not corrected for tidal stage as the northern IRL is microtidal with primarily wind driven differences (Smith, 1993;Schaefer et al., 2019). ...
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.
... Dominant vegetation growing along Mosquito Lagoon shorelines include R. mangle, A. germinans, Myrica cerifera (wax myrtle), and Borrichia frutescens (sea oxeye) [88]. This area experiences an annual high-water season each fall, and water movement is primarily wind-driven [89][90][91]. Mean water depth in Mosquito Lagoon is 1.5 m with a tidal range of 0.7 m at Ponce de Leon Inlet [88]. Historical water gauge data, collected from Haulover Canal by USGS between the years of 2008 and 2020, show the mean water level within the intertidal zone was 23.7 cm, ranging from 18.6 cm (2008) to 30.4 cm (2020). ...
By combatting erosion and increasing habitat, mangrove living shorelines are an effective alternative to hard-armoring in tropical and subtropical areas. An experimental red mangrove living shoreline was deployed within Mosquito Lagoon, Florida, using a factorial design to test the impact of mangrove age, breakwater presence, and mangrove placement on mangrove survival within the first year of deployment. Mixed mangrove age treatments were included to identify if seedling (11-month-old) survival could be enhanced by the presence of transitional (23-month-old) and adult (35 to 47-month-old) mangroves. Environmental factors were monitored to detect possible causes of mangrove mortalities. Approximately half (50.6%) of mangroves died, and of those, 90.7% occurred within the annual high-water season, and 88.9% showed signs of flooding stress. Planting seedlings haphazardly among older mangroves did not attenuate enough wave energy to significantly increase seedling survival. Breakwaters alleviated stress through a reduction in water velocity and wave height, increasing the odds of survival by 197% and 437% when mangroves were planted in the landward and seaward rows, respectively. Compared to seedlings, deployment of adult mangroves increased survival odds by 1087%. Collectively, our results indicate that sites with a high-water season should utilize a breakwater structure and mangroves with a woody stem.
... As such, in the 1990s urban areas covered 30% of the land-water margin in the IRL with single family residences and commercial businesses comprising most of this category (Larson, 1995). Limited flushing in some segments of the IRL (Smith, 1993) combined with intense coastal development in the artificially enlarged and tributary-rich watershed have made the IRL highly susceptible to eutrophication and subsequent reductions to ecosystem diversity (Bricker et al., 2008). ...
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.
... Mosquito Lagoon, the northernmost region of the Indian River Lagoon system (IRL), is characterized by extensive development along shorelines in its northern half, and limited development along southern shorelines connected to Canaveral National Seashore (CANA) and Merritt Island National Wildlife Refuge (Phlips et al. 2015). Mosquito Lagoon has a mean water depth of 1.7 m and is characterized by wind-driven circulation, is microtidal along much of its length (range: 1 cm -1m; 10 cm in study region), and is subject to long water residence times, high salinities and, more recently, high nutrient loadings (Smith 1993, Steward et al. 2006. Lagoon water temperatures range from 4 -33 8C, salinities range from 22.6 -45.2 ppt, and vertical stratification is limited due to the shallowness of the estuary (Walters et al. 2001, Phlips et al. 2015. ...
In Mosquito Lagoon, Florida, there has been a 24% loss of intertidal oyster (Crassostrea virginica) habitat since 1943; many live reefs have been replaced by steep piles of disarticulated shell. To understand the relationship between boating and reef loss, we determined boating intensity and numbers of boat wakes contacting reefs. We then asked if oyster restoration could be successfully undertaken in areas where disarticulated shell had accumulated. We documented 1290 boats passing near Mosquito Lagoon reefs, with 0-51.4 boats producing wakes each hour. Maximizing boating distances to limit wakes would help protect oyster reefs. Community-based restoration began in 2007 and was tracked through 2020. Restoration footprint (density, shell height, profile, thickness, bridges) and off-footprint (density, seagrass) data documented success, suggesting that stabilizing oyster shell was all that was needed in the region. These results provide guidance for boating management and future oyster restoration efforts in microtidal estuaries.
... Since 2012, 'super blooms' of the brown tide pelagophyte Aureoumbra lagunensis have occurred in the IRL, a narrow, shallow, poorly flushed (Smith, 1993) 240 km long estuary on Florida's east coast (Gobler et al., 2013;Kang et al., 2015;Lapointe et al., 2015Lapointe et al., , 2017Judice et al., 2020). Although not toxic, these blooms are an example of an ecosystem disruption algal bloom (EDAB, Sunda et al., 2006;Gobler and Sunda, 2012), or an algal bloom which significantly alters or degrades ecosystem function. ...
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.
... This density gap area is characterized by reduced tidal influence and current energy bordered by greater energy near Ft. Pierce and the St. Lucie Estuary (Bilskie et al., 2017;Smith, 1993), although relatively greater prey species richness was found within this region. These results suggest that tidal influence may be a determining factor affecting dolphin habitat use within the IRL. ...
Anthropogenic impacts in estuarine systems can influence marine mammal habitat use, population dynamics, fitness, and mortality events. The objective was to examine habitat use among the resident common bottlenose dolphin (Tursiops truncatus) population inhabiting the Indian River Lagoon, Florida, and the influences of variation in environmental factors and prey availability in 2003-2015. We utilized photo-identification surveys, stratified random samples of prey, and environmental variables collected monthly. Kernel density estimation was used to determine the magnitude-per-unit area of dolphins across the IRL by wet and dry seasons each year, the values were used as a response variable in classification and regression tree analyses with fish community and environmental variables as predictors. Spatial patterns in dolphin density in the IRL were associated with salinity and dissolved oxygen levels, which are in part associated with freshwater discharges of nutrient and algae laden waters from the region's storm water management system. These findings isolate locations of concern for management of dolphin habitat, and anthro-pogenic drivers of dolphin distributions requiring further research.
... The region is characterized by lower average water temperatures and higher submerged aquatic vegetation (SAV), salt marsh, and mangrove density in comparison to southern regions of the IRL (Adams & Paperno, 2012). Moving southward, currents and tidal exchange increase due to proximity to four inlets and associated tidal influence (Hanisak & Davis, 2018;Smith, 1993). Variations in habitat types and environmental parameters affect the distribution and composition of the local ichthyofauna (Gilmore, 1977), and fish species richness and diversity increase on a north-south gradient within the IRL (Gilmore et al., 1981). ...
A previously undescribed skin abnormality, referred to as “linear skin markings” (LSM), has been identified in free‐ranging common bottlenose dolphins (Tursiops truncatus) in the Indian River Lagoon, Florida (IRL). The lesions were identified during photo‐identification surveys conducted from 2002 and 2015. LSM presented as distinct, parallel lines running dorso‐ventrally on the torso and varied in length and width. The goals of this study were to determine (1) prevalence of the condition in IRL dolphins, (2) age and sex distribution of affected animals, (3) spatial and temporal distribution patterns, (4) duration of the condition, and (5) development of hypotheses regarding the etiology of the condition. Among 1,357 individual dolphins identified during the study period, 96 (7.0%) showed evidence of LSM. Nearly all (98.8%) cases with an established home range occurred in the northern and central regions of the IRL. The majority of cases of known sex were female (85%), of which 100% had given birth to one or more calves. The mean age of animals with LSM when first observed was 7.3 with a range of 1–20 years. The maximum observed duration of LSM was 15 years. Once observed, the condition persisted indefinitely. The etiology of LSM has not been established.
... This collection site exhibited strong within-range-core differentiation and lowest neutral genetic diversity along this distribution range. Land modifications associated with this site's conversion into a conservation area, plus limited hydrological exchange because this portion of the EFL lagoon system experiences highest water residence times (Smith, 1993), probably explain this anomalous pattern. Identifying effects of human activity on intraspecific genetic variation is a research priority (Guo, 2012), and this example highlights that deviations from CMH predictions may also be the product of anthropogenic changes and context-specific environmental factors that may restrict recruitment to local sources. ...
The central‐marginal hypothesis (CMH) posits that range margins exhibit less genetic diversity and greater inter‐population genetic differentiation compared to range cores. CMH predictions are based on long‐held ‘abundant‐centre’ assumptions of a decline in ecological conditions and abundances towards range margins. Although much empirical research has confirmed CMH, exceptions remain almost as common. We contend that mangroves provide a model system to test CMH that alleviates common confounding factors and may help clarify this lack of consensus. Here, we document changes in black mangrove (Avicennia germinans) population genetics with 12 nuclear microsatellite loci along three replicate coastlines in the United States (only 2 of 3 conform to underlying ‘abundant‐centre’ assumptions). We then test an implicit prediction of CMH (reduced genetic diversity may constrain adaptation at range margins) by measuring functional traits of leaves associated with cold tolerance, the climatic factor that controls these mangrove distributional limits. CMH predictions were confirmed only along the coastlines that conform to ‘abundant‐centre’ assumptions and, in contrast to theory, range margin A. germinans exhibited functional traits consistent with greater cold tolerance compared to range cores. These findings support previous accounts that CMH may not be a general rule across species and that reduced neutral genetic diversity at range margins may not be a constraint to shifts in functional trait variation along climatic gradients.
... Skin Hg concentrations reported by Damseaux et al. (2017) in bottlenose dolphins from the Florida Coastal Everglades are the highest in the literature for the Gulf of Mexico region; mangrove forests in this region are rich in organic content, which can support anaerobic bacteria which in turn may facilitate the conversion of Hg 2+ to MeHg that can be incorporated into the food web (Bergamaschi et al., 2012). The IRL-a shallow estuary on the east coast of FL-has low flushing rates which may result in the accumulation of Hg (Smith, 1993). ...
... Skin Hg concentrations reported by Damseaux et al. (2017) in bottlenose dolphins from the Florida Coastal Everglades are the highest in the literature for the Gulf of Mexico region; mangrove forests in this region are rich in organic content, which can support anaerobic bacteria which in turn may facilitate the conversion of Hg 2+ to MeHg that can be incorporated into the food web (Bergamaschi et al., 2012). The IRL-a shallow estuary on the east coast of FL-has low flushing rates which may result in the accumulation of Hg (Smith, 1993). ...
Due to their long life-span and top trophic position, odontocetes can accumulate high concentrations of mercury (Hg) in their tissues. This study measured the concentration of total Hg (THg) in the blubber and skin of bottlenose dolphins (Tursiops truncatus) that stranded along the Florida (FL) panhandle and Louisiana (LA) coasts and investigated the relationship between total Hg (THg) concentration and sex, body length, age, stranding location, diet/trophic position (δ13C and δ15N, respectively), and foraging habitat (δ34S). Additionally, we compared models using body length and age as explanatory variables to determine which was a better predictor of THg concentration. In both tissues, sex was not an influential predictor of THg concentration and there was a positive relationship between body length/age and THg concentration (p < 0.001). Florida dolphins had greater mean blubber and skin THg concentrations compared to LA dolphins (p < 0.001). There was a modest improvement in model fit when age was used in place of body length. δ13C, δ15N, and δ34S differed between stranding locations and together with age were significant predictors of THg concentrations (R2 = 0.52, P < 0.001). Florida dolphins were δ13C enriched compared to LA dolphins (p < 0.001) and THg concentrations were positively correlated with δ13C (R2 = 0.22, p < 0.001). Our results demonstrate spatial variability in THg concentrations from stranded bottlenose dolphins from the northern Gulf of Mexico; however, future research is required to understand how fine-scale population structuring of dolphins within FL and LA impacts THg concentrations, particularly among inshore (bay, sound, and estuary) stocks and between inshore and offshore stocks, as variations in biotic and abiotic conditions can influence both stable isotope ratios and THg concentrations.
... A statistically significant isolation-by-distance relationship was found, indicating that geographic distance contributed to genetic differentiation. Unexpectedly, Mosquito Lagoon and Parrish Park (both northern Indian River Lagoon) populations displayed lower differentiation from a North Carolina site than suggested by their distance from the nearest inlet and the Indian River Lagoon's flushing period of 230 days (Smith, 1993). Mosquito Lagoon and Parrish Park are likely experiencing genetic drift due to their isolation, dispersal limitation, and potential inbreeding (e.g. ...
The genetic population structure of Halodule wrightii at locations in Florida, North Carolina, and Bermuda was investigated using 11 polymorphic microsatellite loci on samples representing 15 sites. We measured allelic diversity and genotypic richness and determined population differentiation and gene flow using principal components and k-means population clustering. Halodule wrightii sites were highly clonal with a mean genotypic richness of 0.09. Genetic differentiation followed a statistically significant isolation-by-distance relationship. Population clustering identified two groups 1) Bermuda and Florida Bay, and 2) the Indian River Lagoon, Gulf of Mexico, and North Carolina. Results from this study indicate that vegetative growth is important for H. wrightii at multiple spatial scales and that isolated populations of H. wrightii likely originated from founder effects. In addition, many of the identified clones included samples that displayed variable copy number of some loci, suggestive that there may be an abnormal chromosome complement and/or may be indicative of aneuploidy. Given the low genotypic diversity observed overall, genetic diversity accumulated without sexual reproduction through genetic mosaicism and other derived somatic mutations will affect fitness and clonal persistence.
... This Act permitted the creation of canals which drained upland areas, increasing the areal extent of the watershed and also storm water discharge volumes (SJRWMD 2007). Because of the small number of outlets, water residence times can be very high (> 1 year ;Smith 1993) in parts of the lagoon, which means that increased nutrient loads from agriculture and increased urbanization have resulted in eutrophication issues including extremely frequent and persistent algal blooms, increased turbidity, and rapidly declining seagrass populations (Morris et al. 2018). This decline has been documented through annual monitoring by the South Florida and St. Johns River Water Management Districts. ...
There is a reciprocal relationship between disturbance and diversity such that disturbance can result in changes to diversity that in turn impact a population’s response to disturbance. Seagrasses are systems that are experiencing increasing disturbances and loss, and it is therefore important to understand this diversity–disturbance relationship. In this study, we observe changes in diversity and population differentiation of shoal grass (Halodule wrightii) during a large scale dieoff in the Indian River Lagoon, Florida USA. While allelic richness and heterozygosity were relatively high and do not change over time, population differentiation increased (estimated using FST), indicating genetic drift. This maintenance of diversity is important since seagrasses with high genetic diversity have been shown to withstand several environmental disturbances (grazing, low light, and high temperature) better than meadows with low diversity. This small increase in differentiation was only detectable because of replicate collection over time, which is rare in the literature and in monitoring programs. However, it is important since it indicates potential dispersal limitation which could hinder large scale recovery. We recommend plant nurseries as management tools in this system to preserve existing diversity and to aid in large scale restoration.
... Given its morphology and topography, the IRL ranges from micro-tidal in the north to being influenced by ∼ 1 m tides in the south. Accordingly, circulation is driven primarily by wind in the north, which yields water residence times that vary from weeks to a year or more, while in the south, circulation is influenced by tides, leading to shorter residence times (Smith 1993). The lagoon is also one of the most biologically diverse estuaries in North America (Swain 1995), in part because it spans two biogeographical provinces (temperate and sub-tropical). ...
The Indian River Lagoon (IRL) is a large and complex barrier island estuary on Florida’s East coast. The system is also one of the nation’s most biologically diverse, a major spawning and nursery ground for numerous species of fish and shellfish, and home to significant populations of dolphins and manatees. Ocean observing systems can play an integral role in evaluating the effects of both natural (e.g. climate change) and anthropogenic impacts (e.g. nutrient pollution) on such a complex system. In this paper we present an integrated multidisciplinary approach to studying the recurrent large-scale harmful algal bloom (HAB) events that have threatened both the ecological and economic stability of the IRL and represent a significant public health hazard. Due to the complex biological, chemical and physical interactions associated with IRL HABs, the integration of classical observing methodology, such as phytoplankton surveys, with real-time water quality monitoring, innovative technology, and biological sentinels, is essential. The open sharing of data for research, education and public engagement is another key component of our approach. There are multiple stakeholders and end users that rely on these efforts to understand HAB dynamics in a unique marine system.
... Variation in d 13 C values is likely due to inputs of organic carbon from a combination of marine phytoplankton (d 13 C values of -18‰ to -24‰) and detritus from terrestrial C 3 plants such as mangroves (-35‰ to -25‰) and seagrasses (-13.5‰ and -5.2‰) (Deegan & Garritt, 1997;Michener & Kaufman, 2007 study that range from ∼3 to 8‰ therefore suggest a continuum of impact from anthropogenically-derived nutrients across sites in the IRL. High levels of dissolved inorganic nitrogen and total dissolved nitrogen have been reported previously in regions of the northern IRL resulting from long water residence times and inputs of anthropogenically-derived nitrogen via surface water runoff and groundwater from septic tanks (Smith, 1993;Lapointe et al., 2015). Our data suggest that sites close to human development in the Banana River and southern sites in the Indian River (d 15 N values of ∼6 to 8‰) are more impacted by these 15 N-enriched sources than those in the more sparsely populated Mosquito Lagoon and northern IRL sites; our POM values are in general agreement with the magnitude of 15 N enrichment found in macroalgae from this region of the IRL (Lapointe et al., 2015). ...
The success of many sessile invertebrates in marine benthic communities is linked to their ability to efficiently remove suspended organic matter from the surrounding water column. To investigate the diet of the barnacle Amphibalanus eburneus , a dominant suspension feeder within the Indian River Lagoon (IRL) of central Florida, we compared the stable isotopes ratios (δ ¹³ C and δ ¹⁵ N) of barnacle tissue to those of particulate organic matter (POM). Collections were carried out quarterly for a year from 29 permanent sites and at sites impacted by an Aureoumbra lagunensis bloom. δ ¹³ C and δ ¹⁵ N values of Amphibalanus eburneus varied across sites, but δ ¹⁵ N was more stable over time. There was a range of δ ¹⁵ N values of Amphibalanus eburneus tissue from 6.0‰ to 10.5‰ across sites. Because land-based sources such as sewage are generally enriched in ¹⁵ N, this suggests a continuum of anthropogenic influence across sites in the IRL. Over 70% of the variation in δ ¹⁵ N values of Amphibalanus eburneus across sites was driven by the δ ¹⁵ N values of POM, supporting a generalist feeding strategy on available sources of suspended organic matter. The dominance of this generalist consumer in the IRL may be linked to its ability to consume spatially and temporally variable food resources derived from natural and anthropogenic sources, as well as Aureoumbra lagunensis cells. Generalist consumers such as Amphibalanus eburneus serve an important ecological role in this ecosystem and act as a sentinel species and recorder of local, site-specific isotopic baselines.
... With the exception of the dredged Intracoastal Waterway and channels, the average depth of the IRL is approximately 1.5 m (Woodward-Clyde Consultants, 1994). Due to its shallow depth and the limited tidal exchange between it and the Atlantic Ocean, the lagoon has minimal flushing and, thus, chemical and microbiological agents may become concentrated (Smith, 1993). Dense human development along the eastern coast of Florida and intense agricultural activity have resulted in increased freshwater inputs and altered water quality characterized by chemical contamination, high nutrient input, decreased salinity, decreased seagrass habitat, and eutrophication (Sigua et al., 2000;Sime, 2005). ...
The objective of this study was to test the potential influence of short-term changes in water quality on the frequency of sightings of common dolphins (Tursiops truncatus) in the Indian River Lagoon, Florida. The study was based on two data sources: (1) Land/Ocean Biogeochemical Observatories (LOBOs) that provided real-time monitoring of multiple water quality and weather parameters, and (2) standardized methods for identifying and counting individual dolphins using photo-identification techniques. Water quality parameters included salinity, water color (chromophoric dissolved organic matter), conductivity, dissolved oxygen concentration, oxygen saturation, chlorophyll, nitrate and phosphate concentrations, temperature, and turbidity. Weather was assessed using data for air temperature, barometric pressure, humidity, light, and wind speed and direction. Variables were measured continuously over a one-year period and analyzed as the mean for each parameter the hour before, during, and after each dolphin sighting period. Short-term variations in sightings within 0.5 km of the LOBO were measured using previously established photo-identification techniques on a weekly basis. In multivariable regression analyses, statistically significant inverse associations were found between air temperature and the frequency of dolphin sightings for all three time periods. The results demonstrate the feasibility of integrating variation in weather and water chemistry data with dolphin movements as potential indicators of ecosystem quality and climate change.
... The narrow and poorly-flushed IRL system (Smith, 1993) has experienced nitrogen and phosphorus over-enrichment at levels exceeding concentration thresholds for restoration of sub-tropical seagrass ecosystems (see Sigua et al., 2000;Tomasko and Lapointe, 2001), a keystone habitat component. The Florida Department of Environmental Protection (FDEP, 2013) adopted Total Maximum Daily Loads (TMDL) for 3 basins (sub-sections) of the IRL system, with respective Basin Management Action Plans (BMAP) designed to reduce loads of nitrogen and phosphorus loading to the IRL system. ...
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 for bloom-forming macroalgae and analyzed for del-15N, % nitrogen, % phosphorus, carbon:nitrogen, carbon:phosphorus, and nitrogen:phosphorus ratios. Data were fitted to geospatial models showing elevated del-15N values (>+5‰), matching human wastewater in most of the IRL system, with elevated enrichment (del-15N = >+7‰ to +10‰) in urbanized portions of the central IRL and Banana River Lagoon. Results suggest increased mobilization of onsite sewage disposal system (OSDS, septic tank and package plant) NH4+ during the wetter 2014 season. Resource managers must improve municipal wastewater treatment infrastructure and commence significant septic-to-sewer conversion to mitigate nitrogen over-enrichment, water quality decline and habitat loss as mandated in the Tampa and Sarasota Bays and the Florida Keys.
Mortality patterns in cetaceans are critical to understanding population health. Common bottlenose dolphins (Tursiops truncatus truncatus) inhabiting the Indian River Lagoon (IRL), Florida have been subjected to four unusual mortality events (UMEs), highlighting the need to evaluate morbidity and mortality patterns. Complete gross examinations were conducted on 392 stranded dolphins and histopathological analyses were conducted for 178 animals (2002-2020). The probable causes of mortality were grouped by etiologic category: degenerative, metabolic, nutritional, inflammatory (infectious and noninfectious disease), and trauma. Probable cause of mortality was determined in 57% (223/392) of cases. Inflammatory disease (infectious/noninfectious) and trauma were the most common. Inflammatory disease accounted for 41% of cases (91/223), with the lungs (pneumonia) most commonly affected. Trauma accounted for 36% of strandings (80/223). The majority of trauma cases were due to anthropogenic activities (entanglement, fishing gear or other debris ingestion, and propeller strikes), accounting for 58% of trauma cases (46/80). Natural trauma (prey-associated esophageal obstruction or asphyxiation, shark bites, and stingray interactions) accounted for 12% of all cases (26/223), and trauma of undetermined origin was identified in 4% of cases (8/223). Starvation or inanition (nutritional) were the probable cause of mortality in 17% of cases and peaked during the 2013 UME (61% of cases). Degenerative and metabolic etiologies accounted for 5% of cases. This study represents the most comprehensive evaluation of morbidity and mortality patterns in IRL dolphins. Because IRL dolphins are routinely exposed to anthropogenic threats and have endured multiple UMEs, these baseline data are critical to the conservation and management of this population.
Meteoric groundwater discharge (MGD) to coastal regions transports terrestrial freshwater and nutrients that may alter coastal ecosystems by supporting harmful algal blooms. Estimation of MGD-driven nutrients is crucial to assess potential effects on coastal zones. These estimates require a reliable assessment of MGD rates and pore water nutrient concentrations below subterranean estuaries. To estimate nutrient delivery into a subterranean estuary in the Indian River Lagoon, FL., pore water and surface water samples were collected from nested piezometers along a selected transect on five sampling episodes. Groundwater hydraulic head and salinity were measured in thirteen onshore and offshore piezometers. Numerical models were developed, calibrated, and validated using SEAWAT to simulate MGD flow rates. Lagoon surface water salinity exhibits no spatial but mild temporal variation between 21 and 31. Pore water salinity shows tremendous variation in time and space throughout the transect except in the middle region of the lagoon which exhibits uniform but elevated salinities up to 40. Pore water salinity as low as that of freshwater happens to occur in the shoreline regions during most of the sampling episodes. Both pore water and surface water show remarkably higher total nitrogen TN than total phosphorus TP concentrations and most TN is exported as NH4, reflecting the effect of mangroves on the geochemical reactions that reduce NO3 into NH4. Nutrient contributions of pore water and lagoon water exceed the Redfield TN/TP molar ratio in all sampling trips by up to a factor of 48 and 4, respectively. Estimated TP and TN fluxes receives by the lagoon via MGD are 41-106 and 113-1478 mg/d/m of shoreline. The molar TN/TP ratio of nutrient fluxes exceeds the Redfield ratio by a factor of up to 3.5 which indicates the potential of MGD-driven nutrients to alter the lagoon water quality and support harmful algal blooms.
Florida's Indian River Lagoon (IRL) has experienced large-scale, frequent blooms of toxic harmful algae in recent decades. Sentinel, or indicator, species can provide an integrated picture of contaminants in the environment and may be useful to understanding phycotoxin prevalence in the IRL. This study evaluated the presence of phycotoxins in the IRL ecosystem by using the bull shark (Carcharhinus leucas) as a sentinel species. Concentrations of phycotoxins were measured in samples collected from 50 immature bull sharks captured in the IRL between 2018 and 2020. Ultra-performance liquid chromatography/tandem mass spectrometry was used to measure toxins in shark gut contents, plasma, and liver. Analysis of samples (n = 123) demonstrated the presence of multiple phycotoxins (microcystin, nodularin, teleocidin, cylindrospermopsin, domoic acid, okadaic acid, and brevetoxin) in 82 % of sampled bull sharks. However, most detected toxins were in low prevalence (≤25 % of samples, per sample type). This study provides valuable baseline information on presence of multiple phycotoxins in a species occupying a high trophic position in this estuary of national significance.
Microplastics (MPs) are a ubiquitous pollutant, emphasizing the need to understand their abundance and the factors that influence these patterns around the globe. In a prior study, high numbers of MPs were found in surface waters and tissues of the oyster Crassostrea virginica collected from one location in the Indian River Lagoon (IRL, FL, USA). To better understand spatial and temporal variability of MPs throughout the IRL, for one year, monthly surface water samples were collected from 35 sites, while oysters were collected quarterly from 12 sites. Microscopy and ATR-FTIR were used to quantify MP. In total, 3755 MPs were found in 44% of water samples (mean density ± CI: 1.47 ± 0.09 MP/L). South IRL water had the most MPs, likely associated with proximity to urbanization, inlets (MP sinks) and tributaries (MP sources). MP (n = 3181) were found in 70% of examined C. virginica (n = 1402). Abundances of MP in oysters were lower in the spring and in north IRL. The overall mean abundance was 2.26 ± 0.16 MP/oyster, and the density was 2.43 ± 0.52 MP/g wet tissue weight. Our results provide a more complete picture of MPs in the IRL, a subtropical, shallow-water estuarine system.
Seven species of seagrass have been found in the Indian River Lagoon (IRL), making it an unusually diverse location at the global scale. From 1994 to 2019, the lagoon-wide distribution of these species reflected variations in temperature, salinity, and the availability of light at depth, which were related to latitudinal differences in hydrology and hydrodynamics along the IRL. In general, species richness was higher near the four southern inlets, and fewer species were found in areas with longer residence times for water. At a finer scale, the distribution of species varied among depths, with the greatest number of species found at mid-depths (~0.4-0.9 m). Prior to 2011, these patterns remained relatively consistent for~40 years, but several, intense and prolonged phytoplankton blooms disrupted them. The areal extent of all seagrasses decreased by over 50%, the offshore ends of canopies moved shoreward and shallower, distributions of species along gradients of latitude and depth were disrupted, and mean percent cover decreased. Major changes in distribution and abundance of seagrasses arose when salinity, temperature, and availability of light at depth exceeded limits derived for each species. These substantial and widespread changes engendered concerns for recovery or rehabilitation of seagrasses in the lagoon.
Within the Indian River Lagoon (IRL), blooms of the marine microalga Aureoumbra lagunensis in excess of 1310 6 cells ml À1 have occurred on three occasions after first being locally identified in 2012. All blooms coincided with times of peak reproduction and growth of the eastern oyster Crassostrea virginica in Mosquito Lagoon (northern IRL). Over six years of field data on monthly recruitment of C. virginica were compared to bimonthly cell counts of A. lagunensis. In addition to expected temperature and salinity-driven variations in oyster recruitment, cell counts of A. lagunensis in excess of 10,000 ml À1 reduced oyster recruitment. A second method of analysis similarly found a negative association with oyster recruitment when cell counts exceeded 9658 ml À1. Understanding the impact of blooms of A. lagunensis is essential for managing harvesting, aquaculture, and restoration of this foundation shellfish species.
Accurate estimates of abundance are critical to species management and conservation. Common bottlenose dolphins (Tursiops truncatus truncatus) inhabiting the Indian River Lagoon (IRL) estuarine system along the east coast of Florida are impacted by anthropogenic activities and have had multiple unexplained mortality events, necessitating precise estimates of demographic and abundance parameters to implement management strategies. Mark-recapture methodology following a Robust Design survey was used to estimate abundance, adult survival, and temporary emigration for the IRL estuarine system stock of bottlenose dolphins. Models included a parameter (time since first capture) to assess evidence for transient individuals. Boat-based photo-identification surveys ( n = 135) were conducted along predetermined contour and transect lines throughout the entire IRL (2016-2017). The best fitting model included the “transient” parameter to survival, allowed survival to vary by primary period, detection to vary by secondary session, and did not allow temporary emigration. Dolphin abundance ranged from 981 (95% CI: 882-1,090) in winter to 1,078 (95% CI: 968-1,201) in summer with a mean of 1,032 (95% CI: 969 -1,098). Model averaged seasonal survival rate for marked residents ranged from 0.85-1.00. Capture probability ranged from 0.20 to 0.42 during secondary sessions and transient rate from 0.06 to 0.07. This study represents the first Robust design mark-recapture survey effort to estimate abundance for IRL dolphins and provides parameter estimates to optimize sampling design of future studies. Transients included individuals with home ranges extending north of the IRL requiring further assessment of stock delineation. Results were remarkably similar to prior abundance estimates resulting from line-transect aerial surveys and were consistent with a stable population. Data will enable managers to evaluate the impact of fisheries-related takes as well as enable future comparisons of demographic parameters for a dolphin population that continues to sustain large scale mortality events and anthropogenic impacts.
Increases in resistance to commonly used antibiotics have been reported globally in isolates from humans, wildlife, and the environment. To date, few studies have examined long-term trends in antibiotic resistance in organisms isolated from marine mammal populations. The objective of this study was to examine temporal trends in resistance to antibiotics among pathogens isolated from common bottlenose dolphins (Tursiops truncatus) between 2003 and 2015. Dolphins were captured and released in the Indian River Lagoon, Florida, an ecosystem with a large coastal human population and significant environmental impacts. Swab samples for microbiology were taken from the blowhole, gastric fluid, and feces and cultured on standard media under aerobic conditions. Isolates were identified using gram stain morphology and growth on selective media. Antibiotic resistance was measured using disc diffusion on Mueller Hinton agar and the Multiple Antibiotic Resistance (MAR) index calculated for each pathogen. A total of 733 isolates was obtained from 171 individual dolphins. The most commonly cultured pathogens included Aeromonas hydrophila, Escherichia coli, Edwardsiella tarda, and Vibrio alginolyticus. The overall prevalence of resistance to at least one antibiotic for the 733 isolates was 88.2%. The MAR index increased significantly between 2003 and 2007 and 2010 and 2015 for Pseudomonas aeruginosa and V. alginolyticus. For all bacterial isolates, resistance to cefotaxime, ceftazidime, and gentamicin increased significantly between sampling periods. This is one of few studies to use the MAR index for bacterial isolates from a marine mammal. The significant increases in resistance for some bacterial species likely reflect shared environmental exposures to antibiotics and transfer of resistance to dolphins from terrestrial sources or from animal or human populations.
Crassostrea virginica, the eastern oyster, is a native foundational species that inhabits coastal and estuarine ecosystems along the western Atlantic seaboard. Introduction of C. virginica into estuarine areas with limited or no extant populations is gaining popularity as a pro‐active approach for improving estuarine water quality and creating natural wave breaks for shoreline stabilization. Adult oysters, grown by 113 community members under their private docks, were collected and deployed at 3 county‐owned sites along the Indian River Lagoon within Brevard County, Florida. In this shallow, warm‐water estuary, replicate treatments deployed at each site included bagged adult oysters collected from gardeners in fall 2014, bagged adult oysters from spring 2015 gardeners, bagged blank (clean) shell, and empty plots (control). Prior to deployment, morphometric data (shell length, weight) were collected on all gardened oysters. Morphometric data were then collected quarterly for all surviving and recruited oysters for 18 months. Our monitoring timeframe was sufficient for assessing survival of gardened oysters, but likely not sufficient to understand recruitment patterns. In areas with no recruitment and limited gardened oyster survival, regular enhancement with live oysters would be needed for long‐term success. In areas with natural recruitment, the blank shell treatment was most successful. Lessons learned from this study include: 1) need for better tracking of abiotic variables (e.g. salinity) where gardening occurred, 2) role of seasonality in initial post‐deployment survival, even in a warm‐water estuary, and 3) importance of pilot studies prior to large‐scale gardened oyster deployments.
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Fish communities in tidal tributaries have received considerable attention, but the relative value of nontidal tributaries (having a tidal amplitude of < 5 cm) may represent an under-valued habitat. A multi-gear sampling approach was used to collect fish and macroinvertebrates from one tidal and two nontidal tributaries to describe and compare the respective nekton communities and habitat use patterns. Nekton communities in tidal and nontidal tributaries were markedly different even though habitats were similar (e.g., temperature, DO, depths, shoreline vegetation). While catch-per-unit-effort (CPUE) of estuarine-dependent species (e.g., red drum, spot, common snook) was lower in nontidal tributaries, the overall nekton CPUE was twice that of the tidal tributary, and the community was comprised mostly of freshwater marsh species (e.g., eastern mosquitofish, sailfin molly, bluefin killifish). Based on the life histories of the fishes that differed between tributary types, the proximity of coastal inlets and availability of effective larval transport mechanisms for estuarine-dependent species may be greater determinants of community differences than factors related to tributary size or shoreline habitat type. These results recognize smaller nontidal tributaries as undervalued nursery habitats and suggest the function as secondary nursery habitats is a critical service to the overall estuarine community.
Astronomic tides and nonlinear tidal dispersion were assessed for the Indian River lagoon system, a tropical coastal estuary (located in central east Florida) with engineered features (causeways). The four inlets, which choke the tides entering the system, together with the expansive size and shallowness of the estuary (and the associated energy dissipation) are the prominent mechanisms leading to the microtidal environment of the lagoon. Inside the shallows, there are 12 causeway abutments that cause a compartmentalization of the waters into separate basins, whereby the causeway openings act mechanistically as acceleration-inducing throttles to promote local regions of high kinetic energy (velocities). The causeways lead to a furthered decay of tidal amplitudes, phase lags in the tides and an enhanced generation of harmonic overtides and tidal residuals relative to the natural domain (i.e., fully open-no causeways). Numerical modeling of astronomic tidal flows (Advanced Circulation-ADCIRC) employed an unstructured, triangular mesh that resolved the entire scale of the lagoonal system with element sizes of 10-100 m and captured its many intricate domain features, including: the causeways in Indian River lagoon proper and Banana River lagoon; over 150 km of sinuous channels in Mosquito lagoon; and the hydraulic connections of the individual lagoons-one of which, Haulover Canal, is only 55 m wide. The model performed well with an index of agreement of (on average) 94% when compared with tidal data from 23 stations located throughout the system. Tides in the shallows are small at just millimeters in range; the model captured the tidal signal at the stations located there with an index of agreement of (at worst) 79%. Considering previous tidal studies of the Indian River lagoon system and tropical coastal estuaries in general, this level of domain definition and model validation of astronomic tide behavior is unprecedented and provides a benchmark for numerical simulation of lagoonal tidal flow.
The new concept is that, over many tidal cycles, the tidally averaged "flow' (Q g) of water from the Gulf of Mexico, with a salinity of 35‰, can be treated as a constant at any point in the estuary. This flow is used in a simple mixing equation to predict salinity in the estuary at different river inflows, and the predicted salinities are used to compute residence times for water in the estuary. The techniques developed to achieve optimal precision in the relation between river inflow and salinity include a newly derived equation to fit Q g by a least-squares method and a procedure to determine the optimal averaging period for river inflow. Results from Charlotte Harbor indicate that, under average (70 m+3 s-1) river inflow, 95% of the original water present in the harbor flushes into the gulf in 130 d. -from Authors
Results from a hydrological survey of the Nichupté Lagoon System are presented, providing basic information on an area which is increasingly affected by environmental stresses from development activities. Depth, as well as diurnal and annual cycles of salinity and temperature distributions, were sampled during 1982 and 1983. Spatial variations were only significant in salinity in the horizontal plane with an east-west gradient apparently a characteristic of the system. A model is presented which explains nearly all the observed salinity variations in time, in terms of the rainfall. A flushing time of 1·3 years was computed for the system during the study period. Rainfall statistics for the area indicate that strong variations in flushing intensity on the seasonal and annual scales are to be expected about an average of 1·9 years.
The salinity distribution in an idealized estuary where mining is predominantly due to the tides is computed, using an eddy diffusivity based on the distribution of tidal currents and excursions. Comparison is made to the salinity distribution in real estuaries.
Tidal contributions to a sea‐level record can be reduced by a large factor by taking special weighted averages of hourly values. In the residual record it is possible to recognize changes of as little as a few millimeters taking place in a few days. The method might be useful in other geophysical problems.
Segmented tidal prism models have considerable merit, especially for pedagogical purposes, in that they can incorporate mixing processes in an easily visualized, if over simplified, way. The present paper attempts to expose some flaws in Ketchum's original model of this type and proposes a more general approach. This appears to give quite satisfactory results when applied to test cases, in particular to the prediction of salinity distribution for the Thames estuary.
The paper describes a model which combines the simple, but effective ideas underlying previous models developed by Ketchum, and Dyer & Taylor. Ketchum's data on the Raritan Estuary is used to demonstrate the application of the model. An alternative interpretation of inter-segment transfers in terms of an average dispersion coefficient is shown to yield values consistent with those quoted in the literature.
Observations of the spatial distribution of salinity and tidal salinity fluctuations along the length of the Fleet are presented and different structures are identified with different freshwater runoff conditions. The salinity distribution appears to be the result of a balance between weak tidal flushing and a small freshwater input. A tidal exchange box model is developed to represent this weak balance and is able to reproduce the semidiurnal, fortnightly and seasonal fluctuations of salinity. By use of the tuned model, estimates are made of the flushing times of different segments of the lagoon, the distribution of water from particular stream inputs, and hence their polluting potential, and the likely effect on the salinity structure of changes in the tidal regime which could result from sediment deposition.
Water level records from two study sites in Indian River Lagoon, along Florida’s Atlantic Coast, are used to characterize
the vertical displacement of the estuarine intertidal zone in response to subtidal frequency forcing. A 22-year water level
record indicates that the seasonal cycle has a range approximately one-quarter greater than the mean tidal range. The intertidal
zone thus rises and falls to such an extent that over time scales in excess of several weeks there is no layer which consistently
experiences an alternating exposure and inundation. Six-year sets of high and low tide extremes from the second study site
are expressed in the form of cummulative histograms to determine the probabilities with which high tide and low tide levels
lying outside of median values will occur in response to the interaction of tidal constituents and low-frequency forcing.
High and low water values are then stratified by month, and probability distributions are recomputed for each subset. In this
study area, unpredictable, low-frequency water level fluctuations perturb the intertidal zone to such an extent that the probabilities
of extreme high and low water levels, in addition to mean high and low water, must be determined to characterize the stuarine
intertidal zone adequately. *** DIRECT SUPPORT *** A01BY034 00002
Lunar barometric tidal determinations (L
2) have been made by the Chapman-Miller method for Zrich (493 m) and Sntis (2000 m) based on 49 years' data. The seasonal variations ofL
2 are much larger at Zrich than on the Sntis summit. However, a comparison with the five other pairs of stations for which tidal determinations at different altitudes, but short horizontal distances, are available do not indicate that this result is as an altitude effect, nor do they show any other systematic differences betweenL
2 at the lower and the higher station. The solar tidal determinations agree well with those made byEggenberger (1944) and fit in with those obtained for other stations. From the difference between the pressure oscillations at Zrich and on Sntis the corresponding meantemperature oscillations of the air column between the two stations has been computed.
Chincoteague Bay is a bar-built estuary with two inlets from the Atlantic Ocean—one at Ocean City, Maryland, and the other
some 30 miles southward at Chincoteague Inlet. All available salinity data collected in the years 1951 through 1956 are utilized
here to evaluate the processes which control the average monthly salinity in the bay. The major features of the salt balance
are satisfactorily explained by a simple model equating the rate of change of salinity to terms involving net fresh water
inflow and exchange rate through the inlets. An estimation of the exchange rate is made which indicates that approximately
seven percent of the volume of the bay waters are renewed each day.
The doping of molecular beam epitaxial GaAs with erbium up to a concentration of 2×10<sup>1</sup><sup>9</sup> cm<sup>-</sup><sup>3</sup> has been successfully demonstrated. Up to a concentration of about 5×10<sup>1</sup><sup>8</sup> cm<sup>-</sup><sup>3</sup> the surface morphology remained good but for higher doping levels the surface became structured. Hall and profile measurements indicate that erbium doping gives rise to a trapping level capable of compensating silicon‐doped layers. For the first time photoluminescence from a rare earth element incorporated in a III‐V semiconductor has been observed at room temperature.
The probable lowest average salinity in the Indian River
- F Chew
Manual of harmonic analysis and pre-dictions of tides Special Publication Number 98, revised edi-tion, United States Government Printing Otfice Numerical mod-eling of tidal hydrodynamics and salinity transport in the Indian River Lagoon
- P Schureman
SCHUREMAN, P. 1958. Manual of harmonic analysis and pre-dictions of tides. Special Publication Number 98, revised edi-tion, United States Government Printing Otfice, Washington, D.C. 317 p. SHENG, Y. P., S. PEENE, AND Y. M. LIU. 1990. Numerical mod-eling of tidal hydrodynamics and salinity transport in the Indian River Lagoon. Florida Scientist 53:147-168.
A user's guide to a computer program for harmonic analysis of data at tidal fre-quencies. National Oceanic and Atmospheric Administration United States Department of Com-merce A simple, segmented prism model of tidal mixing in well-mixed estuaries
- R E Dennis
- E E Ant
- Long
DENNIS, R. E. ANt) E. E. LONG. 1971. A user's guide to a computer program for harmonic analysis of data at tidal fre-quencies. National Oceanic and Atmospheric Administration Technical Report 41, United States Department of Com-merce, Rockville, Maryland. DYER, K. ANn P. TAYLOR. 1973. A simple, segmented prism model of tidal mixing in well-mixed estuaries. Estuarine and Coastal Marine Science 1:411-418.
Some Applications of Sta-tistics to Meteorology A fortran program for the calculation of hourly values of astronomical tide and height of high and low water. Technical Memorandum TDL-6, Na-tional Weather Service Salt balance and exchange rate for Chincoteague Bay
- H Panofsku
- G Brier And
- N And
- R Cummings
PANOFSKu H. AND G. BRIER. 1958. Some Applications of Sta-tistics to Meteorology, 1st ed. Pennsylvania State University, University Park, Pennsylvania. 224 p. PORE, N. AND R. CUMMINGS. 1967. A fortran program for the calculation of hourly values of astronomical tide and height of high and low water. Technical Memorandum TDL-6, Na-tional Weather Service, Silver Spring, Maryland. 127 p. PRITCHARD, D. W. 1960. Salt balance and exchange rate for Chincoteague Bay. Chesapeake Science 1:48-57.
A fortran program for the calculation of hourly values of astronomical tide and height of high and low water
- N Pore
- R Cummings
On the circulation and tidal flushing of Mobile Bay, Alabama, Part 1. Department of Oceanography (Reference 54-20'I"), Texas A&M University, College Station, Texas. 63 p. CHEW, F. 1956. The probable lowest average salinity in the Indian River
- G B Austin
AUSTIN, G. B. 1954. On the circulation and tidal flushing of Mobile Bay, Alabama, Part 1. Department of Oceanography (Reference 54-20'I"), Texas A&M University, College Station, Texas. 63 p. CHEW, F. 1956. The probable lowest average salinity in the Indian River. Qua rterlyJou rnal of the Florida Academy of Sciences 19:241-250.
Surface water hydrology, Ch. 2
- D Rao
Manual of harmonic analysis predictions of tides. Special Publication Number 98, revised edition, United States Goverment Printing Office
- P Schureman
Water budget for the Indian River Lagoon: An overview of land use effects. M.S. Thesis, Department of Oceanography, Florida Institute of Technology
- K Glatzel
GLATZEL, K. 1986. Water budget for the Indian River Lagoon: An overview of land use effects. M.S. Thesis, Department of Oceanography, Florida Institute of Technology, Melbourne, Florida. 109 p. GLATZEt., K. AND S. DA COSTA. 1988. Hydrology of the Indian River Lagoon. In Indian River Lagoon Estuarine Monograph, Marine Resources Council, Florida Institute of Technology, Melbourne, Florida.
Hydrology of the Indian River Lagoon
- K Glatzel
- S. Da Costa