Joseph Bay Research Articles

Spatial Variation in Mercury Accumulation in Bottlenose Dolphins (Tursiops spp.) in Southeastern U.S.A.

Bottlenose dolphins (Tursiops spp.) inhabit bays, sounds, and estuaries (BSEs) throughout the southeast region of the U.S.A. and are sentinel species for human and ecosystem-level health. Dolphins are vulnerable to the bioaccumulation of contaminants through the coastal food chain because they are high-level predators. Currently, there is limited information on the spatial dynamics of mercury accumulation in these dolphins. Total mercury (THg) was measured in dolphin skin from multiple populations across the U.S. Southeast Atlantic and Gulf of Mexico coasts, and the influence of geographic origin, sex, and age class was investigated. Mercury varied significantly among sampling sites and was greatest in dolphins in St. Joseph Bay, Florida Everglades, and Choctawhatchee Bay (14,193 ng/g ± 2196 ng/g, 10,916 ng/g ± 1532 ng/g, and 7333 ng/g ± 1405 ng/g wet mass (wm), respectively) and lowest in dolphins in Charleston and Skidaway River Estuary (509 ng/g ± 32.1 ng/g and 530 ng/g ± 58.4 ng/g wm, respectively). Spatial mercury patterns were consistent regardless of sex or age class. Bottlenose dolphin mercury exposure can effectively represent regional trends and reflect large-scale atmospheric mercury input and local biogeochemical processes. As a sentinel species, the bottlenose dolphin data presented here can direct future studies to evaluate mercury exposure to human residents in St. Joseph Bay, Choctawhatchee Bay, and Florida Coastal Everglades, as well as additional sites with similar geographical, oceanographic, or anthropogenic parameters. These data may also inform state and federal authorities that establish fish consumption advisories to determine if residents in these locales are at heightened risk for mercury toxicity.

Satellite telemetry reveals space use of diamondback terrapins

Movement and space use information of exploited and imperiled coastal species is critical to management and conservation actions. While satellite telemetry has been successfully used to document movements of marine turtles, the large tag sizes available have limited use on smaller turtle species. We used small Argos-based satellite tags to document movement patterns of diamondback terrapins (Malaclemys terrapin), the only estuarine turtle species in North America. Movement data from ten terrapins in St. Joseph Bay, Florida were gathered between July 13, 2018 and July 22, 2021. We estimated seasonal space use using the daily locations generated from a Bayesian hierarchical state-space model to calculate minimum convex polygons (95% MCP) and kernel density estimates (50% and 95% KDE). Mean tracking duration was 125 days and mean home range size was 9.4 km2 (95% MCP) and 8.1 km2 (95% KDE). Seagrass habitat comprised 55.8% of all home ranges on average, whereas salt marsh comprised a mean of 3.0%. Mean elevation used by terrapins was − 0.13 m (95% MCP) and -0.35 m (95% KDE). Satellite telemetry provided broad-scale spatiotemporal movement and space use data; however, Argos error produced considerable noise relative to true terrapin movements given their size, speed, and behavior. Terrapin home ranges were greater than previously reported and three of the ten terrapins exhibited repeated long-distance, directed movements within the bay. Small patches of salt marsh habitat were centralized within home ranges, despite comprising only a small percentage for each terrapin. Moreover, the percentage of salt marsh present in each core use area was positively correlated with terrapin mass. Although considered an estuarine species, seagrass habitat comprised a large portion of terrapin home ranges; however, our data did not provide the detail necessary to understand how terrapins were using this habitat. As northward-expanding mangroves continue to infringe upon salt marsh habitat, there is potential for negative impacts to terrapin populations across the northern Gulf of Mexico. As salt marsh habitat continues to be infringed upon by northward-expanding mangroves impacts to terrapins across the northern Gulf of Mexico.

Symbiotic survey of the bay scallop (Argopecten irradians) from the Gulf coast of Florida, USA

The bay scallop Argopecten irradians supported a commercial fishery in Florida but their population declined and the fishery closed in 1994. A recreational fishery remains open along the west coast of Florida despite continued threats from overfishing and a changing environment. Disease is among those threats, as it is for bivalve fisheries globally. We examined the relationship between bay scallop population density, its symbiotic microbiome, and geographic location. We focused on three sites within the range of Florida’s recreational scallop fishery: St. Joseph Bay (northern extent), offshore of the Steinhatchee River (central), and offshore of Hernando County (southern extent). The study was conducted prior to the seasonal opening of the fishery to minimize the impact of fishing on our results. We also sampled caged scallops that are used for restocking in St. Joseph Bay to assess the effect of artificially high density and confinement on the scallop pathobiome. Using a combination of traditional histological methods, molecular diagnostics, and metagenomics, a suite of 15 symbionts were identified. Among them, RNA-seq data revealed four novel + ssRNA viral genomes: three picorna-like viruses and one hepe-like virus. The DNA-seq library revealed a novel Mycoplasma species. Histological evaluation revealed that protozoan, helminth and crustacean infections were common in A. irradians. These potential pathogens add to those already known for A. irradians and underscores the risk they pose to the fishery.

Impact of Atmospheric Correction on Classification and Quantification of Seagrass Density from WorldView-2 Imagery.

Mapping the seagrass distribution and density in the underwater landscape can improve global Blue Carbon estimates. However, atmospheric absorption and scattering introduce errors in space-based sensors' retrieval of sea surface reflectance, affecting seagrass presence, density, and above-ground carbon () estimates. This study assessed atmospheric correction's impact on mapping seagrass using WorldView-2 satellite imagery from Saint Joseph Bay, Saint George Sound, and Keaton Beach in Florida, USA. Coincident in situ measurements of water-leaving radiance (), optical properties, and seagrass leaf area index (LAI) were collected. Seagrass classification and the retrieval of LAI were compared after empirical line height (ELH) and dark-object subtraction (DOS) methods were used for atmospheric correction. DOS left residual brightness in the blue and green bands but had minimal impact on the seagrass classification accuracy. However, the brighter reflectance values reduced LAI retrievals by up to 50% compared to ELH-corrected images and ground-based observations. This study offers a potential correction for LAI underestimation due to incomplete atmospheric correction, enhancing the retrieval of seagrass density and above-ground Blue Carbon from WorldView-2 imagery without in situ observations for accurate atmospheric interference correction.

Seasonal abundance and distribution patterns of common bottlenose dolphins (Tursiops truncatus) near St. Joseph Bay, Florida, USA

Three unusual mortalities events involving bottlenose dolphins (Tursiops truncatus Montagu 1821) occurred along Florida’s northern Gulf of Mexico coast between 1999 and 2006. The causes of these events, in which over 300 bottlenose dolphins are known to have died, are still under investigation. The impact of these mortality events cannot be fully evaluated, because little prior information on bottlenose dolphin abundance and distribution patterns exist in this region. Thus, the goals of this study were to estimate seasonal abundance, develop site-fidelity indices, and describe distribution patterns of bottlenose dolphins in St. Joseph Bay, Gulf County, Florida, USA. This study site was chosen because it was impacted by all three unusual mortality events and was the geographic focus of the 2004 event. Mark-recapture photo-identification surveys were conducted across multiple seasons from February 2005 through July 2007. Site-fidelity indices were calculated for each identifiable dolphin based upon all photo-ID efforts undertaken in the area. Distribution patterns were investigated by short-term (12-94 days) radio-tracking of tagged individuals across seasons (April-July, n=9; July-October, n=15). Mark-recapture closed and robust abundance estimates, as well as site-fidelity indices suggest that St. Joseph Bay supports a resident community of 78-152 bottlenose dolphins. During spring and autumn, this region experiences an influx of dolphins, as demonstrated by closed and robust abundance estimates of 313-410 and 237-340, respectively. These results are supported by the distribution patterns of radio-tagged individuals. Individuals tagged in summer tended to stay within or near St. Joseph Bay, whereas two individuals tagged in spring ranged more than 40km from the study site. This study provides the first detailed examination of bottlenose dolphin abundance and distribution patterns for this region of the northern Gulf coast of Florida. These results suggest that unusual mortality events probably had, and will in the future have, seasonally variable effects on bottlenose dolphins in St. Joseph Bay. Future mortality events that occur during the summer and winter in St. Joseph Bay may predominantly affect resident individuals, while those that occur during the spring and autumn will probably affect both residents and seasonal visitors.

United States Gulf of Mexico Waters provide important nursery habitat for Mexico’s Green turtle nesting populations

Resolving natal populations for juvenile green turtles is challenging given their potential for extensive dispersal during the oceanic stage and ontogenetic shifts among nursery habitats. Mitochondrial DNA markers have elucidated patterns of connectivity between green turtle nesting populations (rookeries) and juvenile foraging aggregations. However, missing rookery baseline data and haplotype sharing among populations have often impeded inferences, including estimating origins of Gulf of Mexico juveniles. Here, we assessed genetic structure among seven foraging aggregations spanning southern Texas (TX) to southwestern Florida (SWFL), including Port Fourchon, Louisiana (LA); a surface-pelagic aggregation (SP) offshore of Louisiana and Florida; Santa Rosa Island, Florida (SRI); St. Joseph Bay, Florida (SJB); and the Big Bend region, Florida (BB). We estimated source contributions to aggregations with novel genetic data (excluding SP and BB) using a Bayesian many-to-one mixed stock analysis (MSA) approach. Haplotype frequencies for western (TX, LA, SP, SRI) and eastern (SJB, BB, SWFL) aggregations were significantly differentiated. The largest shift in haplotype frequencies between proximal nursery sites occurred between SRI and SJB, separated by only 150 km, highlighting the lack of a geographic yardstick for predicting genetic structure. In contrast to previous MSA results, there was no signal of Florida juveniles at any foraging site. Mexican contributions dominated in all aggregations, with strong connectivity between western Bay of Campeche (Tamaulipas/Veracruz) rookeries and western foraging aggregations. MSA indicated more diverse Mexican origins for eastern aggregations, with larger inputs from the eastern Bay of Campeche (Campeche/Yucatán), Campeche Bank, and Quintana Roo rookeries. These results demonstrate the significance of the Gulf of Mexico coast and offshore waters of the United States as important nursery habitat for green turtles of Mexican origin and highlight the need for international coordination for management of these populations.

Biomass and Productivity of Thalassia testudinum in Estuaries of the Florida Panhandle

Thalassia testudinum often dominates seagrass meadows of the Florida panhandle but few measurements of productivity, biomass, density, turnover or leaf area index in this region have been made. We targeted 5 estuaries located at similar latitudes, 30⁰ ± 0.3⁰N: Big Lagoon, Santa Rosa Sound, St. Andrew Bay, St. Joseph Bay, and St. George Sound. This study was one component of a collaborative partnership of state and local researchers examining factors preventing recovery in panhandle estuarine areas that had historically contained seagrass in the 1940s and 1950s. Measurements were made twice in 2016, once in June and then again in summer or fall, except in Santa Rosa Sound where measurements were made 3 times. In the estuaries sampled for the second time in July or August, aboveground productivity was greater than in June. St. Joseph Bay had the highest aboveground productivity (4.3 g/m2/d) and 1—sided leaf area index (4.2) while St. George Sound had the lowest values (0.41 g/m2/d and 1.0). Principal component analysis suggested that St. Andrew Bay, Big Lagoon and Santa Rosa Sound were the most similar, with higher values for shoot densities and leaf turnover and lower salinities and watershed:water ratios. St. Joseph Bay had high aboveground productivity and salinity, and low turbidity. St. George Sound had low aboveground productivity, high total suspended solids and the highest watershed:water ratio. These baseline productivity estimates will be useful to assess the success of restoration efforts targeting seagrasses in the Florida panhandle and evaluate impacts of climate change on seagrasses.

Effects of varying types and amounts of herbivory and nutrient enrichment on a tropicalizing seagrass meadow

Climate change is impacting marine ecosystem community dynamics on a global scale. While many have assessed direct effects of climate change, indirect effects on marine ecosystems produced by biotic interactions remain poorly understood. For example, warming-induced range expansions and increased consumption rates of herbivores can lead to significant and unexpected changes in seagrass-dominated ecosystems. To better understand the threats tropicalization presents for the functioning of turtlegrass (Thalassia testudinum) meadows, we focused on the extensive turtlegrass beds of St. Joseph Bay, Florida in the northern Gulf of Mexico, a location with increasing numbers of tropically-associated green turtles. Our goals were to investigate experimentally how different grazing rates (natural and simulated),including high levels reflective of green turtle herbivory, coupled with nutrient supply, might alter turtlegrass structure and functioning in a higher latitude, subtropical turtlegrass meadow. We found that 4 months of varying levels of herbivory did not affect turtlegrass productivity, while 7 months of herbivory reduced percent cover, and 10 months reduced shoot density. Nutrient additions had few important effects. Ten months into the study, a massive recruitment of the herbivorous sea urchin (Lytechinus variegatus), whose densities reached 19 urchins/m2 completely overgrazed our study area and a large portion of the lush turtlegrass meadows of St. Joseph Bay. While local turtlegrass overgrazing had been previously noted at these urchin densities, a total loss of seagrass in such a large area has rarely ever been recorded. Overgrazing of the kind we observed, likely a result of both urchin and increasing green turtle grazing, can result in the loss of many key ecosystem services. As tropicalization continues, understanding how changes in biotic interactions, such as increased herbivory, affect higher latitude seagrass meadows will be necessary for their proper management and conservation.

Interspecific interactions among three species of sea turtle using a common resting area.

Interspecific interactions among three species of sea turtle using a common resting area.

Long‐term apparent survival of a cold‐stunned subpopulation of juvenile green turtles

AbstractUnderstanding the effects of extreme weather on animal populations is fundamental to ecological and conservation sciences and species management. Climate change has resulted in both warm and cold temperature extremes, including an increased frequency of severe cold snaps at middle latitudes in North America. These unusually cold air masses cause rapid declines in nearshore ocean temperatures in coastal areas, with detrimental effects on marine organisms. Acute cold‐stun events (hereafter cold stuns) occur when hundreds to thousands of resident juvenile sea turtles fail to escape shallow water during cold snaps. Human intervention through rescue and recovery largely mitigates direct juvenile sea turtle mortality, but delayed effects of cold stuns on rescued individuals are not well understood. Our objective was to examine long‐term juvenile green turtle (Chelonia mydas) survival across four cold stuns of varying severity in St. Joseph Bay, Florida, between 2010 and 2018. We used the classic Cormack–Jolly–Seber model in a hierarchical Bayesian framework to estimate apparent survival (i.e., emigration and mortality) of rescued turtles at different time intervals. Our results indicated about half of a cohort rescued during a severe cold stun in January 2010 likely remained in the population 1 year later, with 10%–20% remaining 4 years later, and as few as 5% by 2018. The results also suggested higher apparent survival for cohorts rescued during two subsequent milder cold stuns. Emigration was a more plausible ecological explanation for low apparent survival than delayed mortality. Potential ecological mechanisms underlying emigration include a reduction in food availability and a behavioral response to either the severe weather event or handling during rescue (or both). However, the typical annual turnover of juvenile green turtles, though assumed low, is not well known in St. Joseph Bay. Thus, our apparent survival estimates may be reflective of higher‐than‐expected emigration in the broader population. Our study provides important baseline information about long‐term juvenile sea turtle survival after cold stuns in temperate regions. We also highlight the importance of strategic monitoring between cold stuns to examine additional ecological questions.

Simulated response of St. Joseph Bay, Florida, seagrass meadows and their belowground carbon to anthropogenic and climate impacts

Seagrass meadows are degraded globally and continue to decline in areal extent due to human pressures and climate change. This study used the bio-optical model GrassLight to explore the impact of climate change and anthropogenic stressors on seagrass extent, leaf area index (LAI) and belowground organic carbon (BGC) in St. Joseph Bay, Florida, using water quality data and remotely-sensed sea surface temperature (SST) from 2002 to 2020. Model predictions were compared with satellite-derived measurements of seagrass extent and shoot density from the Landsat images for the same period. The GrassLight-derived area of potential seagrass habitat ranged from 36.2 km2 to 39.2 km2, averaging 38.0 ± 0.8 km2 compared to an observed seagrass extent of 23.0 ± 3.0 km2 derived from Landsat (range = 17.9–27.4 km2). GrassLight predicted a mean seagrass LAI of 2.7 m2 leaf m−2 seabed, compared to a mean LAI of 1.9 m2 m−2 estimated from Landsat, indicating that seagrass density in St. Joseph Bay may have been below its light-limited ecological potential. Climate and anthropogenic change simulations using GrassLight predicted the impact of changes in temperature, pH, chlorophyll a, chromophoric dissolved organic matter and turbidity on seagrass meadows. Simulations predicted a 2–8% decline in seagrass extent with rising temperatures that was offset by a 3–11% expansion in seagrass extent in response to ocean acidification when compared to present conditions. Simulations of water quality impacts showed that a doubling of turbidity would reduce seagrass extent by 18% and total leaf area by 21%. Combining climate and water quality scenarios showed that ocean acidification may increase seagrass productivity to offset the negative effects of both thermal stress and declining water quality on the seagrasses growing in St. Joseph Bay. This research highlights the importance of considering multiple limiting factors in understanding the effects of environmental change on seagrass ecosystems.

Temporal Stability of Seagrass Extent, Leaf Area, and Carbon Storage in St. Joseph Bay, Florida: a Semi-automated Remote Sensing Analysis

Seagrasses are globally recognized for their contribution to blue carbon sequestration. However, accurate quantification of their carbon storage capacity remains uncertain due, in part, to an incomplete inventory of global seagrass extent and assessment of its temporal variability. Furthermore, seagrasses are undergoing significant decline globally, which highlights the urgent need to develop change detection techniques applicable to both the scale of loss and the spatial complexity of coastal environments. This study applied a deep learning algorithm to a 30-year time series of Landsat 5 through 8 imagery to quantify seagrass extent, leaf area index (LAI), and belowground organic carbon (BGC) in St. Joseph Bay, Florida, between 1990 and 2020. Consistent with previous field-based observations regarding stability of seagrass extent throughout St. Joseph Bay, there was no temporal trend in seagrass extent (23 ± 3 km2, τ = 0.09, p = 0.59, n = 31), LAI (1.6 ± 0.2, τ = -0.13, p = 0.42, n = 31), or BGC (165 ± 19 g C m−2, τ = - 0.01, p = 0.1, n = 31) over the 30-year study period. There were, however, six brief declines in seagrass extent between the years 2004 and 2019 following tropical cyclones, from which seagrasses recovered rapidly. Fine-scale interannual variability in seagrass extent, LAI, and BGC was unrelated to sea surface temperature or to climate variability associated with the El Niño-Southern Oscillation or the North Atlantic Oscillation. Although our temporal assessment showed that seagrass and its belowground carbon were stable in St. Joseph Bay from 1990 to 2020, forecasts suggest that environmental and climate pressures are ongoing, which highlights the importance of the method and time series presented here as a valuable tool to quantify decadal-scale variability in seagrass dynamics. Perhaps more importantly, our results can serve as a baseline against which we can monitor future change in seagrass communities and their blue carbon.

Ontogenetic Scaling of Skeletal Components in the Common Sea Urchin Lytechinus variegatus

Ontogenetic allometric analyses can provide novel insights into aspects of evolution, ecology, and conservation. The present study exploits a model sea urchin to evaluate the ontogenetic allometry of skeletal defense and feeding efficiency. Individuals of Lytechinus variegatus were sampled from St. Joseph Bay, FL, and a range of different-sized late juvenile to adult individuals were weighed, measured, and dissected into skeletal components. Skeletal defense was evaluated by examining whole-body wet mass versus primary spine density (number/cm2), length (mm), breakage strength (N), and magnesium calcite levels (%). Feeding efficiency was indirectly inferred from the relationship between whole-body wet mass versus whole lantern dry weight and magnesium calcite content. It was found that between the late juvenile to adult growth phase, L. variegatus displays nonlinear and isometric scaling between body size and various metrics of skeletal spine defense. Intriguingly, most metrics of spine defense against predators displayed a nonsignificant, body-size-independent relationship, indicating L. variegatus invests heavily in spine defenses at an early age. In contrast, hyperallometric scaling best described the relationship between body size and lantern size (feeding efficiency) reflecting the potential importance of elevating food intake with increasing age.

Adaptive management as a foundational framework for developing collaborative estuary management programs

Collaborative nonregulatory programs can benefit the long-term sustainability of environmental resources. Such programs benefit from extensive planning and assessment relative to ecological systems as well as public participation. While many programs use adaptive management as a guiding programmatic framework, few programs successfully integrate social and human context into their adaptive management frameworks. While this adaptive governance framework can be successful, many potential challenges arise when incorporating public stakeholders into the adaptive management framework. To reduce those challenges, programs need participation from diverse stakeholder groups that represent multiple communities of interest, place, and identity. The participatory process benefits from a diverse group of stakeholders and can result in successful management of environmental resources. We highlight the participatory co-management process of three newly developing nonregulatory programs that are modeled after the United States EPA's National Estuary Program in the Perdido and Pensacola Bay systems, Choctawhatchee Bay, and the St. Andrew and St. Joseph Bay systems (Florida USA). This case study illustrates how collaborative nonregulatory programs can be implemented not only in the United States, but also in other regions of the world.

Patterns of Dispersion, Movement and Feeding of the Sea Urchin Lytechinus variegatus, and the Potential Implications for Grazing Impact on Live Seagrass

The sea urchin Lytechinus variegatus is a known grazer of both living and dead tissue of turtlegrass, Thalassia testudinum, occasionally denuding large areas of seagrass. Field studies have attempted to assess effects of herbivory on seagrass by enclosing urchins at various densities. However, it is unclear how unrestricted urchins affect seagrass at lower densities more typically observed in the field. This study describes movement, feeding, and distribution of L. variegatus within beds of T. testudinum in St. Joseph Bay, Florida (USA) to quantify this urchin’s impact as a seagrass grazer. Urchins were absent from portions of seagrass beds closest to shore, present at low densities midway across the bed, and at highest densities (up to ~5 individuals/m2) at the offshore edge of the bed. Urchins tended not to aggregate, moved twice as rapidly where seagrass cover was reduced, and moved > 20X faster when placed in areas of open sand. Dead seagrass tissue occurred 4—30X more frequently on oral surfaces than living seagrass tissue. Fecal pellets with dead seagrass tissue were > 3X more common than pellets with live seagrass tissue. Injury to seagrass leaves was more common along dead leaf sections than live sections (> 2—10X). Overall, spatial distributions, movement, and diet indicate that L. variegatus at densities observed in this study would tend to have minimal effects on living seagrass. Episodic periods of denuding grassbeds reported in the literature suggest L. variegatus switches to live seagrass tissue as dead tissue becomes scarce during times of high urchin density.

Approaching a Tipping Point? Herbivore Carrying Capacity Estimates in a Rapidly Changing, Seagrass-Dominated Florida Bay

Herbivory is a key structuring force that can have negative, positive, or mixed impacts on seagrasses. The identity and abundance of herbivores, as well environmental conditions such as solar insulation, can influence the impacts of herbivory. To understand the impact of herbivores on turtlegrass in warm, temperate St. Joseph Bay (SJB) in the northeastern Gulf of Mexico, we estimated densities of the most common herbivores: variegated sea urchins and green turtles. We also estimated SJB’s herbivore carrying capacities by estimating annual average turtlegrass production and variegated urchin consumption rates and by using previously calculated juvenile green turtle consumption rates and seagrass area. During summer, turtlegrass exhibited compensatory growth due to urchin herbivory, but during winter, turtlegrass growth was negatively affected by urchin grazing. Given our calculated annual turtlegrass production, urchin ingestion rates, and the average urchin density of 5.89 ± 0.09 (SE) urchins ha−1, the turtlegrass production not consumed by urchins can sustain 278.0 juveniles ha−1, or about 556,010 turtles, putting current average green turtle abundance of 26 ± 3.7 individuals ha−1 at 4.0–14.6% of carrying capacity. Previous work in this system has shown that simulated turtle herbivory can reduce turtlegrass productivity—with this potential reduction in production, SJB could not sustain a green turtle population at current urchin densities. Given the rapid global green turtle increase, evaluating densities and future carrying capacities of herbivores in higher latitude seagrass pastures is critical for updating and achieving recovery goals for both green turtles and globally declining seagrass meadows.

Densities of Large Marine Gastropods in Seagrass, Oyster Reef, and Sandy Habitats in Tampa Bay and along the Gulf Coast of Florida

Marine gastropods in Florida are harvested by the marine-life trade, tourists (for shells), and traditional commercial fisheries, but stocks are not formally assessed for most species. The main goal of this project was to estimate biological variables that may be used to evaluate the Species of Greatest Conservation Need status of the banded tulip Cinctura lilium and six other large marine gastropod species that are commonly encountered in the targeted habitats. The principal target, C. lilium, was listed in the 2012 State Wildlife Action Plan. The densities and size structures of C. lilium and six co-occurring species of large marine gastropods in Tampa Bay were examined to evaluate population dynamics, seasonal variation, and habitat preferences of these species. Long-term trends in the densities of large, predatory marine gastropods in 10 regions from 2009 to 2017 were included. In Tampa Bay, strong habitat preferences were observed for all species studied: C. lilium and Melongena corona were most likely to be observed on oyster reefs, and Fasciolaria tulipa was found only in seagrass, whereas Strombus alatus, Triplofusus gigantea, Sinistrofulgur sinistrum, and Fulguropsis spirata were more common on soft sediments. Seasonal variations in densities were weak; seasonal differences in size structure were more pronounced. The smallest individuals of C. lilium appeared in spring and summer; F. spirata, S. alatus, and S. sinistrum reached a detectable size in fall. The smallest detectable M. corona appeared in winter. Regionally, there were more gastropods in southwestern bay grass beds (Tampa Bay, Sarasota Bay, and Pine Island Sound) than in coastal seagrass beds (Big Bend, Citrus, Hernando, Pasco, and coastal Pinellas) or northern bays (St. Joseph Bay and St. Andrew Bay), and each region had characteristic species. As a group, tulip snails exhibited modest local declines in densities at two sites, whereas the whelks and T. gigantea varied annually but did not exhibit consistent trends during 2009 to 2017. The present study establishes a baseline of abundance for seven species of common marine gastropods and recommends expanded monitoring in multiple habitats to improve future analyses of abundance trends.

Performance across WorldView-2 and RapidEye for reproducible seagrass mapping

Satellite remote sensing offers an effective remedy to challenges in ground-based and aerial mapping that have previously impeded quantitative assessments of global seagrass extent. Commercial satellite platforms offer fine spatial resolution, an important consideration in patchy seagrass ecosystems. Currently, no consistent protocol exists for image processing of commercial data, limiting reproducibility and comparison across space and time. Additionally, the radiometric performance of commercial satellite sensors has not been assessed against the dark and variable targets characteristic of coastal waters. This study compared data products derived from two commercial satellites: DigitalGlobe's WorldView-2 and Planet's RapidEye. A single scene from each platform was obtained at St. Joseph Bay in Florida, USA, corresponding to a November 2010 field campaign. A reproducible processing regime was developed to transform imagery from basic products, as delivered from each company, into analysis-ready data usable for various scientific applications. Satellite-derived surface reflectances were compared against field measurements. WorldView-2 imagery exhibited high disagreement in the coastal blue and blue spectral bands, chronically overpredicting. RapidEye exhibited better agreement than WorldView-2, but overpredicted slightly across all spectral bands. A deep convolutional neural network was used to classify imagery into deep water, land, submerged sand, seagrass, and intertidal classes. Classification results were compared to seagrass maps derived from photointerpreted aerial imagery. This study offers the first radiometric assessment of WorldView-2 and RapidEye over a coastal system, revealing inherent calibration issues in shorter wavelengths of WorldView-2. Both platforms demonstrated as much as 97% agreement with aerial estimates, despite differing resolutions. Thus, calibration issues in WorldView-2 did not appear to interfere with classification accuracy, but could be problematic if estimating biomass. The image processing routine developed here offers a reproducible workflow for WorldView-2 and RapidEye imagery, which was tested in two additional coastal systems. This approach may become platform independent as more sensors become available.

Microplastics in sandy environments in the Florida Keys and the panhandle of Florida, and the ingestion by sea cucumbers (Echinodermata: Holothuroidea) and sand dollars (Echinodermata: Echinoidea)

Microplastic pollution is an increasing problem in the marine environment. This study had three objectives: 1) determine if seagrass beds and adjacent sand flats in the Florida Keys differed in microplastics concentration, 2) determine if sea cucumbers from the Florida Keys and sand dollars from the panhandle of Florida contain microplastics, and 3) conduct a laboratory experiment on the sand dollar Mellita tenuis to determine if it will ingest plastic microbeads contained in sediment. Both seagrass beds and sand flats in the Florida Keys contained microplastics. Sediment near Pensacola Beach and in St. Joseph Bay contained microplastics. Sea cucumbers from the Florida Keys and sand dollars from the panhandle of Florida contained microplastics in their gut contents. In the laboratory, M. tenuis ingested microbeads in slightly lower proportions compared to surrounding sediment. Both sea cucumbers and sand dollars may make useful animals for monitoring sandy environments for microplastics pollution.

Green turtle herbivory and its effects on the warm, temperate seagrass meadows of St. Joseph Bay, Florida (USA)

Green turtles Chelonia mydas occur sporadically in tropical and subtropical latitudes, but effective conservation efforts are leading to increasing abundances at higher latitudes. One consequence of increased green turtle abundance in some locations has been the overgrazing of seagrasses, their preferred food item. Recent, large increases in juvenile green turtle abundance in the warm temperate northern Gulf of Mexico, especially in the clear waters of St Joseph Bay, FL, make this a prime location to study effects of their feeding activities on the extensive turtlegrass Thalassia testudinum-dominated meadows. Using caging and simulated grazing to quantify green turtle effects, we found that excluding green turtles led to increased Thalassia shoot density, and that simulating turtle grazing resulted in narrowed leaves and decreased turtlegrass productivity. Naturally grazed areas protected from further turtle grazing did not recover after 14 wk of protection. Two years following relaxation of simulated grazing, turtlegrass continued to show residual stress symptoms, with narrower and fewer leaves per shoot than control areas. The future success of sea turtle conservation efforts is critically linked, and dependent on, the protection and sustainability of globally decreasing sea turtle feeding grounds. Thus, continued study of how increasing green turtle populations affect warm temperate turtlegrass meadows will provide important information on how best to manage both turtle and seagrass resources.