Apalachicola Bay Research Articles

Determining the influence of abiotic factors on spatial–temporal patterns of marine catfish (family: Ariidae) within the Apalachicola Bay System, Florida

Determining the influence of abiotic factors on spatial–temporal patterns of marine catfish (family: Ariidae) within the Apalachicola Bay System, Florida

Geomorphic response to historic and ongoing human impacts in a large lowland river

AbstractLowland coastal plain rivers are important for navigation and ecosystems, having unique concerns regarding water and sediment management. The Apalachicola River in Florida, the lower end of the ACF (Apalachicola–Chattahoochee–Flint) system, had historical modifications beginning in the 1800s. Most impacts are attributable to the Apalachicola Navigation Project in the latter half of the 20th century, which included dredging, disposal, rock and snag removal, artificial cutoffs, and wing‐dike building.As one of few studies using paired hydrographic surveys over a long reach and time (170 km, 50 years), we defined four zones of bed elevation change between 1960 and 2010 based on the cumulative thalweg elevation plots. The river has four bed change zones: (1) uppermost, marked degradation from river mile (RM) 106 to 85 because of dam construction; (2) middle, minimal degradation from RM 85 to 34; (3) artificial cutoff zone, highest degradation, from RM 34 to 27; and (4) lowermost zone, aggradation from RM 27 to Apalachicola Bay because of upstream bed and bank sediment disturbances. Artificial cutoffs and lithology influence lateral migration, with rates being highest in cutoff zones and least in areas with some bedrock upstream and finer sediments downstream. Length changes from 1941 to 2019 are stable, except for the middle reach, which lengthened nearly 10%, and the lower non‐tidal reach, where length shortened with cutoffs then regained in subsequent decades. Minimizing disturbance has led to 18% of the sand bar area revegetating since a decade of dredging ended. This framework helps in understanding historic and ongoing human activities, notably upstream water consumption, connectivity changes, sediment inputs, and climate change, that will affect the water and sediment management of the river, its floodplain, and bay, thus varying approaches for restoration.

Environmental correlates of elasmobranch and large fish distribution in a river-dominated estuary

Coastal areas serve as vital habitat for many marine fishes and often host broad gradients of environmental conditions that result in diverse species assemblages. Understanding the influence of environmental variables on the distribution and abundance of fishes is especially important for devising appropriate management strategies. We documented large fish community structure in the Apalachicola Bay system from 2018 to 2021 using fishery-independent longline and gillnet surveys. Spatiotemporal variation in fish assemblages was evaluated with permutational multivariate ANOVA, while community- and species-level habitat relationships were described across gradients of environmental variables with non-metric multidimensional scaling and generalized additive models. We captured 5085 fishes from 17 elasmobranch and 33 bony fish species, with gafftopsail catfish Bagre marinus, blacktip shark Carcharhinus limbatus, Atlantic sharpnose shark Rhizoprionodon terraenovae, and hardhead catfish Ariopsis felis comprising 82.1% of the total catch. Fish communities varied spatially throughout the system, and changes in these communities were most strongly correlated with gradients in salinity, clarity, and depth. We documented higher species richness and density of young elasmobranchs in our surveys compared to adjacent systems, supporting past suggestions that this area serves as important juvenile shark habitat. We suggest that flow from the Apalachicola River, transporting nutrients to the system and supporting numerous environmental niches across spatiotemporal scales, plays an influential role in maintaining the elevated diversity and density of elasmobranchs observed in this study.

Effect of Mississippi River discharge and local hydrological variables on salinity of nearby estuaries using a machine learning algorithm

Estuarine water salinity is important to coastal ecosystems and the economy. To examine the potential effect of the Mississippi River freshwater discharge on water salinity of other estuaries, we used the machine learning Cubist algorithm to model salinity of three estuaries (Apalachicola Bay, Weeks Bay, and Grand Bay) of the northern Gulf of Mexico (GoM). The models were trained — both with and without the Mississippi River discharge as input — to examine its effect on the salinity of other estuaries along with other variables including wind, discharge, and water depth. By including the Mississippi discharge, the Root Mean Squared Error (RMSE) of the model training sets decreased by 0.81, 1.06 and 1.73 for the Apalachicola Bay, Weeks Bay, and Grand Bay, respectively, while the decrease of the model testing sets was 0.20, 0.64, and 0.84, respectively, using the practical salinity scale. The rank of predictor importance of the Mississippi discharge increased as the modeled estuary proximity increased to the Mississippi outlet. The results showed that the Mississippi River discharge can affect the water quality of other estuaries along the northern GoM, although the variation of the salinity explained by this flow was smaller than that explained by local river flow (except for the Grand Bay where there is no local river flow) and local wind.

A novel interpretation of speciation, hybridization, and genetic population structure of the stone crabsMenippe mercenaria(Say, 1817–1818) andM. adinaWilliams & Felder, 1986 (Decapoda: Brachyura: Menippidae)

AbstractMitochondrial DNA cytochrome oxidase (COI) and microsatellite DNA loci were used to better explain the speciation events, history of hybridization, and genetic population structure of the stone crabs Menippe adinaWilliams & Felder, 1986 and M. mercenaria (Say, 1817–1818). A survey of a 670-bp COI sequence of 711 stone crabs collected from Texas to North Carolina and from Belize, Central America showed the presence of two well-defined mtDNA lineages, Lin-A and Lin-B. Based on molecular clock calibrations of a published study these lineages shared a common ancestor between 1.5 to 1.8 million years. Lin-A was evident throughout the range of the two Menippe species, but Lin-B was found only in the eastern Gulf of Mexico and does not represent any of the two species. Our findings refute the claim that the eastern Gulf hybrid zone is the product of hybridization between M. adina and M. mercenaria. We propose that the hybrid zone is instead a relic of introgressive hybridization between the M. mercenaria of eastern Gulf stone crab nDNA Lin-AA that carries Lin-A and the new nDNA Lin-BB that carries Lin-B, forming the hybrid nDNA Lin-AB. Lin-B emerged from a founder effect in the Okefenokee Trough and introgressed into the eastern Gulf. There is no Lin-B in the Atlantic, hence no hybridization in that region. Using stone crab-specific microsatellite markers we found no evidence of an ongoing hybridization in the eastern Gulf and this region cannot be called a hybrid zone since hybridization here ceased probably soon after the last glacial episode. The microsatellite-marker analyses also suggested that the stone crab was geographically divided into four genetic clusters by three barriers to gene flow, the strongest of which is the one between the two species, M. adina and M. mercenaria, around Cape San Blas, Apalachicola Bay, Florida.

Long-term Salinity, Hydrology, and Forested Wetlands Along a Tidal Freshwater Gradient

Tidal freshwater forested wetlands (TFFWs) commonly occur along coastal rivers; however, sea level rise and changes to river discharge may impact these wetlands. Information that characterizes the hydrology and salinity regime of the TFFW zone is needed to assess risk and predict future viability. A combination of field data and modeling were used to characterize TFFW hydrology, salinity, and vegetation along two distributaries (the East River and St. Marks River) of the Apalachicola River in west Florida, USA. Six gaging stations were established (three per river) roughly equidistant along the TFFW tidal gradient to monitor salinity and water levels at the river-wetland interface. Eighteen 500-m2 forest survey stations (nine per river) were also established roughly equidistant between (and including) the upper and lower gaging stations to measure canopy trees (> 2.54 cm DBH) and calculate species importance values (IV200). Field measures, along with other monitoring and model data, were used to develop a 30-year salinity record (1985–2015) for each gaging station based on an artificial neural network (ANN) model. Optimal ANN models for each TFFW gaging station were selected based on Akaike’s Information Criteria, and 30-year mean daily salinity was interpolated to all forest survey stations based on river distance. Important input variables for the ANN models included daily Apalachicola River discharge, Apalachicola Bay tidal stage, and bay salinity, among others. Based on 30-year salinity models, mean daily salinity ranged between 0.30 and 0.63 ppt at the downriver stations of East and St. Marks Rivers, respectively, to 0.14 and 0.14 ppt at the upriver stations, respectively. Results showed a predictable reduction in mean salinity and salinity ranges further upriver at both rivers; however, the St. Marks River showed a distinct inflection point in reduced salinity compared with the East River. Evaluating tree species IV200, there was a shift to species indicative of non-tidal conditions midway up the study reach of the St. Marks River while tidal species remained prominent throughout the East River study reach. Comparison of salinity, tidal reach, and species IV200 for each river suggests hydrology may be the most important contributor to the downriver extent of TFFWs while salinity may be an important driver of TFFW community composition.

Identifying Information Gaps in Predicting Winter Foraging Habitat for Juvenile Gulf Sturgeon

AbstractThe Gulf Sturgeon Acipenser oxyrinchus desotoi is an anadromous species that inhabits Gulf of Mexico coastal waters from Louisiana to Florida and is listed as threatened under the U.S. Endangered Species Act. Seasonal cues (e.g., freshwater discharge) determine the timing of spawning and migration and may influence the availability of critical habitat during winter months in six estuaries. Large information gaps, especially related to critical estuarine habitat for juveniles, hinder recovery efforts to protect these habitats and assess risks from emerging threats. Using Apalachicola Bay, Florida, as a model system, we developed and analyzed a preliminary Bayesian network model so that we could identify knowledge gaps (i.e., where expert knowledge was lacking) and data gaps (i.e., where data were unavailable) that limit the ability to assess the quantity of critical estuarine habitat for juvenile Gulf Sturgeon. The model hypothesized habitat availability per winter month in estuarine habitat under alternative scenarios of river discharge and length of the winter foraging season. A search for geospatial data sets revealed that the largest gap involved salinity, temperature, and oxygen (i.e., water condition) monitoring data, with data available only for Apalachicola Bay. For the Apalachicola Bay model, data gaps prevented the development of 53% of water condition geospatial data sets and a sensitivity analysis showed that water condition data most limited the ability to predict habitat availability. Expert knowledge was low, and conditional certainty scores showed that the relationships with the lowest certainty were abiotic suitability and habitat availability. Reducing information gaps could aid the development of a model that is appropriate for informing management. Future efforts could prioritize the expansion of water monitoring within critical habitat estuaries and predicting abiotic suitability and habitat availability. Bayesian network models can easily incorporate prior and new information for complex systems. Thus, our model could be updated as future research and monitoring efforts close these information gaps.

Comparative Genomic Analysis of Three Pseudomonas Species Isolated from the Eastern Oyster (Crassostrea virginica) Tissues, Mantle Fluid, and the Overlying Estuarine Water Column.

The eastern oysters serve as important keystone species in the United States, especially in the Gulf of Mexico estuarine waters, and at the same time, provide unparalleled economic, ecological, environmental, and cultural services. One ecosystem service that has garnered recent attention is the ability of oysters to sequester impurities and nutrients, such as nitrogen (N), from the estuarine water that feeds them, via their exceptional filtration mechanism coupled with microbially-mediated denitrification processes. It is the oyster-associated microbiomes that essentially provide these myriads of ecological functions, yet not much is known on these microbiota at the genomic scale, especially from warm temperate and tropical water habitats. Among the suite of bacterial genera that appear to interplay with the oyster host species, pseudomonads deserve further assessment because of their immense metabolic and ecological potential. To obtain a comprehensive understanding on this aspect, we previously reported on the isolation and preliminary genomic characterization of three Pseudomonas species isolated from minced oyster tissue (P. alcaligenes strain OT69); oyster mantle fluid (P. stutzeri strain MF28) and the water collected from top of the oyster reef (P. aeruginosa strain WC55), respectively. In this comparative genomic analysis study conducted on these three targeted pseudomonads, native to the eastern oyster and its surrounding environment, provided further insights into their unique functional traits, conserved gene pools between the selected pseudomonads, as well as genes that render unique characteristics in context to metabolic traits recruited during their evolutionary history via horizontal gene transfer events as well as phage-mediated incorporation of genes. Moreover, the strains also supported extensively developed resistomes, which suggests that environmental microorganisms native to relatively pristine environments, such as Apalachicola Bay, Florida, have also recruited an arsenal of antibiotic resistant gene determinants, thus posing an emerging public health concern.

Validation of Oil Trajectory and Fate Modeling of the Deepwater Horizon Oil Spill

Trajectory and fate modeling of the oil released during the Deepwater Horizon blowout was performed for April to September of 2010 using a variety of input data sets, including combinations of seven hydrodynamic and four wind models, to determine the inputs leading to the best agreement with observations and to evaluate their reliability for quantifying exposure of marine resources to floating and subsurface oil. Remote sensing (satellite imagery) data were used to estimate the amount and distribution of floating oil over time for comparison with the model’s predictions. The model-predicted locations and amounts of shoreline oiling were compared to documentation of stranded oil by shoreline assessment teams. Surface floating oil trajectory and distribution was largely wind driven. However, trajectories varied with the hydrodynamic model used as input, and was closest to observations when using specific implementations of the HYbrid Coordinate Ocean Model modeled currents that accounted for both offshore and nearshore currents. Shoreline oiling distributions reflected the paths of the surface oil trajectories and were more accurate when westward flows near the Mississippi Delta were simulated. The modeled movements and amounts of oil floating over time were in good agreement with estimates from interpretation of remote sensing data, indicating initial oil droplet distributions and oil transport and fate processes produced oil distribution results reliable for evaluating environmental exposures in the water column and from floating oil at water surface. The model-estimated daily average water surface area affected by floating oil >1.0 g/m2 was 6,720 km2, within the range of uncertainty for the 11,200 km2 estimate based on remote sensing. Modeled shoreline oiling extended over 2,600 km from the Apalachicola Bay area of Florida to Terrebonne Bay area of Louisiana, comparing well to the estimated 2,100 km oiled based on incomplete shoreline surveys.

Potential economic benefits of restoring commercial oyster harvest levels in Apalachicola Bay, Florida

Florida’s Apalachicola Bay has long been known for its oyster harvesting and processing industry, but a steady decline in oyster landings in the Bay has threatened the industry. The complex nature of the human and natural systems that together affect Apalachicola’s oyster reefs has created uncertainty about the long-term sustainability of the oyster fishing industry in Franklin County, which has prompted many questions about the ecology of the Bay and the economy of the region from a variety of stakeholders that directly or indirectly depend on the survival and successful restoration of the Apalachicola Bay oyster fishery. This 5-page fact sheet estimates the potential economic impacts associated with a successfully restored oyster reef in Apalachicola Bay, basing estimates on different hypothetical oyster harvest goals. Written by Robert Botta, Ed Camp, Christa Court, Caleb Stair, and Charles Adams and published by the UF/IFAS Food and Resource Economics Department, it is designed to inform decision making and discussions related to restoration and resource management in the region. https://edis.ifas.ufl.edu/fe1085

Diminishing returns in habitat restoration by adding biogenic materials: a test using estuarine oysters and recycled oyster shell

Restoration of degraded estuarine oyster reefs typically involves deploying recycled oyster shell. In low‐salinity, low‐predation areas of estuaries, high‐volume shell deployments are known to improve flow conditions and thus oyster survival and growth. It is also hypothesized that the physical structure of restored reefs could suppress foraging by oyster predators in high‐salinity, high‐predation zones. That hypothesis is untested. Given limited resources, it is important to determine how much shell is needed for successful restoration and whether there are diminishing returns in shell addition. In Apalachicola Bay, Florida, we manipulated shell volume on an oyster reef to create three 0.4 ha areas of low (no shell addition), moderate (153 m3 shell), and high (306 m3 shell) habitat structure. We repeated experiments and surveys over 2 years to determine if restoration success increased with habitat structure. Predation on oysters was greater on the non‐shelled area than on the reshelled reefs, but similar between the two reshelled reefs. Oyster larval supply did not differ among the reef areas, but by the end of the experiment, oyster density (per unit area) increased quadratically with habitat structure, plateauing at high levels of structure. Model selection indicated that the most parsimonious explanation for these patterns was that increased habitat structure reduced predation and increased overall recruitment, but that the higher reshelling treatment did not have better outcomes than moderate reshelling. Thus, restoration could be optimized by deploying a moderate amount of shell per unit area.

Morphological and Sedimentological Impacts of Hurricane Michael along the Northwest Florida Coast

Wang, P.; Adam, J.D.; Cheng, J., and Vallee, M., 2020. Morphological and sedimentological impacts of Hurricane Michael along the northwest Florida coast. Journal of Coastal Research, 36(5), 932–950. Coconut Creek (Florida), ISSN 0749-0208.On October 10, 2018, category 5 Hurricane Michael made landfall at Mexico Beach, generating a nearly 5-m storm surge. The greater landfall area is characteristic of a cuspate headland protruding into the Gulf of Mexico for up to 50 km. The headland is composed of several barrier islands with different orientations fronting a large estuary. The hurricane-impacted areas include densely developed small beachfront communities, modestly to sparsely developed shoreline communities, mostly pristine state parks, and a completely pristine national wildlife refuge. Therefore, Hurricane Michael provides an excellent opportunity to study the impact of an extreme storm over various coastal environments with different degrees of human developments. Because of the shoreline orientation and bathymetry changes induced by the headland, the wave field associated with the hurricane is complicated, with different locations for the highest wave and the landfall site where the surge and wind speed were the greatest. Numerical wave modeling revealed two wave-focusing points along the headland where barrier-island breaching occurred. Beach-dune erosion and impact to infrastructure were examined and compared among various natural–human coastal systems. The magnitude of dune erosion was mostly controlled by the storm wave height and prestorm beach width, but the height of the prestorm dune was not a determining factor. Sedimentological characteristics of storm deposits along the barrier islands, within Apalachicola Bay, and in the surrounding coastal marsh were examined using 116 sediment cores and 40 grab sediment samples. Characteristics of storm deposits and their preservation are described for various subenvironments, including beaches, dunes, interior wetlands, back-barrier bay, and coastal marsh along the landward side of the estuary. The landward penetrations of identifiable sandy overwash deposits were less than 150 m along the barrier islands and less than 30 m along the mainland marshes. These results should have potential implications on paleostorm study.

Wetland Dynamics Inferred from Spectral Analyses of Hydro-Meteorological Signals and Landsat Derived Vegetation Indices

The dynamic response of coastal wetlands (CWs) to hydro-meteorological signals is a key indicator for understanding climate driven variations in wetland ecosystems. This study explored the response of CW dynamics to hydro-meteorological signals using time series of Landsat-derived normalized difference vegetation index (NDVI) values at six locations and hydro-meteorological time-series from 1984 to 2015 in Apalachicola Bay, Florida. Spectral analysis revealed more persistence in NDVI values for forested wetlands in the annual frequency domain, compared to scrub and emergent wetlands. This behavior reversed in the decadal frequency domain, where scrub and emergent wetlands had a more persistent NDVI than forested wetlands. The wetland dynamics were found to be driven mostly by the Apalachicola Bay water level and precipitation. Cross-spectral analysis indicated a maximum time-lag of 2.7 months between temperature and NDVI, whereas NDVI lagged water level by a maximum of 2.2 months. The quantification of persistent behavior and subsequent understanding that CW dynamics are mostly driven by water level and precipitation suggests that the severity of droughts, floods, and storm surges will be a driving factor in the future sustainability of CW ecosystems.

Biogeochemical Response of Apalachicola Bay and the Shelf Waters to Hurricane Michael Using Ocean Color Semi-Analytic/Inversion and Hydrodynamic Models

Hurricanes are increasingly being recognized as important episodic drivers in ocean biogeochemical cycling; however, spatiotemporal response of their impacts on coastal and estuarine ecosystems are limited. Hurricane Michael, which made landfall just west of Apalachicola Bay (ApB) on October 10, 2018 as a Category 5 hurricane with sustained winds of 250 km h-1, caused widespread damage to the northwest Florida coast, and adverse effects on oyster reefs and water quality in ApB due to winds and coastal flooding associated with a strong storm surge. The impact of wind forcing and retreating storm surges on coastal and shelf biogeochemical properties remains however, largely unknown. In this study, we use a combination of pre-hurricane field observations, ocean-color satellite imagery and the outputs (salinity, currents, sea surface height and temperature) of a nested high-resolution 3-dimensional hydrodynamic model (NCOM) to examine the biogeochemical response of ApB and the surrounding shelf waters to Hurricane Michael. MODIS-derived optical proxies (e.g., absorption of colored dissolved organic matter or CDOM and particle backscattering coefficients) of dissolved and particulate organic carbon (DOC and POC) were derived for a series of clear-sky imagery (prior to and following the hurricane) using a combination of estuarine-tuned semi-analytic and empirical algorithms. Following the hurricane, spatiotemporal distribution of both DOC and POC in ApB and the nearshore coastal waters showed a strong response to storm surge, increasing river discharge, currents, and wind field. Average flux estimates of organic carbon exported from ApB between October 5-21, 2018 to the coastal ocean were much greater for DOC (0.86106 kg C d-1) than POC (0.21106 kg C d-1) and increased with increasing river discharge and the wind field. A bio-optical inversion algorithm applied to Sentinel-3A OLCI imagery of 13 October, 2018 immediately following the hurricane’s passage, showed a strong, week-long biological response with spatially distinct phytoplankton blooms of Karenia brevis and Emiliania Huxleyi, as detected by satellite imagery of pigments, an approach that could revolutionize our understanding of environmental impacts on phytoplankton. This study revealed spatiotemporal changes in estuarine and coastal ocean biogeochemistry reflective of a systematic regional ecosystem response to Hurricane Michael.

Radiocarbon in Marsh Periwinkle (Littorina Irrorata) Conchiolin: Applications for Archaeology

ABSTRACTIn coastal and island archaeology, carbonate mollusk shells are often among the most abundant materials available for radiocarbon (14C) dating. The marsh periwinkle (Littorina irrorata) is one of these such species, ubiquitously found along the Atlantic and Gulf coasts of the United States in both modern and archaeological contexts. This paper presents a novel approach to dating estuarine mollusks where rather than attempting to characterize the size and variability of reservoir effects to “correct” shell carbonate dates, we describe a compound-specific approach that isolates conchiolin, the organic matter bound with the shell matrix of the L. irrorata. Conchiolin typically constitutes <5% of shell weight. In L. irrorata, it is derived from the snail’s terrestrial diet and is thus not strongly influenced by marine, hardwater, or other carbon reservoir effects. We compare the carbon isotopes (δ13C and Δ14C) of L. irrorata shell carbonate, conchiolin, and bulk soft tissue from six modern, live-collected specimens from Apalachicola Bay, Florida, with samples that represent possible sources of carbon within their environment including surface sediments, marsh plant tissues, and dissolved inorganic carbon (DIC) in water. Ultimately, this paper demonstrates that samples obtained from wet chemical oxidation of L. irrorata conchiolin produces accurate 14C dates.

Spatial Variability in Size Structure, Growth, and Recruitment of Spotted Seatrout among Six Florida Estuaries

AbstractSpotted Seatrout Cynoscion nebulosus in Florida, USA, are managed under four geographical regions, including Apalachicola Bay and Cedar Key (northwest region), Tampa Bay and Charlotte Harbor (southwest region), northeast Florida (northeast region), and the northern Indian River Lagoon (southeast region). Two of these management regions are composed of more than one major estuary system (northwest and southwest regions). However, previous life history research suggests that the management regions do not accurately reflect the unique biological populations of Spotted Seatrout in Florida. Our objective was to determine (1) whether there is significant spatial variation in size structure, the age–length relationship, and recruitment patterns among populations of Spotted Seatrout in Florida; and (2) whether there is agreement in these life history parameters among estuary populations comprising individual management regions. We used long‐term fishery‐independent and fishery‐dependent data sets on recruitment, age, and size structure among six estuaries and the four management regions. Young‐of‐the‐year recruitment patterns and the length‐at‐age relationship over all ages differed significantly among estuarine populations and within management regions. Additionally, all estuaries differed significantly in length distributions of Spotted Seatrout caught by the recreational fishery. Our results highlight the need to understand the relative contributions of estuary‐specific data to regional assessment models if the four‐region boundary scheme for Florida is continued. Moreover, as variation in growth and recruitment among estuaries likely reflects estuary‐specific environmental conditions, we suggest that environmental variables be considered in future assessments and management of this recreationally valuable species.

Survey and genetic characterization of Vibrio cholerae in Apalachicola Bay, Florida (2012-2014).

A small outbreak of gastroenteritis in 2011 in Apalachicola Bay, FL was attributed to consumption of raw oysters carrying Vibrio cholerae serotype O75. To better understand possible health risks, V. cholerae was surveyed in oysters, fish and seawater, and results were compared to data for Vibrio vulnificus and Vibrioparahaemolyticus. Enrichment protocols were used to compare prevalence of V. cholerae (0, 48, 50%), V. vulnificus (89, 97, 100%) and V. parahaemolyticus (83, 83, 100%) in fish, seawater and oysters respectively. Compared to other species, Most probable number results indicated significantly (P<0·001) lower abundance of V. cholerae, which was also detected more frequently at lower salinity, near-shore sites; other species were more widely distributed throughout the bay. Genes for expression (ctxA, ctxB) and acquisition (tcpA) of cholera toxin were absent in all strains by PCR, which was confirmed by whole genome sequencing; however, other putative virulence genes (toxR, rtxA, hlyA, opmU) were common. Multi-locus sequence typing revealed 78% of isolates were genetically closer to V.cholerae O75 lineage or other non-O1 serogroups than to O1 or O139 serogroups. Resistance to amoxicillin, kanamycin, streptomycin, amikacin, tetracycline and cephalothin, as well as multidrug resistance, was noted. Results indicated minimal human health risk posed by V. cholerae, as all isolates recovered from Apalachicola Bay did not have the genetic capacity to produce cholera toxin. Vibrio cholerae was less prevalent and abundant relative to other pathogenic Vibrio species. These studies provide important baseline observations for V.cholerae virulence potential regarding: (i) genetic relatedness to V. cholerae O75, (ii) antibiotic resistance and (iii) prevalence of multiple virulence genes. These data will serve as a biomonitoring tool to better understand ecosystem status and management if bacterial densities and virulence potential are altered by environmental and climatic changes over time.

Distribution and Condition of Intertidal Eastern Oyster (Crassostrea virginica) Reefs in Apalachicola Bay Florida Based on High-Resolution Satellite Imagery

The Eastern Oyster Crassostrea virginica is an important component of the ecology of Apalachicola Bay, Florida, and the economy of the region. Although oyster reefs in the Bay occur in both tidal zones, subtidal reefs have received the most attention because they support most of the oyster fishery. The present study provides new information on the distribution, condition, and ecology of the intertidal reefs, and assessed the general utility of high-resolution satellite imagery for routine monitoring of the extent and condition of intertidal oysters. Using online, freely available color imagery and manual interpretation, a total of 782 individual reefs ranging in size from ∼3 m2 to 3.9 ha (= 9.7 acres) and covering a total of 94 ha (233 ac) of bottom area were mapped. Field inspection and sampling of 100 individual intertidal reefs on November 12–16, 2016, confirmed wide differences in the number and areal coverage of reefs in the three major geographic regions in the Bay: 433 reefs covering a total of 56 ha (139 acres) in the western area (St. Vincent Sound); 113 reefs covering 8 ha (19 acres) in the central area; and 236 reefs covering 30 ha (75 acres) in the eastern area (St. George Sound). Most reefs in the western portion of the bay consisted of recently dead (“box”) oysters in all size classes, suggesting a recent massive mortality event. Mean densities (all size classes combined) of live oysters in the central and eastern areas were 42.9/m2 (±7.39; 1 SE) and 99.3/m2 (±13.22; 1 SE), respectively, with an overall mean shell height of 23.6 mm. Size-frequency histograms indicated only two year classes of live oysters, and the largest oyster collected was 84 mm. Although detailed quantitative comparisons with subtidal reefs were not possible, data from the present study suggest that intertidal reefs cover much less bottom area of the bay, but may contain much higher live oyster densities. The present study also demonstrated the use of high-resolution satellite imagery for mapping reefs as small as a few square meters in surface area, and the potential for estimating relative reef condition measured by live oyster density.

Predation on oysters is inhibited by intense or chronically mild, low salinity events

AbstractEnvironmental stress gradients can affect species distributions and interspecific interactions. Because environmental stress depends on both intensity and duration, understanding the consequences of stress requires experiments that simultaneously manipulate both dimensions. In Apalachicola Bay, Florida (U.S.A.) the southern oyster drill (Stramonita haemastoma) is a major predator of the eastern oyster (Crassostrea virginica). Drill predation appears to be salinity‐dependent: in a recent field study, predation rates were positively correlated with salinity. Salinity in the bay is typically high (&gt; 20) during the dry summer months, conditions that favor both oysters and the drill. However, periodic freshets can dramatically reduce salinity, which inhibits (or kills) drills, but not oysters. In this study, we used field measurements of salinity and drill densities to inform mesocosm experiments. We investigated the specific combinations of intensity and duration of low‐salinity stress that inhibit drill predation. In these experiments, more intense salinity reductions reduced feeding both during and after the low‐salinity stress event. During the event, longer durations (15 d) were necessary for mild salinity reductions (−5) to reduce the feeding rate by the same amount as a short (5 d) exposure of more intense (−10 or −15) salinity reduction. Both conditions may create a predation refuge for oysters, consistent with field observations. Given that the recent collapse of the Apalachicola Bay oyster population was preceded by several years without low‐salinity events to inhibit predation, our results provide a mechanism by which a predator may have contributed to the loss of a historically productive and sustainable fishery.

Assessing the Resilience of Coastal Wetlands to Extreme Hydrologic Events Using Vegetation Indices: A Review

Coastal wetlands (CWs) offer numerous imperative functions that support a diverse array of life forms that are poorly adapted for other environments and provide an economic base for human communities. Unfortunately, CWs have been experiencing significant threats due to meteorological and climatic fluctuations as well as anthropogenic impacts. The wetlands and marshes in Apalachicola Bay, Florida have endured the impacts of several extreme hydrologic events (EHEs) over the past few decades. These extreme hydrologic events include drought, hurricane, heavy precipitation and fluvial flooding. Remote sensing has been used and continues to demonstrate promise for acquiring spatial and temporal information about CWs thereby making it easier to track and quantify long term changes driven by EHEs. These wetland ecosystems are also adversely impacted by increased human activities such as wetland conversion to agricultural, aquaculture, industrial or residential use; construction of dikes along the shoreline; and sprawl of built areas. In this paper, we review previous works on coastal wetland resilience to EHEs. We synthesize these concepts in the context of remote sensing as the primary assessment tool with focus on derived vegetation indices to monitor CWs at regional and global scales.