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Shifts from saltmarsh to mangroves are well-documented at mangrove poleward boundaries. A regime shift from intertidal oyster (Crassostrea virginica) reefs to mangrove islands has recently been documented in transitional phases in Florida, USA. To understand the local drivers of an oyster/mangrove regime shift and potential tipping points leading to a permanent mangrove state, we tracked all mangrove propagules (n = 1681) across 15 intertidal oyster reefs with or without adult mangroves for 15 months in Mosquito Lagoon, FL. While no propagule bottleneck was observed, few (3.2%) mangrove propagules/seedlings survived on reefs with no prior encroachment, compared to 11.3% and 16.1% on reefs with established older (pre-1943) or newer (1943 to present) adult mangrove stands, respectively. In total, 90.6% of the arriving propagules were from the red mangrove Rhizophora mangle; 13.2% of these were alive at the end of this study. Survival was <1% for black (Avicenna germinans) and 0% for white (Laguncularia racemosa) mangroves. Factors that promoted red mangrove success included close proximity (≤0.3 m) to adult mangroves, especially black mangroves; partial, upright burial of propagules in sediment; and arrival on reefs after annual high-water season. Additionally, once reefs had 50% mangrove cover, the density of red mangrove seedlings increased from 0.04 to 0.46 individuals m−2. Although climate change has alleviated the impact of extreme freezes on mangroves, local factors determine whether the regime shift will be complete and permanent; positive feedback loops associated with established mangroves suggest mangrove recruitment on intertidal oyster reefs will continue to increase. [ABSTRACT FROM AUTHOR]

Demand for oysters in the premium half-shell market drives the need for research to optimize and improve oyster aquaculture production methods. After setting, oysters are typically maintained in nursery upwellers that provide nutrients and oxygen while removing waste. They remain in the nursery until they are large enough to be deployed in aquaculture gear. Land-based upweller systems include silo and bottle upwellers, with bottles requiring less space and maintenance. However, it is unknown if upweller type influences oyster growth, shape, or survival after field deployment. This study reared Eastern oysters, Crassostrea virginica, to 2 mm in silo or bottle upwellers and deployed them to floating bags for a six-week grow-out period. Oysters were sampled initially, then size graded, counted, and redeployed every two weeks. Changes in growth parameters, quality ratios, survival, and hinge backbend deformity prevalence were determined after six weeks. Initially, silo-reared oysters were larger than those reared in bottles, likely due to the need for flow rate optimization and/or the tumbling action that breaks the fragile growing edge of the shell. Despite these initial differences, there were minimal size differences between upweller types after six weeks of growth in the field. There were no significant differences in survival, hinge backbend abnormality prevalence, or size class distribution between upweller types. These results indicate that upweller choice has minimal impact on the grow-out phase of oyster production and both systems are acceptable for Eastern oyster production in the northern Gulf of Mexico. [ABSTRACT FROM AUTHOR]

Salinity is a major environmental factor that influences the population dynamics of fish and shellfish along coasts and estuaries, yet empirical methods for hindcasting salinity at specific sampling stations are not widely available. The specific aim of this research was to predict the salinity experienced by juvenile and adult oysters (Crassostrea virginica) collected at sampling stations in Delaware Bay. To do so, empirical relationships were created to predict salinity at five oyster bed stations using observing systems data. These relationships were then applied to construct indices of salinity exposure over an oyster's lifetime. Three independent salinity data sources were used in conjunction with observing systems data to construct and validate the predictive relationships. The root mean square error (RMSE) of the models ranged from 0.5 to 1.6 psu when model predictions were compared with the three independent data sets. Results demonstrated that data from an observing system near the head of Delaware Bay could be used to predict salinity within ± 2 psu at oyster bed stations as far down-estuary as 39 km. When these models were applied to estimate low salinity exposure of 2-year-old oysters via the metric of consecutive days below 5 psu, the indices suggested that there could be as much as a 42-day difference in low salinity exposure for oysters at stations just 31 km apart. The approach of using observing systems data to hindcast salinity could be applied to advance understanding of salt distribution and the effect of low salinity exposure on organisms in other estuaries, especially bottom-associated species. [ABSTRACT FROM AUTHOR]

Anthropogenic carbon emissions have resulted in drastic oceanic changes, including increased acidity, increased temperature, and decreased salinity. Anthropogenic carbon emissions have resulted in drastic oceanic changes, including increased acidity, increased temperature, and decreased salinity. Few studies have directly assessed the compounded impact of alterations to oceanic conditions on oyster physiology and the relation to the presence of V. parahaemolyticus. This project investigated the relationship between projected climate scenarios and their influence on both eastern oyster, Crassostrea virginica, and the aquatic bacteria, Vibrio parahaemolyticus. Specifically, we examined whether an increase in water temperature and/or decrease in salinity would impair oyster resistance to V. parahaemolyticus, a human food and waterborne pathogen. Using a culture-dependent approach, our data revealed that the alterations in environmental conditions did not significantly impact the numbers of V. parahaemolyticus numbers within oyster hemolymph or tissues. However, we did observe a dramatic increase in the total amount of bacteria and pathogenic native Vibrio species, Vibrio aestuarianus and Vibrio harveyi. Despite detecting V. parahaemolyticus in most tissues at 7 days post-challenge, oysters were able to reduce bacterial levels below our limit of detection by 28 days of exposure. Furthermore, in our second experimental trial exploring single vs. multiple inoculation of bacteria, we observed that oysters were either able to reduce total bacterial levels to pre-treatment burdens (i.e., below our limit of detection) or die. This study demonstrates that the synergistic effects of elevated temperature and decreased salinity do not inhibit oysters from preventing the long-term colonization of exogenous V. parahaemolyticus. However, our data do show these environmental stressors impact oyster physiology and the native microbiota. This can lead to the proliferation of opportunistic pathogens, which could have impacts on oyster population numbers and ecosystem and human health. [ABSTRACT FROM AUTHOR]

This publication provides information on the status of oyster fisheries and aquaculture in Florida as well as general information about how oysters are grown in agricultural and restoration systems. It then introduces a series of technologies that have been developed in other US states and in other countries, strategies that may have utility in Florida. Finally, it covers some specifics of the permitting process as it relates to oyster aquaculture in Florida.

The development of science‐based restoration goals that reflect the primary motivation of stakeholders is a key factor leading to large‐scale, long‐term restoration successes. The ability to predict the potential ecosystem service delivery from restoration can inform the setting of appropriate goals and facilitate the strategic planning of restoration activities. While recovery of the ecosystem services provided by oyster reefs is a regularly cited reason for undertaking restoration, few examples exist where large‐scale oyster habitat restoration plans have been informed using ecosystem service functions. Such an approach is currently being implemented in the Pensacola Bay System, Florida, where a broad coalition of partners and community stakeholders are utilizing a watershed approach to restoring oysters with the aim of restoring oysters for multiple objectives including habitat, ecosystem services, and wild harvest and aquaculture. Through the process of developing a habitat management plan, water filtration was identified as a key ecosystem service by the stakeholders. To support restoration planning we derived a spatially explicit estimate of water filtration services provided by the eastern oyster in the Pensacola Bay system by linking an oyster habitat suitability map to a hydrodynamic‐oyster filtration model. This spatially explicit model allowed us to identify the areas where restored oyster reefs have the potential to provide the greatest increase in filtration service as well as provide spatially explicit estimates of the potential filtration provided by oyster habitat restored. Such information is useful in restoration planning and management and for stakeholder engagement, outreach, and education programs. [ABSTRACT FROM AUTHOR]

Anthropogenic carbon emissions have resulted in drastic oceanic changes, including increased acidity, increased temperature, and decreased salinity. Anthropogenic carbon emissions have resulted in drastic oceanic changes, including increased acidity, increased temperature, and decreased salinity. Few studies have directly assessed the compounded impact of alterations to oceanic conditions on oyster physiology and the relation to the presence of V. parahaemolyticus. This project investigated the relationship between projected climate scenarios and their influence on both eastern oyster, Crassostrea virginica, and the aquatic bacteria, Vibrio parahaemolyticus. Specifically, we examined whether an increase in water temperature and/or decrease in salinity would impair oyster resistance to V. parahaemolyticus, a human food and waterborne pathogen. Using a culture-dependent approach, our data revealed that the alterations in environmental conditions did not significantly impact the numbers of V. parahaemolyticus numbers within oyster hemolymph or tissues. However, we did observe a dramatic increase in the total amount of bacteria and pathogenic native Vibrio species, Vibrio aestuarianus and Vibrio harveyi. Despite detecting V. parahaemolyticus in most tissues at 7 days post-challenge, oysters were able to reduce bacterial levels below our limit of detection by 28 days of exposure. Furthermore, in our second experimental trial exploring single vs. multiple inoculation of bacteria, we observed that oysters were either able to reduce total bacterial levels to pre-treatment burdens (i.e., below our limit of detection) or die. This study demonstrates that the synergistic effects of elevated temperature and decreased salinity do not inhibit oysters from preventing the long-term colonization of exogenous V. parahaemolyticus. However, our data do show these environmental stressors impact oyster physiology and the native microbiota. This can lead to the proliferation of opportunistic pathogens, which could have impacts on oyster population numbers and ecosystem and human health.

Shifts from saltmarsh to mangroves are well-documented at mangrove poleward boundaries. A regime shift from intertidal oyster (Crassostrea virginica) reefs to mangrove islands has recently been documented in transitional phases in Florida, USA. To understand the local drivers of an oyster/mangrove regime shift and potential tipping points leading to a permanent mangrove state, we tracked all mangrove propagules (n = 1681) across 15 intertidal oyster reefs with or without adult mangroves for 15 months in Mosquito Lagoon, FL. While no propagule bottleneck was observed, few (3.2%) mangrove propagules/seedlings survived on reefs with no prior encroachment, compared to 11.3% and 16.1% on reefs with established older (pre-1943) or newer (1943 to present) adult mangrove stands, respectively. In total, 90.6% of the arriving propagules were from the red mangrove Rhizophora mangle; 13.2% of these were alive at the end of this study. Survival was Avicenna germinans) and 0% for white (Laguncularia racemosa) mangroves. Factors that promoted red mangrove success included close proximity (≤0.3 m) to adult mangroves, especially black mangroves; partial, upright burial of propagules in sediment; and arrival on reefs after annual high-water season. Additionally, once reefs had 50% mangrove cover, the density of red mangrove seedlings increased from 0.04 to 0.46 individuals m−2. Although climate change has alleviated the impact of extreme freezes on mangroves, local factors determine whether the regime shift will be complete and permanent; positive feedback loops associated with established mangroves suggest mangrove recruitment on intertidal oyster reefs will continue to increase.

Abstract The development of science‐based restoration goals that reflect the primary motivation of stakeholders is a key factor leading to large‐scale, long‐term restoration successes. The ability to predict the potential ecosystem service delivery from restoration can inform the setting of appropriate goals and facilitate the strategic planning of restoration activities. While recovery of the ecosystem services provided by oyster reefs is a regularly cited reason for undertaking restoration, few examples exist where large‐scale oyster habitat restoration plans have been informed using ecosystem service functions. Such an approach is currently being implemented in the Pensacola Bay System, Florida, where a broad coalition of partners and community stakeholders are utilizing a watershed approach to restoring oysters with the aim of restoring oysters for multiple objectives including habitat, ecosystem services, and wild harvest and aquaculture. Through the process of developing a habitat management plan, water filtration was identified as a key ecosystem service by the stakeholders. To support restoration planning we derived a spatially explicit estimate of water filtration services provided by the eastern oyster in the Pensacola Bay system by linking an oyster habitat suitability map to a hydrodynamic‐oyster filtration model. This spatially explicit model allowed us to identify the areas where restored oyster reefs have the potential to provide the greatest increase in filtration service as well as provide spatially explicit estimates of the potential filtration provided by oyster habitat restored. Such information is useful in restoration planning and management and for stakeholder engagement, outreach, and education programs.

Demand for oysters in the premium half-shell market drives the need for research to optimize and improve oyster aquaculture production methods. After setting, oysters are typically maintained in nursery upwellers that provide nutrients and oxygen while removing waste. They remain in the nursery until they are large enough to be deployed in aquaculture gear. Land-based upweller systems include silo and bottle upwellers, with bottles requiring less space and maintenance. However, it is unknown if upweller type influences oyster growth, shape, or survival after field deployment. This study reared Eastern oysters, Crassostrea virginica, to 2 mm in silo or bottle upwellers and deployed them to floating bags for a six-week grow-out period. Oysters were sampled initially, then size graded, counted, and redeployed every two weeks. Changes in growth parameters, quality ratios, survival, and hinge backbend deformity prevalence were determined after six weeks. Initially, silo-reared oysters were larger than those reared in bottles, likely due to the need for flow rate optimization and/or the tumbling action that breaks the fragile growing edge of the shell. Despite these initial differences, there were minimal size differences between upweller types after six weeks of growth in the field. There were no significant differences in survival, hinge backbend abnormality prevalence, or size class distribution between upweller types. These results indicate that upweller choice has minimal impact on the grow-out phase of oyster production and both systems are acceptable for Eastern oyster production in the northern Gulf of Mexico. [ABSTRACT FROM AUTHOR]

Eastern oysters, Crassostrea virginica, are commercially important coastal species that provide many ecosystem services for coastal communities. Unfortunately, 85% of oyster reefs have been lost globally, prompting investments in restoration efforts to rebuild populations. Managers often consider several well-studied environmental and water quality parameters when making restoration site decisions. However, recent research suggests that submarine groundwater discharge (SGD) may play a role in driving the distribution of oysters in some estuaries. Specifically, SGD may result in localized areas of low dissolved oxygen and low pH that could inhibit oyster recruitment and survival. However, SGD may interact with other potential oyster stressors, including creek geomorphology. On point bars, sediment accumulation could alter growth rates of oysters and physiology, and it is possible that the two factors, SGD and creek geomorphology, could interact to impact oyster growth. We conducted a field experiment to examine the effects of SGD and creek geomorphology on oyster growth rates in a marsh-lined tidal creek in Georgia, USA. High and low SGD sites were paired within point bars and cut banks. Oysters were deployed in cages for 72 days and growth rates were determined. We found a significant interaction between SGD and creek geomorphology on oyster growth rates. Oysters grew at significantly faster rates at locations on accretionary point bars regardless of SGD flux, whereas, on erosional cut banks, high SGD flux significantly reduced oyster growth rate relative to low SGD flux. It appears that SGD may negatively influence oyster growth at specific creek locations, likely due to the presence of other stressors. Therefore, it is important to consider potential interacting and confounding stressors when managing oyster populations. As SGD is still a relatively understudied potential stressor for oysters, it is critical to continue to examine how groundwater might influence oysters in other locations and in combination with other stressors. Regardless, this study provides further evidence that SGD should be considered in future management efforts. [ABSTRACT FROM AUTHOR]

Demand for oysters in the premium half-shell market drives the need for research to optimize and improve oyster aquaculture production methods. After setting, oysters are typically maintained in nursery upwellers that provide nutrients and oxygen while removing waste. They remain in the nursery until they are large enough to be deployed in aquaculture gear. Land-based upweller systems include silo and bottle upwellers, with bottles requiring less space and maintenance. However, it is unknown if upweller type influences oyster growth, shape, or survival after field deployment. This study reared Eastern oysters, Crassostrea virginica, to 2 mm in silo or bottle upwellers and deployed them to floating bags for a six-week grow-out period. Oysters were sampled initially, then size graded, counted, and redeployed every two weeks. Changes in growth parameters, quality ratios, survival, and hinge backbend deformity prevalence were determined after six weeks. Initially, silo-reared oysters were larger than those reared in bottles, likely due to the need for flow rate optimization and/or the tumbling action that breaks the fragile growing edge of the shell. Despite these initial differences, there were minimal size differences between upweller types after six weeks of growth in the field. There were no significant differences in survival, hinge backbend abnormality prevalence, or size class distribution between upweller types. These results indicate that upweller choice has minimal impact on the grow-out phase of oyster production and both systems are acceptable for Eastern oyster production in the northern Gulf of Mexico.

Eastern oysters, Crassostrea virginica, are commercially important coastal species that provide many ecosystem services for coastal communities. Unfortunately, 85% of oyster reefs have been lost globally, prompting investments in restoration efforts to rebuild populations. Managers often consider several well-studied environmental and water quality parameters when making restoration site decisions. However, recent research suggests that submarine groundwater discharge (SGD) may play a role in driving the distribution of oysters in some estuaries. Specifically, SGD may result in localized areas of low dissolved oxygen and low pH that could inhibit oyster recruitment and survival. However, SGD may interact with other potential oyster stressors, including creek geomorphology. On point bars, sediment accumulation could alter growth rates of oysters and physiology, and it is possible that the two factors, SGD and creek geomorphology, could interact to impact oyster growth. We conducted a field experiment to examine the effects of SGD and creek geomorphology on oyster growth rates in a marsh-lined tidal creek in Georgia, USA. High and low SGD sites were paired within point bars and cut banks. Oysters were deployed in cages for 72 days and growth rates were determined. We found a significant interaction between SGD and creek geomorphology on oyster growth rates. Oysters grew at significantly faster rates at locations on accretionary point bars regardless of SGD flux, whereas, on erosional cut banks, high SGD flux significantly reduced oyster growth rate relative to low SGD flux. It appears that SGD may negatively influence oyster growth at specific creek locations, likely due to the presence of other stressors. Therefore, it is important to consider potential interacting and confounding stressors when managing oyster populations. As SGD is still a relatively understudied potential stressor for oysters, it is critical to continue to examine how groundwater might influence oysters in other locations and in combination with other stressors. Regardless, this study provides further evidence that SGD should be considered in future management efforts.

Eastern oysters, Crassostrea virginica, are ecologically and economically important coastal species which provide a commercially valuable food product while also improving water quality through filtration, protecting shorelines, and providing habitat. The protozoan parasites Perkinsus marinus and Haplosporidium nesloni commonly infect oysters along the United States Atlantic and Gulf coasts and have been linked to poor oyster health and mass mortality events. In this study, wild oysters were collected from multiple reefs within four tidal creeks along the coast of Georgia to investigate P. marinus and H. nelsoni prevalence and intensity, their potential impact on oyster health, and identify possible drivers of the parasites. A second study occurred on four sites on Sapelo Island, Georgia, with continuous water quality monitoring data to further elucidate potential drivers. Oyster density and condition index, a proxy for health, were measured, and parasites were quantified using a TaqMan probe based quantitative real-time PCR within gill tissue. Real-time PCR showed that 86% of oysters tested were infected by one or both parasites in the coast-wide survey, and 93% of oysters from Sapelo Island were also infected by one or both parasites. Prevalence and infection intensity for both P. marinus and H. nelsoni varied across sites. Overall impacts on oysters were complex—intensity was not linked to oyster metrics in the coastwide study, but oyster condition was negatively correlated with P. marinus prevalence in the Sapelo Island study. Several relationships between both parasites and water quality parameters were identified, providing valuable information about potential drivers that should be investigated further. [ABSTRACT FROM AUTHOR]

Dense single nucleotide polymorphism (SNP) arrays are essential tools for rapid high-throughput genotyping for many genetic analyses, including genomic selection and high-resolution population genomic assessments. We present a high-density (200 K) SNP array developed for the Eastern oyster (Crassostrea virginica), which is a species of significant aquaculture production and restoration efforts throughout its native range. SNP discovery was performed using low-coverage whole-genome sequencing of 435 F1 oysters from families from 11 founder populations in New Brunswick, Canada. An Affymetrix Axiom Custom array was created with 219,447 SNPs meeting stringent selection criteria and validated by genotyping more than 4,000 oysters across 2 generations. In total, 144,570 SNPs had a call rate >90%, most of which (96%) were polymorphic and were distributed across the Eastern oyster reference genome, with similar levels of genetic diversity observed in both generations. Linkage disequilibrium was low (maximum r² ~0.32) and decayed moderately with increasing distance between SNP pairs. Taking advantage of our intergenerational data set, we quantified Mendelian inheritance errors to validate SNP selection. Although most of SNPs exhibited low Mendelian inheritance error rates overall, with 72% of called SNPs having an error rate of <1%, many loci had elevated Mendelian inheritance error rates, potentially indicating the presence of null alleles. This SNP panel provides a necessary tool to enable routine application of genomic approaches, including genomic selection, in C. virginica selective breeding programs. As demand for production increases, this resource will be essential for accelerating production and sustaining the Canadian oyster aquaculture industry. [ABSTRACT FROM AUTHOR]

Disease tolerance, a host's ability to limit damage from a given parasite burden, is quantified by the relationship between pathogen load and host survival or reproduction. Dermo disease, caused by the protozoan parasite P. marinus, negatively impacts survival in both wild and cultured eastern oyster (C. virginica) populations. Resistance to P. marinus has been the focus of previous studies, but tolerance also has important consequences for disease management in cultured and wild populations. In this study we measured dermo tolerance and evaluated global expression patterns of two sensitive and two tolerant eastern oyster families experimentally challenged with distinct doses of P. marinus (0, 106, 107, and 108 parasite spores per gram wet weight, n = 3-5 individuals per family per dose). Weighted Gene Correlation Network Analysis (WGCNA) identified several modules correlated with increasing parasite dose/infection intensity, as well as phenotype. Modules positively correlated with dose included transcripts and enriched GO terms related to hemocyte activation and cell cycle activity. Additionally, these modules included G-protein coupled receptor, toll-like receptor, and tumor necrosis factor pathways, which are important for immune effector molecule and apoptosis activation. Increased metabolic activity was also positively correlated with treatment. The module negatively correlated with infection intensity was enriched withGOterms associated with normal cellular activity and growth, indicating a tradeoff with increased immune response. The module positively correlated with the tolerant phenotype was enriched for transcripts associated with "programmed cell death" and contained a large number of tripartite motif-containing proteins. Differential expression analysis was also performed on the 108 dosed group using the most sensitive family as the comparison reference. Results were consistent with the network analysis, but signals for "programmed cell death" and serine protease inhibitors were stronger in one tolerant family than the other, suggesting that there are multiple avenues for disease tolerance. These results provide new insight for defining dermo response traits and have important implications for applying selective breeding for disease management. [ABSTRACT FROM AUTHOR]

Two bag float configurations (on-side; on-top) for the culture of four length classes of Eastern oyster (Crassostrea virginica) were tested at two sites in Tracadie Bay, Canada. An interaction between the site and the float configurations was observed at the northern site for the 21–30, 31–45 and 46–65 mm oyster classes for their length, and in the 46–65 mm for width as well. The observed differences give a potential increase of 32.5% in growth on a 4-year cycle when on-top configuration is used. About 12.7% more market size oysters were produced in this configuration representing an increase of $9.24 (CAN) per bag. This study shows the potential benefit of the on-top configuration, but also the interaction between the site and the float configurations. Since the on-top configuration needs more maintenance time, it is suggested that the float configurations be chosen based on biofouling, growth variation, effect on oyster shape, and cost/advantage. [ABSTRACT FROM AUTHOR]

Projected increases in temperature and decreases in salinity associated with global climate change will likely have detrimental impacts on eastern oyster, Crassostrea virginica , as these variables can influence physiological processes in these keystone species. We set out to determine how the interactive effects of temperature (20 °C or 27 °C) and/or salinity (27‰ or 17‰) impacted the energetic reserves, aerobic and anaerobic metabolism, and changes to oxidative stress or total antioxidant potential as a consequence of an altered environment over a 21-day exposure. Gill and adductor muscle were used to quantify changes in total glycogen and lipid content, Electron Transport System and Citrate Synthase activities, Malate Dehydrogenase activity, Protein Carbonyl formation, lipid peroxidation, and total antioxidant potential. A second exposure was performed to determine if these environmental factors influenced the ingestion of microfibers, which are now one of the leading forms of marine debris. Elevated temperature and the combination of elevated temperature and decreased salinity led to an overall decline in oyster mass, which was exacerbated by the presence of microfibers. Changes in metabolism and oxidative stress were largely influenced by time, but exposure to elevated temperature, decreased salinity, the combination of these stressors or exposure to microfibers had small impacts on oyster physiology and survival. Overall these studies demonstrate that oyster are fairly resilient to changes in salinity in short-term exposures, and elevations in temperature or temperature combined with salinity result in changes to the oyster energetic response, which can be further impacted by the presence of microfibers. [Display omitted] • Microfiber exposure amplified temperature and salinity effects on C. virginica mass. • Temperature and/or salinity resulted in a decrease in stored glycogen. • Temperature, salinity and microfibers decreased Malate Dehydrogenase activity. • Microfibers enhanced lipid peroxidation levels in gill and adductor muscles. [ABSTRACT FROM AUTHOR]

Methylmercury is a toxin of local, regional, and global concern, with estuarine habitats possessing ecological characteristics that support conversion of inorganic mercury into this methylated form. We monitored Hg concentrations in species within the food web of the lower Cape Fear River (CFR) estuary in 2018–2020. Samples were analyzed for Hg concentrations and nitrogen isotopes (a measure of trophic level), and we found a positive relationship within this food web each year (p < 0.0001), indicating biomagnification is occurring. The highest Hg concentrations were among the upper trophic level species (Royal Terns, 4.300 ppm). While the Hg concentrations we documented are below assumed thresholds for toxic effects, we found spikes in Hg concentrations after Hurricane Florence in 2018 and with other disturbances to the CFR that resuspended bottom sediments. Continued monitoring is needed to understand the cause of annual variations, health implications, and conservation needs. • Methylation of mercury is driven by anthropogenic and ecological factors • This region has many features that drive methylation rates, posing health risks • Mercury in the Cape Fear River has never been studied on a food web scale • Large fluctuations in mercury followed Hurricane Florence [ABSTRACT FROM AUTHOR]

Disease tolerance, a host’s ability to limit damage from a given parasite burden, is quantified by the relationship between pathogen load and host survival or reproduction. Dermo disease, caused by the protozoan parasite P. marinus, negatively impacts survival in both wild and cultured eastern oyster (C. virginica) populations. Resistance to P. marinus has been the focus of previous studies, but tolerance also has important consequences for disease management in cultured and wild populations. In this study we measured dermo tolerance and evaluated global expression patterns of two sensitive and two tolerant eastern oyster families experimentally challenged with distinct doses of P. marinus (0, 106, 107, and 108 parasite spores per gram wet weight, n = 3–5 individuals per family per dose). Weighted Gene Correlation Network Analysis (WGCNA) identified several modules correlated with increasing parasite dose/infection intensity, as well as phenotype. Modules positively correlated with dose included transcripts and enriched GO terms related to hemocyte activation and cell cycle activity. Additionally, these modules included G-protein coupled receptor, toll-like receptor, and tumor necrosis factor pathways, which are important for immune effector molecule and apoptosis activation. Increased metabolic activity was also positively correlated with treatment. The module negatively correlated with infection intensity was enriched with GO terms associated with normal cellular activity and growth, indicating a trade-off with increased immune response. The module positively correlated with the tolerant phenotype was enriched for transcripts associated with “programmed cell death” and contained a large number of tripartite motif-containing proteins. Differential expression analysis was also performed on the 108 dosed group using the most sensitive family as the comparison reference. Results were consistent with the network analysis, but signals for “programmed cell death” and serine protease inhibitors were stronger in one tolerant family than the other, suggesting that there are multiple avenues for disease tolerance. These results provide new insight for defining dermo response traits and have important implications for applying selective breeding for disease management.

Eastern oysters, Crassostrea virginica, are ecologically and economically important coastal species which provide a commercially valuable food product while also improving water quality through filtration, protecting shorelines, and providing habitat. The protozoan parasites Perkinsus marinus and Haplosporidium nesloni commonly infect oysters along the United States Atlantic and Gulf coasts and have been linked to poor oyster health and mass mortality events. In this study, wild oysters were collected from multiple reefs within four tidal creeks along the coast of Georgia to investigate P. marinus and H. nelsoni prevalence and intensity, their potential impact on oyster health, and identify possible drivers of the parasites. A second study occurred on four sites on Sapelo Island, Georgia, with continuous water quality monitoring data to further elucidate potential drivers. Oyster density and condition index, a proxy for health, were measured, and parasites were quantified using a TaqMan probe based quantitative real-time PCR within gill tissue. Real-time PCR showed that 86% of oysters tested were infected by one or both parasites in the coast-wide survey, and 93% of oysters from Sapelo Island were also infected by one or both parasites. Prevalence and infection intensity for both P. marinus and H. nelsoni varied across sites. Overall impacts on oysters were complex—intensity was not linked to oyster metrics in the coastwide study, but oyster condition was negatively correlated with P. marinus prevalence in the Sapelo Island study. Several relationships between both parasites and water quality parameters were identified, providing valuable information about potential drivers that should be investigated further.

Management decisions for the eastern oyster (Crassostrea virginica) fishery in Maryland are made at a finer spatial scale than the spatial data resolution of the current stock assessment. This mismatch creates concerns that the consequences of management actions and fishing activities are not being adequately represented when assessing fishery status. To produce a model that could support a participatory modeling process intended to differentiate results of fine-scale management actions we developed a method for conditioning a down-scaled oyster stock assessment model to produce a spatially-explicit operating model at the scale of individual oyster bars for eastern oysters in Chesapeake Bay, Maryland. To ensure that parameter values of the operating model were consistent with data at multiple scales we fitted the model to bar-specific harvest data during 2004–2020 and regional abundance estimates from the current Maryland Oyster Stock Assessment during 1999–2020. The operating model can then predict effects of different management actions, such as planting hatchery-reared oysters, addition of substrate, or modifying fishing regulations, at a bar-specific scale and compare outcomes among different scenarios. Model outputs included a suite of management performance metrics, including but not limited to oyster abundance and fishery harvest, that were important to stakeholders. These bar-specific scenarios would not have been possible using an operating model with the same spatial resolution as the current Maryland Oyster Stock Assessment. Accounting for fine scale spatial processes can be important to engaging participants and our model provides an expedient option to develop an operating model that downscales stock assessment models. [ABSTRACT FROM AUTHOR]

This study developed RNA-based predictive models describing the survival of Vibrio parahaemolyticus in Eastern oysters (Crassostrea virginica) during storage at 0, 4, and 10°C. Postharvested oysters were inoculated with a cocktail of five V. parahaemolyticus strains and were then stored at 0, 4, and 10°C for 21 or 11 days. A real-time reverse transcription-PCR (RT-PCR) assay targeting expression of the tlh gene was used to evaluate the number of surviving V. parahaemolyticus cells, which was then used to establish primary molecular models (MMs). Before construction of the MMs, consistent expression levels of the tlh gene at 0, 4, and 10°C were confirmed, and this gene was used to monitor the survival of the total V. parahaemolyticus cells. In addition, the tdh and trh genes were used for monitoring the survival of virulent V. parahaemolyticus Traditional models (TMs) were built based on data collected using a plate counting method. From the MMs, V. parahaemolyticus populations had decreased 0.493, 0.362, and 0.238 log10 CFU/g by the end of storage at 0, 4, and 10°C, respectively. Rates of reduction of V. parahaemolyticus shown in the TMs were 2.109, 1.579, and 0.894 log10 CFU/g for storage at 0, 4, and 10°C, respectively. Bacterial inactivation rates (IRs) estimated with the TMs (-0.245, -0.152, and -0.121 log10 CFU/day, respectively) were higher than those estimated with the MMs (-0.134, -0.0887, and -0.0732 log10 CFU/day, respectively) for storage at 0, 4, and 10°C. Higher viable V. parahaemolyticus numbers were predicted using the MMs than using the TMs. On the basis of this study, RNA-based predictive MMs are the more accurate and reliable models and can prevent false-negative results compared to TMs.IMPORTANCE One important method for validating postharvest techniques and for monitoring the behavior of V. parahaemolyticus is to establish predictive models. Unfortunately, previous predictive models established based on plate counting methods or on DNA-based PCR can underestimate or overestimate the number of surviving cells. This study developed and validated RNA-based molecular predictive models to describe the survival of V. parahaemolyticus in oysters during low-temperature storage (0, 4, and 10°C). The RNA-based predictive models show the advantage of being able to count all of the culturable, nonculturable, and stressed cells. By using primers targeting the tlh gene and pathogenesis-associated genes (tdh and trh), real-time RT-PCR can evaluate the total surviving V. parahaemolyticus population as well as differentiate the pathogenic ones from the total population. Reliable and accurate predictive models are very important for conducting risk assessment and management of pathogens in food.

Despite the social, economic, and ecological benefits that shellfish aquaculture provides, there are significant barriers to expansion of the aquaculture industry as a result of possible environmental impacts (real or perceived) and social concerns from coastal communities. Coastal residents may perceive aquaculture as a nuisance, and the sentiment of not in my backyard (NIMBYism) is a common response and potential barrier to proposed increases in local shellfish aquaculture operations. To better understand these societal concerns and determine the potential drivers behind perceptions of oyster aquaculture, we surveyed coastal communities along the Eastern US using an online survey through Qualtrics panels. Most coastal residents indicated that they would support aquaculture expansion; however, residents who perceived oyster aquaculture as beneficial to their local economy were more supportive of expansion, whereas those who perceived oyster aquaculture as harmful to it were less likely to support expansion. These findings have important management implications as they can help inform managers on how to effectively engage with the public and better support industry and community relations. Furthermore, they could help inform how policies, practices, and education could change perceptions of aquaculture stakeholders, including coastal residents, and thereby the future of the aquaculture industry in the US. • Majority of eastern US coastal residents surveyed would support shellfish aquaculture expansion in their respective states. • Coastal resident's support for shellfish aquaculture is driven by perceived socio-economic and environmental impacts. • Support for aquaculture expansion varies regionally in the eastern US. [ABSTRACT FROM AUTHOR]

Oyster aquaculture is a growing industry both globally and nationally. Productive coastal waters support high-density containerized culture of oysters, but also sustain many other macrofaunal species which can settle on oysters and cage materials (biofouling), causing problems for oyster farms. Desiccation, or periodic air drying, of farm infrastructure and oysters has been used to control colonization and growth of biofouling organisms on oyster farms worldwide, but the minimum necessary interval of desiccation has yet to be thoroughly assessed. Given the known stresses to oysters associated with periods of emersion, an understanding of the effects of different weekly desiccation intervals is needed. This study investigated the use of desiccation in controlling biofouling and the associated impacts to oyster growth and mortality at three oyster farms within Maryland's portion of the Chesapeake Bay, including one low salinity site in an upper Chesapeake Bay tributary and two sites in the middle portion of the Chesapeake Bay. Three desiccation treatments were applied at each site: control (no desiccation), 8 consecutive hours of desiccation per week, and 24 consecutive hours of desiccation per week. Oysters were deployed between July–December 2018 and the percent valve coverage by individual biofouling species was monitored, along with worm abundance, oyster growth, and oyster mortality. Total biofouling was significantly greater on non-desiccated oysters but minimal differences in biofouling coverage were observed among oysters desiccated for 8 or 24 h weekly. Seven biofouling species were observed among the sites, and all except for a single macroalgal species (Ulva intestinalis) were controlled by the 8- and 24-h desiccation treatments. No clear treatment-derived differences in oyster growth or mortality were observed. Overall, results suggest desiccating weekly for either 8 or 24 consecutive hours may be a suitable biofouling management strategy for gross biofouling reduction on oyster farms. • Weekly desiccation for 8 or 24 h controlled gross biofouling coverage in cultured oysters, Crassostrea virginica. • A macroalgal species, Ulva intestinalis, was the only species not consistently controlled using desiccation. • Weekly desiccation for 8 or 24 h reduced worm abundance in cultured oysters, Crassostrea virginica. [ABSTRACT FROM AUTHOR]

Oyster recruitment to spat collectors can result in the clumping of two or more individuals, whereby they naturally cement to each other's shells. On‐bottom oyster farmers typically separate these oysters and re‐deploy them on the seafloor, potentially exposing them to predators. This raises the question of whether refraining from separating these oysters might provide an advantage against predation. We addressed this question using eastern oysters (Crassostrea virginica) and the non‐indigenous European green crab (Carcinus maenas) from part of their invaded range in Atlantic Canada. We assessed the influence of oyster arrangement (single vs. paired) and oyster size (small‐ vs. mid‐size) on mortality caused by two sizes of this invasive predator. Mortality rates were assessed with 24 h trials in which 30 oysters of a given size and arrangement were exposed to green crab predation. We found a significant influence of oyster arrangement (paired

Remote-setting of oyster, Crassostrea virginica, larvae from the disease-resistant Haskin NEH line is performed every other year in Delaware to supply small-scale oyster enhancement efforts, citizen oyster gardening program. Over the past four remote sets (2009, 2011, 2013, 2015), three types of shell containment gear were utilized to monitor and compare the setting efficiency rate and post-set survival. Shell containment gears included diamond, plastic mesh bags (2009, 2011), wire baskets (2011, 2015), and plastic aquaculture trays (2013, 2015). Average setting efficiency was estimated at 28%, 23%, 17%, and 29% in the respective 2009, 2011, 2013, and 2015 remote sets while gear specific settling efficiency (%) include 28% for mesh bags in 2009, 22% for mesh bags and 33% for wire baskets in 2011, 17% for aquaculture trays in 2013, and 30% for aquaculture trays and 22% for wire baskets in 2015. Settling efficiency was lowest in 2013 using aquaculture trays compared to other years while aquaculture trays in 2015 and wire baskets in 2011 resulted equally higher settling efficiency. For small-scale growers, the stacked aquaculture trays are advantageous for several reasons: reducing handling time, uniform shell distribution within tanks, environmentally friendly alternative, and ease of cleaning detritus between shell layers.

Clionaid boring sponges (Cliona sp.) may affect individual oyster growth and condition while destroying oyster habitats, which can impact restoration efforts and aquaculture for eastern oysters (Crassostrea virginica). Since both oysters and boring sponges are affected by similar abiotic variables (i.e., salinity, tidal exposure), this study explored the potential trade-offs between these abiotic variables and sponge presence on growth, condition index, and survival of oysters using a fully-factorial in situ experiment across 3 sites in coastal GA, USA. Across all sites and tide heights, oysters with sponge grew 20% slower and had 10% lower condition index than oysters without sponge. Savannah State, the site with the lowest salinity (mean ± SD = 24.5 ± 2.1, range 20–28), exhibited growth rates that were 1.4–1.7 times faster than the other two sites, with even sponge-infested oysters exhibiting higher growth rates than uninfested oysters at the other two sites. In addition, growth rates of sponge-infested oysters were reduced by 26% relative to uninfested individuals in the low intertidal tier, but only by 12% in the upper intertidal zone, suggesting the negative impact also varies with tidal location. Therefore, oysters exposed to air for prolonged periods and placed in areas with polyhaline salinity exhibit fast growth and high relative condition index, although salinity may be confounded by other variables (food availability, fouling organisms). This study highlights the importance of considering site and tidal location for oyster restoration and culture. [ABSTRACT FROM AUTHOR]

Diseases are important drivers of population and ecosystem dynamics. This review synthesizes the effects of infectious diseases on the population dynamics of nine species of marine organisms in the Chesapeake Bay. Diseases generally caused increases in mortality and decreases in growth and reproduction. Effects of diseases on eastern oyster (Crassostrea virginica) appear to be low in the 2000s compared to effects in the 1980s–1990s. However, the effects of disease were not well monitored for most of the diseases in marine organisms of the Chesapeake Bay, and few studies considered effects on growth and reproduction. Climate change and other anthropogenic effects are expected to alter host-pathogen dynamics, with diseases of some species expected to worsen under predicted future conditions (e.g., increased temperature). Additional study of disease prevalence, drivers of disease, and effects on population dynamics could improve fisheries management and forecasting of climate change effects on marine organisms in the Chesapeake Bay. [ABSTRACT FROM AUTHOR]

A 2-year study was undertaken to understand feeding preferences of the eastern oyster Crassostrea virginica when growing in conditions of eutrophication and variable flow. Oysters were suspended in the Rhode River, a tributary of Chesapeake Bay, Maryland, USA, and a subset of these oysters was collected monthly, measured in height to determine growth, and the phytoplankton in their gut were examined both microscopically and using indicator pigments and compared with phytoplankton abundance and composition in the water column. The data herein summarize the oyster growth and the gut contents with respect to phytoplankton cell numbers and composition and with respect to signature pigments.

A 2-year study was undertaken to understand feeding preferences of the eastern oyster Crassostrea virginica in the eutrophic Rhode River, a tributary of Chesapeake Bay, Maryland, USA. A subset of experimentally suspended oysters was collected monthly and environmental parameters were simultaneously measured. Oysters were measured in height to determine growth, and the phytoplankton in their gut were examined both microscopically and using indicator pigments and compared with phytoplankton abundance and composition in the water column. Growth was higher in the second year of the study when flow was lower and salinity higher. Food selectivity was calculated using a modified electivity index (Ei), which relates phytoplankton composition in the gut to that in the water. Oysters appeared to preferentially graze–or at least preferentially retain in the gut–various (unidentified) flagellates, Ochrophyta (diatoms) and Myzozoa (dinoflagellates), and appeared to generally reject cyanobacteria, especially picocyanobacteria, from their diet. The Myzozoa included several common harmful algal bloom taxa, including Prorocentum minimum (=P. cordatum) and Heterocapsa rotundatum, that can detrimentally affect oyster growth. Reductions in eutrophication will likely be beneficial for oyster diets if such reductions result in fewer dinoflagellate blooms and in picocyanobacteria abundance during the critical feeding summer months.

The eastern oyster (Crassostrea virginica) is a keystone species in the estuaries of the mid-Atlantic of the United States. Its population experienced drastic declines in the last century due to overfishing, habitat loss, and disease. Much interest has been focused on restoring this important commercial and ecological species. This research focused on evaluating the suitability of using recycled concrete aggregate (RCA) from road projects as an alternative bottom conditioning material for oyster restoration and aquaculture in the Chesapeake Bay. Three types of substrate (RCA, natural oyster shell, and RCA with a veneer of oyster shell) were used as bottom conditioning materials and tested their impacts on benthic epifaunal community and oyster recruitment at two sites in the Chesapeake Bay over the summer and fall of 2013. The diversity and abundance of the epifaunal community, and oyster spat density associated with these bottom conditioning materials were sampled. The results showed there was no significant difference across substrate type (RCA, oyster shell, and RCA with oyster shell) in terms of their impacts on benthic community diversity and oyster recruitment, demonstrating that RCA, as an alternative material, was generally similar to natural oyster shell with regards to ecosystem services provided, and could be a potential source for much needed bottom substrate for oyster restoration and aquaculture.

In Great Bay Estuary, New Hampshire, USA, Haplosporidium nelsoni and Perkinsus marinus are 2 active pathogens of the eastern oyster Crassostrea virginica (Gmelin), that cause MSX (multinucleated sphere with unknown affinity 'X') and dermo mortalities, respectively. Whereas studies have quantified infection intensities in oyster populations and determined whether these parasites exist in certain planktonic organisms, no studies thus far have examined both infectious agents simultaneously in water associated with areas that do and do not have oyster populations. As in other estuaries, both organisms are present in estuarine waters throughout the Bay, especially during June through November, when oysters are most active. Waters associated with oyster habitats had higher, more variable DNA concentrations from these pathogenic organisms than waters at a non-oyster site. This finding allows for enhanced understanding of disease-causing organisms in New England estuaries, where oyster restoration is a priority.

Remote-setting of oyster, Crassostrea virginica , larvae from the disease-resistant Haskin NEH line is performed every other year in Delaware to supply small-scale oyster enhancement efforts, citizen oyster gardening program. Over the past four remote sets (2009, 2011, 2013, 2015), three types of shell containment gear were utilized to monitor and compare the setting efficiency rate and post-set survival. Shell containment gears included diamond, plastic mesh bags (2009, 2011), wire baskets (2011, 2015), and plastic aquaculture trays (2013, 2015). Average setting efficiency was estimated at 28%, 23%, 17%, and 29% in the respective 2009, 2011, 2013, and 2015 remote sets while gear specific settling efficiency (%) include 28% for mesh bags in 2009, 22% for mesh bags and 33% for wire baskets in 2011, 17% for aquaculture trays in 2013, and 30% for aquaculture trays and 22% for wire baskets in 2015. Settling efficiency was lowest in 2013 using aquaculture trays compared to other years while aquaculture trays in 2015 and wire baskets in 2011 resulted equally higher settling efficiency. For small-scale growers, the stacked aquaculture trays are advantageous for several reasons: reducing handling time, uniform shell distribution within tanks, environmentally friendly alternative, and ease of cleaning detritus between shell layers. [ABSTRACT FROM AUTHOR]

Epigenetic modification, specifically DNA methylation, is one possible mechanism for intergenerational plasticity. Before inheritance of methylation patterns can be characterized, we need a better understanding of how environmental change modifies the parental epigenome. To examine the influence of experimental ocean acidification on eastern oyster (Crassostrea virginica) gonad tissue, oysters were cultured in the laboratory under control (491 ± 49 μatm) or high (2550 ± 211 μatm) pCO2 conditions for 4 weeks. DNA from reproductive tissue was isolated from five oysters per treatment, then subjected to bisulfite treatment and DNA sequencing. Irrespective of treatment, DNA methylation was primarily found in gene bodies with approximately 22% of CpGs (2.7% of total cytosines) in the C. virginica genome predicted to be methylated. In response to elevated pCO2, we found 598 differentially methylated loci primarily overlapping with gene bodies. A majority of differentially methylated loci were in exons (61.5%) with less intron overlap (31.9%). While there was no evidence of a significant tendency for the genes with differentially methylated loci to be associated with distinct biological processes, the concentration of these loci in gene bodies, including genes involved in protein ubiquitination and biomineralization, suggests DNA methylation may be important for transcriptional control in response to ocean acidification. Changes in gonad methylation also indicate potential for these methylation patterns to be inherited by offspring. Understanding how experimental ocean acidification conditions modify the oyster epigenome, and if these modifications are inherited, allows for a better understanding of how ecosystems will respond to environmental change.

Quantifying and comparing stocks of oysters (Crassostrea virginica) within and among estuaries across the Gulf of Mexico is difficult because the sampling equipment used is either inconsistent among studies, or inefficient. In Texas, USA, stock assessments of oyster populations are made using an oyster dredge, which is an inefficient sampling tool. We compared sampling densities estimated by oyster dredges with more accurate estimates taken by diver-quadrat samples to determine a dredge efficiency rate. Our calculated efficiency rate (0.125) was negatively affected by the number of dead oysters, and the number and volume of total oysters in an area, but not affected by sediment grain size, water quality, and other oyster metrics. The dredge efficiency rate calculated in this study can be applied to past and future dredge-collected oyster quantity data to provide more realistic estimates of oyster densities and allow more accurate stock assessments and comparisons among studies and regions.

Dermo disease, caused by the protozoan parasite Perkinsus marinus , negatively impacts wild and cultured Eastern oyster populations, yet our knowledge of the mechanistic bases for parasite pathogenicity and the Eastern oyster's response to it is limited. To better understand host responses to the parasite and identify molecular mechanisms underlying disease-resistance phenotypes, we experimentally challenged two families exhibiting divergent Dermo-resistance phenotypes with the parasite, generated global expression profiles using RNAseq and identified differentially expressed transcripts between control and challenged oysters from each family at multiple time points post-parasite injection. The susceptible and resistant families exhibited strikingly different transcriptomic responses to the parasite over a 28-day time period. The resistant family exhibited a strong, focused, early response to P. marinus infection, where many significantly upregulated transcripts were associated with the biological processes "regulation of proteolysis" and "oxidation-reduction process." P. marinus virulence factors are mainly comprised of proteases that facilitate parasite invasion and weaken host humoral defenses, thus host upregulation of transcripts associated with negative regulation of proteolysis is consistent with a Dermo-resistant phenotype. In contrast, the susceptible family mounted a very weak, disorganized, initial response to the parasite. Few transcripts were differentially expressed between control and injected oysters, and no functional enrichment was detected among them. At the final 28 d time point 2450 differentially expressed transcripts were identified and were associated with either "G-protein coupled receptor activity" (upregulated) or "microtubule-based process" (downregulated). A handful of protease inhibitors were differentially expressed between control and injected susceptible oysters, but this function was not enriched in the susceptible data set. The differential expression patterns observed in this study provide valuable insight into the functional basis of Dermo resistance and suggest that the timing of expression is just as important as the transcripts being expressed. • Advances in genomics and phenotyping methods enabled exploration of the basis of Dermo resistance in the eastern oyster. • Susceptible and resistant phenotypes exhibit different transcriptomic responses to the disease-causing parasite over time. • Response to the parasite is dynamic, underscoring the need to assess gene expression at different stages of infection. • Resistant oysters respond with protease inhibitors and transcripts associated with oxidation reduction processes. • In susceptible oysters, early response is weak; as disease progresses gene expression reflects negative effects on growth. [ABSTRACT FROM AUTHOR]

Perkinsus marinus, the causative agent of Dermo disease, is responsible for mass mortalities and negatively impacts aquaculture production of the eastern oyster, Crassostrea virginica. Selective breeding is a viable option for Dermo disease management; however, fluctuations in natural selection pressure and environmental noise hinder accumulation of genetic gains acquired through field performance trials. The purpose of this study was to adapt and apply laboratory disease challenge methods to eastern oysters, better characterize resistance‐specific traits and assess the potential for genetic variation in Dermo resistance among distinct families within a breeding population. Two challenge experiments were conducted, one in 2014 and the other in 2015. Significant treatment (control vs. challenged) and family effects on survival (measured as per cent survival and days to death) were detected in the 2014 challenge, while overall high survival precluded the detection of a significant family effect in the 2015 challenge. An alternate measure of resistance, parasite elimination rate, was also measured in the 2015 challenge, and this varied significantly among families. Thus, both survival and the change in parasite concentration in oyster tissues over time represent Dermo resistance phenotypes that can be measured accurately with the adapted laboratory disease challenge protocol described here. The obvious next step is to incorporate the challenge protocol in eastern oyster breeding programmes to assess whether well‐defined, accurately measured, Dermo‐resistant phenotypes result in enhanced genetic improvement for this commercially important trait. [ABSTRACT FROM AUTHOR]

• We compare different formulations for filtration for the eastern oyster (Crassostrea virginica). • These formulations use functions of temperature, salinity, and suspended solids to limit filtration. • We found that the choice of TSS function caused significant variation in the model output. Oysters directly impact water quality through filter feeding and have been extensively studied due to the potential ecological benefits of population restoration. Numerical models have been developed that simulate the environmental impact of oysters on estimating current water quality conditions and evaluating prospective restoration strategies. Accurately representing oyster filtration in these models is essential to their value as management tools. However, the formulation of filtration in response to environmental variables differs between models. Here we compare different formulations for filtration for the eastern oyster (Crassostrea virginica) from several studies (Cerco and Noel, 2005; Fulford et al., 2007; North et al., 2010 ; Ehrich and Harris, 2015), which use functions of temperature, salinity, and suspended solids concentration (TSS) to limit filtration rate. Using outputs from a water quality model with controlled forcing conditions we investigated how sensitive model output can be to the environmental limitation functions used. We found that due to feedback between TSS and filtration rate, the choice of TSS function caused significant variation in the model output beyond the scale of the differences in the functions themselves. From our results and a theoretical understanding of model construction, we discuss the implications for the accuracy of water quality models with oyster filtration and provide recommendations for future modeling efforts. [ABSTRACT FROM AUTHOR]

The decline of the eastern oyster (Crassostrea virginica) has prompted various restoration and aquaculture efforts. Recent field surveys in Rhode Island suggest that wild populations are increasing, yet the factors contributing to expansion are unknown. We used a population genetic approach to characterize genetic differences between wild and cultured oyster populations and explore the extent of connectivity and admixture between groups. Individual oysters from four wild, three farmed, and two restored populations were collected within or just outside Ninigret Pond, a coastal lagoon highly influenced by human activity, and genotyped at 13 microsatellite loci. Results from the multi-locus genotype data showed that wild populations were more genetically diverse than the cultured populations. We also observed significant genetic differentiation between paired wild and cultured populations but not between pairs of wild populations. A cluster analysis detected substantial admixture between wild and cultured groups. As oyster aquaculture and restoration activities are forecasted to increase in the future, this study highlights the potential degree of genetic introgression between remnant wild populations and less diverse, hatchery-reared stocks. Those tasked with preserving our living natural resources should carefully consider how the juxtaposition of aquaculture, restored, and wild populations at small spatial scales will impact the genetic composition and evolutionary trajectories of species in decline for generations to come. [ABSTRACT FROM AUTHOR]

Abstract The Crassostrea virginica oyster has biological and economic importance in the Gulf of Mexico, an area with a high extraction and production of hydrocarbons. Exposure to hydrocarbons affects the reproductive processes in bivalves. In C. virginica , the effect of hydrocarbons on the gonad of the undifferentiated organism has not been evaluated to determine the possible damage during the maturation process. To evaluate this effect, RNA-seq data was generated from C. virginica gonads exposed to a 200 μg/L of hydrocarbons at different exposure times (7, 14 and 21 days) and a control treatment (without hydrocarbons). The analysis of the gonad transcriptome showed the negative effect of hydrocarbons on maturation, with a sub-expression of 22 genes involved in different stages of this process. Additionally, genes in the immune system were down-regulated, which may indicate that exposure to hydrocarbons causes immunosuppression in bivalves. A group of oxidative stress genes was also reduced. These data contribute to a better understanding of the effect of hydrocarbons on the reproductive process in bivalves and, at the same time, allow us to identify possible biomarkers associated with hydrocarbon contamination in the gonad of C. virginica. [ABSTRACT FROM AUTHOR]

Intertidal habitats like oyster reefs and salt marshes provide vital ecosystem services including shoreline erosion control, habitat provision, and water filtration. However, these systems face significant global change as a result of a combination of anthropogenic stressors like coastal development and environmental stressors such as sea-level rise and disease. Traditional intertidal habitat monitoring techniques are cost and time-intensive, thus limiting how frequently resources are mapped in a way that is often insufficient to make informed management decisions. Unoccupied aircraft systems (UASs) have demonstrated the potential to mitigate these costs as they provide a platform to rapidly, safely, and inexpensively collect data in coastal areas. In this study, a UAS was used to survey intertidal habitats along the Gulf of Mexico coastline in Florida, USA. The structure from motion photogrammetry techniques were used to generate an orthomosaic and a digital surface model from the UAS imagery. These products were used in a geographic object-based image analysis (GEOBIA) workflow to classify mudflat, salt marsh, and oyster reef habitats. GEOBIA allows for a more informed classification than traditional techniques by providing textural and geometric context to habitat covers. We developed a ruleset to allow for a repeatable workflow, further decreasing the temporal cost of monitoring. The classification produced an overall accuracy of 79% in classifying habitats in a coastal environment with little spectral and textural separability, indicating that GEOBIA can differentiate intertidal habitats. This method allows for effective monitoring that can inform management and restoration efforts.