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Abstract The effect of individual and population-level egg mortality is important to quantify to maintain sustainable crustacean fisheries. The nemertean worm Carcinonemertes carcinophila (Kölliker, 1845) is an egg predator of the Atlantic blue crab, Callinectes sapidusRathbun, 1896; however, little is known about the impact this nemertean has on the reproduction of the blue crab. We assessed the prevalence and intensity of the infestation of nemerteans in ovigerous blue crabs using a fishery-independent trawl survey. During the primary spawning period of the crab, May–September 2022, 126 ovigerous females were collected and analyzed for worms. Prevalence over this time was 66.6% and mean brood infestation was 53.9 worms per infested crab host. Nemertean egg consumption was quantified with a six-day microcosm experiment. Of the 48 worms in the experiment, 71% actively fed on crab eggs and their consumption ranged 0.16–4.5 eggs day–1. Consumption rates were used to estimate population-level impact of nemertean feeding on crab brood mortality. Modeled proportions of brood loss per crab ranged 0–0.0044%. At the current prevalence and intensity of infestation, egg consumption by nemerteans has a negligible effect on blue crab reproductive output and batch fecundity in Chesapeake Bay. We also investigated the use of mature nemertean worms as a biomarker for establishing the spawning history of ovigerous female blue crabs and determined that the presence of worms in the clutch and in the gills can be used to indicate parity in ovigerous female crabs. 

Seasonal fluctuations are key features of high-latitude marine ecosystems, where zooplankton exhibit a wide array of adaptations within their life cycles. Repeated, sub-seasonal sampling of Antarctic zooplankton is rare, even along the West Antarctic Peninsula (WAP), where multidecadal changes in sea ice and phytoplankton are well documented. We quantified zooplankton biomass, size structure, and composition at 2 coastal time-series stations in the northern WAP over 3 field seasons (November-March) with different sea-ice, temperature, and phytoplankton conditions. Seasonal peaks in zooplankton biomass followed weeks after phytoplankton blooms. Biomass of mesozooplankton (0.2-2 mm) was consistent and low, while high biomass of macrozooplankton (>2 mm) occasionally resulted in a size distribution dominated by krill and salps, which appears to be a characteristic phenomenon of the Southern Ocean. Zooplankton composition and size changed between years and from spring to summer as the water column warmed after sea-ice breakup. Seasonal succession was apparent typically in decreasing zooplankton size and a shift to species that are less dependent upon phytoplankton. Mean central abundance dates varied by 54 d across 14 taxa, and specific feeding preferences and life-history traits explained the different seasonal abundance patterns. In all 3 yr, the dominant euphausiid species switched from Euphausia superba in spring to Thysanoessa macrura in late summer. Various taxa shifted their phenology between years in response to the timing of sea-ice breakup and the onset of phytoplankton productivity, a level of natural environmental variability to which they appear resilient. Nevertheless, the limits to this resilience in response to climate change remain uncertain. 

How ocean acidification (OA) interacts with other stressors is understudied, particularly for predators and prey. We assessed long-term exposure to decreased pH and low salinity on (1) juvenile blue crab Callinectes sapidus claw pinch force, (2) juvenile hard clam Mercenaria mercenaria survival, growth, and shell structure, and (3) blue crab and hard clam interactions in filmed mesocosm trials. In 2018 and 2019, we held crabs and clams from the Chesapeake Bay, USA, in crossed pH (low: 7.0, high: 8.0) and salinity (low: 15, high: 30) treatments for 11 and 10 wk, respectively. Afterwards, we assessed crab claw pinch force and clam survival, growth, shell structure, and ridge rugosity. Claw pinch force increased with size in both years but weakened in low pH. Clam growth was negative, indicative of shell dissolution, in low pH in both years compared to the control. Growth was also negative in the 2019 high-pH/low-salinity treatment. Clam survival in both years was lowest in the low-pH/low-salinity treatment and highest in the high-pH/high-salinity treatment. Shell damage and ridge rugosity (indicative of deterioration) were intensified under low pH and negatively correlated with clam survival. Overall, clams were more severely affected by both stressors than crabs. In the filmed predator-prey interactions, pH did not substantially alter crab behavior, but crabs spent more time eating and burying in high-salinity treatments and more time moving in low-salinity treatments. Given the complex effects of pH and salinity on blue crabs and hard clams, projections about climate change on predator-prey interactions will be difficult and must consider multiple stressors. 

Environmental history (regimes of water quality to which an organism has been exposed in the past) may influence how the physiology of eastern oysters Crassostrea virginica responds to future environmental conditions caused by climate change. Previous research has examined environmental history in a 1-dimensional framework, failing to capture environmental history complexity through space and time. In this study, we examined environmental history as a multi-faceted parameter, incorporating abiotic water quality components, such as temperature, pH, and salinity, that differ among locations. We also assessed how different lengths of environmental histories, defined as proximal and distal, affected oyster physiology and stress response. Finally, we compared the relative influence of abiotic components of environmental history on oyster physiology. We found that physiology and stress response are differentially affected by proximal and distal environmental history, demonstrating the importance of examining environmental history as a multi-faceted and dynamic parameter. Specifically, distal environmental history primarily influenced condition index and total antioxidant potential, while proximal environmental history primarily influenced glycogen content. Salinity of distal environmental history significantly shaped condition index, establishing salinity as a principal factor when considering acclimatization to variable environments. No water quality components were significant influences on glycogen and total antioxidant potential, providing opportunities for research on other components of environmental history. Identifying the temporal portion of oysters’ environmental history that influences physiology supports future efforts to predict population tolerance to climate change. Additionally, examining multiple abiotic and biotic components of environmental history can elucidate means of acclimatization to future environmental change. 

As the oyster aquaculture industry grows and becomes incorporated into management practices, it is important to understand its effects on local environments. This study investigated how water quality and hydrodynamics varied among farms as well as inside versus outside the extent of caged grow-out areas located in southern Chesapeake Bay. Current speed and water quality variables (chlorophyll-a fluorescence, turbidity, and dissolved oxygen) were measured along multiple transects within and adjacent to four oyster farms during two seasons. At the scale of individual aquaculture sites, we were able to detect statistically significant differences in current speed and water quality variables between the areas inside and outside the farms. However, the magnitudes of the water quality differences were minor. Differences between sites and between seasons for water quality variables were typically an order of magnitude greater than those observed within each site (i.e. inside and outside the farm footprint). The relatively small effect of the presence of oysters on water quality is likely attributable to a combination of high background variability, relatively high flushing rates, relatively low oyster density, and small farm footprints. Minimal impacts overall suggest that low-density oyster farms located in adequately-flushed areas are unlikely to negatively impact local water quality.