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Globally, the occurrence of contaminants of emerging concern (CECs) in the environment has raised critical questions on ecological and human health, but few efforts have focused on the Chesapeake Bay, the largest estuary in the United States. Here, 43 antibiotics, 3 estrogenic hormones, and 5 ultraviolet-filters (UV-filters), which are active ingredients in a variety of personal care products, were measured in water, sediment, and oyster tissue from 14 sites along the Eastern Shore of the Chesapeake Bay in Maryland. Fluoroquinolone, macrolide, and sulfonamide antibiotics were detected in water samples. As both human- and animal-labeled antibiotics were found, wastewater effluent and agricultural runoff were identified as potential sources. The highest aqueous-phase concentrations were recorded for norfloxacin (94.1 ng/L), enrofloxacin (17.8 ng/L), sulfamethoxazole (14.8 ng/L), and clarithromycin (9.7 ng/L). Estrone and four UV-filters, namely 2-ethylhexyl-4-methoxycinnamate, benzophenone-3, homosalate, and octocrylene, were frequently detected in Chesapeake Bay water (93–100%), sediment (100%), and oyster tissue (79–100%). High sediment-phase concentrations of estrone (58.4 ng/g) and 17β-estradiol (11.5 ng/g) were detected at the mouth of the Manokin River. Homosalate and benzophenone-3 were present at concentrations as high as 187.9 and 113.7 ng/L in water, 74.2 and 10.8 ng/g in sediment, and 158.3 and 118.0 ng/g in oyster tissue, respectively. These results demonstrate the ubiquitous presence of CECs in the Chesapeake Bay, confirm UV-filter bioaccumulation in oysters, and suggest the need for improved CEC removal during municipal wastewater treatment and agricultural waste management within the Chesapeake Bay watershed.

Incorporating spatial information can improve estimates from stock assessment models when there are differences in population processes (e.g., natural mortality) among areas. Population dynamics of the eastern oyster Crassostrea virginica vary spatially within the Chesapeake Bay, Maryland, and our objective was to better characterize oyster population dynamics by estimating changes in natural mortality, fishing mortality, abundance, and recruitment over time and space. We developed statistical stage-structured models for 36 regions and fit the models to fishery dependent and independent data sources. Regional patterns in population dynamics emerged that would have been lost in a spatially aggregated approach. Regions that were closer together tended to have similar patterns in natural mortality, exploitation rates, abundance, and recruitment over time. We were able to estimate time-varying natural mortality because ancillary data on the number of dead individuals were incorporated into the population dynamics model. This approach to estimating time-varying natural mortality may be more widely applicable to species where dead individuals are observed in routine surveys.

Bivalves leave behind articulated valves when they die that can be used to estimate natural mortality. However, a common method used to estimate natural mortality in bivalves, known as the box count method, includes several assumptions that may be violated for eastern oysters Crassostrea virginica in Chesapeake Bay, Maryland. We developed a Bayesian model alternative to the box count method that included modifications to account for potential violations of assumptions. The model was applied to oysters in 32 areas in Maryland during 1991–2017 using dredge survey data, and the natural mortality estimates from the model were compared to ones derived from the box count method. The spatial and temporal trends in natural mortality from the model were summarized using dynamic factor analysis. Natural mortality showed considerable spatial and temporal variation, with median mortality rates ranging between 0.00 and 0.96 yr−1. Natural mortality spiked in most regions in 2002 and was lower in more recent years. The Bayesian model estimated slightly higher (0.02 yr−1 on average) natural mortality than the box count method, except for years following high natural mortality, after which the Bayesian model estimated lower natural mortality than the box count method. The dynamic factor analysis revealed two common trends in natural mortality and a north-south gradient in the loadings on the trends. This work improves our understanding of the variability of oyster natural mortality in Maryland and the Bayesian model could be modified for use with oysters in other regions or with other species.

The eastern oyster, Crassostrea virginica, is an important ecological and commercial species along the Eastern Seaboard of North America, although its abundance in Chesapeake Bay (Maryland and Virginia) has declined precipitously since the mid-1800s. Management activities, including efforts to enhance larval settlement, to rebuild the Chesapeake Bay eastern oyster population have met with limited success. Since 1939, juvenile oyster abundance has been measured at oyster bars in the northern portion of Chesapeake Bay. Prior analyses of those data indicate that juvenile oyster abundance is influenced by environmental conditions, which are related to regional climate. We quantified a regional scale (1,000 km2) climate signal using a synoptic climatology approach by identifying predominant weather patterns. We related these weather patterns to Susquehanna River freshwater discharge, a major influencing factor on Chesapeake Bay salinity, and the Palmer Hydrological Drought Index (PHDI), an indicator of...

Stocks of eastern oysters (Crassostrea virginica, Gmelin 1791) have undergone dramatic declines in the Chesapeake Bay since the mid 1800s. As a result, substantial efforts have been made to try and reverse this decline to provide support for a commercially and socially important fishery and, more recently, to restore the oyster's important ecological role. Since 1939, juvenile oyster abundance has been measured at sentinel oyster bars in the northern portion of Chesapeake Bay, Maryland. We conducted a cluster analysis on these data and detected 4 distinct spatial patterns. These patterns were related to juvenile oyster abundance (i.e., bars that experienced high overall juvenile abundance grouped together) and salinity. Of the sentinel bars sampled since the mid 1980s, our analysis identified 13 bars that were characterized by high juvenile oyster abundance and low variation among years, which makes them prime candidate bars for protection to aid in restoration. A comparison with bars already pro...

In an effort to restore the ecological role of oysters in Chesapeake Bay and the economic benefits of a commercial fishery, the states of Maryland and Virginia are considering introducing the nonnative Asian oyster (Crassostrea ariakensis) into the Bay. As part of an ecological risk assessment (ERA) to evaluate the proposed action and alternatives, demographic modeling is being used to project the change in populations of both the Asian and the native eastern oyster (C. virginica) in the Bay across space and time. Annual mortality rates are vital input to the demographic model. We present two approaches for parameterizing mortality rates for C. virginica by salinity ranges and disease-intensity categories and discuss how these rates could be applied to project population growth for the Asian oyster. We estimated mortality rates from empirical data collected during annual dredge surveys of oyster beds in Maryland. We compared counts of recent boxes (dead oysters without fouling or sedimentation on...