Incidence of stress in benthic communities along the U.S. Atlantic and Gulf of Mexico coasts within different ranges of sediment contamination from chemical mixtures.
ABSTRACT Synoptic data on concentrations of sediment-associated chemical contaminants and benthic macroinfaunal community structure were collected from 1,389 stations in estuaries along the U.S. Atlantic and Gulf of Mexico coasts as part of the nationwide Environmental Monitoring and Assessment Program (EMAP). These data were used to develop an empirical framework for evaluating risks of benthic community-level effects within different ranges of sediment contamination from mixtures of multiple chemicals present at varying concentrations. Sediment contamination was expressed as the mean ratio of individual chemical concentrations relative to corresponding sediment quality guidelines (SQGs), including Effects Range-Median (ERM) and Probable Effects Level (PEL) values. Benthic condition was assessed using diagnostic, multi-metric indices developed for each of three EMAP provinces (Virginian, Carolinian, and Louisianian). Cumulative percentages of stations with a degraded benthic community were plotted against ascending values of the mean ERM and PEL quotients. Based on the observed relationships, mean SQG quotients were divided into four ranges corresponding to either a low, moderate, high, or very high incidence of degraded benthic condition. Results showed that condition of the ambient benthic community provides a reliable and sensitive indicator for evaluating the biological significance of sediment-associated stressors. Mean SQG quotients marking the beginning of the contaminant range associated with the highest incidence of benthic impacts (73-100% of samples, depending on the province and type of SQG) were well below those linked to high risks of sediment toxicity as determined by short-term toxicity tests with single species. Measures of the ambient benthic community reflect the sensitivities of multiple species and life stages to persistent exposures under actual field conditions. Similar results were obtained with preliminary data from the west coast (Puget Sound).
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ABSTRACT: Blue crabs, Callinectes sapidus, from the Atlantic coast of Florida were analyzed for total mercury, methylmercury, lead, and cadmium. Paired samples of two tissue types were analyzed for each crab, (1) muscle tissue (cheliped and body muscles) and (2) whole-body tissue (all organs, muscle tissue and connective tissue), for evaluation of the concentration of metals available to human consumers as well as estuarine predators. There were clear patterns of tissue-specific partitioning for each metal. Total mercury was significantly greater in muscle tissue (mean=0.078 µg/g) than in whole-body tissue (mean=0.055 µg/g). Conversely, whole-body concentrations of lead and cadmium (means=0.131 and 0.079 µg/g, respectively) were significantly greater than concentrations in muscle (means=0.02 and 0.029 µg/g, respectively). There were no significant correlations between any metal contaminant and crab size. Cadmium levels were significantly greater in the muscle tissue of females, but, no other sex-related differences were seen for other metals or tissue types. Methylmercury composed 93–100% of the total mercury in tissues. Compared to previous blue crab studies from different regions of the United States, mean concentrations of mercury, lead, and cadmium were relatively low, although isolated groups or individual blue crabs accumulated high metal concentrations.Ecotoxicology and Environmental Safety 04/2014; DOI:10.1016/j.ecoenv.2013.11.029 · 2.48 Impact Factor
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ABSTRACT: Ecosystems modified by human activities are generally predicted to be biologically impoverished. However, much pollution impact theory stems from laboratory or small-scale field studies, and few studies replicate at the level of estuary. Furthermore, assessments are often based on sediment contamination and infauna, and impacts to epibiota (sessile invertebrates and algae) are seldom considered. We surveyed epibiota in six estuaries in south-east Australia. Half the estuaries were relatively pristine, and half were subject to internationally high levels of contamination, urbanisation, and industrialisation. Contrary to predictions, epibiota in modified estuaries had greater coverage and were similarly diverse as those in unmodified estuaries. Change in epibiota community structure was linearly correlated with sediment-bound copper, and the tubeworm Hydroides elegans showed a strong positive correlation with sediment metals. Stressors such as metal contamination can reduce biodiversity and productivity, but others such as nutrient enrichment and resource provision may obscure signals of impact.Environmental Pollution 01/2015; 196:12–20. DOI:10.1016/j.envpol.2014.09.017 · 3.90 Impact Factor