No abstract

In the present study, we investigated the applicability of the Pearson-Rosenberg (P-R) conceptual model describing a generalized pattern of response of benthic communities in relation to organic 25 enrichment to a specific typology of marine systems, i.e. coastal lagoons. The study was performed with independent matching data on the structure of macrobenthic communities and total organic carbon (TOC) content of sediments obtained from 349 stations representing three of the most ecologically and economically relevant coastal lagoons in the Mediterranean Sea, i.e. the lagoons of Cabras, Orbetello, and Venice (Italy). Consistent with P-R model predictions, we 30 found two different peaks in benthic diversity and abundance at low (> 2.5-5 mg g -1 ) and high (> 25-30 mg g -1 ) TOC ranges, respectively. We identified TOC thresholds indicating that risks of reduced benthic diversity from organic loading and other associated stressors in sediments should be relatively low at TOC values < about 10 mg g -1 , high at TOC values > about 28 mg g -1 , andintermediate at values in-between. Predictive ability within these ranges was high based on 35 results of re-sampling simulation. Our results validate and support a prior independent study that identified similar TOC thresholds for assessing risks of benthic impacts in samples from seven coastal regions of the world. While not a measure of causality, it is anticipated that these TOC thresholds should serve as a general screening-level indicator for evaluating the likelihood of reduced sediment quality and associated bioeffects in such eutrophic systems of the 40 Mediterranean Sea, which also are exposed to a variety of stressors from multiple human uses.

Aroclor 1268 is a highly chlorinated PCB mixture that was released into the aquatic environment near Brunswick, GA (BR), as a result of decades of local industrial activity. This extensive contamination has led to US EPA Superfund designation in estuarine areas in and around Purvis Creek, GA. Roughly 50 km to the northeast is the Sapelo Island National Estuarine Research Reserve (SI) where previous studies have documented unexpectedly high Aroclor 1268-like PCB levels in blubber and plasma samples of resident bottlenose dolphins. This result led to a collaborative effort to assess the PCB patterns and concentrations in SI sediment and fish (as potential vectors for PCB transfer to SI resident dolphins). Thirty SI randomly assigned stations were sampled for sediment PCB levels. Additionally, fish were collected and analyzed from SI (n = 31) and BR (n = 33). Results were pooled with regional assessments of PCB concentrations from South Carolina and North Carolina in an effort to determine the association of Aroclor 1268 levels in SI samples. Results indicated that PCB levels in sediment and fish are much lower in the SI estuary compared to BR sediment and fish concentrations. However, PCB congener profiles for both sediments and fish were similar between the two locations and consistent with the Aroclor 1268 signature, indicating possible transport from the Brunswick area. A likely source of Aroclor 1268 in dolphins from SI is contaminated fish prey.