Contaminant Flux from Sediments:
Impacts on Chesapeake Bay Food Webs
Sediments in certain regions of the Chesapeake Bay contain elevated amounts of toxic substances: these represent a potential reservoir for continuous flux of toxics into the ecosystem, long after control measures have seemingly reduced their direct inputs. Processes which control the release of sediment-bound contaminants to overlying waters or which make them available to organisms are thus of primary concern for the Chesapeake Bay restoration program.
This research is using a mesocosm system (tanks that mimic the natural environment) to study the effects on estuarine food webs of toxic contaminants in sediments. Among the factors to be tested: how the absence of oxygen (anoxia)-a seasonal phenomenon in much of the Bay-affects the chemical behavior of compounds such as arsenic, cadmium and copper. The researchers have found, for example, that under anoxic conditions, copper and arsenic behave differently with potentially significant effects on the composition of phytoplankton species. Over the long term, changes in the phytoplankton community within the mesocosms will be related to the extent of release and exposure of these sediment-bound toxicants.
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Gerhardt F. Riedel
James G. Sanders
Cynthia C. Gilmour
Benedict Estuarine Research Center
The Academy of Natural Sciences
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