Among the report's significant conclusions are the following:
- Monitoring has shown that contaminants emanating from diffuse sources (such as car exhaust and other air deposition, stormwater runoff, household and boating solvents and other chemicals) are becoming relatively more important than industrial sources, which have been dramatically reduced since the passage of Clean Water and Clean Air legislation.
In addition to identified "hot spots" (Regions of Concern) evidence exists that low-levels of contaminants in the Chesapeake Bay have an impact on organisms at several major levels of the food web.
Specifically, research shows that oysters exposed to chemical contaminants in the Bay are more vulnerable to diseases such as Dermo. This may be especially significant, given current efforts to restore oyster reefs and oyster populations in the Chesapeake.
Exposure to trace metals and other contaminants can affect phytoplankton populations under research conditions, causing shifts in species composition, for example. Since phytoplankton form an important base of the Bay's food web, changes here could have significant impacts throughout the Bay.
Although the consensus among researchers is that herbicides such as Atrazine and pesticides such as Dimilin do not appear to cause widespread damage to the Bay's ecosystem, experimental work has shown that both Atrazine and Dimilin can have deleterious effects in localized areas, if concentrations are high enough. Studies have also indicated that chemical preservatives, such as those used in wooden bulkheads, cause a loss of species diversity in adjacent areas.
Because of the evidence of biological impacts - even at relatively low levels of contamination, and because diffuse sources may be more difficult to control than point sources - it is imperative that we further investigate the effects of contaminants at environmentally realistic levels, on key facets of the Bay's food web.
[Contents][Report Highlights][Executive Summary][Workshop Discussion]
[Summary][References] [Glossary][List of Participants][Credits and Acknowledgements]
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