Volume 14, Number 6 • November-December 1996

Toxics Report Highlights

The following points are among the significant conclusions of a new Maryland Sea Grant report, Contaminants in the Chesapeake Bay, resulting from a December 1995 meeting of researchers:

Monitoring has shown that contaminants emanating from diffuse sources (e.g., 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, for example, causing shifts in species composition. Since phytoplankton form an important base of the Bay's food web, changes here could have significant impacts throughout the Bay.
Studies have indicated that certain chemicals appear to affect both individual species (such as copepods, which can be damaged by Dimilin, a treatment for gypsy moth infestations) and species diversity (as through contact with compounds used as preservatives in wooden bulkheads).
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.

Top of Page

		Contents of this issue	Other Issues