Document Type


Publication Date


Publication Title

Proceedings of the Back Bay Ecological Symposium



Conference Name

Back Bay Ecological Symposium


Studies were conducted at Mackay Island National Wildlife Refuge in 1988 and 1989 to provide baseline data for an assessment of organic chemicals and metal contaminants in the aquatic ecosystem. Longnose gar, gizzard shad, snapping turtles, common rangia clams and sediments were collected from sites in lower Back Bay and upper Currituck Sound for contaminant analyses.

Composite sediment samples were analyzed for the presence of metals, organochlorine pesticides and polycyclic aromatic hydrocarbons (PAHs). Organochlorine pesticides were not detected in the sediments. Various PAH compounds were detected in the sediments, although at trace concentrations which just exceeded the analytical detection limit (detection limit 0.01 parts per million wet weight). Metal residues were not elevated with respect to background levels typical of sediments in eastern North Carolina coastal ecosystems.

Mean metal residues in the fish (wholebody), turtles (livers) and clams (soft tissues) did not indicate contamination above background levels. Organochlorine pesticides were detected at low or trace levels. The most commonly observed organochlorine pesticides were p,p -DOE and p, p - DOD. Polychlorinated biphenyls (PCBs) were detected at overall low levels in those species analyzed (fish, turtles). Aliphatic hydrocarbons were present in rangia clams at levels indicative of chronic low-level exposure.

In summary, the contaminants detected at Mackay Island National Wildlife Refuge in the sediments and biological samples were present at low concentrations typical of background levels. The data do not indicate the presence of toxic "hotspots" on or immediately adjacent to the Refuge. This suggests that the present degradation in water quality in lower Back Bay and upper Currituck Sound may be linked to: 1) more conventional pollutants, such as excess nutrients and turbidity, associated with non-point source run-off; 2) changes in freshwater inflow due to annual fluctuations in rainfall; and/or, 3) other classes of agricultural chemicals, such as carbonates, organophosphates and chlorophenoxy acid herbicides.