While some metals, such as Cu and Zn are biologically essential at trace levels, others such as Cd, Hg, Ni, and Pb do not play any normal biological role, and are toxic at low concentrations. Since the estuary is highly contaminated with many organic contaminants as well as metals, it is difficult to point to a particular pollutant or pollutants as being primarily responsible for a given problem. Long et al. (1996) examined the spatial extent of sediment toxicity in major U.S. estuaries using three standard toxicity tests: the 10-day amphipod survival test with bulk sediments, the 5-minute microbial bioluminescence test, and either the 1-hour sea urchin fertilization or 48-hour mollusk embryo tests with pore water. Amphipod tests indicated that toxicity was most widespread in Newark Bay (85 percent of the area), as well as in other parts of the Hudson-Raritan estuary (38 percent). When spatialpatterns of toxicity were compared with the distribution of toxic chemicals, the results suggested that metals were generally not the cause of the observed toxicity, with the possible exception of mercury (Wolfe, Long, andThursby, 1996).
Was this article helpful?