Spatial and temporal heterogeneity in metallic elements in industrialized aquatic bird habitat

This study examined the potential for exposure of migratory aquatic birds to contaminants in highly industrialized habitats at Baltimore Harbor, Maryland. Seven nearshore, benthic sites were sampled every 3 or 6 months from June 1987 to December 1988. Twenty metallic elements were measured in composites (i.e. annelids, amphipods, and isopods were pooled), clams, and sediments. Elevated concentrations were widespread throughout the sites, depending on the element. Most concentrations in composites were lowest at sites innermost and outside the harbor. Higher concentrations in composites were not related to season. Most concentrations were higher in composites than in sediments or clams, but they varied by element for clams and sediments. The largest flock of wintering waterfowl frequented the site exhibiting the highest concentrations of most elements (p < 0.0001). Average concentrations of known toxic elements were probably not harmful to aquatic birds or their prey, but the highest detected concentrations of eight elements warrant caution. At least eight other elements exceeded background concentrations, but toxicity to birds or their prey are unknown.