Toxicity of saline and organic solvent extracts of sediments from Boston Harbor, Massachusetts and the Hudson River-Raritan Bay estuary, New York using the Microtox® bioassay

Abstract

The toxic effects of organic and saline extracts of sediment samples collected from 16 sites in Boston Harbor, Massachusetts and from 17 sites in the Hudson River-Raritan Bay estuary, New York were tested with the Microtox® bioassay. This bioassay measures changes in light production by bioluminescent marine bacteria exposed to sediment extracts. Organic solvent extracts of all 33 sediments showed some degree of toxicity, with sediment samples from sites in the urban areas of the bays being significantly more toxic than those from less urbanized areas of the bays. Saline extracts, however, were less toxic, only seven of 33 saline extracts produced a significant response using the recommended method of data analyses. The proportional decrease in bacterial light production at the highest concentration of saline sediment extract in the reaction mixture compared to the bacterial light production in the controls (saline light change—SLC) appeared to be a better indicator of sediment toxicity than generating a saline EC50 (the amount of sediment required to reduce bioluminescence 50%) value; 16 of 33 saline extracts produced a significant response (⩾10% reduction in bioluminescence). Organic extracts of sediments previously extracted with saline were also always toxic in the Microtox® bioassay but were less toxic than sediments not previously extracted. Organic EC50 and SLC were inversely related to concentrations of sediment contaminants, principally low- and high-molecular-weight polycyclic aromatic hydrocarbons (PAHs). This relationship was strongest for the organic solvent extracts of sediments tested in the bioassay. Organic solvent extracts of sediments from Boston Harbor were also significantly more toxic in the Microtox® bioassay than those from the Hudson-Raritan estuary, even though sediment concentrations of PAHs, a measure of anthropogenic contamination, were similar. The cause for the differential toxicity is unknown at this time, but chemical contaminants other than chlorinated hydrocarbons (CHs) and PAHs may be contributing to the observed toxicity in the Microtox® bioassay using organic extracts of sediment. Testing sediment toxicity using organic extracts of sediment with the Microtox® bioassay provides better estimates of toxicity due to sediment contaminants than using saline extracts of sediments.