A survey of the toxicity of sediments throughout Boston Harbor and vicinity was conducted by NOAA’s National Status and Trends (NS&T) Program. The objectives of the survey were to determine the magnitude and spatial extent of toxicity and the relationship between measures of toxicity and the concentrations of chemical toxicants in the sediments. This survey was conducted as a part of a nationwide program supported by the Coastal Ocean Program and the NS&T Program of NOAA in which the biological effects of toxicants are determined in selected estuaries and bays. Major funding for this survey was provided by the Coastal Ocean Program of NOAA.

The survey was conducted in 1993. Surficial sediments were collected from 55 locations (stations) throughout the Harbor. The survey area covered approximately 57 kilometers. Station locations were chosen randomly within specified strata.

Multiple toxicity tests were performed including: an amphipod survival test performed with whole sediments, a microbial bioluminescence test performed with organic solvent extracts of the sediments, and sea urchin fertilization and embryological development tests performed with the pore waters extracted from the sediments. These tests were chosen because: they were consistent with the tests used in similar surveys performed elsewhere in the U.S.: they usually provide complementary, but not duplicative, information on toxicity; the results of these tests often are highly correlated with gradients in toxicant concentrations; and they are known to be dose-responsive to the kinds of toxicants commonly found in urban bays, such as Boston Harbor. Chemical analyses were performed on selected samples for trace metals, polynuclear aromatic hydrocarbons, chlorinated pesticides, PCBs and butyltins.

In the amphipod and microbial bioluminescence tests, 21.8% and 56.4% of the samples, respectively, were significantly different from controls. In the sea urchin tests performed with 100% pore water, 3.6% and 100% of the samples were significantly toxic in fertilization success and normal embryological development tests, respectively. The results of the different toxicity tests generally showed poor concordance with each other, probably as a result of differences in sensitivity and differential responses to the kinds of chemicals in the sediments.

The results of the toxicity tests were weighted to the spatial dimensions of each stratum to estimate the spatial extent of toxicity. Based upon these estimates, 100% of the area was toxic in the sea urchin tests of embryo development in 100% pore water. In contrast, only 6.6% of the area was toxic in the sea urchin fertilization tests performed in 100% pore water. In the microbial bioluminescence and amphipod survival tests, approximately 45% and 10% of the area was estimated to be toxic, respectively.

Toxicity was apparent throughout all regions of the study area. Overall, the incidence of toxicity was highest in portions of the inner harbor where chemical concentrations were the highest.

Toxicity diminished beyond the entrance to the inner harbor. However, some of the inner harbor samples were not toxic and one sample each from central harbor and northwest harbor were the most toxic of the 55 samples tested. Toxicity was lowest in portions of northwest harbor, central harbor, southeast harbor, and in an area beyond the entrance to Boston Harbor.

A determination of the causes of toxicity were not an objective of this survey. Rather, the data

were analyzed to determine which substances, if any, may have contributed to toxicity. Correlations

between toxicity and chemical concentrations were relatively poor. No single substance

or chemical group was highly correlated with toxicity. None of the chemical concentrations

were extremely high relative to estimated toxicity thresholds. Furthermore, the

bioavailability of many of these substances may have been inhibited by high organic carbon

content in the sediments. However, the concentrations of 18 individual substances, including

ammonia, were sufficiently high to have contributed to toxicity. The data suggest that complex

mixtures of potentially toxic substances, including PAHs, PCBs, pesticides, trace metals, and

ammonia probably contributed to the observed toxicity.