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Boston Harbor and Massachusetts Bay
MWRA Environmental Quality Department

Massachusetts Bay Benthic Monitoring: Hard-bottom communities

The rocky habitats in the vicinity of the outfall and at reference locations continue to support robust communities of algae, invertebrates, and fish. Baseline and outfall monitoring shows that the hard-bottom communities in the region are spatially diverse but temporally stable. While there have been some shifts in species composition and abundance, those changes have been modest. There is ush growth of life on the sea floor, particularly of sea anemones, which have thrived on the diffuser heads since the Massachusetts Bay outfall began to discharge.

One measure of interest has been the amount of sediment drape, a visual assessment of the detritus or loose material deposited on hard surfaces. During the post-outfall years, there have been modest increases in the amount of sediment drape at some stations, particularly north of the outfall. There is some evidence that the northern reference stations are being adversely affected by tankers, whose anchors scarred and overturned boulders during some surveys.

Locations of Soft-bottom Farfield Stations

Upper left: light drape south of the outfall; upper right: moderately light drape at a northern reference site; lower left: moderate drape north of the outfall; lower right: heavy drape southwest of the outfall.