The University of Massachusetts Dartmouth School for Marine Science and Technology (SMAST) conducted drop camera surveys to examine the benthic community and substrate in the northern portion of Vineyard Wind’s Outer Continental Shelf (OCS) Lease Area OCS-A 0501 (501N Study Area) and a Control Area located east and adjacent to the lease area. The primary goal of this project was to collect baseline data for future environmental assessment of wind development impacts. Our objectives were to provide:
- distribution and density estimates of dominant benthic megafauna,
- classify substrate types at drop camera stations across the survey domain,
- compare benthic communities and substrate types between the 501N Study Area, Control Area, and broader regions of the U.S. OCS, and
- classify substrate within aliquots sampled by the American Lobster (Homarus americanus), Black Sea Bass (Centropristis striata), and Larval Lobster Abundance Survey, and Lobster Tagging Study (an associated SMAST trap survey also conducted for Vineyard Wind). These aliquots coincided with a subset of the drop camera stations.
We used a centric systematic design to sample survey stations in the 501N Study Area and the Control Area. Stations in the two areas were placed 1.5 kilometers (km) apart following a grid design. At each station, a pyramid mounted with a high-resolution camera was deployed to take four quadrat (2.3 square meter [m2] image) samples. Both areas were surveyed in July/August and October 2020 using a commercial scallop vessel to deploy the sampling pyramid.
The dominant benthic community of the 501N Study Area and the Control Area were mostly benthic invertebrates such as sand dollars, hermit crabs, waved whelks (Buccinum undatum, --not the commercially harvested channeled whelk, Busycotypus canaliculatus), anemones, crabs (cancer spp.), and burrowing species. The vertebrates included in the dominant benthic community were skates, silver hake, and red hake. The density of the dominant benthic animals found in the 501N Study Area and Control Area were similar except for waved whelks which had a higher density in the Control Area during August. By contrast, most of the taxa tracked as present or absent in a quadrat were observed in significantly more quadrats per station in the 501N Study Area. This may be related to the differing water depths of the areas. There was significantly less of most animal groups in October compared to July/August, but future investigations will be needed to confirm this seasonal pattern. The confidence intervals associated with the estimates of dominant benthic megafauna prevalence and the ability to detect significant differences show this sampling intensity is adequate for statistical comparison of variance between impact and control sites over time.
The drop camera survey results indicated the substrates in the 501N Study Area and Control Area were dominated by sand with no gravel, cobble, or boulders observed. The benthic community of the 501N Study Area and Control Area were most similar to each other, compared to the selected broader regions of the U.S. OCS. As the broader regions increased in distance from 10’s to 100’s of kilometers from the 501N Study Area, the similarity decreased. The substrate within trap survey aliquots was entirely comprised of sand.