Abstract
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 and a Control Area 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 development area, Control Area, and broader regions of the U.S.OCS and
- classify substrate within aliquots sampled by the American Lobster, Black Sea Bass, 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 utilized a centric systematic sampling design to sample survey stations in the northern portion of Lease Area OCS-A 0501 (termed the 501N Impact Area) and the Control Area. Stations in the two areas were placed 1.5 km apart following a grid design. At each station a sampling pyramid was deployed, and a high-resolution camera was used take four quadrat (2.3 m2 images) samples. Both areas were surveyed in July and October 2019 using a commercial scallop vessel to deploy the sampling pyramid.
The dominant benthic community of Impact and the Control Areas 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 Impact and Control Areas were similar with the exception of waved whelks which had a higher density in the Control Area during July. 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 Impact Area. This may be related to the differing water depths of the areas. A significant decline in the abundance and presence of most animal groups occurred between July and October, but future investigations will be needed to confirm seasonal patterns. The confidence intervals associated with the estimates of dominant benthic megafauna prevalence and the ability to detect significant differences shows 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 Impact Area and Control Areas were dominated by sand with gravel observed at few stations; no cobble or boulders were observed. The benthic community of the 501N Impact 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 Impact Area, the similarity decreased. The substrate within trap survey aliquots was predominately sand, but the aliquots in the northwest part of the 501N Impact Area contained gravel.