Impact of a scallop drag on the sediment chemistry, microbiota, and faunal assemblages of a shallow subtidal marine benthic community

Scallops are usually obtained by means of a heavy metal dredge that is pulled over the sea bottom. Most studies of the impact of this gear type have shown that larger invertebrates, in particular, are severely disturbed. These studies, however, have been conducted on coarse sediments, ranging from sands to cobble, and have dealt only with faunal changes. In this paper the impact of a New England type scallop dredge on the fauna and sedimentary nutritional characteristics of a silty sand community is detailed. The site, in the Damariscotta River, Maine, USA, was sampled during the fall and winter prior to, then again immediately following, the dragging event, and twice more over the ensuing six months. Loss of surficial sediment, lowered food quality of the sediment (as measured by microbial populations, enzyme hydrolysable amino acids, and chlorophyll a), and changes in the faunal composition of the dragged site were observed. While some taxa returned to the drag track relatively quickly, others such as the cumaceans, phoxocephalid and photid amphipods, and nephtyid polychaetes, were not seen in abundances comparable to those of the adjacent undragged site until the food quality also recovered.