Impact of Shellfish Aquaculture on Benthic-Pelagic Coupling

Project Description

Polychaete worms and other infaunal species residing in marine sediments create bioturbation (mixing and overturn of sediments) through their feeding, tube-building, burrowing, and ventilating activities. These activities influence nutrient fluxes between the sediments and overlying water, and the composition of sedimentary communities. Changes in organic deposition can significantly alter community structure and the rates and patterns of bioturbation. Aquaculture activity and other processes in the water column are intimately linked to processes in sediments via the exchange of solutes, organic detritus, and associated fluxes of nutrients and metals. This project studies the effect of shellfish aquaculture and any associated changes in organic deposition on the infaunal community structure and benthic-pelagic coupling in select areas, within at least two of the three bioregions.

Results and Accomplishments

During the past year, project personnel completed detailed analyses of the patterns of diversity and abundance for benthic invertebrates sampled under and adjacent to suspended oyster cages at three shellfish farms. While the benthic community differed at each farm, species composition was more than 70% similar, except at the one site in central Maine (43%). Capitellid dominance was higher under cages, reaching its maximum (35%) at one farm on the Bagaduce River. However, personnel did not find evidence of severe organic enrichment as the sediments under the oyster cages at all farms were only slightly enriched for organic matter. Taxonomic diversity was relatively high except at one farm on the Damariscotta River, which was dominated by the spionid polychaete Streblospio benedicti. Differences in benthic invertebrate diversity under oyster cages suggest relatively minor impact of the oyster operations studied on local benthic communities. The team’s analyses supported presentations at two national meetings this past year.

Summary of Data Being Collected

Data	Type	Quantity	Location
Benthic Community Composition	Frequency of Individual species, diversity of species	Two sampling dates (multiple grabs per date)	Blackstone Farm, Damariscotta River, Damariscotta, Maine
Benthic Community Composition	Frequency of Individual species, diversity of species	Two sampling dates (multiple grabs per date)	Weskeag River Oyster Co., So. Thomaston, Maine
Benthic Community Composition	Frequency of Individual species, diversity of species	Two sampling dates (multiple grabs per date)	Bagaduce River Oyster Co., Brooksville, Maine
Benthic Community Composition	Frequency of Individual species, diversity of species	One sampling date in 2016; to be paired with macrofauna data from similar sampling conducted in 2010	Pemaquid Oyster Co., Damariscotta River, Damariscotta, Maine