Assessing Impacts of Oyster Aquaculture in Rhode Island Coastal Salt Ponds Using Subaqueous Soils and Benthic Macroinfauna.

Coastal lagoons are unique estuaries at the interface of marine and terrestrial ecosystems that are currently experiencing the expansion of oyster (Crassostrea virgnica) aquaculture in southern New England. Although it is well established that native shellfish can provide improve water quality, few studies have examined the environmental impacts of continuous shellfish aquaculture on the benthic environment. We assessed the effects of oyster aquaculture on three coastal lagoons in southern New England using benthic infauna and subaqueous soils as indicators of environmental impact. Sampling locations were stratified based on the number of years the location was utilized for aquaculture (4-20 years). Samples were collected from the upper 20 cm of the soil surface in aquaculture areas and in adjacent, non-aquaculture locations, as a control (0 years). Samples were taken for soil analysis (incubation pH, particle size, bulk density), and benthic infauna, which were sorted, identified to species level, and classified by functional feeding group. Aquaculture sites had higher numbers of benthic infauna individuals and larger populations of deposit feeders, compared to areas not previously used for aquaculture.  Time in aquaculture had no clear effect on most functional feeding groups, except for deposit feeders which were most abundant after eight years of aquaculture use. Preliminary soil analysis revealed no apparent differences in soil incubation pH, particle size distribution, or bulk density between aquaculture and control sites. Our results suggest that continuous aquaculture does not affect physical soil properties, and may have a positive impact on the lagoon environment by increasing the size of benthic infauna communities.