| Plots of three treatment types (industry-standard screens with clams, screens without clams, and control) were installed at Sedge Island, Barnegat Bay, in 2012. 177 species from eight phyla were collected. Hard-clam plots had lower Shannon-Weiner Index values and higher sedimentary sorting coefficients as compared to both control treatments. ANOSIM identified benthic communities inside hard clam plots as statistically distinct from the two control treatments. There was no significant effect of treatment on functional groups assigned by burrowing depth. Seasonal peaks in May are clear for Polydora cornuta and Tritia obsoleta, as well as for suspension feeders and omnivores. All burrowing-depth guilds except deep-burrowing taxa also peak in May. Grazer density, and Microdeutopus gryllotalpa in particular, peak in October. Shannon-Weiner and species richness do not differ significantly by season, though evenness is higher in August than May, reflecting the peaks of certain species evening out during the summer. The trends seen suggest bottom-up controls of the benthic invertebrate community structure in the Sedge Island area, which therefore has the potential to be disrupted either by the overconsumption of available seston from increased aquaculture or increased phytoplankton from increased eutrophication. These data can serve as a baseline for environmental monitors given either of these scenarios. These results do not provide any immediate reason to limit hard clam aquaculture acreage in the region. However, the observed increase in maldanid polychaetes and decrease in mobile suspension feeders could prove problematic if leasing acreage is increased. Full-scale within-industry research is recommended before increasing hard-clam aquaculture acreage, either as part of an environmental management strategy for eutrophication mitigation or for economic purposes. |
