Benthic suspension-feeding clams affect sedimentary microbial communities and nitrogen cycling in seawater pond IMTA

Suspension-feeding bivalves are the key driver unit for cycling of material and energy in integrated multi-trophic aquaculture (IMTA) system, but only few studies have examined their bioturbation effects in land-based aquaculture system. In the present study we explored the effects of different species (Ruditapes philippinarum, Sinonovacula constricta and Mercenaria mercenaria) and stocking density of benthic clams on the structure and function (specifically, nitrification and denitrification) in pond IMTA using a medium-scale mesocosm incubation system. It was found that co-cultured with 3 benthic clam species respectively decreased the inorganic nitrogen and phosphate in water column, affected the sediment microbial communities, and increased abundance of nitrogen cycling related genes, such as AOB, nifH and nosZ, in sediment. Moreover, the moderate density of R. philippinarum (125 ind. /m2, weight of clam at 4.5 g ind.−1) have a higher activities of nitrogen cycling. The results are of great value on discovering the ecological mechanism of pond IMTA and improve the current IMTA models.