Bioturbation by the razor clam Sinonovacula constricta affects benthic nutrient fluxes in aquaculture wastewater treatment ecosystems

Abstract

The rapid development of the aquaculture industry has led to the growth of environmental problems. Bioremediation is an effective method for treating aquaculture effluents. A 30 d laboratory experiment was conducted to investigate the effects of Sinonovacula constricta bioturbation on sediment and nutrient fluxes across the sediment-water interface in aquaculture wastewater treatment ecosystems. The experiment was designed with 3 treatment groups and 1 control with 3 replicates each. The rates of sediment oxygen consumption (SOC) and the physical and chemical properties of the sediment and nutrient fluxes (NH4+, NO3- + NO2- and PO43-) were determined. After the experiment, the levels of total organic nitrogen, total organic carbon, and total phosphorus in the surficial sediment of the treatment groups had declined significantly, and the alkaline phosphatase content and microbial activity had increased significantly (p < 0.05). SOC rate in all treatment groups was significantly higher than that in the control group before Day 24 and increased with clam density (no. of clams per unit area) (p < 0.05); in most treatment groups, nutrients (NH4+, NO3- + NO2- and PO43-) were released from the sediment into the overlying water, and the rate of release increased with clam density and time. The results obtained in this study revealed that bioturbation by S. constricta reduced organic matter accumulation and accelerated the mineralization of organic matter in the sediments, which may promote nutrient recycling in aquaculture wastewater treatment ecosystems and eventually bioremediate aquaculture effluents.