Dual benefits of biofouling reduction in non-fed aquaculture: On-site heat treatment enhances oyster production and mitigates local environmental impacts

Abstract

We experimentally evaluated the biofouling reduction by on-site heat treatment in enhancing oyster aquaculture production and mitigating its environmental impacts. Specifically, we compared oyster growth, settling flux of particulate organic matter (POM), and its oxygen consumption rate (OCR) between heat-treated (HT) and non-treated (N) sections within suspension oyster farms in a temperate bay. HT demonstrated a substantial reduction of 81–99% in fouling mussel biomass and approximately 20–30% increases in cultivated oysters’ growth and condition index. The settling flux of POM was 10–57% smaller in HT mainly due to the reduction in biodeposition from fouling mussels. However, OCR of settling POM at a unit mass was 6–62% higher in HT than in N; overall, the short-term oxygen consumption by settling POM did not significantly differ between HT and N. The increase in OCR of settling POM in HT may be attributable to the decrease in biodeposits from fouling organisms and increase in the relative contribution of fresh POM entering from unfarmed areas. Meanwhile, from the longer-term perspective, the substantial reduction in settling POM by the heat treatment lower the potential for oxygen consumption in the bottom layers over the half-year farming operation by 31%. In conclusion, on-site heat treatment is a simple tactic for controlling nutrient and POM flows at production sites, simultaneously enhancing oyster production and mitigating the local environmental impact of non-fed oyster aquaculture. Furthermore, this approach exemplifies an effective tactic to enhance the sustainability of primary food production processes.