Effect of abalone farming on seawater movement and benthic foraminiferal assemblage of Zostera marina in the inner bay of Wando, South Korea

Influence of intensive net cage farming on hydrodynamic and geochemical environmental conditions and the mass mortality of abalone in South Korea

The abalone aquaculture industry in South Korea has grown rapidly since the 2000s. In this study, we investigated the sedimentary pollution at four major abalone farms responsible for ~60% of all South Korean abalone produced. We also surveyed the current statuses of cage facilities, abalone mass mortality, and current velocities within and outside farm cages. The concentrations of total organic carbon in the study area were 7.92 ± 2.09 mg g^-1, indicating a mild level of sedimentary pollution. We observed higher mortality rates in rectangular-shaped shelter cages than in triangular shelters. With increases in the number and size of abalone farming facilities, current velocities inside the cages declined by an average of 45% relative to those outside the cages, leading to poor habitat conditions for farmed abalone. Our results provide insights into the current status of the benthic environments and major causes of mass mortality in the abalone farms of South Korea.

A novel approach to evaluate potential risk of organic enrichment in marine aquaculture farms: a case study in Sanggou Bay

A novel approach was proposed to evaluate the potential risk of organic enrichment in marine aquaculture farms without obvious environmental degradation. The approach was based on historical environmental records preserved in sediment cores, and potential risk of organic enrichment can be effectively evaluated by comparing burial fluxes of marine organic carbon (OC_M) during times before and after large-scale aquaculture. A case study was conducted in Sanggou Bay. The change trends on burial fluxes of organic carbon in sediment over the past 150 years were rebuilt. OC_M burial fluxes have greatly increased since the beginning of large-scale aquaculture in 1980s, reaching 16.0~16.5 times higher than that before large-scale aquaculture. The results indicate that aquaculture activities have resulted in obvious accumulation of aquacultural organic matters, although sedimental environment has not degraded seriously. Besides, if the OC_M burial fluxes further increase to 3.5~7.0 times higher than that in present, sedimental environment may degrade obviously. Therefore, potential risks of organic enrichment still exist with aquaculture development in Sanggou Bay.