Green tide development associated with submarine groundwater discharge and land-based aquaculture farm effluent in the Bangdu bay, Jeju, Korea

Abstract

The coast of Jeju island is rapidly change marine environment by affected global climate change and subtropicalization is in progress. Recently, increases in coastal pollutants, reduction of resources, damage to fisheries, and disturbance of marine ecosystems have frequently occurred. In the coast of Jeju Island, green tides of Ulva spp. have occurred annually since the early 2000s. It is affecting the coastal ecosystem disturbing and seriously damaging the coastal fishery and tourism industry. In the Bangdu bay, submarine fresh groundwater discharge (SFGD) and land-based Aquaculture farm effluent (LAFE) are flowing into the bay. The mouth of bay is narrow due to the construction of a seawall, so the circulation of seawater is very slow in inner bay. SFGD and LAFE have high concentration of nitrate, and stagnant current in inner bay increase the residence time of seawater, contributing to the growth of Ulva spp. Nitrogen and phosphorus contents in Ulva were in the range of 1.8% to 3.1% and 0.11% to 0.20%, respectively, and nitrogen and phosphorus contents were particularly high around the inflow of LAFE. It is estimated that the green tide in Bangdu Bay is more affected by LAFE than SFGD.