Monitoring of Discharged Water from Groundwater and Land-based Aquaculture Effluent using CTD Data in Shinyang Bangdu Bay, Jeju Island, Korea

Abstract

The Sinyang Bangdu Bay in Jeju Island, a semi-inclosed sea, is introduced by the discharged water of the groundwater and land-based aquaculture effluent (LAE) from the surrounding land. To investigate the distribution of the discharged water into the Sinyang Bangdu Bay, 370 Conductivity-Temperature-Depth (CTD) casting data (temperature and salinity) were collected on the nine sampling points from April to September 2019. To understand the spatial and temporal variation of the influent water with changing tide, CTD observation was continuously performed 1-5 times at a 1-hour interval in the daytime. CTD hydrographic data were used the downcast data controlled by constant speed. CTD casting data, water temperature and salinity, were averaged at 0.1 m intervals using the filter mean. The groundwater and LAE in the study area show relatively lower salinity than surrounding waters, and this feature was shown on the west coast in the study area. The both influent waters into the study area had a different spatial influence with changing tidal current. During the flood tide, the west coast of the study area was influenced by the LAE because the discharged water moved to northward along the west coastline of the bay. During the ebb tide, the west coast of the study area was influenced by the groundwater because the discharged water moved southward along the west coastline of the bay. The vertical variation of the discharged water sharply changed within 1 m, and the feature was not observed at more than 1 m wa ter depth.

Keywords

• groundwater
• land-based aquaculture effluent
• ctd
• bangdu bay
• jeju island