Change in Marine Environment after Artificial Reef Deployment in the South Sea of Korea

In order to study the change of marine environment after artificial reef deployment in the South Sea of Korea, water temperature, currents and nutrients distributions were investigated during the strongly stratified summer season. Before the deployment of artificial reef, the maximum thermocline of water column (MTWC) formed at depths of 30 similar to 40 m in almost all of the studied area. However, after the deployment of the artificial reef, depending on tide time, variations in MTWC were observed about 10 similar to 17 m shallower in areas within 1 km in radius of the artificial reef due to uplifting of isotherms. In waters surrounding the artificial reef, vertical currents alternate between local downwelling flow (LDF) and local upwelling flow (LUF), and this type of phenomenon is dependent on tide time and takes on various patterns of spatial distribution. In addition, the degree of vertical mixing, which can be deduced from areas with strong current shears, especially in the surrounding area of the artificial reef from which the LUF originates, was found to be distributed in a similar manner. Although there are tide time-dependent differences in the Richardson number (Ri), in depths of 30 similar to 40 m or deeper, where the Ri is less than 0.25, the water column was destabilized by vertical mixing. In addition, differences in nutrient distribution were noted before and after the artificial reef deployment. Highly stratified nutrients rose to the upper layer after passing the artificial reef, and the accumulation of nutrients can be attributed to the LUF developingat the artificial reel Thus, in periods of strong stratification during the summer, the upward movement of nutrients from the aphotic to the euphotic layer increases the primary production levels, triggering the formation of a marine food chain in those areas.