Macrobenthic faunal change after dike construction in Saemangeum Lake, South Korea, with special emphasis on mollusks

Abstract

The world’s largest Saemangeum Dike was completed on April 21, 2006; however, the water gates were intermittently opened to dilute the polluted water inside the dike with seawater outside the dike. We investigated the macrobenthic faunal change after dike construction in Saemangeum Lake, South Korea, in the summer season. From July 2008 to August 2012, many individuals of bivalve species, such as Arcuatula senhousia, Potamocorbula sp., and Ruditapes philippinarum, were collected from the subtidal zone inside the dike, although the dissolved oxygen content in the bottom water was less than 1 mg/L at many stations, where the water depth was more than 2.7 m. In August 2016 and August 2018, however, most macrobenthic animals disappeared from Saemangeum Lake, because the water became more hypoxic than it was in August 2012. These facts suggest that the Saemangeum Dike negatively affects the water quality and macrobenthic animals inside the dike because of the long closure of sluices.