Intertidal macrobenthic community changes induced by prolonged and irregular tidal regime in Lake Sihwa (Gyeonggi Bay, Yellow Sea, Korea)

초록

Lake Sihwa was a shallow saline lake located in the central part of Gyeonggi Bay, Yellow Sea, Korea. The lake was built up as a result of the dike construction which was connecting Oi-island with Daeboo-island from 1987 to 1994 and the total area was approximately 61,000㎢. From July, 2005, the manner of artificial sluice control was changed from twice a day to every five days. Then intertidal macrobenthos had been experienced another prolonged and irregular tidal regime that were three days ebb tide and two days flood tide and the tidal range expanded from 0.5m to 1.0m.We investigated changes of intertidal macrobenthic communities in Lake Sihwa under prolonged and irregular tidal cycle through comparison of sampling campaigns between 2004 and 2008. Number of species of higher zone decreased and those of lower zone increased although total species number was not changed significantly. Different patterns of changes were observed in abundance and biomass. One decreased through the all of sites and the other decreased markedly on the higher zone. Ecological indices appeared similar with number of species along the tidal level. Intertidal macrobenthic community in Lake Sihwa was changed during the last 4 years. It appeared that the highest part of the intertidal flats became terrestrial grassland ecosystem with the increment of terrestrial insects and the middle part was as unstable as ever evidenced by opportunistic species. On the other hand, those of the lowest part of intertidal flats showed the sign of the positive succession. The development of coastal area such as the embankment resulted in the alteration of hydrodynamic condition, sediment composition and consequently affected the reproduction, feeding and mortality of macrobenthos (Hummel et al., 1994; Seys et al., 1994). Ironically, prolonged and irregular tidal regime in Lake Sihwa resulted in both of harsh and stable environment according to tidal level.