Abstract

Cih Lake is an important habitat for numerous aquatic organisms. However, since the construction of a dike in 1969, the lake has become a closed reservoir, relying solely on sluice gates for water exchange. This limited exchange has led to significant deterioration in water quality. In response, the Kinmen National Park Headquarters began operating the sluice gates in 2017 to enhance seawater exchange. This study evaluates the effects of three different sluice gate operation modes: no seawater exchange (current operation), seawater exchange once per month, and seawater exchange twice per month. Water quality, sediment conditions, and benthic invertebrate communities were surveyed after each operational mode to assess the impact. Results showed that seawater exchange effectively diluted nutrient concentrations within the lake. However, the impact on sediment was not significant. Polychaete abundance appeared to increase following the water exchange operations, whereas mollusks and crustaceans did not exhibit notable changes. Based on these findings, we recommend conducting seawater exchange operations at least once per month to improve water quality and enhance polychaete abundance.

Keyword: Benthic macroinvertebrates, sediment condition, sluice gate operation, water quality