Relationship between phytoplankton distribution and salinity in the giant artificial brackish Lake Saemangeum

Abstract

In 2021, an abundance of phytoplankton species was observed in Lake Saemangeum. We analyzed the relationship between phytoplankton abundance and salinity by comparing the distribution of salinity that changed because of freshwater inflow and drainage sluice gate operation. Thirteen field surveys were conducted: monthly basic surveys from January to November 2021 and additional surveys after rainfall in August and September at seven sites. During the survey period, 46–94 species were recorded. Pearson correlation coefficients were used to analyze the relationship between salinity and abundance of the dominant phytoplankton species. The result showed that Cyclotella atomus, Stephanodiscus hantzschii, Phormidium tenue, and Chaetoceros spp. were correlated with salinity. Chaetoceros spp. was significantly positively correlated (p < 0.001), whereas all other species were negatively correlated. Moreover, the correlation coefficient between seven species and salinity was close to zero. Compared with the general correlation coefficient of salinity and abundance, the point-biserial correlation coefficient showed a higher overall absolute value. Four species (Skeletonema spp., Cyclotella atomus, Phormidium tenue, Chaetoceros spp.) exhibited p < 0.001. Particularly, the correlation coefficient of Cyclotella atomus changed significantly from -0.237 to -0.451, whereas that of Phormidium tenue changed from -0.207 to -0.431. The results imply that salinity can affect the distribution and survival of euryhaline species. Therefore, high salinity may inhibit some freshwater and euryhaline species in the lake. However, further research is required to validate our findings.