\2023 Survey dataset on the composition and species diversity of phytoplankton communities in the nearshore waters of Hainan

Hainan Province is surrounded by the sea on all sides, and the ecological environment quality of its surrounding waters has become an important factor restricting sustainable social and economic development. In August 2023, we conducted a sampling survey on four sea areas in Hainan Province, including Huanglong Port in Lingao, Baosuo Port in Dongfang, Shimei Bay in Wanning, and Xinbu Sea in Wenchang. A total of 36 microalgae and seawater samples were collected, and water quality testing and microscopic observation analysis were conducted on the samples. And based on the Shannon Wiener diversity index, Pielou evenness index, dominance and richness index, as well as water quality testing, the characteristics of phytoplankton communities and water quality environment in the nearshore waters around Hainan Province were investigated and analyzed. The survey results are as follows: A total of 254 species of phytoplankton were identified through microscopic examination of samples collected from various sea areas, including 214 species of diatoms, 24 species of dinoflagellates, and 15 species of blue-green algae. Diatom species account for 84.48% of the total number of species. Shimei Bay has the most abundant species of phytoplankton, while Xinbuhai has the least number of phytoplankton species. The diversity indices of Basuo Port and Shimei Bay are both greater than 3, with Shimei Bay having the highest diversity index and Huanglong Port having a diversity index of less than 1. The evenness index of the four surveyed bays is all less than 1, with the highest being 0.81 in Shimei Bay. After water quality testing, it was found that the COD, ammonia nitrogen, total nitrogen, total phosphorus, and nitrite nitrogen in Shimei Bay were the lowest in all four sea areas. The water quality indicators in Huanglong Port were higher than those in the other three areas, and the density of Microcystis in Huanglong Port accounted for 92.32%, indicating that a red tide has been formed.