EDNA metabarcoding revealed the seasonal and spatial variation of phytoplankton functional groups in the Chai river and their relationship with environmental factors

Abstract

Environmental DNA (eDNA) metabarcoding permits a new measurement to monitor biodiversity in aquatic ecosystems. This study utilized eDNA metabarcoding to examine the seasonal and spatial distribution of phytoplankton and their relationship with environmental factors in the Chai River, Kunming, China, in the dry, and wet seasons. The process detected 108 genera of phytoplankton, which were members of 11 phyla, 41 orders, and 60 families. Distinct differences in seasonal and spatial distribution patterns of phytoplankton diversity, including community structure, α-diversity, and representative functional groups, were observed. In the dry season, Pseudanabaena, Microcystis, and Synechococcus were the predominant genera in Cyanophyta, and Chlorophyta, Bacillariophyta and Euglenophyta were predominant in the eukaryotic phytoplankton. While in the wet season, Cylindrospermopsis, Microcystis, and Planktothrix predominated in the Cyanophyta, and Bacillariophyta, Chlorophyta and Xanthophyta predominated in the eukaryotic phytoplankton. Significant differences were shown by a principal coordinate analysis and PERMANOVA test among the upper, middle, and lower reaches of the phytoplankton communities except for the cyanobacterial community structure between the upper and lower reaches at the wet season (p > 0.05). The representative functional groups of phytoplankton varied from A, D, E, LM, L0, N, S1, MP, P, TB, TC, U, W0, W1, Xph, Y, and Z in the dry season to A, B, D, E, F, J, MP, LM, S1, SN, TC, P, W0, W1, X2, and Y in the wet season. Significant differences in the water temperature (WT), pH, chemical oxygen demand, oxygen consumed, nitrate nitrogen (NO3-N), and chlorophyll a were exhibited between the dry and wet seasons (p < 0.05). In the dry season, WT, NO3-N, and pH had a substantial influence on the functional groups LM, N, and L0 of the cyanobacteria. The EC and total nitrogen (TN) had a substantial influence on the functional groups A and Y of the eukaryotic phytoplankton. In the wet season, the electrical conductivity (EC), TN, and dissolvable total phosphorus (DTP) primarily affected the functional groups LM and S1, while EC, DPI, and soluble reactive phosphorus had a substantial influence on the functional groups A and Y. This study provides insights on the conservation of phytoplankton diversity and healthy management of the Chai River.