Responses of Plankton Microeukaryotic Community to Increasing Temperatures Created by Power Plant Thermal Discharges

Abstract

Plankton microeukaryotes are primary producers, bacterial grazers and parasites in the ocean, thus contributing essential roles in marine ecosystem stability. For this reason, understanding how the microeukaryotic community responds to increasing temperature created by thermal discharges is key to evaluating the ecological and environmental consequences of a power plant. In this study, using an Illumina sequencing based analysis of eukaryotic 18S rDNA gene, we investigated the compositions of microeukaryotic community along a thermal gradient caused by the discharge from the Wusha Mountain power plant in Xiangshan Bay. The plankton microeukaryotic communities were dominated by Protalveolata, Ciliophora, Dinoflagellata and Cercozoa. A multivariate regression tree revealed that mircoeukaryotic diversity was primarily controlled by dissolved oxygen (DO), followed by nitrate and temperature. Thermal discharge significantly altered the compositions of microeukaryotic community, evidenced by an analysis of similarity (Global RANOSIM=0.422, P<0.001). A forward selection procedure showed that the variations of microeukaryotic community were primarily shaped by geographic distance, DO, chlorophyll a, and temperature. The spatial distribution of microeukaryotic community followed a distance-decay for similarity relationship, with a turnover of 0.002. In addition, 15 sensitive eukaryotic families were screened, the relative abundances of which were significantly associated with the discharge-induced temperature gradient. For a given eukaryotic family, the pattern of enrichment or decline was consistent with its known ecological function, which could be served as bio-indicators for temperature anomalies. Collectively, this study demonstrates the spatial pattern of microeukaryotic community in responses to increasing temperature, and provides sensitive bio-indicators for evaluating the ecological consequences of thermal discharge.