浮游微型真核生物群落对电厂温排水增温的响应

浮游微型真核生物作为初级生产者,细菌捕食者和较大型生物寄生者,在维持生态系统稳定中起核心作用.因此,研究浮游微型真核生物对温排水增温的响应对评价近年来大量电厂兴建的环境效应具有重要意义.沿象山港乌沙山电厂温排水水流采集表层水样,利用Illumina技术测定18S r DNA基因研究浮游微型真核生物群落组成.真核浮游生物的主要组成为囊泡虫门(Protalveolata)、纤毛亚门(Ciliophora)、甲藻门(Dinoflagellata)和丝足虫类(Cercozoa).多元回归树分析发现浮游微型真核生物多样性主要受溶解氧、硝态氮和温度的控制.温排水造成的增温梯度显著地改变了浮游微型真核生物的群落组成(Global RANOSIM=0.422,P0.001);反向选择筛选到空间距离、溶解氧、叶绿素a和温度是造成群落变异的主要因子.浮游微型真核生物的空间分布遵循空间距离-群落相似性衰减模型(R=-0.192,P=0.039),周转速率为0.002.此外,筛选到15个敏感的真核生物科,其相对丰度与增温幅度显著相关.重要的是对某一特定的科,其相对丰度随温度的变化与其已知的生态功能相吻合,可以作为评价温排水增温的指示种群.本研究阐明了温排水增温梯度下真核浮游生物群落的空间分布规律,并为评价温排水对微生态效应提供了灵敏的生物学指标.

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

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 R_ANOSIM=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.