Community succession and mechanisms of community assembly of macroinvertebrates over the past three decades in Lake Baoan

保安湖是江汉湖群的一个典型浅水湖泊。近几十年来,随着经济的快速发展,保安湖面临多重人类压力影响,富营养化问题日趋严重。历史上曾开展过数次的保安湖底栖动物调查,但有关群落结构的长期变化及其驱动机制改变的认知仍为空白。本研究基于30余年(1986-2019)的多次调查数据,探索保安湖底栖动物的群落演变规律及其群落构建机制。研究共记录保安湖底栖动物5门10纲25目49科110属170种(历史记录154种,现场调查51种)。总物种数由1992年的107种降为2019年的51种;平均密度由1992年的433 ind./m2增加到2019年的2177.6 ind./m2;平均生物量由2001年的160.6 g/m2降低为2019年的26.7 g/m2。优势种在1987年有寡毛类、水生昆虫和软体动物多个类群,其后逐步演变为现阶段少数几种耐污的寡毛类和摇蚊类,如霍甫水丝蚓(Limnodrilus hoffmeisteri)、中国长足摇蚊(Tanypus chinensis)、红裸须摇蚊(Propsilocerus akamusi)等,而多年生大型软体动物衰退明显。PERMANOVA和SIMPER分析结果表明,2001和2019年底栖动物群落结构差异显著,不同时期特征种差异较大。近20年间,底栖动物群落构建机制发生变化,主要驱动力由环境过滤(2001年)转变为中性过程(质量效应)(2019年)。现阶段(2019年),不同季节的群落结构存在一定差异,春冬两季的物种数、密度以及生物量均大于夏秋两季,但不同季节的特征种相似。同时,群落构建的关键因子及驱动机制在不同季节间也存在一定差异,除秋季外,其他季节的空间因子解释率均大于环境因子解释率。;As a typical shallow lake along the middle-lower reach of Changjiang River, Lake Baoan, located in Jianghan District, has been suffered from multiple anthropogenic pressures for several decades, leading to severe eutrophication. As consequence, its macroinvertebrate fauna experienced biodiversity decline and compositional change. Our understanding community succession associated with assembly shift, however, remains limited, although investigations have carried out this lake. Here, we explored mechanisms based on combined datasets historical records field 2019-2020. A total 170 taxa (154 51 investigations) were recorded, belonging 49 families 110 genera. Species richness declined significantly over recent three peak value 107 1992 now, but aquatic insects still dominant groups at various times. The variation trend average density increased, 433 ind./m2 2177.6 while biomass was opposite trend, 160.6 g/m2 2001 26.7 now. species changed comprising oligochaeta, mollusks those highly pollution-tolerant widespread species, including Limnodrilus hoffmeisteri, Tanypus chinensis Propsilocerus akamusi, long-life large communities deteriorated gradually. In addition, PERMANOVA SIMPER analyses revealed significant variations structure macroinvertebrates characteristic among different years. Variance partitioning analysis showed that 20 years, had changed, spatial processes (mass effect) stronger effects than environmental filtering processes. RDA/CCA results demonstrated variables (total nitrogen ammonia ) factors (PCNM2, PCNM7, PCNM9) pivotal driving affecting communities. 2019, there some differences composition across seasons. richness, spring winter all higher summer autumn, seasons similar. Moreover, key also most seasons, explanation by better except autumn.