巢湖后生浮游动物群落及不同湖区营养状态评价

为了给巢湖水质管理及富营养化防治提供科学依据，根据水系特征，在巢湖东、西湖区湖心、裕溪河出湖口、丰乐河、派河和南淝河共设置8个采样点，2013年12月至2014年11月共采样12次，分别代表冬季(12月-次年2月)、春季(3-5月)、夏季(6-8月)和秋季(9-11月)，对巢湖水体理化因子和后生浮游动物（枝角类、桡足类、轮虫）群落进行逐月周年调查。基于叶绿素(Chl-a)、总磷(TP)、总氮(TN)、化学需氧量(CODMn)、透明度(SD)等水体理化指标，运用综合营养状态指数(TLI)和生物多样性指数，对不同湖区受污染程度和营养状态进行综合评价。结果显示，巢湖共检出后生浮游动物42种（属），优势种矩形龟甲轮虫(Keratella quadrata)、萼花臂尾轮虫(Brachionus calyciflorus)为富营养化水体或有机质较多水体的常见种，不同季节的优势种存在较大差异；总体上，后生浮游动物全年平均丰度371.6 个/L（191.5~600.0 个/L）和全年平均生物量3.0 mg/L（2.0~4.6 mg/L）均呈现西半湖高于东半湖、夏秋季高于冬春季的分布特点；其群落结构也存在显著的季节差异和空间差异，矩形龟甲轮虫、萼花臂尾轮虫等是造成差异的主要种类。水温(WT)和Chl-a是影响枝角类丰度的重要因子，桡足类丰度与WT呈显著正相关，而轮虫丰度受TLI(∑)指数的显著影响。TLI(∑)指数均值为60.33（52.18~66.28），指示巢湖总体处于轻度至中度富营养化状态。Shannon-Wiener多样性指数和Margalef丰富度指数表明，巢湖总体处于中度污染状态，不同湖区水体具有明显的不均衡性。

Metazooplankton Community Structure and Trophic State Assessment of Chaohu Lake

In this study, metazooplankton (rotifers, cladocerans, and copepods) community structure and physicochemical factors of the water in Chaohu Lake were investigated periodically. The comprehensive trophic status index (TLI, based on Chl-a, TP, TN, transparency and COD), and the biodiversity index were used to comprehensively evaluate the pollution and trophic state of the lake. From December 2013 to November 2014, monthly monitoring of metazooplankton and water quality was carried out at eight sampling sites (CH1-4 in eastern Chaohu Lake and CH5-8 in western Chaohu Lake). A total of 42 metazooplankton species were detected, including 24 rotifers, 10 cladocerans and 8 copepods. The dominant species, varying by season, were Keratella quadrata and Brachionus calyciflorus, indicators of eutrophic water or water bodies with abundant organic matter. The range of annual metazooplankton abundance and biomass in Chaohu Lake were 191.5-600.0 ind/L and 2.0-4.6 mg/L, with average values of 371.6 ind/L and 3.0 mg/L. Both measures were higher in the western area of the lake than in the eastern, and higher in summer and autumn than in winter and spring. The metazooplankton community structure differed significantly with season and location, primarily due to fluctuations in the two dominant species. Water temperature and Chl-a were the important factors affecting cladoceran abundance, while copepod abundance displayed a significant positive correlation with water temperature and rotifer density correlated significantly with TLI. The range of TLI in Chaohu Lake was 52.18-66.28, with an average value of 58.41, indicating mild to moderate eutrophication, while the metazooplankton biodiversity indices (Shannon-Wiener diversity index, Margalef richness index) indicate moderate pollution, although the pollution status varied with location. Our results provide a scientific basis for managing water quality and controlling eutrophication in Chaohu Lake.