Dianchi Lake macroinvertebrate community succession trends and retrogressive analysis

Wang Chou-Ming, Xie Zhi-Cai, Song Li-Rong, Xiao Bang-Ding, Gen-Bao Li, Lin Li
物种损失率高达 44%。其中软体动物损失率高达 75%:其次是水生昆虫(39%) 。滇池全湖底栖动物密度为 1 776 ind/m 2 (其中寡毛类 1 706 ind/m 2 ; 摇蚊科 68 ind/m 2 ) 。近 20 年滇池全湖底栖动物的丰度比较发现, 寡毛类的密度 和生物量呈一种先急剧上升, 而后明显下降的过程, 而摇蚊科的密度和生物量呈现出减少的趋势。寡毛类中的耐 污种相对丰度增加, 如霍甫水丝蚓(Limnodrilus hoffmeisteri)成为绝对优势种, 其平均相对丰度达到了 74.1%。摇 Abstract: Historical records and data from yield surveys conducted in 2009 and 2010 were used to investigate macroinvertebrate community succession trends in Dianchi Lake. Species richness has declined from 57 in the 1980s to 32 in 2010,
more » ... 80s to 32 in 2010, representing a species loss of 44%. Among the major benthic groups, the highest rate of loss was recorded for mollusks (75%) and aquatic insects (39%). Surveys in 2009 and 2010 across the lake revealed that the total density was 1776 ind/m 2 , comprising oligochaetes (1706 ind/m 2) and chironomids (68 ind/m 2). Over a nearly twenty-year span (1992 − 2010), the density and biomass of oligochaetes first increased sharply (1992-2002) and then declined gradually (2002-2010). Further, chironomids have decreased gradually while the proportion of abundant species has increased. Limnodrilus hoffmeisteri became the sole dominant species with an average relative abundance of 74.1%. Cosmopolitan species, such as Einfeldia sp., disappeared across the lake; instead, tolerant species such as Chironomus plumosus, Ch. attenuatus and Tanypus chinensis became the common. Mollusk community structure has become simpler and many native species have gone extinct. Species of concern include Margarya melanioides, M. mondi, M. mansugi and Cipangopaludina dianchiensis, all rated as critically endangered by the IUCN. We found that the Shannon-Wiener index declined in Dianchi Lake, particularly in Caohai Lake, from 2.70 in the 1950s to 0.30 in 2009 and 2010. Species richness and biodiversity was significantly negative correlated with total phosphorus and total nitrogen. Factors responsible for the benthic community retrogression described here include habitat destruction, lowering of water quality, outbreaks of