滇池大型无脊椎动物的群落演变与成因分析

Dianchi Lake macroinvertebrate community succession trends and retrogressive analysis

该文综合滇池大型无脊椎动物的历史资料,并结合2009—2010年的现场调查数据,对其群落演替进行了研究,并对群落衰退的成因进行了探讨。物种数下降明显,由20世纪80年代的57种降为现在的32种,群落的物种损失率高达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1776ind/m2(其中寡毛类1706ind/m2;摇蚊科68ind/m2)。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%。摇蚊科相对丰度减少,以前广泛分布的异腹鳃摇蚊(Einfeldiasp.)基本消失,取而代之的是羽摇蚊(Chironomus plumosus)、细长摇蚊(Ch.attenuatus)、中国长足摇蚊(Tanypus chinensis)等耐污种;软体动物种类变得单一,许多高原湖泊特有的软体动物均已消失,螺蛳(Margarya melanioides)、牟氏螺蛳(M.mondi)、光肋螺蛳(M.mansugi)在2009年被世界自然保护联盟列入了极危物种,滇池圆田螺(Cipangopaludina dianchiensis)也被列入了濒危物种。滇池的Shannon-Wiener多样性指数显著降低,尤其是草海物种多样性从20世纪50年代的2.70降到现在的0.30。半个多世纪以来总氮、总磷与物种数和多样性呈现显著负相关。底栖动物群落衰退的成因主要是生境破坏、水质恶化、蓝藻爆发、沉水植物消失、种质库匮乏等。

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,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 blue-green algae,extinction of submerged plants and lack of germplasm resources.