Changes Of Benthic Invertebrate Communities In Dianchi Lake In Recent 100 Years

Eutrophication leads to one of the most serious environmental problems forsurface waters around the world during the past decades, including many plateau lakesof Yunnan. Dianchi Lake is located besides the city of Kunming on theYunnan-Guizhou Plateau. In recent decades, due to intensive human disturbances likewastewater discharge and overexploitation, this lake faces severe ecologicalchallenges, including deteriorating water quality, decreased water level, shrinkingaquatic vegetation, and decrease in ecosystem functioning and services. All these mayhave significantly affected the benthic invertebrates, an important component of lakeecosystem. To date, modern surveys of lake benthos have been sporadically but thereis a lack of consistent and systematic data on the history of the change in benthicinvertebrates at Diachi Lake. Here we applied multi-proxy analysis of lake sedimentsand aims to uncover the history of the changes in production and structure ofChironomid larva during the past century. Specifically, algae pigment, chironomidae,benthic diatoms, and other sedimentary records were analysed on the basis of210Pb-based chronological sequence.Our sedimentary pigment data showed a stable and low productivity during thepre-1960period at Dianchi Lake, corresponding to a low production of Chironomidlarvae as recorded in lake sediments. Since around1960AD, an increase in lakeproductivity was associated with an elevated density of sedimentary Chironmid headcapsules, suggesting a nutrient enrichment effect on benthic invertebrate community.However, despite the consistent increase in lake productivity since1980s, Chironomidproduction decreased steadily suggesting a negative effect of lake hypo-eutrophicationand the increasing importance of habitat availability and the level of dissolved oxygenin diriving benthic invertebrate community. In consistence with modern surveysduring the past decades, the Chirnomid density at Dianchi Lake showing a decreasingtrend, while Chironomus became the dominant taxon possibly due to its tolerance ofhypoxia in eutrophic waters, which may enable it to survive better in nutrient-enrichedwater than other common taxa like Einfeldia, which has recently have disappeared oroccurred at low abundance.Our results suggest that eutrophication of water bodies can plays an importantinfluence on changes in community structure of chironomids, but it can also affect theinvertebrate community structure through reducing the concentrations of dissolved oxygen and also affecting the quality and quantity of aquatic plants that areavailable to benthic invertebrates. This study suggests that nutrient enrichment canstrongly affect the ecosystem functioning through the benthic pathway of lake foodwebs. One implication from this study is that benthic invertebrates are a sensitiveindicator for ecosystem structure and functioning at Dianchi. Effective ecologicalrestoration and lake monitoring program should highlight the role of benthicinvertebrates in evaluating water quality and ecosystem functioning for large andshallow lakes like Dianchi.