The effects of soil erosion on chironomid assemblages in Lugu Lake over the past 120 years

Abstract

AbstractLakes in Yunnan Province, SW China, have been subjected to increased environmental stress over the last century. In order to assess the impacts of these stresses on the biota, a sediment core was collected from Lugu Lake covering the past 120 years, and detailed chemical, biological (subfossil chironomids), and physical analyses of the lake sediments were undertaken. The analyses indicated consistent trends of increased soil erosion since the early 1970s associated with significant changes in chironomid assemblages, which occurred simultaneously with the sedimentological proxies. A redundancy analysis (RDA) using a range of sedimentary proxies indicated that the shifts in the chironomid communities were mainly attributable to soil erosion. Constant soil erosion caused dramatic reductions in the available organic materials and large increases in fine sediments, leading to changes in the chironomid fauna and reduced chironomid abundance. The chironomid succession revealed that Procladius, the likely top predator in the chironomid community food chain, decreased in abundance under the impact of soil erosion, whereas the proportion of small forms of filter feeders, represented by Tanytarsus mendax‐type, increased rapidly. Due to the loss of suitable habitats, the population of some bottom collector‐gatherers (e.g., Polypedilum nubeculosum‐type) decreased sharply. The results of this study suggest that increased catchment soil erosion may seriously impact benthic communities and potentially alter ecosystem functioning.