Long-Term and Spatial Variation in the Diversity of Littoral Benthic Macroinvertebrate Fauna in Lake Biwa, Japan

Abstract

Freshwater ecosystems provide ecosystem services essential to human well-being, such as provisioning of water and fishery resources, but they are the most vulnerable to human disturbances and concerns have been raised about their loss of biodiversity. The ancient Lake Biwa is one of valuable Asian freshwater ecosystem because of its high biodiversity and endemism but it has been exposed to various severe anthropogenic environmental changes during the past half century. Although we have great concern about the biodiversity loss in this lake, it remains highly unknown what kind of human disturbances cause deterioration of the ecosystem. Elucidation of environmental pressures for the biodiversity loss is important to illuminate subjects for conservation of biodiversity. We particularly focus on a littoral benthic macroinvertebrate fauna because its habitats, located in the interface between aquatic and terrestrial ecosystems, are those most vulnerable to human activities. We found that littoral benthic macroinvertebrate diversity was largely affected by pH, temperature, phytoplankton biomass, benthic microalgae biomass, and coverage of submerged plants. These environmental variables are largely associated with environmental problems that occurred in the Lake Biwa: eutrophication, warming, and massive submerged plant expansion. This finding suggests that past environmental problems caused serious impacts on the biodiversity of Lake Biwa.