Species Richness and Abundance of Freshwater Mussels in Tributaries of the Lower Pearl River Basin

Abstract

Freshwater mussels play a vital role in their ecosystems, influencing processes such as nutrient cycling and water filtration. In addition, they provide and improve habitat for other organisms. North America is home to the most species-rich freshwater bivalve fauna in the world, but most stream systems in the U.S. have been severely degraded, and future freshwater mussel extinction rates are estimated at 6.4 percent per decade. The Pearl River Basin is a significant area of aquatic species diversity and has a complex watershed land use mosaic, providing an excellent opportunity to investigate the relative importance of local and landscape level factors on freshwater mussel assemblages. The objectives of this study were to identify freshwater mussel species richness and relative abundance in tributary streams of the Pearl River Basin, and to identify relationships between microhabitat and landscape-level environmental variables and freshwater mussel diversity in these streams. Freshwater mussel and local habitat surveys were conducted on 36 tributary streams over two summers. In addition, percent area coverage of seven land use categories and seven geology categories were estimated for each sample site. Mussel surveys revealed nine species, with total abundance ranging from 0-66 mussels per sites and species richness ranging from 0-5 species per sites. Although there were relatively few mussels at survey sites, where mussels were present, substrate composition and water chemistry appeared to be important factors influencing richness and abundance. In general, associations between local habitat variables and landscape variables were low, suggesting that local habitat features were more important in explaining mussel assemblages encountered during this study. However, other studies have documented associations between mussel assemblage characteristics and landscape scale variables. Therefore, knowledge of land use and geology should be integrated with local habitat data to accurately assess population and assemblage characteristics of these organisms in order to assist the informed development of effective management and conservation strategies for the Pearl River Basin.