Snail (Mollusca: Gastropoda) assemblages as indicators of ecological condition in freshwater wetlands of Northeastern China

Abstract

The utility of aquatic macroinvertebrates as indicators of the ecological conditions has long been established in rivers and streams. However, useful invertebrate indicators of wetland conditions remain more poorly developed probably because wetland macroinvertebrates have many attributes that reduce their ability to reflect wetland environmental quality. Snails, however, possess several attributes that should make them useful as potential environmental indicators. In this study, we sampled snail assemblages in 16 wetlands across a range of conditions, from relatively pristine “best available” reference sites to obviously human-impacted sites in Northeastern China’s Sanjiang Plain. We aimed to investigate the utility of snail taxa for indicating environmental variation across these wetland habitats. Results showed that study wetlands divided into three major groups using multivariate analyses: the five wetlands provided the most protection and having the least impacts grouped as apparent “references”, and ten other wetlands in obviously developed areas separated into two other groups of wetlands. Overall snail abundance was higher in the reference wetlands than the impacted wetlands. Seven of the snail species were indicators of specific wetland types. Five pulmonate species including Segmentina nitida, Segmentina hemisphaerula, and Planorbis corneus, Aplexa hypnorum (Physidae), and Galba pervia (Lymnaeidae) were indicators of reference wetlands. Non-pulmonate Bithynia ussuriensis (Bithyniidae) and Valvata sibirica (Valvatidae) were indicators of one of the categories of impacted wetlands. In NE China, snail assemblages and certain indicator species may provide a robust and rapid indicator of environmental impacts on wetlands. Because snails are distributed widely and are generally easy to sample and identify, this overall approach should have applicability in the many wetlands worldwide where diverse snail assemblages naturally occur.