Effects of lowhead dams on aquatic gastropods

摘要

Freshwater gastropods are a diverse group of invertebrates that are vital components of stream ecosystems. Not only does their sensitivity to stream disturbances make them good biological indicators of stream integrity, but they also occupy a central position in food webs by grazing on periphyton and providing a food source for predators (e.g., fishes, turtles, and birds). They constitute a high percentage of the biomass in many habitats, making them critically important in ecosystem and community dynamics. Aquatic gastropods are, however, among the most rapidly declining groups of organisms on Earth, and have become one of the most imperiled groups of organisms in North America. Nearly 75% of the approximately 700 species have become extinct or are endangered, threatened, or in need of conservation status. Among factors affecting the group are anthropogenic disturbances that result in habitat destruction and fragmentation. Impoundments are one of the major sources of anthropogenic disturbances on streams by affecting both the physical and chemical conditions of streams.