Endangered Freshwater Invertebrates David L Strayer, Cary Institute of Ecosystem Studies, Millbrook, NY, USA r 2013 Elsevier Inc All rights reserved Glossary Aquifer A geological formation that contains and allows movement of ground water Endangered species A species that is at substantial risk of extinction as a result of human activities Endemic species A species that occurs only over a limited geographical range Eutrophication The process of increasing the productivity of an ecosystem by enriching it with nutrients The Earth’s fresh waters contain an impressive diversity of invertebrate life More than 100,000 species of have already been described, and tens of thousands of species remain to be discovered and described by scientists This diversity is not spread evenly over the surface of the globe, but concentrated in local ‘‘hot spots,’’ usually ancient lakes, streams, or ground waters These ‘‘hot spots’’ often contain dozens to hundreds of species of freshwater invertebrates that are found nowhere else in the world Because fresh waters are such an important resource for people, and have been used intensively for water supply, power, irrigation, fisheries, navigation, waste disposal, and as sites for cities, environmental conditions in many of the world’s fresh waters have been altered greatly from their original states Especially where ‘‘hot spots’’ of diversity coincide with areas of intensive human development, many freshwater invertebrates have disappeared from their native habitats Some invertebrate species already have become extinct, and thousands more are in danger of disappearing from the Earth Careful management of fresh waters, especially in ‘‘hot spots’’ of high biological diversity, is needed to prevent catastrophic extinctions of freshwater invertebrates in the next century Ground water Water that occurs in saturated soils and geological formations beneath the Earth’s surface Nonnative species A species that has been moved and established outside of its native range as a result of human activities; also called alien species, exotic species, introduced species, nonindigenous species habitats; lakes, rivers, brooks, ephemeral ponds, wetlands, caves, alluvial ground waters, and even hot springs each contain a rich and characteristic invertebrate community Among important freshwater habitats, perhaps only the deepest ground waters usually lack invertebrates A typical lake or stream contains a few hundred species of invertebrates representing several dozen families and eight to 12 phyla By comparison with the better-known vertebrates, freshwater invertebrates possess a wide range of biological traits Life spans range from days to more than a century Many invertebrates reproduce sexually, while others reproduce asexually by budding or parthenogenesis, or change their sexuality or mode of reproduction depending on environmental conditions Some invertebrates produce eggs or other reproductive bodies that remain viable for years to centuries Freshwater invertebrates include herbivores, bacteriovores, fungivores, predators, and parasites, and exhibit a wide range of specialized morphologies and behaviors to aid in food-gathering Some even use symbiotic algae to photosynthesize! Table NatureServe’s system for ranking global conservation status of species Introduction GX Freshwater Invertebrates of the World GH Over 100,000 species of freshwater invertebrates have been described, representing about 750 families and 15 phyla (Balian et al., 2008) The world’s freshwater invertebrate fauna is actually much larger than this; probably 10,000–100,000 species await discovery, and new genera and families are discovered regularly We are particularly ignorant about what lives in ground waters, what lives outside of Europe and parts of North America, and small, soft-bodied invertebrates The most widespread and species-rich groups of freshwater invertebrates are the insects, crustaceans, mollusks, mites, nematodes, and rotifers, but many other groups are common as well Invertebrates live in nearly all kinds of freshwater 176 G1 G2 G3 G4 G5 Presumed extinct: not located despite intensive searches and virtually no likelihood of rediscovery Possibly extinct: known only from historical occurrences but still some hope of rediscovery Critically imperiled: at very high risk of extinction due to extreme rarity (often five or fewer populations) very steep declines, or other factors Imperiled: at high risk of extinction or elimination due to very restricted range, very few populations, steep declines, or other factors Vulnerable: at moderate risk of extinction due to a restricted range, relatively few populations, recent and widespread declines, or other factors Apparently secure: uncommon but not rare; some cause for long-term concern due to declines or other factors Secure: common; widespread and abundant Encyclopedia of Biodiversity, Volume http://dx.doi.org/10.1016/B978-0-12-384719-5.00270-7