Biodiversity Five broad threats to freshwater
biodiversity include
overexploitation,
water pollution, flow modification,
destruction or degradation of habitat, and invasion by
exotic species. Recent extinction trends can be attributed largely to sedimentation, stream fragmentation, chemical and organic pollutants, dams, and invasive species. Freshwater biodiversity faces many threats. The World Wide Fund for Nature's
Living Planet Index noted an 83% decline in the populations of freshwater vertebrates between 1970 and 2014. These declines continue to outpace contemporaneous declines in marine or terrestrial systems. The causes of these declines are related to: in many cases outcompeting native species and altering water conditions. Introduced species are especially devastating to ecosystems that are home to
endangered species. An example of this being the
Asian carp competing with the
paddlefish in the
Mississippi river. Common causes of invasive species in freshwater ecosystems include
aquarium releases, introduction for
sport fishing, and introduction for use as a food fish.
Extinction of freshwater fauna Over 123 freshwater fauna species have gone extinct in North America since 1900. Of North American freshwater species, an estimated 48.5% of mussels, 22.8% of
gastropods, 32.7% of crayfishes, 25.9% of amphibians, and 21.2% of fish are either endangered or threatened. Extinction rates of many species may increase severely into the next century because of invasive species, loss of keystone species, and species which are already functionally extinct (e.g., species which are not reproducing). Projected extinction rates for freshwater animals are around five times greater than for land animals, and are comparable to the rates for rainforest communities. Current freshwater biomonitoring techniques focus primarily on community structure, but some programs measure functional indicators like biochemical (or biological) oxygen demand, sediment oxygen demand, and dissolved oxygen. Additionally, algal community structure (often using diatoms) is measured in biomonitoring programs. Algae are also taxonomically diverse, easily collected, sensitive to a range of stressors, and overall valuable to the ecosystem. Algae grow very quickly and communities may represent fast changes in environmental conditions. invertebrates, phytoplankton, and other organisms. Climate change is increasing the average temperature of water bodies, and worsening other issues such as changes in
substrate composition, oxygen concentration, and other system changes that have ripple effects on the biology of the system. Water temperatures have already increased by around 1 °C, and significant declines in ice coverage have caused subsequent ecosystem stresses. ==See also==