Freshwater ecosystem
Freshwater ecosystems are a subset of Earth's
Freshwater ecosystems have undergone substantial transformations over time, which has impacted various characteristics of the ecosystems.
Threats to freshwater biodiversity include overexploitation, water pollution, flow modification, destruction or degradation of habitat, and invasion by exotic species.[7] Climate change is putting further pressure on these ecosystems because water temperatures have already increased by about 1 °C, and there have been significant declines in ice coverage which have caused subsequent ecosystem stresses.[8]
Types
There are three basic types of freshwater ecosystems:
Lentic ecosystems
A
. Together, these two ecosystems are examples of freshwater ecosystems. Lentic systems are diverse, ranging from a small, temporary rainwater pool a few inches deep toLotic ecosystems
The food base of streams within riparian forests is mostly derived from the trees, but wider streams and those that lack a
Wetlands
A
Wetlands occur naturally on every
(although reed swamps in Europe are dominated by reeds, not trees). Besides being prominent and abundant modern environments and ecosystems, wetlands were also very common throughout Earth history and many sedimentary rock units have been interpreted as representing the geological record of ancient freshwater[21] or coastal wetlands.[22]Threats
Biodiversity
Five broad threats to freshwater biodiversity include overexploitation, water pollution, flow modification, destruction or degradation of habitat, and invasion by exotic species.[7] Recent extinction trends can be attributed largely to sedimentation, stream fragmentation, chemical and organic pollutants, dams, and invasive species.[23] Common chemical stresses on freshwater ecosystem health include acidification, eutrophication and copper and pesticide contamination.[24]
Freshwater biodiversity faces many threats.[25] The World Wide Fund for Nature's Living Planet Index noted an 83% decline in the populations of freshwater vertebrates between 1970 and 2014.[26] These declines continue to outpace contemporaneous declines in marine or terrestrial systems. The causes of these declines are related to:[27][25]
- A rapidly changing climate
- Online wildlife trade and invasive species
- Infectious disease
- Toxic algae blooms
- Hydropower damming and fragmenting of half the world's rivers
- Emerging contaminants, such as hormones
- Engineered nanomaterials
- Microplastic pollution
- Light and noise interference
- Saltier coastal freshwaters due to sea level rise
- Calcium concentrations falling below the needs of some freshwater organisms
- The additive—and possibly synergistic—effects of these threats
Invasive species
Invasive plants and animals are a major issue to freshwater ecosystems,[28] 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.[29] Common causes of invasive species in freshwater ecosystems include aquarium releases, introduction for sport fishing, and introduction for use as a food fish.[30]
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
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.[6] Macroinvertebrate community structure is commonly monitored because of the diverse taxonomy, ease of collection, sensitivity to a range of stressors, and overall value to the ecosystem.[33] 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.[34] Algae grow very quickly and communities may represent fast changes in environmental conditions.[34]
In addition to community structure, responses to freshwater stressors are investigated by experimental studies that measure organism behavioural changes, altered rates of growth, reproduction or mortality.[6] Experimental results on single species under controlled conditions may not always reflect natural conditions and multi-species communities.[6]
The use of reference sites is common when defining the idealized "health" of a freshwater ecosystem. Reference sites can be selected spatially by choosing sites with minimal impacts from human disturbance and influence.[6] However, reference conditions may also be established temporally by using preserved indicators such as diatom valves, macrophyte pollen, insect chitin and fish scales can be used to determine conditions prior to large scale human disturbance.[6] These temporal reference conditions are often easier to reconstruct in standing water than moving water because stable sediments can better preserve biological indicator materials.
Climate change
The effects of climate change greatly complicate and frequently exacerbate the impacts of other stressors that threaten many fish,[35] invertebrates,[36] phytoplankton,[37] 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.[8] Water temperatures have already increased by around 1 °C, and significant declines in ice coverage have caused subsequent ecosystem stresses.[8]
See also
- Ecology
- Freshwater
References
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- ^ "Living Planet Report 2018 | WWF". wwf.panda.org. Retrieved 2019-04-09.
- ^ Reid, Andrea Jane; Cooke, Steven J. (22 January 2019). "Freshwater wildlife face an uncertain future". The Conversation. Retrieved 2019-04-09.
- ^ Capps, Krista; Flecker, Alexander (22 October 2013). "Invasive aquarium fish transform ecosystem nutrient dynamics". National Library of Medicine.
- ^ Station, Julia Hampton, Great Rivers Field. "Asian carp species". blogs.illinois.edu. Retrieved 2024-04-15.
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