Freshwater ecosystem

There are three basic types of freshwater ecosystems: Lentic (slow moving water, including pools, ponds, and lakes), lotic (faster moving water, for example streams and rivers) and wetlands (areas where the soil is saturated or inundated for at least part of the time). Limnology (and its branch freshwater biology) is a study about freshwater ecosystems.

{{excerpt|Lentic ecosystem|paragraphs=1-3}}

{{excerpt|Lotic ecosystem|paragraphs=1-3}}

{{excerpt|Wetland|paragraphs=1-3}}

{{Further|Lake ecosystem#Human impacts|River ecosystem#Human impacts|Ecosystem#Human interactions with ecosystems}}

Five broad threats to freshwater biodiversity include overexploitation, water pollution, flow modification, destruction or degradation of habitat, and invasion by exotic species.{{Cite journal|last1=Dudgeon|first1=David|last2=Arthington|first2=Angela H.|last3=Gessner|first3=Mark O.|last4=Kawabata|first4=Zen-Ichiro|last5=Knowler|first5=Duncan J.|last6=Lévêque|first6=Christian|last7=Naiman|first7=Robert J.|last8=Prieur-Richard|first8=Anne-Hélène|last9=Soto|first9=Doris|date=2005-12-12|title=Freshwater biodiversity: importance, threats, status and conservation challenges|journal=Biological Reviews|volume=81|issue=2|pages=163–82|doi=10.1017/s1464793105006950|pmid=16336747|issn=1464-7931|citeseerx=10.1.1.568.4047|s2cid=15921269}} Recent extinction trends can be attributed largely to sedimentation, stream fragmentation, chemical and organic pollutants, dams, and invasive species. Common chemical stresses on freshwater ecosystem health include acidification, eutrophication and copper and pesticide contamination.{{Cite journal|last=Xu|first=F|date=September 2001|title=Lake Ecosystem Health Assessment: Indicators and Methods|journal=Water Research|volume=35|issue=13|pages=3157–3167|doi=10.1016/s0043-1354(01)00040-9|pmid=11487113|bibcode=2001WatRe..35.3157X|issn=0043-1354}}

Freshwater biodiversity faces many threats.{{Cite journal|last=Reid|first=AJ|display-authors=etal|date=2019|title=Emerging threats and persistent conservation challenges for freshwater biodiversity|journal=Biological Reviews|volume=94|issue=3|pages=849–873|doi=10.1111/brv.12480|pmid=30467930|doi-access=free}} The World Wide Fund for Nature's Living Planet Index noted an 83% decline in the populations of freshwater vertebrates between 1970 and 2014.{{Cite web|title=Living Planet Report 2018 {{!}} WWF|url=https://wwf.panda.org/knowledge_hub/all_publications/living_planet_report_2018/|access-date=2019-04-09|website=wwf.panda.org}} These declines continue to outpace contemporaneous declines in marine or terrestrial systems. The causes of these declines are related to:{{Cite web|last1=Reid|first1=Andrea Jane|last2=Cooke|first2=Steven J.|title=Freshwater wildlife face an uncertain future|url=http://theconversation.com/freshwater-wildlife-face-an-uncertain-future-108863|access-date=2019-04-09|website=The Conversation|date=22 January 2019 |language=en}}

1. A rapidly changing climate
2. Online wildlife trade and invasive species
3. Infectious disease
4. Toxic algae blooms
5. Hydropower damming and fragmenting of half the world's rivers
6. Emerging contaminants, such as hormones
7. Engineered nanomaterials
8. Microplastic pollution
9. Light and noise interference
10. Saltier coastal freshwaters due to sea level rise
11. Calcium concentrations falling below the needs of some freshwater organisms
12. The additive—and possibly synergistic—effects of these threats

Invasive plants and animals are a major issue to freshwater ecosystems,{{Cite journal |last1=Capps |first1=Krista |last2=Flecker |first2=Alexander |date=22 October 2013 |title=Invasive aquarium fish transform ecosystem nutrient dynamics |journal=Proceedings of the Royal Society B: Biological Sciences |volume=280 |issue=1769 |doi=10.1098/rspb.2013.1520 |pmid=23966642 |pmc=3768308 }} 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.{{Cite web |last=Station |first=Julia Hampton, Great Rivers Field |title=Asian carp species |url=https://blogs.illinois.edu/view/7362/966400817 |access-date=2024-04-15 |website=blogs.illinois.edu |language=en-US}} Common causes of invasive species in freshwater ecosystems include aquarium releases, introduction for sport fishing, and introduction for use as a food fish.{{Cite web |title=Northern snakehead fish |url=https://nationalzoo.si.edu/animals/northern-snakehead-fish |access-date=2024-04-15 |website=Smithsonian's National Zoo and Conservation Biology Institute |language=en}}

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.{{Cite journal|last1=Ricciardi|first1=Anthony|last2=Rasmussen|first2=Joseph B.|date=1999-10-23|title=Extinction Rates of North American Freshwater Fauna|journal=Conservation Biology|volume=13|issue=5|pages=1220–1222|doi=10.1046/j.1523-1739.1999.98380.x|bibcode=1999ConBi..13.1220R |s2cid=85338348 |issn=0888-8892}} 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). Even using conservative estimates, freshwater fish extinction rates in North America are 877 times higher than background extinction rates (1 in 3,000,000 years).{{Cite journal|last=Burkhead|first=Noel M.|date=September 2012|title=Extinction Rates in North American Freshwater Fishes, 1900–2010|journal=BioScience|volume=62|issue=9|pages=798–808|doi=10.1525/bio.2012.62.9.5|issn=1525-3244|doi-access=free|bibcode=2012BiSci..62..798B }} Projected extinction rates for freshwater animals are around five times greater than for land animals, and are comparable to the rates for rainforest communities. Given the dire state of freshwater biodiversity, a team of scientists and practitioners from around the globe recently drafted an Emergency Action plan to try and restore freshwater biodiversity. {{Cite journal|last1=Tickner|first1=David|last2=Opperman|first2=Jeffrey J|last3=Abell|first3=Robin|last4=Acreman|first4=Mike|last5=Arthington|first5=Angela H|last6=Bunn|first6=Stuart E|last7=Cooke|first7=Steven J|last8=Dalton|first8=James|last9=Darwall|first9=Will|last10=Edwards|first10=Gavin|last11=Harrison|first11=Ian|date=2020-04-01|title=Bending the Curve of Global Freshwater Biodiversity Loss: An Emergency Recovery Plan|url=https://doi.org/10.1093/biosci/biaa002|journal=BioScience|volume=70|issue=4|pages=330–342|doi=10.1093/biosci/biaa002|pmid=32284631 |issn=0006-3568|pmc=7138689}}

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. 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.{{Cite book|title=Freshwater biomonitoring and benthic macroinvertebrates, 40-158.|last1=Johnson|first1=R. K.|last2=Wiederholm|first2=T.|last3=Rosenberg|first3=D. M.|year=1993|pages=40–158}} 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.{{Citation|last1=Stevenson|first1=R. Jan|date=2003|pages=775–804|publisher=Elsevier|doi=10.1016/b978-012741550-5/50024-6|isbn=9780127415505|last2=Smol|first2=John P.|chapter=Use of Algae in Environmental Assessments|title=Freshwater Algae of North America}} Algae grow very quickly and communities may represent fast changes in environmental conditions.

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. Experimental results on single species under controlled conditions may not always reflect natural conditions and multi-species communities.

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. 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. These temporal reference conditions are often easier to reconstruct in standing water than moving water because stable sediments can better preserve biological indicator materials.

{{See also|Effects of climate change on the water cycle#Impacts on freshwater ecosystems}}

The effects of climate change greatly complicate and frequently exacerbate the impacts of other stressors that threaten many fish,{{Cite journal |last1=Arthington |first1=Angela H. |last2=Dulvy |first2=Nicholas K. |last3=Gladstone |first3=William |last4=Winfield |first4=Ian J. |date=2016 |title=Fish conservation in freshwater and marine realms: status, threats and management |journal=Aquatic Conservation: Marine and Freshwater Ecosystems |language=en |volume=26 |issue=5 |pages=838–857 |doi=10.1002/aqc.2712 |issn=1099-0755 |doi-access=free|bibcode=2016ACMFE..26..838A |hdl=10072/143075 |hdl-access=free }} invertebrates,{{Cite journal |last1=Prather |first1=Chelse M. |last2=Pelini |first2=Shannon L. |last3=Laws |first3=Angela |last4=Rivest |first4=Emily |last5=Woltz |first5=Megan |last6=Bloch |first6=Christopher P. |last7=Del Toro |first7=Israel |last8=Ho |first8=Chuan-Kai |last9=Kominoski |first9=John |last10=Newbold |first10=T. A. Scott |last11=Parsons |first11=Sheena |last12=Joern |first12=A. |date=2012 |title=Invertebrates, ecosystem services and climate change: Invertebrates, ecosystems and climate change |url=https://onlinelibrary.wiley.com/doi/10.1111/brv.12002 |journal=Biological Reviews |language=en |volume=88 |issue=2 |pages=327–348 |doi=10.1111/brv.12002|pmid=23217156 |s2cid=23578609 |url-access=subscription }} phytoplankton,{{Cite journal |last1=Winder |first1=Monika |last2=Sommer |first2=Ulrich |date=2012 |title=Phytoplankton response to a changing climate |url=http://link.springer.com/10.1007/s10750-012-1149-2 |journal=Hydrobiologia |language=en |volume=698 |issue=1 |pages=5–16 |doi=10.1007/s10750-012-1149-2 |bibcode=2012HyBio.698....5W |s2cid=16907349 |issn=0018-8158|url-access=subscription }} 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.

{{portal box|Ecology|Water}}

• Ecology
• Freshwater

{{Reflist}}

{{commonscat|Freshwater ecosystems}}

{{Aquatic ecosystem topics|expanded=freshwater}}

{{Aquatic organisms}}

{{Modelling ecosystems|expanded=none}}

Category:Freshwater ecology

Category:Ecosystems

Category:Limnology

Category:Fisheries science

Category:Systems ecology

Category:Water