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A pond is a small, still, land-based body of water formed by pooling inside a depression, either natural or artificial, that is smaller than a lake.^[1] Defining them to be less than 5 hectares (12 acres) in area, less than 5 meters (16 ft) deep, and with less than 30% emergent vegetation helps in distinguishing their ecology from that of lakes and wetlands.^[2]^[3]^: 460 Ponds can be created by a wide variety of natural processes (e.g. on floodplains as cutoff river channels, by glacial processes, by peatland formation, in coastal dune systems, by beavers), or they can simply be isolated depressions (such as a kettle hole, vernal pool, prairie pothole, or simply natural undulations in undrained land) filled by runoff, groundwater, or precipitation, or all three of these.^[4] They can be further divided into four zones: vegetation zone, open water, bottom mud and surface film.^[3]^{: 160–163} The size and depth of ponds often varies greatly with the time of year; many ponds are produced by spring flooding from rivers. Ponds may be freshwater or brackish in nature. 'Ponds' with saltwater, with a direct connection to the sea that maintains full salinity, would normally be regarded as part of the marine environment because they would not support fresh or brackish water organisms, so not really within the realm of freshwater science.

Ponds are usually by definition quite shallow water bodies with varying abundances of aquatic plants and animals. Depth, seasonal water level variations, nutrients fluxes, amount of light reaching the ponds, the shape, the presence of visiting large mammals, the composition of any fish communities and salinity can all affect the types of plant and animal communities present.^[5] Food webs are based both on free-floating algae and upon aquatic plants. There is usually a diverse array of aquatic life, with a few examples including algae, snails, fish, beetles, water bugs, frogs, turtles, otters and muskrats. Top predators may include large fish, herons, or alligators. Since fish are a major predator upon amphibian larvae, ponds that dry up each year, thereby killing resident fish, provide important refugia for amphibian breeding.^[5] Ponds that dry up completely each year are often known as vernal pools. Some ponds are produced by animal activity, including alligator holes and beaver ponds, and these add important diversity to landscapes.^[5]

Ponds are frequently manmade or expanded beyond their original depths and bounds by anthropogenic causes. Apart from their role as highly biodiverse, fundamentally natural, freshwater ecosystems ponds have had, and still have, many uses, including providing water for agriculture, livestock and communities, aiding in habitat restoration, serving as breeding grounds for local and migrating species, decorative components of landscape architecture, flood control basins, general urbanization, interception basins for pollutants and sources and sinks of greenhouse gases.

Classification

The technical distinction between a pond and a lake has not been universally standardized. Limnologists and freshwater biologists have proposed formal definitions for pond, in part to include 'bodies of water where light penetrates to the bottom of the waterbody,' 'bodies of water shallow enough for rooted water plants to grow throughout,' and 'bodies of water which lack wave action on the shoreline.' Each of these definitions are difficult to measure or verify in practice and are of limited practical use, and are mostly not now used. Accordingly, some organizations and researchers have settled on technical definitions of pond and lake that rely on size alone.^[6]

Some regions of the United States define a pond as a body of water with a surface area of less than 10 acres (4.0 ha). Minnesota, known as the "land of 10,000 lakes", is commonly said to distinguish lakes from ponds, bogs and other water features by this definition,^[7] but also says that a lake is distinguished primarily by wave action reaching the shore.^[8] Even among organizations and researchers who distinguish lakes from ponds by size alone, there is no universally recognized standard for the maximum size of a pond. The international Ramsar wetland convention sets the upper limit for pond size as 8 hectares (80,000 m²; 20 acres).^[9] Researchers for the British charity Pond Conservation (now called Freshwater Habitats Trust) have defined a pond to be 'a man-made or natural waterbody that is between 1 m²(0.00010 hectares; 0.00025 acres) and 20,000 m² (2.0 hectares; 4.9 acres) in area, which holds water for four months of the year or more.' Other European biologists have set the upper size limit at 5 hectares (50,000 m²; 12 acres).^[10]

In North America, even larger bodies of water have been called ponds; for example, Crystal Lake at 33 acres (130,000 m²; 13 ha), Walden Pond in Concord, Massachusetts at 61 acres (250,000 m²; 25 ha), and nearby Spot Pond at 340 acres (140 ha). There are numerous examples in other states, where bodies of water less than 10 acres (40,000 m²; 4.0 ha) are being called lakes. As the case of Crystal Lake shows, marketing purposes can sometimes be the driving factor behind the categorization.^[11]

In practice, a body of water is called a pond or a lake on an individual basis, as conventions change from place to place and over time. In origin, a pond is a variant form of the word pound, meaning a confining enclosure.^[12] In earlier times, ponds were artificial and utilitarian, as stew ponds, mill ponds and so on. The significance of this feature seems, in some cases, to have been lost when the word was carried abroad with emigrants. However, some parts of New England contain "ponds" that are actually the size of a small lake when compared to other countries. In the United States, natural pools are often called ponds. Ponds for a specific purpose keep the adjective, such as "stock pond", used for watering livestock. The term is also used for temporary accumulation of water from surface runoff (ponded water).

There are various regional names for naturally occurring ponds. In Scotland, one of the terms is lochan, which may also apply to a large body of water such as a lake. In the South Western parts of North American, lakes or ponds that are temporary and often dried up for most parts of the year are called playas.^[13] These playas are simply shallow depressions in dry areas that may only fill with water on certain occasion like excess local drainage, groundwater seeping, or rain.

Formation

Any depression in the ground which collects and retains a sufficient amount of water can be considered a pond, and such, can be formed by a variety of geological, ecological, and human terraforming events.

Natural ponds are those caused by environmental occurrences. These can vary from glacial, volcanic, fluvial, or even tectonic events. Since the Pleistocene epoch, glacial processes have created most of the Northern hemispheric ponds; an example is the Prairie Pothole Region of North America.^[14]^[15] When glaciers retreat, they may leave behind uneven ground due to bedrock elastic rebound and sediment outwash plains.^[16] These areas may develop depressions that can fill up with excess precipitation or seeping ground water, forming a small pond. Kettle lakes and ponds are formed when ice breaks off from a larger glacier, is eventually buried by the surrounding glacial till, and over time melts.^[17] Orogenies and other tectonic uplifting events have created some of the oldest lakes and ponds on the globe. These indentions have the tendency to quickly fill with groundwater if they occur below the local water table. Other tectonic rifts or depressions can fill with precipitation, local mountain runoff, or be fed by mountain streams.^[18] Volcanic activity can also lead to lake and pond formation through collapsed lava tubes or volcanic cones. Natural floodplains along rivers, as well as landscapes that contain many depressions, may experience spring/rainy season flooding and snow melt. Temporary or vernal ponds are created this way and are important for breeding fish, insects, and amphibians, particularly in large river systems like the Amazon.^[19] Some ponds are solely created by animals species such as beavers, bison, alligators and other crocodilians through damning and nest excavation respectively.^[20]^[21] In landscapes with organic soils, local fires can create depressions during periods of drought. These have the tendency to fill up with small amounts of precipitation until normal water levels return, turning these isolated ponds into open water.^[22]

Manmade ponds are those created by human intervention for the sake of the local environment, industrial settings, or for recreational/ornamental use.

Uses

Many ecosystems are linked by water and ponds have been found to hold a greater biodiversity of species than larger freshwater lakes or river systems.^[23] As such, ponds are habitats for many varieties of organisms including plants, amphibians, fish, reptiles, waterfowl, insects and even some mammals. Ponds are used for breeding grounds for these species but also as shelter and even drinking/feeding locations for other wildlife.^[24]^[25] Aquaculture practices lean heavily on artificial ponds in order to grow and care for many different type of fish either for human consumption, research, species conservation or recreational sport.

In agriculture practices, treatment ponds can be created to reduce nutrient runoff from reaching local streams or groundwater storages. Pollutants that enter ponds can often be mitigated by natural sedimentation and other biological and chemical activities within the water. As such, waste stabilization ponds are becoming popular low-cost methods for general wastewater treatment. They may also provide irrigation reservoirs for struggling farms during times of drought.

As urbanization continues to spread, retention ponds are becoming more common in new housing developments. These ponds reduce the risk of flooding and erosion damage from excess storm water runoff in local communities.^[26]

Experimental ponds are used to test hypotheses in the fields of environmental science, chemistry, aquatic biology, and limnology.^[27]

Some ponds are the life blood of many small villages in arid countries such as those in sub-Saharan Africa where bathing, sanitation, fishing, socialization, and rituals are held.^[28] In the Indian subcontinent, Hindu temple monks care for sacred ponds used for religious practices and bathing pilgrims alike.^[29] In Europe during medieval times, it was typical for many monastery and castles (small, partly self-sufficient communities) to have fish ponds. These are still common in Europe and in East Asia (notably Japan), where koi may be kept or raised.

In Nepal artificial ponds were essential elements of the ancient drinking water supply system. These ponds were fed with rainwater, water coming in through canals, their own springs, or a combination of these sources. They were designed to retain the water, while at the same time letting some water seep away to feed the local aquifers.^[30]

Pond biodiversity

A defining feature of a pond is the presence of standing water which provides habitat for a biological community commonly referred to as pond life. Because of this, many ponds and lakes contain large numbers of endemic species that have gone through adaptive radiation to become specialized to their preferred habitat.^[18] Familiar examples might include water lilies and other aquatic plants, frogs, turtles, and fish.

Often, the entire margin of the pond is fringed by wetland, and these wetlands support the aquatic food web, provide shelter for wildlife, and stabilize the shore of the pond. This margin is also known as the littoral zone and contains much of the photosynthetic algae and plants of this ecosystem called macrophytes. Other photosynthetic organisms such as phytoplankton (suspended algae) and periphytons (organisms including cyanobacteria, detritus, and other microbes) thrive here and stand as the primary producers of pond food webs.^[18] Some grazing animals like geese and muskrats consume the wetland plants directly as a source of food. In many other cases, pond plants will decay in the water. Many invertebrates and herbivorous zooplankton then feed on the decaying plants, and these lower trophic level organisms provide food for wetland species including fish, dragonflies, and herons both in the littoral zone and the limnetic zone.^[18] The open water limnetic zone may allow algae to grow as sunlight still penetrates here. These algae may support yet another food web that includes aquatic insects and other small fish species. A pond, therefore, may have combinations of three different food webs, one based on larger plants, one based upon decayed plants, and one based upon algae and their specific upper trophic level consumers and predators.^[18] Hence, ponds often have many different animal species using the wide array of food sources though biotic interaction. They, therefore, provide an important source of biological diversity in landscapes.

Opposite to long standing ponds are vernal ponds. These ponds dry up for part of the year and are so called because they are typically at their peak depth in the spring (the meaning of "vernal" comes form the Latin word for spring). Naturally occurring vernal ponds do not usually have fish, a major higher tropic level consumer, as these ponds frequently dry up. The absence of fish is a very important characteristic of these ponds since it prevents long chained biotic interactions from establishing. Ponds without these competitive predation pressures provides breeding locations and safe havens for endangered or migrating species. Hence, introducing fish to a pond can have seriously detrimental consequences. In some parts of the world, such as California, the vernal ponds have rare and endangered plant species. On the coastal plain, they provide habitat for endangered frogs such as the Mississippi Gopher Frog.^[20]

Often groups of ponds in a given landscape - so called 'pondscapes' - offer especially high biodiversity benefits compared to single ponds. A group of ponds provides a higher degree of habitat complexity and habitat connectivity.^[31]^[32]

Stratification

Many ponds undergo a regular yearly process in the same matter as larger lakes if they are deep enough and/or protected from the wind. Abiotic factors such as UV radiation, general temperature, wind speed, water density, and even size, all have important roles to play when it comes to the seasonal effects on lakes and ponds.^[33] Spring overturn, summer stratification, autumn turnover, and an inverse winter stratification, ponds adjust their stratification or their vertical zonation of temperature due to these influences. These environmental factors affect pond circulation and temperature gradients within the water itself producing distant layers; the epilimnion, metalimnion, and hypolimnion.^[18]

Each zone has varied traits that sustain or harm specific organisms and biotic interactions below the surface depending on the season. Winter surface ice begins to melt in the Spring. This allows the water column to begin mixing thanks to solar convection and wind velocity. As the pond mixes, an overall constant temperature is reached. As temperatures increase through the summer, thermal stratification takes place. Summer stratification allows for the epilimnion to be mixed by winds, keeping a consistent warm temperature throughout this zone. Here, photosynthesis and primary production flourishes. However, those species that need cooler water with higher dissolved oxygen concentrations will favor the lower metalimnion or hypolimnion. Air temperature drops as fall approaches and a deep mixing layer occurs. Autumn turnover results in isothermal lakes with high levels of dissolved oxygen as the water reaches an average colder temperature. Finally, winter stratification occurs inversely to summer stratification as surface ice begins to form yet again. This ice cover remains until solar radiation and convection return in the spring.

Due to this constant change in vertical zonation, seasonal stratification causes habitats to grow and shrink accordingly. Certain species are bound to these distinct layers of the water column where they can thrive and survive with the best efficiency possible.

For more information regarding seasonal thermal stratification of ponds and lakes, please look at "Lake Stratification".

Conservation and management

Ponds provide not only environmental values, but practical benefits to society. One increasingly crucial benefit that ponds provide is their ability to act as greenhouse gas sinks. Most natural lakes and ponds are greenhouse gas sources and aid in the flux of these dissolved compounds. However, manmade farm ponds are becoming significant sinks for gas mitigation and the fight against climate change.^[34] These agriculture runoff ponds receive high pH level water from surrounding soils. Highly acidic drainage ponds act as catalysis for excess CO₂ (carbon dioxide) to be converted into forms of carbon that can easily be stored in sediments.^[35] When these new drainage ponds are constructed, concentrations of bacteria that normally break down dead organic matter, such as algae, are low. As a result, breakdown and release of nitrogen gases from these organic materials such as N₂O does not occur and thus, not added to our atmosphere.^[36] This process is also used with regular denitrification in anoxic layer of ponds. However, not all ponds have the ability to become sinks for greenhouse gasses. Most ponds experience eutrophication where faced with excessive nutrient input from fertilizers and runoff. This over-nitrifies the pond water and results in mass algae blooms and local fish kills.

Some farm ponds are not used for runoff control but rather for livestock like cattle or buffalo as watering and bathing holes. As mentioned in the use section, ponds are important hotspots for biodiversity. Sometimes this becomes an issue with invasive or introduced species that disrupt pond ecosystem dynamics such as food-web structure, niche partitioning, and guild assignments.^[37] This varies from introduced fish species such as the Common Carp that eat native water plants or Northern Snakeheads that attack breeding amphibians, aquatic snails that carry infectious parasites that kill other species, and even rapid spreading aquatic plants like Hydrilla and Duckweed that can restrict water flow and cause overbank flooding.^[37]

Ponds, depending on their orientation and size, can spread their wetland habitats into the local riparian zones or watershed boundaries. Gentle slopes of land into ponds provides an expanse of habitat for wetland plants and wet meadows to expand beyond the limitation of the pond.^[38] However, the construction of retaining walls, lawns, and other urbanized developments can severely degrade the range of pond habitats and the longevity of the pond itself. Roads and highways act in the same manor, but they also interfere with amphibians and turtles that migrate to and from ponds as part of their annual breeding cycle and should be kept as far away from established ponds as possible.^[39] Because of these factors, gently sloping shorelines with broad expanses of wetland plants not only provide the best conditions for wildlife, but they help protect water quality from sources in the surrounding landscapes. It is also beneficial to allow water levels to fall each year during drier periods in order to re-establish these gentile shorelines.^[39]

In landscapes where ponds are artificially constructed, they are done so to provide wildlife viewing and conservation opportunities, to treat wastewater, for sequestration and pollution containment, or for simply aesthetic purposes. For natural pond conservation and development, one way to stimulate this is with general stream and river restoration. Many small rivers and streams feed into or from local ponds within the same watershed. When these rivers and streams flood and begin to meander, large numbers of natural ponds, including vernal pools and wetlands, develop.^[40]

Examples

Some notable ponds are:

Big Pond, Nova Scotia, Canada
Christian Pond, Wyoming, United States
Walden Pond, Massachusetts, United States, associated with Henry David Thoreau
Hampstead Ponds, London
Kuttam Pokuna, Medieval artificial pond in Anuradhapura, Sri Lanka
Rani Pokhari, 17th-century artificial pond in Kathmandu, Nepal
Rožmberk Pond, Czech Republic

References

^ STANLEY, E. G. (1 June 1975). "The Merriam-Webster Dictionary – The Oxford Illustrated Dictionary". Notes and Queries. 22 (6): 242–243. doi:10.1093/nq/22-6-242. ISSN 1471-6941.
^ "A functional definition to distinguish ponds from lakes and wetlands". Scientific Reports. 12 (1): 10472. 2022. Bibcode:2022NatSR..1210472R. doi:10.1038/s41598-022-14569-0. PMC 9213426. PMID 35729265. {{cite journal}}: Unknown parameter |authors= ignored (help)
^ ^a ^b Clegg, J. (1986). Observer's Book of Pond Life. Frederick Warne, London
^ Clegg, John, 1909-1998. (1986). The new observer's book of pond life (4th ed.). Harmondsworth: Frederick Warne. ISBN 0-7232-3338-1. OCLC 15197655.{{cite book}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
^ ^a ^b ^c Keddy, Paul A. (2010). Wetland ecology : principles and conservation (2nd ed.). Cambridge: Cambridge University Press. ISBN 978-1-139-22365-2. OCLC 801405617.
^ Biggs, Jeremy; Williams, Penny; Whitfield, Mericia; Nicolet, Pascale; Weatherby, Anita (2005). "15 years of pond assessment in Britain: results and lessons learned from the work of Pond Conservation". Aquatic Conservation: Marine and Freshwater Ecosystems. 15 (6): 693–714. doi:10.1002/aqc.745. ISSN 1052-7613.
^ Hartman, Travis; Tyson, Jeff; Page, Kevin; Stott, Wendylee (2019). "Evaluation of potential sources of sauger Sander canadensis for reintroduction into Lake Erie". Journal of Great Lakes Research. 45 (6): 1299–1309. doi:10.1016/j.jglr.2019.09.027. ISSN 0380-1330. S2CID 209565712.
^ Adamson, David; Newell, Charles (1 February 2014). "Frequently Asked Questions about Monitored Natural Attenuation in Groundwater". Fort Belvoir, VA. doi:10.21236/ada627131. {{cite journal}}: Cite journal requires |journal= (help)
^ Karki, Jhamak B (1 January 1970). "Koshi Tappu Ramsar Site: Updates on Ramsar Information Sheet on Wetlands". The Initiation. 2 (1): 10–16. doi:10.3126/init.v2i1.2513. ISSN 2091-0088.
^ Céréghino, R.; Biggs, J.; Oertli, B.; Declerck, S. (2008). "The ecology of European ponds: defining the characteristics of a neglected freshwater habitat". Hydrobiologia. 597 (1): 1–6. doi:10.1007/s10750-007-9225-8. ISSN 0018-8158. S2CID 30857970.
^ "Newton of Braintree, Baron, (Antony Harold Newton) (1937–25 March 2012)", Who Was Who, Oxford University Press, 1 December 2007, doi:10.1093/ww/9780199540884.013.u29423, retrieved 16 November 2020
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^ Davis, Craig A.; Smith, Loren M.; Conway, Warren C. (2005). "Lipid Reserves of Migrant Shorebirds During Spring in Playas of the Southern Great Plains". The Condor. 107 (2): 457. doi:10.1650/7584. ISSN 0010-5422. S2CID 85609044.
^ Brönmark, Christer; Hansson, Lars-Anders (21 December 2017). "The Biology of Lakes and Ponds". Oxford Scholarship Online. Biology of Habitats Series. doi:10.1093/oso/9780198713593.001.0001. ISBN 978-0-19-871359-3.
^ Northern prairie wetlands. Valk, Arnoud van der., National Wetlands Technical Council (U.S.) (1st ed.). Ames: Iowa State University. 1989. ISBN 0-8138-0037-4. OCLC 17842267.{{cite book}}: CS1 maint: others (link)
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^ ^a ^b ^c ^d ^e ^f Johnson, Pieter T. J.; Preston, Daniel L.; Hoverman, Jason T.; Richgels, Katherine L. D. (2013). "Biodiversity decreases disease through predictable changes in host community competence". Nature. 494 (7436): 230–233. Bibcode:2013Natur.494..230J. doi:10.1038/nature11883. ISSN 0028-0836. PMID 23407539. S2CID 205232648.
^ Bagenal, T. B.; Lowe-McConnell, R. H. (1976). "Fish Communities in Tropical Freshwaters: Their Distribution, Ecology and Evolution". The Journal of Animal Ecology. 45 (2): 616. doi:10.2307/3911. ISSN 0021-8790. JSTOR 3911.
^ ^a ^b Keddy, Paul A. (2010), "Conservation and management", Wetland Ecology, Cambridge: Cambridge University Press, pp. 390–426, doi:10.1017/cbo9780511778179.016, ISBN 978-0-511-77817-9, retrieved 16 November 2020
^ Cutko, Andrew; Rawinski, Thomas (13 August 2007), "Flora of Northeastern Vernal Pools", Science and Conservation of Vernal Pools in Northeastern North America, CRC Press, pp. 71–104, doi:10.1201/9781420005394.sec2, ISBN 978-0-8493-3675-1, retrieved 16 November 2020
^ "Toward Ecosystem Restoration", Everglades, CRC Press, pp. 797–824, 1 January 1994, doi:10.1201/9781466571754-41, ISBN 978-0-429-10199-1, retrieved 16 November 2020
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^ "Why are ponds important?". Ghost Ponds : Resurrecting lost ponds and species to assist aquatic biodiversity conservation. 30 December 2013. Retrieved 16 November 2020.
^ "Why Ponds are Important to the Environment (How you can help)". Pond Informer. 31 December 2018. Retrieved 16 November 2020.
^ Birx-Raybuck, Devynn A.; Price, Steven J.; Dorcas, Michael E. (21 November 2009). "Pond age and riparian zone proximity influence anuran occupancy of urban retention ponds". Urban Ecosystems. 13 (2): 181–190. doi:10.1007/s11252-009-0116-9. ISSN 1083-8155. S2CID 3118057.
^ "Water Chemistry Testing". www.ponds.org. Retrieved 16 November 2020.
^ Zongo, Bilassé; Zongo, Frédéric; Toguyeni, Aboubacar; Boussim, Joseph I. (1 February 2017). "Water quality in forest and village ponds in Burkina Faso (western Africa)". Journal of Forestry Research. 28 (5): 1039–1048. doi:10.1007/s11676-017-0369-8. ISSN 1007-662X. S2CID 42654869.
^ "Regional Perspectives : Local Traditions", Continuum Companion to Hindu Studies, Bloomsbury Academic, 2011, doi:10.5040/9781472549419.ch-006, ISBN 978-1-4411-0334-5, retrieved 16 November 2020
^ Traditional Ponds – The Water Urban-ism of Newar Civilization Archived 2021-03-22 at the Wayback Machine by Padma Sunder Joshi, Spaces Nepal, April 2018, retrieved 11 October 2019
^ Boothby, John (1999). "Framing a Strategy for Pond Landscape Conservation: aims, objectives and issues". Landscape Research. 24:1: 67–83. doi:10.1080/01426399908706551 – via Taylor & Francis Online.
^ Hill, Matthew J.; et al. (2018). "New policy directions for global pond conservation". Conservation Letters. 11 (5): e12447. doi:10.1111/conl.12447. S2CID 55293639 – via Wiley.
^ Encyclopedia of inland waters. Likens, Gene E., 1935-. [Amsterdam]. 19 March 2009. ISBN 978-0-12-370626-3. OCLC 351296306.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: others (link)
^ Ridgwell, A.; Edwards, U. (2007), "Geological carbon sinks.", Greenhouse gas sinks, Wallingford: CABI, pp. 74–97, CiteSeerX 10.1.1.371.7116, doi:10.1079/9781845931896.0074, ISBN 978-1-84593-189-6, retrieved 16 November 2020
^ Reay, D. S.; Grace, J. (2007), "Carbon dioxide: importance, sources and sinks.", Greenhouse gas sinks, Wallingford: CABI, pp. 1–10, doi:10.1079/9781845931896.0001, ISBN 978-1-84593-189-6, retrieved 16 November 2020
^ Burke, Ty (21 May 2019). "Farm Ponds Sequester Greenhouse Gases". Eos. 100. doi:10.1029/2019EO124083. ISSN 2324-9250.
^ ^a ^b Radosevich, Steven R. (2007). Ecology of weeds and invasive plants : relationship to agriculture and natural resource management. Holt, Jodie S., Ghersa, Claudio., Radosevich, Steven R. (3rd ed.). Hoboken, N.J.: Wiley-Interscience. ISBN 978-0-470-16894-3. OCLC 181348071.
^ Genet, John A.; Olsen, Anthony R. (2008). "Assessing depressional wetland quantity and quality using a probabilistic sampling design in the Redwood River watershed, Minnesota, USA". Wetlands. 28 (2): 324–335. doi:10.1672/06-150.1. ISSN 0277-5212. S2CID 29365811.
^ ^a ^b Dufour, Simon; Piégay, Hervé (2005), "Restoring Floodplain Forests", Forest Restoration in Landscapes, New York: Springer-Verlag, pp. 306–312, doi:10.1007/0-387-29112-1_44, ISBN 0-387-25525-7, retrieved 16 November 2020
^ Geist, Juergen; Hawkins, Stephen J. (31 August 2016). "Habitat recovery and restoration in aquatic ecosystems: current progress and future challenges". Aquatic Conservation: Marine and Freshwater Ecosystems. 26 (5): 942–962. doi:10.1002/aqc.2702. ISSN 1052-7613.

@@ Line 6: / Line 6: @@
 {{Use dmy dates|date=July 2017}}[[File:Early_Pond.jpg|thumb|A man made pond at sunset in Montgomery County, Ohio.]]
 [[File:Central City Park, pond, circa 1877 - DPLA - cc8aa37aab5110ef47c1df80638969a5.jpeg|thumb|Stereoscopic image of a pond in Central City Park, Macon, GA, circa 1877.]]
-A '''pond''' is a small, still-flowing, land-based [[body of water]] formed by pooling inside a [[depression (geology)|depression]], either natural or [[artificiality|artificial]], that is smaller than a [[lake]].<ref>{{Cite journal|last=STANLEY|first=E. G.|date=1975-06-01|title=The Merriam-Webster Dictionary – The Oxford Illustrated Dictionary|url=http://dx.doi.org/10.1093/nq/22-6-242|journal=Notes and Queries|volume=22|issue=6|pages=242–243|doi=10.1093/nq/22-6-242|issn=1471-6941|via=}}</ref> Defining them to be less than {{Convert|5|hectare|acre}} in area, less than {{Convert|5|meter|feet}} deep, and with less than 30% [[Aquatic plant|emergent vegetation]] helps in distinguishing their [[ecology]] from that of lakes and wetlands.<ref>{{Cite journal |authors=David C. Richardson, Meredith A. Holgerson, Matthew J. Farragher, Kathryn K. Hoffman, Katelyn B. S. King, María B. Alfonso, Mikkel R. Andersen, Kendra Spence Cheruveil, Kristen A. Coleman, Mary Jade Farruggia, Rocio Luz Fernandez, Kelly L. Hondula, Gregorio A. López Moreira Mazacotte, Katherine Paul, Benjamin L. Peierls, Joseph S. Rabaey, Steven Sadro, María Laura Sánchez, Robyn L. Smyth & Jon N. Sweetman |date=2022 |title=A functional definition to distinguish ponds from lakes and wetlands |journal=Scientific Reports |volume=12 |issue=1 |page=10472 |doi=10.1038/s41598-022-14569-0 |pmid=35729265 |pmc=9213426 |bibcode=2022NatSR..1210472R |language=en}}</ref><ref name=":02">Clegg, J. (1986). Observer's Book of Pond Life. Frederick Warne, London</ref>{{rp|460}} Ponds can be created by a wide variety of natural processes (e.g. on [[floodplain]]s as cutoff [[river]] channels, by glacial processes, by peatland formation, in coastal dune systems, by beavers), or they can simply be isolated depressions (such as a [[Kettle (landform)|kettle]] hole, [[vernal pool]], [[Prairie Pothole Region|prairie pothole]], or simply natural undulations in undrained land) filled by runoff, groundwater, or precipitation, or all three of these.<ref>{{Cite book|last=Clegg, John, 1909-1998.|url=https://www.worldcat.org/oclc/15197655|title=The new observer's book of pond life|date=1986|publisher=Frederick Warne|isbn=0-7232-3338-1|edition=4th|location=Harmondsworth|oclc=15197655}}</ref> They can be further divided into four zones: vegetation zone, open water, bottom mud and surface film.<ref name=":02" />{{rp|160–163}} The size and depth of ponds often varies greatly with the time of year; many ponds are produced by spring flooding from rivers. Ponds may be [[Fresh water|freshwater]] or [[Brackish water|brackish]] in nature. 'Ponds' with [[Saline water|saltwater]], with a direct connection to the sea that maintains full salinity, would normally be regarded as part of the marine environment because they would not support fresh or brackish water organisms, so not really within the realm of freshwater science.
+A '''pond''' is a small, still, land-based [[body of water]] formed by pooling inside a [[depression (geology)|depression]], either natural or [[artificiality|artificial]], that is smaller than a [[lake]].<ref>{{Cite journal|last=STANLEY|first=E. G.|date=1975-06-01|title=The Merriam-Webster Dictionary – The Oxford Illustrated Dictionary|url=http://dx.doi.org/10.1093/nq/22-6-242|journal=Notes and Queries|volume=22|issue=6|pages=242–243|doi=10.1093/nq/22-6-242|issn=1471-6941|via=}}</ref> Defining them to be less than {{Convert|5|hectare|acre}} in area, less than {{Convert|5|meter|feet}} deep, and with less than 30% [[Aquatic plant|emergent vegetation]] helps in distinguishing their [[ecology]] from that of lakes and wetlands.<ref>{{Cite journal |authors=David C. Richardson, Meredith A. Holgerson, Matthew J. Farragher, Kathryn K. Hoffman, Katelyn B. S. King, María B. Alfonso, Mikkel R. Andersen, Kendra Spence Cheruveil, Kristen A. Coleman, Mary Jade Farruggia, Rocio Luz Fernandez, Kelly L. Hondula, Gregorio A. López Moreira Mazacotte, Katherine Paul, Benjamin L. Peierls, Joseph S. Rabaey, Steven Sadro, María Laura Sánchez, Robyn L. Smyth & Jon N. Sweetman |date=2022 |title=A functional definition to distinguish ponds from lakes and wetlands |journal=Scientific Reports |volume=12 |issue=1 |page=10472 |doi=10.1038/s41598-022-14569-0 |pmid=35729265 |pmc=9213426 |bibcode=2022NatSR..1210472R |language=en}}</ref><ref name=":02">Clegg, J. (1986). Observer's Book of Pond Life. Frederick Warne, London</ref>{{rp|460}} Ponds can be created by a wide variety of natural processes (e.g. on [[floodplain]]s as cutoff [[river]] channels, by glacial processes, by peatland formation, in coastal dune systems, by beavers), or they can simply be isolated depressions (such as a [[Kettle (landform)|kettle]] hole, [[vernal pool]], [[Prairie Pothole Region|prairie pothole]], or simply natural undulations in undrained land) filled by runoff, groundwater, or precipitation, or all three of these.<ref>{{Cite book|last=Clegg, John, 1909-1998.|url=https://www.worldcat.org/oclc/15197655|title=The new observer's book of pond life|date=1986|publisher=Frederick Warne|isbn=0-7232-3338-1|edition=4th|location=Harmondsworth|oclc=15197655}}</ref> They can be further divided into four zones: vegetation zone, open water, bottom mud and surface film.<ref name=":02" />{{rp|160–163}} The size and depth of ponds often varies greatly with the time of year; many ponds are produced by spring flooding from rivers. Ponds may be [[Fresh water|freshwater]] or [[Brackish water|brackish]] in nature. 'Ponds' with [[Saline water|saltwater]], with a direct connection to the sea that maintains full salinity, would normally be regarded as part of the marine environment because they would not support fresh or brackish water organisms, so not really within the realm of freshwater science.
 Ponds are usually by definition quite shallow water bodies with varying abundances of [[aquatic plant]]s and animals. Depth, seasonal water level variations, nutrients fluxes, amount of light reaching the ponds, the shape, the presence of visiting large mammals, the composition of any fish communities and salinity can all affect the types of plant and animal communities present.<ref name=":2">{{Cite book|last=Keddy|first=Paul A.|url=https://www.worldcat.org/oclc/801405617|title=Wetland ecology : principles and conservation|date=2010|publisher=Cambridge University Press|isbn=978-1-139-22365-2|edition=2nd|location=Cambridge|oclc=801405617}}</ref> [[Food web]]s are based both on free-floating [[algae]] and upon aquatic plants. There is usually a diverse array of aquatic life, with a few examples including algae, snails, fish, beetles, water bugs, frogs, turtles, otters and muskrats. Top predators may include large fish, herons, or alligators.  Since fish are a major predator upon amphibian larvae, ponds that dry up each year, thereby killing resident fish, provide important refugia for amphibian breeding.<ref name=":2" /> Ponds that dry up completely each year are often known as [[vernal pools]]. Some ponds are produced by animal activity, including alligator holes and beaver ponds, and these add important diversity to landscapes.<ref name=":2" />

v t e Ponds, pools, and puddles
Ponds	Ash pond Balancing lake Ballast pond Beel Cooling pond Detention pond Dew pond Evaporation pond Facultative lagoon Garden pond Ice pond Immersion pond Infiltration basin Kettle pond Log pond Melt pond Mill pond Polishing pond Raceway pond Retention pond Sag pond Salt evaporation pond Sediment pond Settling pond Solar pond Stepwell Stew pond Tailings Tarn Waste pond Waste stabilization pond
Pools	Anchialine pool Brine pool Infinity pool Natural pool Ocean pool Plunge pool Reflecting pool Spent fuel pool Stream pool Swimming pool Tide pool Vernal pool
Puddles	Bird bath Coffee ring effect Puddle Puddles on a surface Seep puddle
Biome	Beaver dam Duck pond Fish pond Goldfish pond Koi pond
Ecosystems	Aquatic ecosystem Freshwater ecosystem Lake ecosystem
Related	Aerated lagoon Bakki shower Big fish–little pond Body of water Constructed wetland Full pond Hydric soil Phytotelma Pond of Abundance Pond liner Ponding Puddle (M C Escher) Spring Swimming hole Water aeration Water garden Water Lilies (Monet) Well