Freshwater biology

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Oxsjon, a lake in Sweden. Freshwater biology focuses on environments like lakes. Oxsjon Vastergotland Sweden from E looking N May 29 2021.jpg
Oxsjön, a lake in Sweden. Freshwater biology focuses on environments like lakes.
A pond in the Oconee River Floodplain in Georgia, whose surface is covered in duckweed but still contains fish. Duckweed Pond (15317740476).jpg
A pond in the Oconee River Floodplain in Georgia, whose surface is covered in duckweed but still contains fish.

Freshwater biology is the scientific biological study of freshwater ecosystems and is a branch of limnology. This field seeks to understand the relationships between living organisms in their physical environment. These physical environments may include rivers, lakes, streams, ponds, lakes, reservoirs, or wetlands. [1] Knowledge from this discipline is also widely used in industrial processes to make use of biological processes involved with sewage treatment [2] and water purification. Water presence and flow is an essential aspect to species distribution and influences when and where species interact in freshwater environments. [1]

Contents

In the UK, the Freshwater Biological Association based near Windermere in Cumbria was one of the early institutions to research the biology of freshwater and promote the concepts of trophism in lakes and demonstrated the process of migration from oligotrophic water through mesotrophic to marsh. [3]

Freshwater biology is also used to study the effects of climate change and increased human impact on both aquatic systems and wider ecosystems. [4] Freshwater organisms, vertebrates especially, appear to be at a higher extinction risk from climate change than terrestrial or marine organisms. [5]

Freshwater habitats

Freshwater habitats support a wide variety of organisms with habitats including rivers, streams, lakes, ponds, and wetlands. [6]

Rivers and streams

Running water is a type of freshwater habitat that mainly consists of rivers and streams. Running, fast-moving waters have a higher oxygen content, allowing different species to thrive and making pollution easier to combat. [6] Running water is an open system, meaning it is not isolate and exchanges matter and energy with other systems. [6] Being an open system, a lot of organic matter found in running water is from land runoff or further sediment upstream and this matter is an important source of food for many species. Flowing bodies of water begin at the headwaters, which include springs, lakes, and snowmelt,  and travel to their mouths, typically another moving water channel or the ocean. [7] The characteristics of the streams and rivers change throughout their journey from the source to the mouth. For example, the water at the source is clearer, has a higher oxygen content, lower temperatures, and heterotrophs common species. In the middle, the width usually expands and the species diversity increases due to temperature and oxygen content changes, including aquatic green plants and algae. The water at the mouth has a lower oxygen concentration and is murkier due to the sediment that has been collected and traveled along the length of the river or stream. This increased sediment decreases the amount of light that is able to penetrate the water and there is less diversity of flora and the lower oxygen lowers the diversity of fauna. [7]

The riparian zone is the area along a riverbank or streambank that is home to vital, high moisture plants. These plants create a buffer between the land and the running water system, protecting it from pollution and flooding. Additionally, these plants provide a large habitat for many wetland species, a large number of which are endangered or threatened. Lastly, riparian plants shade the water from sunlight, reducing the heat stress on the water and aquatic life, while also providing nutrients in the form of organic matter. [6]

Lakes and ponds

Standing water is a type of freshwater habitat that mainly consists of lakes and ponds. This habitat has limited species diversity because they are isolated from one another and other water systems, unlike running water. [7] Standing water experiences the process of stratification, which is when water is layered due to the oxygen content. [6] Stratification does not occur in running water because of the fast moving water that mixes water with varying oxygen content together. The topmost layer has the most oxygen and as depth increases, the oxygen decreases. [6] Stratification can be physically felt in the temperature of the water, as the uppermost layer of water is warmer than deeper water because it has been heated by the sun.

Standing water can be divided into three zones based on depth and distance from shore. The littoral zone is the uppermost layer and the warmest water found in lakes and ponds, as the sun directly heats is. [7] This zone hosts the most biodiversity in standing water, with a wide variety of organisms found here, vital to the health of the ecosystem and an important aspect of the diet of organisms in the habitat, like algae, aquatic plants, clams, insects, fish, crustaceans, and amphibians. [7] The limnetic zone is found below the littoral zone. This zone has lower temperatures, is fairly well-lit, and is occupied by a smaller variety of organisms, including phytoplankton, zooplankton, and fish. [7] The plankton found in this zone play a crucial role in the food web of the habitat and support the diet of many important organisms. The deepest zone is the profundal zone, with very little light, colder temperatures, and higher density than the previous layers. [7] When plankton die they fall into this layer and provide nutrients to the fauna that live in this layer. These faunas are called heterotrophs, meaning they eat dead organisms and use oxygen for cellular respiration, resulting in lower oxygen content in the profundal zone. [7]

The thermocline is the transitionary zone between the warm, surface water and the deeper water at a cooler temperature. [6] The limited mixing and movement of water that occurs in standing water occurs at the thermocline. The mixing of the layers of water in standing water mostly comes from seasonal overturn. During the fall and spring, there is a mixing of layers usually due to wind that circulates oxygen and creates a more uniform temperature throughout the water system. [7] The shore zone is the transitional zone between the water systems and land, similar to the riparian zone seen in running water systems. [6] This area functions in much the same way as the riparian zone, the plants protecting the water from pollution, flooding, and heat stress, while also providing nutrients and habitats for aquatic and wetland species.

Wetlands

Wetlands are a specific type of standing water habitats that include marshes, swamps, and bogs. Due to the waterlogged and submerged nature of the land, the anaerobic conditions of wetlands are unique and support the highest species diversity of all ecosystems. [7] Wetlands slow the decomposition of organic matter, creating layers of rich organic material that provides important nutrients for species in the system. The fauna that reside in wetlands are called hydrophytes, meaning they are adapted to very moist and humid conditions. [7] Wetlands are the home to a large number of bird, amphibian, insect, reptile, grass, and tree species that cannot inhabit any other system, making them at risk to endangerment, as wetlands are being destroyed for urban development and agriculture. [6] Wetlands help combat pollution and climate change, as they filter pollutants and store a large amount of carbon from the biosphere in their moist soil and still water, despite the small amount of land they occupy. Additionally, wetlands provide flood and storm protection, as the system can absorb large amounts of excess water. [6] Wetland's ability to absorb water also assists groundwater recharge, which is very important for human water use, as usable freshwater sources are dwindling. Wetlands are not only freshwater habitats and systems, as there are salt marshes and bogs that support different species. [7]

Carolina Bays (also known as pocosins, meaning "swamp on a hill") are a unique form of wetland predominately found in the Carolinas, with a few being found outside of the Carolinas along the East Coast of the United States. [8] Carolina Bays are characterized as elliptical shaped depressions that are surrounded by a sand rim and have a sandy bottom. [8] This depression goes through wet and dry periods, filling with rainwater during the winter and spring months, and drying out in the summer. [8] Carolina Bays often contain rare species, some endemic to the bays. [8]

Freshwater organisms

Freshwater organisms are generally divided into the categories of benthic and pelagic organisms, as these are the two zones of life found in the freshwater biome. Freshwater organism can include invertebrates, insects, fish, amphibians, mammals, birds, aquatic plants, and planktons. [7]

Invertebrates

Freshwater invertebrates include freshwater mollusks, insects, crustaceans, and worms. [9] Freshwater invertebrates provide an important link in freshwater food chains, transporting the nutrients and energy from producers such as algae and aquatic plants to higher consumers such as fish and amphibians. [9] Additionally, invertebrates can act as important bio-indicators for ecosystem health. [9]

Fish

Freshwater fish include a are very diverse, consisting of more than 18,000 species and making up 1/4 of the world's vertebrate species. [10] Around half of fish species live in freshwater environments, the other half living in saltwater. [11] Some fish, such as salmon and some species of shark, are able to travel between the freshwater and saltwater environments, linking the two. [11] These fish are referred to as diadromous fish, stemming from Greek and meaning "to run between", in reference to the fish running between freshwater and saltwater. [12]

Amphibians

Amphibians, which include frogs, toads, salamanders, and caecilians, are a group that predominately exist in freshwater habitats. Amphibians are exotherms that possess thing skin, meaning that they rely on water to remain hydrated. [13] Amphibians are Amphibians can act as an indicator of environmental health, as they are easily affected by changes in the environment, such as pollution or climate change. [13]

Birds

Water birds are a group of birds that rely on aquatic habitats for hunting, resting, and sometimes nesting. [14] Birds that rely on freshwater habitats include birds such as kingfishers, flamingos, and various types of waterfowl. Many species rely on the plants in these freshwater environments for nesting material, habitat, and food. Additionally, freshwater birds act as a control for fish and insects in freshwater environments. [14]

Aquatic Plants

Aquatic plants act much like terrestrial plants, providing the basis for the food chain, removal of carbon dioxide, and production of oxygen. Aquatic plants can be divided into 3 categories: emergent, submergent, and floating. [15] Emergent plants, such as horsetails and cattails, are rooted near the edge of freshwater ecosystems, and commonly stick up out of the water. [15] Submergent plants, such as elodea and pondweed, are those that are completely under the water, and may be either rooted or unrooted. [15] Floating plants, such as water-lilies or duckweed, are plants that may be rooted or unrooted, but whose leaves float to the top of the water. [15]

Threats

The most common cause of water pollution is stormwater runoff from developed areas, like pavement and rooftops. [16] Stormwater runoff is moving rain and snowmelt that has not been absorbed. [16] The impervious surfaces used in domestic and urban construction replace soil that used to absorb stormwater, increasing the amount of runoff traveling farther distances. This excess runoff can collect pollutants as it eventually makes its way into streams, rivers, lakes, wetlands, and even aquifers, polluting important freshwater ecosystems and usable water. [16] Additionally, increased flooding and erosion can be caused by the increased stormwater runoff.

Pollution of flowing water

Rivers and streams drain water that falls on upland areas, and this moving water dissolves pollutants at a faster rate than standing water. [16] However, due to the high production and placement of pollutants in these moving waters, the waters become polluted faster than the pollutant dilution rate, leading to over polluted rivers and streams. All three of the major contributors to pollution – industry, agriculture, and cities – are commonly found along moving waters, adding to the over-pollution of rivers and streams. [16] Just the knowledge that fast moving waters can dilute pollutants has encouraged even more pollution, further adding to the pollution issue. Another issue contributing to the destruction of rivers and streams is the physical alteration of these moving waters, mainly in the form of dams, diversion of water, channel alteration, and land development. [16] These alterations affect water temperature, water flow patterns, and increase sediment, destroying important habitat conditions for many aquatic organisms and reducing water quality. [16]

An area of contention regarding the pollution of streams and rivers is the concept that the pollution upstream affects the people downstream. [16] A factory's waste upstream may contaminate someone's drinking water downstream. This especially becomes an issue with bodies of moving water that border multiple countries or states, as what one country or state does upstream can drastically affect what the downstream country or state is able to do. [16]

Pollution of standing water

Lakes and ponds experience much of the same pollution as rivers and streams, but are polluted at a quicker rate due to slower moving waters, no water flow outlets, and amount of water. [16] Standing water circulates much less than moving waters, with the deeper water layers only moving during seasonal changes twice a year. [16] Lakes and ponds are basins into which running water usually flows and accumulates, meaning that the pollutants also accumulate with no outlet. Lakes and ponds contain less water than most rivers and streams, meaning smaller lakes and ponds are polluted at faster rates.

Eutrophication is the process of abundant plant growth, a dominating threat to standing waters. [16] If chemical nutrients for aquatic plant growth that were previously limited become available, plant populations will increase rapidly. This excessive plant population growth decreases the oxygen content of the water, and other aquatic life suffocates. Human waste often contains these chemical nutrients, like phosphorus in fertilizers, and in combination with the poor water circulation in standing waters, causes pollution and organism depletion. [16] Much of the pollution issues that affect ponds and lakes also affect wetlands, as the water circulation of wetlands is also slow.

Groundwater pollution and depletion

Surface water is where groundwater is being expressed, with wetlands being the largest examples of the water table being near or at the surface. The water found in freshwater habitats are the combination of surface flow, precipitation, and groundwater expression. [16] This relationship between groundwater and surface water means that groundwater pollution affects surface freshwater pollution as well.

According to an Environmental Protection Agency survey, about a quarter of the United States' usable groundwater is contaminated. Groundwater is the only source of drinking water for about half of the United States. [17] As human populations increase and industrialize, the demand for groundwater is increasing, but the pollution of groundwater is also increasing. The pollution of groundwater is easy to achieve due to the slow circulation of water, even slower than that of lakes and ponds. The water must navigate through small holes in the aquifer rock, moving on average only a couple of inches each day. [16] The rate of groundwater recharge is the time it takes for groundwater to replenish itself and extremely slow, leading to water shortages, as humans remove water from aquifers faster than the rate of recharge. [16] Due to such slow circulation of water, groundwater can remain polluted for decades, as the natural purification processes are so slow.

See also

Related Research Articles

<span class="mw-page-title-main">Eutrophication</span> Excessive plant growth in water

Eutrophication is a general term describing a process in which nutrients accumulate in a body of water, resulting in an increased growth of microorganisms that may deplete the water of oxygen. Although eutrophication is a natural process, manmade or cultural eutrophication is far more common and is a rapid process caused by a variety of polluting inputs including poorly treated sewage, industrial wastewater, and fertilizer runoff. Such nutrient pollution usually causes algal blooms and bacterial growth, resulting in the depletion of dissolved oxygen in water and causing substantial environmental degradation.

<span class="mw-page-title-main">Benthos</span> Community of organisms that live in the benthic zone

Benthos, also known as benthon, is the community of organisms that live on, in, or near the bottom of a sea, river, lake, or stream, also known as the benthic zone. This community lives in or near marine or freshwater sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths.

<span class="mw-page-title-main">Estuary</span> Partially enclosed coastal body of brackish water

An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environments and are an example of an ecotone. Estuaries are subject both to marine influences such as tides, waves, and the influx of saline water, and to fluvial influences such as flows of freshwater and sediment. The mixing of seawater and freshwater provides high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world.

<span class="mw-page-title-main">Wetland</span> Land area that is permanently, or seasonally saturated with water

A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently for years or decades or seasonally for a shorter periods. Flooding results in oxygen-free anoxic processes prevailing, especially in the soils. The primary factor that distinguishes wetlands from terrestrial land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique anoxic hydric soils. Wetlands are considered among the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal species. Methods for assessing wetland functions, wetland ecological health, and general wetland condition have been developed for many regions of the world. These methods have contributed to wetland conservation partly by raising public awareness of the functions some wetlands provide. Constructed wetlands are designed and built to treat municipal and industrial wastewater as well as to divert stormwater runoff. Constructed wetlands may also play a role in water-sensitive urban design.

<span class="mw-page-title-main">Limnology</span> Science of inland aquatic ecosystems

Limnology is the study of inland aquatic ecosystems. The study of limnology includes aspects of the biological, chemical, physical, and geological characteristics of fresh and saline, natural and man-made bodies of water. This includes the study of lakes, reservoirs, ponds, rivers, springs, streams, wetlands, and groundwater. Water systems are often categorized as either running (lotic) or standing (lentic).

<span class="mw-page-title-main">Marsh</span> Low-lying and seasonally waterlogged land

In ecology, a marsh is a wetland that is dominated by herbaceous plants rather than by woody plants. More in general, the word can be used for any low-lying and seasonally waterlogged terrain. In Europe and in agricultural literature low-lying meadows that require draining and embanked polderlands are also referred to as marshes or marshland.

<span class="mw-page-title-main">Water pollution</span> Contamination of water bodies

Water pollution is the contamination of water bodies, usually as a result of human activities, that has a negative impact on their uses. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Water pollution results when contaminants mix with these water bodies. Contaminants can come from one of four main sources: sewage discharges, industrial activities, agricultural activities, and urban runoff including stormwater. Water pollution is either surface water pollution or groundwater pollution. This form of pollution can lead to many problems, such as the degradation of aquatic ecosystems or spreading water-borne diseases when people use polluted water for drinking or irrigation. Another problem is that water pollution reduces the ecosystem services that the water resource would otherwise provide.

Freshwater ecosystems are a subset of Earth's aquatic ecosystems. They include lakes, ponds, rivers, streams, springs, bogs, and wetlands. They can be contrasted with marine ecosystems, which have a larger salt content. Freshwater habitats can be classified by different factors, including temperature, light penetration, nutrients, and vegetation. There are three basic types of freshwater ecosystems: Lentic, lotic and wetlands. Freshwater ecosystems contain 41% of the world's known fish species.

<span class="mw-page-title-main">Cape Cod Bay</span> Large bay of the Atlantic Ocean adjacent to the U.S. state of Massachusetts

Cape Cod Bay is a large bay of the Atlantic Ocean adjacent to the U.S. state of Massachusetts. Measuring 604 square miles (1,560 km2) below a line drawn from Brant Rock in Marshfield to Race Point in Provincetown, Massachusetts, it is enclosed by Cape Cod to the south and east, and Plymouth County, Massachusetts, to the west. To the north of Cape Cod Bay lie Massachusetts Bay and the Atlantic Ocean. Cape Cod Bay is the southernmost extremity of the Gulf of Maine. Cape Cod Bay is one of the bays adjacent to Massachusetts that give it the name Bay State. The others are Narragansett Bay, Buzzards Bay, and Massachusetts Bay.

<span class="mw-page-title-main">Thermal pollution</span> Water temperature changes resulting in degraded water quality

Thermal pollution, sometimes called "thermal enrichment", is the degradation of water quality by any process that changes ambient water temperature. Thermal pollution is the rise or drop in the temperature of a natural body of water caused by human influence. Thermal pollution, unlike chemical pollution, results in a change in the physical properties of water. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. Urban runoff—stormwater discharged to surface waters from rooftops, roads, and parking lots—and reservoirs can also be a source of thermal pollution. Thermal pollution can also be caused by the release of very cold water from the base of reservoirs into warmer rivers.

<span class="mw-page-title-main">Aquatic ecosystem</span> Ecosystem in a body of water

An aquatic ecosystem is an ecosystem found in and around a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms—aquatic life—that are dependent on each other and on their environment. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems. Freshwater ecosystems may be lentic ; lotic ; and wetlands.

<span class="mw-page-title-main">River ecosystem</span> Type of aquatic ecosystem with flowing freshwater

River ecosystems are flowing waters that drain the landscape, and include the biotic (living) interactions amongst plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions of its many parts. River ecosystems are part of larger watershed networks or catchments, where smaller headwater streams drain into mid-size streams, which progressively drain into larger river networks. The major zones in river ecosystems are determined by the river bed's gradient or by the velocity of the current. Faster moving turbulent water typically contains greater concentrations of dissolved oxygen, which supports greater biodiversity than the slow-moving water of pools. These distinctions form the basis for the division of rivers into upland and lowland rivers.

<span class="mw-page-title-main">Lake ecosystem</span> Type of ecosystem

A lake ecosystem or lacustrine ecosystem includes biotic (living) plants, animals and micro-organisms, as well as abiotic (non-living) physical and chemical interactions. Lake ecosystems are a prime example of lentic ecosystems, which include ponds, lakes and wetlands, and much of this article applies to lentic ecosystems in general. Lentic ecosystems can be compared with lotic ecosystems, which involve flowing terrestrial waters such as rivers and streams. Together, these two ecosystems are examples of freshwater ecosystems.

<span class="mw-page-title-main">Garden pond</span> Water feature in gardens

A garden pond is a water feature constructed in a water garden or designed landscape, normally for aesthetic purposes, to provide wildlife habitat, or for swimming.

<span class="mw-page-title-main">Perennial stream</span> Type of river

A perennial stream is a stream that has continuous flow of surface water throughout the year in at least parts of its catchment during seasons of normal rainfall, as opposed to one whose flow is intermittent. In the absence of irregular, prolonged or extreme drought, a perennial stream is a watercourse, or segment, element or emerging body of water which continually delivers groundwater. For example, an artificial disruption of stream, variability in flow or stream selection associated with the activity in hydropower installations, do not affect this status. Perennial streams do not include stagnant water, reservoirs, cutoff lakes and ponds that persist throughout the year. All other streams, or parts of them, should be considered seasonal rivers or lakes. The stream can cycle from intermittent to perpetual through multiple iterations.

<span class="mw-page-title-main">Trophic state index</span> Measure of the ability of water to sustain biological productivity

The Trophic State Index (TSI) is a classification system designed to rate water bodies based on the amount of biological productivity they sustain. Although the term "trophic index" is commonly applied to lakes, any surface water body may be indexed.

<span class="mw-page-title-main">Pond</span> Relatively small body of standing water

A pond is a small, still, land-based body of water formed by pooling inside a depression, either naturally or artificially. A pond is smaller than a lake and there are no official criteria distinguishing the two, although defining a pond to be less than 5 hectares in area, less than 5 metres (16 ft) in depth and with less than 30% with emergent vegetation helps in distinguishing the ecology of ponds from those of lakes and wetlands. Ponds can be created by a wide variety of natural processes, or they can simply be isolated depressions filled by runoff, groundwater, or precipitation, or all three of these. They can be further divided into four zones: vegetation zone, open water, bottom mud and surface film. The size and depth of ponds often varies greatly with the time of year; many ponds are produced by spring flooding from rivers. Ponds are usually freshwater but may be brackish in nature. Saltwater pools, with a direct connection to the sea to maintain full salinity, may sometimes be called 'ponds' but these are normally regarded as part of the marine environment. They do not support fresh or brackish water-based organisms, and are rather tidal pools or lagoons.

A drought refuge is a site that provides permanent fresh water or moist conditions for plants and animals, acting as a refuge habitat when surrounding areas are affected by drought and allowing ecosystems and core species populations to survive until the drought breaks. Drought refuges are important for conserving ecosystems in places where the effects of climatic variability are exacerbated by human activities.

Vulnerable waters refer to geographically isolated wetlands (GIWs) and to ephemeral and intermittent streams. Ephemeral and intermittent streams are seasonally flowing and are located in headwater position. They are the outer and smallest stems of hydrological networks. Isolated wetlands are located outside floodplain and show poor surface connection to tributaries or floodplains. Geographically isolated wetlands encompass saturated depressions that are the result of fluvial, aeolian, glacial and/or coastal geomorphological processes. They may be natural landforms or the result of human interventions. Vulnerable waters represent the major proportion of river networks.

<span class="mw-page-title-main">Fresh water</span> Naturally occurring water with low amounts of dissolved salts

Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include non-salty mineral-rich waters such as chalybeate springs. Fresh water may encompass frozen and meltwater in ice sheets, ice caps, glaciers, snowfields and icebergs, natural precipitations such as rainfall, snowfall, hail/sleet and graupel, and surface runoffs that form inland bodies of water such as wetlands, ponds, lakes, rivers, streams, as well as groundwater contained in aquifers, subterranean rivers and lakes. Fresh water is the water resource that is of the most and immediate use to humans.

References

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  3. ↑ "History of FBA". Freshwater Biological Association.
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  10. ↑ "One-third of freshwater fish face extinction and other freshwater fish facts". World Wildlife Fund. February 23, 2021. Retrieved April 23, 2024.
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  12. ↑ "Fish That Live in Saltwater and Freshwater". Ocean Conservancy. 2023-03-15. Retrieved 2024-04-23.
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  14. 1 2 "Birds – Minnesota Freshwater Quest". herofortheplanet.org. Retrieved 2024-04-22.
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  17. ↑ US EPA, ORD (2017-11-02). "Ground Water". www.epa.gov. Retrieved 2022-04-28.
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