| Lake zones |
|---|
| Lake stratification |
| Lake types |
| See also |
The profundal zone is a deep zone of an inland body of freestanding water, such as a lake or pond, located below the range of effective light penetration. This is typically below the thermocline, the vertical zone in the water through which temperature drops rapidly. The temperature difference may be large enough to hamper mixing with the littoral zone in some seasons which causes a decrease in oxygen concentrations. [1] The profundal is often defined, as the deepest, vegetation-free, and muddy zone of the lacustrine benthal. [2] The profundal zone is often part of the aphotic zone. Sediment in the profundal zone primarily comprises silt and mud. [1]
The lack of light and oxygen in the profundal zone determines the type of biological community that can live in this region, which is distinctly different from the community in the overlying waters. [3] The profundal macrofauna is therefore characterized by physiological and behavioural adaptations to low oxygen concentration. While benthic fauna differs between lakes, Chironomidae and Oligochaetae often dominate the benthic fauna of the profundal zone because they possess hemoglobin-like molecules to extract oxygen from poorly oxygenated water. [4] Due to the low productivity of the profundal zone, organisms rely on detritus sinking from the photic zone. [1] Species richness in the profundal zone is often similar to that in the limnetic zone. [5] Microbial levels in the profundal benthos are higher than those in the littoral benthos, potentially due to a smaller average sediment particle size. [6] Benthic macroinvertebrates are believed to be regulated by top-down pressure. [7]
Nutrient fluxes in the profundal zone are primarily driven by release from the benthos. [8] The anoxic nature of the profundal zone drives ammonia release from benthic sediment. This can drive phytoplankton production, to the point of a phytoplankton bloom, and create toxic conditions for many organisms, particularly at a high pH. Hypolimnetic anoxia can also contribute to buildups of iron, manganese, and sulfide in the profundal zone. [9]
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.
The littoral zone, also called litoral or nearshore, is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark, to coastal areas that are permanently submerged — known as the foreshore — and the terms are often used interchangeably. However, the geographical meaning of littoral zone extends well beyond the intertidal zone to include all neritic waters within the bounds of continental shelves.
The hypolimnion or under lake is the dense, bottom layer of water in a thermally-stratified lake. The word "hypolimnion" is derived from Ancient Greek: λιμνίον, romanized: limníon, lit. 'lake'. It is the layer that lies below the thermocline.
Dead zones are hypoxic (low-oxygen) areas in the world's oceans and large lakes. Hypoxia occurs when dissolved oxygen (DO) concentration falls to or below 2 mg of O2/liter. When a body of water experiences hypoxic conditions, aquatic flora and fauna begin to change behavior in order to reach sections of water with higher oxygen levels. Once DO declines below 0.5 ml O2/liter in a body of water, mass mortality occurs. With such a low concentration of DO, these bodies of water fail to support the aquatic life living there. Historically, many of these sites were naturally occurring. However, in the 1970s, oceanographers began noting increased instances and expanses of dead zones. These occur near inhabited coastlines, where aquatic life is most concentrated.
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.
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word βένθος (bénthos), meaning "the depths". Organisms living in this zone are called benthos and include microorganisms as well as larger invertebrates, such as crustaceans and polychaetes. Organisms here generally live in close relationship with the substrate and many are permanently attached to the bottom. The benthic boundary layer, which includes the bottom layer of water and the uppermost layer of sediment directly influenced by the overlying water, is an integral part of the benthic zone, as it greatly influences the biological activity that takes place there. Examples of contact soil layers include sand bottoms, rocky outcrops, coral, and bay mud.
Bioturbation is defined as the reworking of soils and sediments by animals or plants. It includes burrowing, ingestion, and defecation of sediment grains. Bioturbating activities have a profound effect on the environment and are thought to be a primary driver of biodiversity. The formal study of bioturbation began in the 1800s by Charles Darwin experimenting in his garden. The disruption of aquatic sediments and terrestrial soils through bioturbating activities provides significant ecosystem services. These include the alteration of nutrients in aquatic sediment and overlying water, shelter to other species in the form of burrows in terrestrial and water ecosystems, and soil production on land.
In oceanography and limnology, the sediment–water interface is the boundary between bed sediment and the overlying water column. The term usually refers to a thin layer of water at the very surface of sediments on the seafloor. In the ocean, estuaries, and lakes, this layer interacts with the water above it through physical flow and chemical reactions mediated by the micro-organisms, animals, and plants living at the bottom of the water body. The topography of this interface is often dynamic, as it is affected by physical processes and biological processes. Physical, biological, and chemical processes occur at the sediment-water interface as a result of a number of gradients such as chemical potential gradients, pore water gradients, and oxygen gradients.
The Chironomidae comprise a family of nematoceran flies with a global distribution. They are closely related to the Ceratopogonidae, Simuliidae, and Thaumaleidae. Many species superficially resemble mosquitoes, but they lack the wing scales and elongated mouthparts of the Culicidae.
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.
Anoxic waters are areas of sea water, fresh water, or groundwater that are depleted of dissolved oxygen. The US Geological Survey defines anoxic groundwater as those with dissolved oxygen concentration of less than 0.5 milligrams per litre. Anoxic waters can be contrasted with hypoxic waters, which are low in dissolved oxygen. This condition is generally found in areas that have restricted water exchange.
The limnetic zone is the open and well-lit area of a freestanding body of freshwater, such as a lake or pond. Not included in this area is the littoral zone, which is the shallow, near-shore area of the water body. The key difference between the littoral zone and the limnetic zone is the presence of rooted plant growth. The floor under the limnetic zone cannot sustain plant growth due to a lack of sunlight for photosynthesis. In extremely shallow bodies of water, light may penetrate all the way to floor even in the deepest center parts of the lake. In this situation, there is an absence of a limnetic zone and the littoral zone spans the entire lake. Together, these two zones comprise the photic zone.
Monomictic lakes are holomictic lakes that mix from top to bottom during one mixing period each year. Monomictic lakes may be subdivided into cold and warm types.
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. Knowledge from this discipline is also widely used in industrial processes to make use of biological processes involved with sewage treatment and water purification. Water presence and flow is an essential aspect to species distribution and influences when and where species interact in freshwater environments.
Chironomus is a genus of nonbiting midges in the subfamily Chironominae of the bloodworm family, Chironomidae, containing several cryptic species that can only be distinguished by experts based on the characteristics of their giant chromosomes.
Hypoxia refers to low oxygen conditions. For air-breathing organisms, hypoxia is problematic but for many anaerobic organisms, hypoxia is essential. Hypoxia applies to many situations, but usually refers to the atmosphere and natural waters.
Gloeotrichia is a large (~2 mm) colonial genus of Cyanobacteria, belonging to the order Nostocales. The name Gloeotrichia is derived from its appearance of filamentous body with mucilage matrix. Found in lakes across the globe, gloeotrichia are notable for the important roles that they play in the nitrogen and phosphorus cycles. Gloeotrichia are also a species of concern for lake managers, as they have been shown to push lakes towards eutrophication and produce deadly toxins.
The term oyster reef refers to dense aggregations of oysters that form large colonial communities. Because oyster larvae need to settle on hard substrates, new oyster reefs may form on stone or other hard marine debris. Eventually the oyster reef will propagate by spat settling on the shells of older or nonliving oysters. The dense aggregations of oysters are often referred to as an oyster reef, oyster bed, oyster bank, oyster bottom, or oyster bar interchangeably. These terms are not well defined and often regionally restricted.
Lake metabolism represents a lake's balance between carbon fixation and biological carbon oxidation. Whole-lake metabolism includes the carbon fixation and oxidation from all organism within the lake, from bacteria to fishes, and is typically estimated by measuring changes in dissolved oxygen or carbon dioxide throughout the day.
Benthic-pelagic coupling are processes that connect the benthic zone and the pelagic zone through the exchange of energy, mass, or nutrients. These processes play a prominent role in both freshwater and marine ecosystems and are influenced by a number of chemical, biological, and physical forces that are crucial to functions from nutrient cycling to energy transfer in food webs.
{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)  | This ecology-related article is a stub. You can help Wikipedia by expanding it. |