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Sediment–water Interface
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 (approximately 1 cm deep, though variable) 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 (e.g. currents causing rippling or resuspension) and biological processes (e.g. bioturbation generating mounds or trenches). 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. Definition The location of the top of the sediment-water interface in th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nur02502
Nur may refer to: In Islam * An-Nur, one of the names of God in Islam, meaning "The Light". * Nūr (Islam), a concept, literally meaning "light" * An-Nur (The Light), the 24th chapter of the Qur'an * ''Risale-i Nur Collection'', a collection of works by Islamic scholar Said Nursî People * Nur (name) Places * Nur, Iran (other) * Nur, Poland * Nur County, in Iran * Nur Mountains "Mountains of Holy Light", a mountain range in Turkey * NUR Reactor, a research reactor in Algiers * Nur University (Bolivia) * National University of Rwanda * Nuristan Province Nuristan, also spelled as Nurestan or Nooristan (Dari: ; Kamkata-vari: ), is one of the 34 provinces of Afghanistan, located in the eastern part of the country. It is divided into seven districts and is Afghanistan's least populous province, wi ..., Afghanistan Other uses * Nur (biology), a family of transcription factors * National Union of Railwaymen, a trade union in the United Kingdom * Nur (Raw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biofilm
A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeric substances (EPSs). The cells within the biofilm produce the EPS components, which are typically a polymeric conglomeration of extracellular polysaccharides, proteins, lipids and DNA. Because they have three-dimensional structure and represent a community lifestyle for microorganisms, they have been metaphorically described as "cities for microbes". Biofilms may form on living or non-living surfaces and can be prevalent in natural, industrial, and hospital settings. They may constitute a microbiome or be a portion of it. The microbial cells growing in a biofilm are physiologically distinct from planktonic cells of the same organism, which, by contrast, are single cells that may float or swim in a liquid medium. Biofilms can form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benthos
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.Benthos from the Census of Antarctic Marine Life website This community lives in or near marine or freshwater sedimentary environments, from s along the , out to the , and t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anoxic Waters
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 (but not lacking) in dissolved oxygen. This condition is generally found in areas that have restricted water exchange. In most cases, oxygen is prevented from reaching the deeper levels by a physical barrier, as well as by a pronounced density stratification, in which, for instance, heavier hypersaline waters rest at the bottom of a basin. Anoxic conditions will occur if the rate of oxidation of organic matter by bacteria is greater than the supply of dissolved oxygen. Anoxic waters are a natural phenomenon, and have occurred throughout geological history. The Permian–Triassic extinction event, a mass extinction of species from the world's oceans, may have resulted from w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methanogenesis
Methanogenesis or biomethanation is the formation of methane coupled to energy conservation by microbes known as methanogens. Organisms capable of producing methane for energy conservation have been identified only from the domain Archaea, a group phylogenetically distinct from both eukaryotes and bacteria, although many live in close association with anaerobic bacteria. Other forms of methane production that are not coupled to ATP synthesis exist within all three domains of life. The production of methane is an important and widespread form of microbial metabolism. In anoxic environments, it is the final step in the decomposition of biomass. Methanogenesis is responsible for significant amounts of natural gas accumulations, the remainder being thermogenic. Biochemistry Methanogenesis in microbes is a form of anaerobic respiration. Methanogens do not use oxygen to respire; in fact, oxygen inhibits the growth of methanogens. The terminal electron acceptor in methanogenesis is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anammox
Anammox, an abbreviation for anaerobic ammonium oxidation, is a globally important microbial process of the nitrogen cycle that takes place in many natural environments. The bacteria mediating this process were identified in 1999, and were a great surprise for the scientific community. In the anammox reaction, nitrite and ammonium ions are converted directly into diatomic nitrogen and water. The bacteria that perform the anammox process are genera that belong to the bacterial phylum Planctomycetota. The anammox bacteria all possess one anammoxosome, a lipid bilayer membrane-bound compartment inside the cytoplasm in which the anammox process takes place. The anammoxosome membranes are rich in ladderane lipids; the presence of these lipids is so far unique in biology. "Anammox" is also the trademarked name for an anammox-based ammonium removal technology developedJetten Michael Silvester Maria, Van Loosdrecht Marinus Corneli; Technische Universiteit Delftpatent WO9807664/ref> by th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Denitrification
Denitrification is a microbially facilitated process where nitrate (NO3−) is reduced and ultimately produces molecular nitrogen (N2) through a series of intermediate gaseous nitrogen oxide products. Facultative anaerobic bacteria perform denitrification as a type of respiration that reduces oxidized forms of nitrogen in response to the oxidation of an electron donor such as organic matter. The preferred nitrogen electron acceptors in order of most to least thermodynamically favorable include nitrate (NO3−), nitrite (NO2−), nitric oxide (NO), nitrous oxide (N2O) finally resulting in the production of dinitrogen (N2) completing the nitrogen cycle. Denitrifying microbes require a very low oxygen concentration of less than 10%, as well as organic C for energy. Since denitrification can remove NO3−, reducing its leaching to groundwater, it can be strategically used to treat sewage or animal residues of high nitrogen content. Denitrification can leak N2O, which is an ozone ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrogen Fixation
Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmospheric nitrogen is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms. Biological nitrogen fixation or ''diazotrophy'' is an important microbials mediated process that converts dinitrogen (N2) gas to ammonia (NH3) using the nitrogenase protein complex (Nif). Nitrogen fixation is essential to life because fixed inorganic nitrogen compounds are required for the biosynthesis of all nitrogen-containing organic compounds, such as amino acids and proteins, nucleoside triphosphates and nucleic acids. As part of the nitrogen cycle, it is essential for agriculture and the manufacture of fertilizer. It is also, indirectly, relevant to the manufacture of all nitrogen chemical c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cellular Respiration
Cellular respiration is the process by which biological fuels are oxidised in the presence of an inorganic electron acceptor such as oxygen to produce large amounts of energy, to drive the bulk production of ATP. Cellular respiration may be described as a set of metabolic reactions and processes that take place in the cells of organisms to convert chemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products. The reactions involved in respiration are catabolic reactions, which break large molecules into smaller ones, releasing energy. Respiration is one of the key ways a cell releases chemical energy to fuel cellular activity. The overall reaction occurs in a series of biochemical steps, some of which are redox reactions. Although cellular respiration is technically a combustion reaction, it is an unusual one because of the slow, controlled release of energy from the series of reactions. Nutrients that are commonly used by animal and plan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Azotobacter
''Azotobacter'' is a genus of usually motile, oval or spherical bacteria that form thick-walled cysts (and also has hard crust) and may produce large quantities of capsular slime. They are aerobic, free-living soil microbes that play an important role in the nitrogen cycle in nature, binding atmospheric nitrogen, which is inaccessible to plants, and releasing it in the form of ammonium ions into the soil (nitrogen fixation). In addition to being a model organism for studying diazotrophs, it is used by humans for the production of biofertilizers, food additives, and some biopolymers. The first representative of the genus, ''Azotobacter chroococcum'', was discovered and described in 1901 by Dutch microbiologist and botanist Martinus Beijerinck. ''Azotobacter'' species are Gram-negative bacteria found in neutral and alkaline soils, in water, and in association with some plants. Biological characteristics Morphology Cells of the genus ''Azotobacter'' are relatively large for b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Profundal Zone
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. The profundal is often defined, as the deepest, vegetation-free, and muddy zone of the lacustrine benthal. The profundal zone is often part of the aphotic zone. Sediment in the profundal zone primarily comprises silt and mud. Organisms 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. The profundal macrofauna is therefore characterized by physiological and behavioural adaptations to low oxygen concentration. While benth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Littoral Zone
The littoral zone 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 (which is rarely inundated), 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. Etymology The word ''littoral'' may be used both as a noun and as an adjective. It derives from the Latin noun ''litus, litoris'', meaning "shore". (The doubled ''t'' is a late-medieval innovation, and the word is sometimes seen in the more classical-looking spelling ''litoral''.) Description The term has no single definition. What is regarded as the full extent of the littoral zone, and the way the littoral zone is divided into subregions, varies in different c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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