Carbonate precipitation is thermodynamically favoured at high temperature and low pressure. Three types of carbonate precipitation are possible: biotically controlled, biotically induced and abiotic. Carbonate precipitation is biotically controlled when organisms (such as corals) are present that exploit carbonate dissolved in seawater to build their calcitic or aragonitic skeletons. Thus they may develop hard reef structures.
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In these platforms precipitation is biotically controlled, mostly by autotrophic organisms.
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These platforms are characterised by abiotic precipitation and biotically induced precipitation.
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Mercury methylation is the process of forming methylmercury (MeHg). The methylation of mercury can occur abiotically or biotically. Biotically, the primary methylators of mercury are sulfate-reducing and iron-reducing bacteria. Three mechanisms have been proposed for the biotic methylation of mercury by sulfate-reducing bacteria.
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The three types of precipitation (abiotic, biotically induced and biotically controlled) cluster into three "carbonate factories". A carbonate factory is the ensemble of the sedimentary environment, the intervening organisms and the precipitation processes that lead to the formation of a carbonate platform. The differences between three factory is the dominant precipitation pathway and skeletal associations. In contrast, a carbonate platform is a geological structure of parautochotonous carbonate sediments and carbonate rocks, having a morphological relief.
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Biotically induced precipitation takes place outside the cell of the organism, thus carbonate is not directly produced by organisms, but precipitates because of their metabolism. Abiotic precipitation, by definition, involves little or no biological influence.
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Slowed decomposition is biotically mediated in an ectomycorrhizal, tropical rain forest. Oecologia, 164: 785-795. A theoretical ecosystem model recently demonstrated that greater access to organic nitrogen by mycorrhizal fungi should slow decomposition of soil carbon by free-living decomposers by inducing nutrient limitation.
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There are several chemical processes that happen abiotically (chemical reactions), as well as biotically (microbial or enzyme mediated reactions). For example, oxidation-reduction (redox) reactions can occur simply through the reactions of elements, or by oxidizing/reducing bacteria. The transformations and turnover of elements between sediments and water occur through abiotic chemical processes and microbiological chemical processes.
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In fact, all our functioning is multi-aspectual, though some aspects might be latent. Things exist by reference to each aspect. For example, a car exists physically as a load of steel, plastic, etc., kinematically as a mode of transport, socially as a status symbol, economically as a dent in our finances, aesthetically as a thing of beauty, biotically as a polluter, pistically as an idol, and so on.
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Hubbell considers the fact that community sizes are constant and interprets it as a general principle: large landscapes are always biotically saturated with individuals. Hubbell thus treats communities as being of a fixed number of individuals, usually denoted by J. Exceptions to the saturation principle include disturbed ecosystems such as the Serengeti, where saplings are trampled by elephants and Blue wildebeests; or gardens, where certain species are systematically removed.
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Such disturbances can cause large changes in plant, animal and microbe populations, as well as soil organic matter content. Disturbance is followed by succession, a "directional change in ecosystem structure and functioning resulting from biotically driven changes in resources supply." The frequency and severity of disturbance determine the way it affects ecosystem function. A major disturbance like a volcanic eruption or glacial advance and retreat leave behind soils that lack plants, animals or organic matter.
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Melittosphex burmensis, the oldest bee fossil, from the Cretaceous The first fossil record for abiotic pollination is from fern-like plants in the late Carboniferous period. Gymnosperms show evidence for biotic pollination as early as the Triassic period. Many fossilized pollen grains show characteristics similar to the biotically dispersed pollen today. Furthermore, the gut contents, wing structures, and mouthpart morphology of fossilized beetles and flies suggest that they acted as early pollinators.
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In these carbonate factories, precipitation is biotically controlled, mostly by autotrophic organisms. Organisms that build this kind of platforms are today mostly corals and green algae, that need sunlight for photosynthesis and thus live in the euphotic zone (i.e., shallow water environments in which sunlight penetrates easily). Tropical carbonate factories are only present today in warm and sunlit waters of the tropical-subtropical belt, and they have high carbonate production rates but only in a narrow depth window.
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Bacteria are more likely to contain such enzymes because of their strong selection for new enzymes and metabolic pathways that supply essential nutrients. In addition, genes move horizontally within microbial populations, spreading newly evolved degradation pathways. Some transformations, particularly substitutions, can proceed both biotically and abiotically, although enzyme-catalyzed reactions typically reach higher rates. For example, the hydrolytic dechlorination of atrazine to hydroxyatrazine in soil by atrazine-dechlorinating bacterial enzymes reached a second-order rate constant of 105/mole/second, likely dominating in the environment.
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In these carbonate factories, precipitation is biotically controlled by heterotrophic organisms, sometimes in association with photo-autotrophic organisms such as red algae. The typical skeletal association includes foraminifers, red algae and molluscs. Despite being autotrophic, red algae are mostly associated to heterotrophic carbonate producers, and need less light than green algae. The range of occurrence of cool-water factories extends from the limit of the tropical factory (at about 30◦) up to polar latitudes, but they could also occur at low latitudes in the thermocline below the warm surface waters or in upwelling areas.
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These factories are characterised by abiotic precipitation and biotically induced precipitation. The typical environmental settings where "mud-mound factories" are found in the Phanerozoic are dysphotic or aphotic, nutrient-rich waters that are low in oxygen but not anoxic. These conditions often prevail in the thermocline, for example at intermediate water depths below the ocean's mixed layer. The most important component of these platforms is fine-grained carbonate that precipitates in situ (automicrite) by a complex interplay of biotic and abiotic reactions with microbes and decaying organic tissue.
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Samples taken from different parts of an organism or an organ can simultaneously be analysed and compared, on the same blot, giving a clear picture of the distribution of enzyme activity. With the same simplicity, corresponding tissues taken from normally and biotically- or abiotically- stressed individuals can be compared for enzyme stimulation or induction. Furthermore, zymoblots can be very helpful in cytochemodissection studies aiming at localising enzymes within cells. Cell fractions representing different parts of the cell (nuclei, mitochondria, lysosomes, peroxisomes, Golgi bodies, cytosol,... etc.) can be tested for a host of enzymes in a relatively short time.
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Microbialite is a rock or benthic sedimentary deposit made of carbonate mud (particle diameter < 5 μm) that is formed with the mediation of microbes. The constituent carbonate mud is a type of automicrite, or authigenic carbonate mud, and therefore it precipitates in situ instead of being transported and deposited. Been formed in situ, a microbialite can be seen as a type of boundstone where reef builders are microbes, and precipitation of carbonate is biotically induced instead of forming tests, shells or skeletons. Bacteria can precipitate carbonate both in shallow and in deep water (except for cyanobacyeria) and so microbialites can form regardless of the sun light.
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8:2 fluorotelomer alcohol, (8:2 FTOH), degrades environmentally to PFOA PFOA can form as a breakdown product from a variety of precursor molecules. In fact, the main products of the fluorotelomer industry, fluorotelomer-based polymers, have been shown to degrade to form PFOA and related compounds, with half-lives of decades, both biotically and by simple abiotic reaction with water. It has been argued that fluorotelomer-based polymers already produced might be major sources of PFOA globally for decades to come. Other precursors that degrade to PFOA include 8:2 fluorotelomer alcohol (F(CF2)8CH2CH2OH), polyfluoroalkyl phosphate surfactants (PAPS), and possibly N-EtFOSE alcohol (F(CF2)8SO2N(Et)CH2CH2OH).
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As an environmental ethic, Leopold's land ethic is a comparatively moderate view that seeks to strike a balance between human interests and a healthy and biotically diverse natural environment. Many of the things mainstream environmentalists favor—preference for native plants and animals over invasive species, hunting or selective culling to control overpopulated species that are damaging to the environment, and a focus on preserving healthy, self-regenerating natural ecosystems both for human benefit and for their own intrinsic value—jibe with Leopold's ecocentric land ethic. A related understanding has been framed as global land as a commons. In this view biodiversity and terrestrial carbon storage - an element of climate change mitigation - are global public goods.
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Redwood tree in northern California forest, where many trees are managed for preservation and longevity Forest ecology is one branch of a biotically- oriented classification of types of ecological study (as opposed to a classification based on organizational level or complexity, for example population or community ecology). Thus, forests are studied at a number of organizational levels, from the individual organism to the ecosystem. However, as the term forest connotes an area inhabited by more than one organism, forest ecology most often concentrates on the level of the population, community or ecosystem. Logically, trees are an important component of forest research, but the wide variety of other life forms and abiotic components in most forests means that other elements, such as wildlife or soil nutrients, are often the focal point.
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