An oligotroph is an organism that can live in an environment that offers very low levels of nutrients. They may be contrasted with copiotrophs, which prefer nutritionally rich environments. Oligotrophs are characterized by slow growth, low rates of metabolism, and generally low population density.
The adjective oligotrophic may be used to refer to environments that offer little to sustain life, organisms that survive in such environments, or the adaptations that support survival. Etymologically, the word "oligotroph" is a combination of the Greek adjective oligos (ὀλίγος) meaning "few" and the adjective trophikos (τροφικός)) meaning "feeding".
Oligotrophic environments include deep oceanic sediments, caves, glacial and polar ice, deep subsurface soil, aquifers, ocean waters, and leached soils.
Examples of oligotrophic organisms are the cave-dwelling olm; the bacterium, Pelagibacter ubique, which is the most abundant organism in the oceans with an estimated 2 × 1028 individuals in total; and the lichens with their extremely low metabolic rate.
Plant adaptations to oligotrophic soils provide for greater and more efficient nutrient uptake, reduced nutrient consumption, and efficient nutrient storage. Improvements in nutrient uptake are facilitated by root adaptations such as nitrogen-fixing root nodules, mycorrhizae and cluster roots. Consumption is reduced by very slow growth rates, and by efficient use of low-availability nutrients; for example, the use of highly available ions to maintain turgor pressure, with low-availability nutrients reserved for the building of tissues. Despite these adaptations, nutrient requirement typically exceed uptake during the growing season, so many oligotrophic plants have the ability to store nutrients, for example, in trunk tissues, when demand is low, and remobilise them when demand increases.
Oligotrophs occupy environments where the available nutrients offer little to sustain life. The term “oligotrophic” is commonly used to describe terrestrial and aquatic environments with very low concentrations of nitrates, iron, phosphates, and carbon sources.
Oligotrophs have acquired survival mechanisms that involve the expression of genes during periods of low nutrient conditions, which has allowed them to find success in various environments. Despite the capability to live in low nutrient concentrations, oligotrophs may find difficulty surviving in nutrient-rich environments.
Antarctic life offers very little to sustain life as most organisms are not well adapted to live under nutrient-limiting conditions and cold temperatures (lower than 5 °C). As such, these environments display a large abundance of psychrophiles that are well adapted to living in an Antarctic biome. Most oligotrophs live in lakes where water helps support biochemical processes for growth and survival. Below are some documented examples of oligotrophic environments in Antarctica:
Lake Vostok, a freshwater lake which has been isolated from the world beneath 4 km (2.5 mi) of Antarctic ice is frequently held to be a primary example of an oligotrophic environment. Analysis of ice samples showed ecologically separated microenvironments. Isolation of microorganisms from each microenvironment led to the discovery of a wide range of different microorganisms present within the ice sheet. Traces of fungi have also been observed which suggests potential for unique symbiotic interactions. The lake’s extensive oligotrophy has led some to believe parts of lake are completely sterile. This lake is a helpful tool for simulating studies regarding extraterrestrial life on frozen planets and other celestial bodies.
Crooked Lake is an ultra-oligotrophic glacial lake with a thin distribution of heterotrophic and autotrophic microorganisms. The microbial loop plays a big role in cycling nutrients and energy within this lake, despite particularly low bacterial abundance and productivity in these environments. The little ecological diversity can be attributed to the lake's low annual temperatures. Species discovered in this lake include Ochromonas, Chlamydomonas, Scourfeldia, Cryptomonas, Akistrodesmus falcatus, and Daphniopsis studeri (a microcrustacean). It is proposed that low competitive selection against Daphniopsis studeri has allowed the species to survive long enough to reproduce in nutrient limiting environments.
The sandplains and lateritic soils of southern Western Australia, where an extremely thick craton has precluded any geological activity since the Cambrian and there has been no glaciation to renew soils since the Carboniferous. Thus, soils are extremely nutrient-poor and most vegetation must use strategies such as cluster roots to gain even the smallest quantities of such nutrients as phosphorus and sulfur.
The vegetation in these regions, however, is remarkable for its biodiversity, which in places is as great as that of a tropical rainforest and produces some of the most spectacular wildflowers in the world. It is however, severely threatened by climate change which has moved the winter rain belt south, and also by clearing for agriculture and through use of fertilizers, which is primarily driven by low land costs which make farming economic even with yields a fraction of those in Europe or North America.
An example of oligotrophic soils are those on white-sands, with soil pH lower than 5.0, on the Rio Negro basin on northern Amazonia that house very low-diversity, extremely fragile forests and savannahs drained by blackwater rivers; dark water colour due to high concentration of tannins, humic acids and other organic compounds derived from the very slow decomposition of plant matter. Similar forests are found in the oligotrophic waters of the Patía River delta on the Pacific side of the Andes.
In the ocean, the subtropical gyres north and south of the equator are regions in which the nutrients required for phytoplankton growth (for instance, nitrate, phosphate and silicic acid) are strongly depleted all year round. These areas are described as oligotrophic and exhibit low surface chlorophyll. They are occasionally described as "ocean deserts".
The oligotrophic soil environments include agricultural soil, frozen soil etc. Various factors, such as decomposition, soil structure, fertilization and temperature, can affect the nutrient-availability in the soil environments.
Generally, the nutrient becomes less available along the depth of the soil environment, because on the surface, the organic compounds decomposed from the plant and animal debris are consumed quickly by other microbes, resulting in the lack of nutrient in the deeper level of soil. In addition, the metabolic waste produced by the microorganisms on the surface also causes the accumulation of toxic chemicals in the deeper area. Furthermore, oxygen and water are important for some metabolic pathways, but it is difficult for water and oxygen to diffuse as the depth increases. Some factors, such as soil aggregates, pores and extracellular enzymes, may help water, oxygen and other nutrients diffuse into the soil. Moreover, the presence of mineral under the soil provides the alternative sources for the species living in the oligotrophic soil. In terms of the agricultural lands, the application of fertilizer has a complicated impact on the source of carbon, either increasing or decreasing the organic carbon in the soil.
Collimonas is one of the species that are capable of living in the oligotrophic soil. One common feature of the environments where Collimonas lives is the presence of fungi, because Collimonas have the ability of not only hydrolyzing the chitin produced by fungi for nutrients, but also producing materials (e.g., P. fluorescens 2-79) to protect themselves from fungal infection. The mutual relationship is common in the oligotrophic environments. Additionally, Collimonas can also obtain electron sources from rocks and minerals by weathering.
In terms of polar areas, such as Antarctic and Arctic region, the soil environment is considered as oligotrophic because the soil is frozen with low biological activities. The most abundant species in the frozen soil are Actinobacteria, Proteobacteria, Acidobacteria and Cyanobacteria, together with a small amount of archaea and fungi. Actinobacteria can maintain the activity of their metabolic enzymes and continue their biochemical reactions under a wide range of low temperature. In addition, the DNA repairing machinery in Actinobacteria protects them from lethal DNA mutation at low temperature.
Aajuitsup Tasia (old spelling: Aujuitsup Tasia) is a large lake in central-western Greenland, in the Qeqqata municipality. It is located approximately 12 km (7.5 mi) northeast of Kangerlussuaq. It is of elongated oval shape, with its western shore at 67°04′45″N 50°30′02″W and its eastern shore at 67°05′35″N 50°16′30″W. Aajuitsup Tasia is an oligotrophic lake of 32 m (105 ft) depth, covering an area of 1,350ha.Cascade effect (ecology)
An ecological cascade effect is a series of secondary extinctions that is triggered by the primary extinction of a key species in an ecosystem. Secondary extinctions are likely to occur when the threatened species are: dependent on a few specific food sources, mutualistic (dependent on the key species in some way), or forced to coexist with an invasive species that is introduced to the ecosystem. Species introductions to a foreign ecosystem can often devastate entire communities, and even entire ecosystems. These exotic species monopolize the ecosystem's resources, and since they have no natural predators to decrease their growth, they are able to increase indefinitely. Olsen et al. showed that exotic species have caused lake and estuary ecosystems to go through cascade effects due to loss of algae, crayfish, mollusks, fish, amphibians, and birds. However, the principal cause of cascade effects is the loss of top predators as the key species. As a result of this loss, a dramatic increase (ecological release) of prey species occurs. The prey is then able to overexploit its own food resources, until the population numbers decrease in abundance, which can lead to extinction. When the prey's food resources disappear, they starve and may go extinct as well. If the prey species is herbivorous, then their initial release and exploitation of the plants may result in a loss of plant biodiversity in the area. If other organisms in the ecosystem also depend upon these plants as food resources, then these species may go extinct as well. An example of the cascade effect caused by the loss of a top predator is apparent in tropical forests. When hunters cause local extinctions of top predators, the predators' prey's population numbers increase, causing an overexploitation of a food resource and a cascade effect of species loss. Recent studies have been performed on approaches to mitigate extinction cascades in food-web networks.Directed panspermia
Directed panspermia is the deliberate transport of microorganisms in space to be used as introduced species on lifeless but habitable astronomical objects.
Historically, Shklovskii and Sagan (1966) and Crick and Orgel (1973) hypothesized that life on the Earth may have been seeded deliberately by other civilizations. Conversely, Mautner and Matloff (1979) and Mautner (1995, 1997) proposed that humanity should seed other planetary systems, protoplanetary discs or star-forming clouds with microorganisms, to secure and expand our organic gene/protein lifeform. To avoid interference with local life, the targets may be young planetary systems where local life is unlikely. Directed panspermia can be motivated by biotic ethics that value the basic patterns of organic gene/protein life with its unique complexity and unity, and its drive for self-propagation.
Directed panspermia is becoming possible due to developments in solar sails, precise astrometry, the discovery of extrasolar planets, extremophiles and microbial genetic engineering. Cosmological projections suggest that life in space can then have a future.Energy flow (ecology)
In ecology, energy flow, also called the calorific flow, refers to the flow of energy through a food chain, and is the focus of study in ecological energetics. In an ecosystem, ecologists seek to quantify the relative importance of different component species and feeding relationships.
A general energy flow scenario follows:
Solar energy is fixed by the photoautotrophs, called primary producers, like green plants. Primary consumers absorb most of the stored energy in the plant through digestion, and transform it into the form of energy they need, such as adenosine triphosphate (ATP), through respiration. A part of the energy received by primary consumers, herbivores, is converted to body heat (an effect of respiration), which is radiated away and lost from the system. The loss of energy through body heat is far greater in warm-blooded animals, which must eat much more frequently than those that are cold-blooded. Energy loss also occurs in the expulsion of undigested food (egesta) by excretion or regurgitation.
Secondary consumers, carnivores, then consume the primary consumers, although omnivores also consume primary producers. Energy that had been used by the primary consumers for growth and storage is thus absorbed into the secondary consumers through the process of digestion. As with primary consumers, secondary consumers convert this energy into a more suitable form (ATP) during respiration. Again, some energy is lost from the system, since energy which the primary consumers had used for respiration and regulation of body temperature cannot be utilized by the secondary consumers.
Tertiary consumers, which may or may not be apex predators, then consume the secondary consumers, with some energy passed on and some lost, as with the lower levels of the food chain.
A final link in the food chain are decomposers which break down the organic matter of the tertiary consumers (or whichever consumer is at the top of the chain) and release nutrients into the soil. They also break down plants, herbivores and carnivores that were not eaten by organisms higher on the food chain, as well as the undigested food that is excreted by herbivores and carnivores. Saprotrophic bacteria and fungi are decomposers, and play a pivotal role in the nitrogen and carbon cycles.The energy is passed on from trophic level to trophic level and each time about 90% of the energy is lost, with some being lost as heat into the environment (an effect of respiration) and some being lost as incompletely digested food (egesta). Therefore, primary consumers get about 10% of the energy produced by autotrophs, while secondary consumers get 1% and tertiary consumers get 0.1%. This means the top consumer of a food chain receives the least energy, as a lot of the food chain's energy has been lost between trophic levels. This loss of energy at each level limits typical food chains to only four to six links.Extremophile
An extremophile (from Latin extremus meaning "extreme" and Greek philiā (φιλία) meaning "love") is an organism that thrives in physically or geochemically extreme conditions that are detrimental to most life on Earth. In contrast, organisms that live in more moderate environments may be termed mesophiles or neutrophiles.Food web
A food web (or food cycle) is the natural interconnection of food chains and a graphical representation (usually an image) of what-eats-what in an ecological community. Another name for food web is consumer-resource system. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs. To maintain their bodies, grow, develop, and to reproduce, autotrophs produce organic matter from inorganic substances, including both minerals and gases such as carbon dioxide. These chemical reactions require energy, which mainly comes from the Sun and largely by photosynthesis, although a very small amount comes from hydrothermal vents and hot springs. A gradient exists between trophic levels running from complete autotrophs that obtain their sole source of carbon from the atmosphere, to mixotrophs (such as carnivorous plants) that are autotrophic organisms that partially obtain organic matter from sources other than the atmosphere, and complete heterotrophs that must feed to obtain organic matter. The linkages in a food web illustrate the feeding pathways, such as where heterotrophs obtain organic matter by feeding on autotrophs and other heterotrophs. The food web is a simplified illustration of the various methods of feeding that links an ecosystem into a unified system of exchange. There are different kinds of feeding relations that can be roughly divided into herbivory, carnivory, scavenging and parasitism. Some of the organic matter eaten by heterotrophs, such as sugars, provides energy. Autotrophs and heterotrophs come in all sizes, from microscopic to many tonnes - from cyanobacteria to giant redwoods, and from viruses and bdellovibrio to blue whales.
Charles Elton pioneered the concept of food cycles, food chains, and food size in his classical 1927 book "Animal Ecology"; Elton's 'food cycle' was replaced by 'food web' in a subsequent ecological text. Elton organized species into functional groups, which was the basis for Raymond Lindeman's classic and landmark paper in 1942 on trophic dynamics. Lindeman emphasized the important role of decomposer organisms in a trophic system of classification. The notion of a food web has a historical foothold in the writings of Charles Darwin and his terminology, including an "entangled bank", "web of life", "web of complex relations", and in reference to the decomposition actions of earthworms he talked about "the continued movement of the particles of earth". Even earlier, in 1768 John Bruckner described nature as "one continued web of life".
Food webs are limited representations of real ecosystems as they necessarily aggregate many species into trophic species, which are functional groups of species that have the same predators and prey in a food web. Ecologists use these simplifications in quantitative (or mathematical representation) models of trophic or consumer-resource systems dynamics. Using these models they can measure and test for generalized patterns in the structure of real food web networks. Ecologists have identified non-random properties in the topographic structure of food webs. Published examples that are used in meta analysis are of variable quality with omissions. However, the number of empirical studies on community webs is on the rise and the mathematical treatment of food webs using network theory had identified patterns that are common to all. Scaling laws, for example, predict a relationship between the topology of food web predator-prey linkages and levels of species richness.Gurre, Denmark
Gurre is a village located five kilometres west of Helsingør and 42 kilometres north of central Copenhagen, Denmark. It is located on the east side of Gurre Lake and is almost surrounded by woodland. As of 1 January 2014, its population was 411. It is most known for the ruin of Gurre Castle.Invasive species
An invasive species is a species that is not native to a specific location (an introduced species), and that has a tendency to spread to a degree believed to cause damage to the environment, human economy or human health.The term as most often used applies to introduced species that adversely affect the habitats and bioregions they invade economically, environmentally, or ecologically. Such species may be either plants or animals and may disrupt by dominating a region, wilderness areas, particular habitats, or wildland–urban interface land from loss of natural controls (such as predators or herbivores). This includes plant species labeled as exotic pest plants and invasive exotics growing in native plant communities. The European Union defines "Invasive Alien Species" as those that are, firstly, outside their natural distribution area, and secondly, threaten biological diversity. The term is also used by land managers, botanists, researchers, horticulturalists, conservationists, and the public for noxious weeds.The term "invasive" is often poorly defined or very subjective and some broaden the term to include indigenous or "native" species, that have colonized natural areas - for example deer considered by some to be overpopulating their native zones and adjacent suburban gardens in the Northeastern and Pacific Coast regions of the United States.The definition of "native" is also sometimes controversial. For example, the ancestors of Equus ferus (modern horses) evolved in North America and radiated to Eurasia before becoming locally extinct. Upon returning to North America in 1493 during their hominid-assisted migration, it is debatable as to whether they were native or exotic to the continent of their evolutionary ancestors.Notable examples of invasive plant species include The kudzu vine, Andean pampas grass, and yellow starthistle. Animal examples include the New Zealand mud snail, feral pigs, European rabbits, grey squirrels, domestic cats, carp and ferrets.Invasion of long-established ecosystems by organisms from distant bio-regions is a natural phenomenon, but has been accelerated massively by humans, from their earliest migrations though to the age of discovery, and now international trade.Mesopredator release hypothesis
The mesopredator release hypothesis is an ecological theory used to describe the interrelated population dynamics between apex predators and mesopredators within an ecosystem, such that a collapsing population of the former results in dramatically-increased populations of the latter. This hypothesis describes the phenomenon of trophic cascade in specific terrestrial communities.
A mesopredator is a medium-sized, middle trophic level predator, which both preys and is preyed upon. Examples are raccoons, skunks, snakes, cownose rays, and small sharks.Mutusjärvi
Mutusjärvi is a medium-sized lake in the Paatsjoki main catchment area in Lapland region in Finland. Lake is Oligotroph.Mycorrhiza
A mycorrhiza (from Greek μύκης mýkēs, "fungus", and ῥίζα rhiza, "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plant's rhizosphere, its root system. Mycorrhizae play important roles in plant nutrition, soil biology and soil chemistry.
In a mycorrhizal association, the fungus colonizes the host plant's root tissues, either intracellularly as in arbuscular mycorrhizal fungi (AMF or AM), or extracellularly as in ectomycorrhizal fungi. The association is sometimes mutualistic. In particular species or in particular circumstances mycorrhizae may have a parasitic association with host plants.Pararheinheimera texasensis
Pararheinheimera texasensis is a Gram-negative, rod-shaped, non-spore-forming and motile bacterium from the genus of Pararheinheimera which has been isolated from the Spring Lake from San Marcos in the United States.Pelagibacter ubique
Pelagibacter, with the single species P. ubique, was isolated in 2002 and given a specific name, although it has not yet been described as required by the bacteriological code. It is an abundant member of the SAR11 clade in the phylum Alphaproteobacteria. SAR11 members are highly dominant organisms found in both salt and fresh water worldwide – possibly the most numerous bacterium in the world, and were originally known only from their rRNA genes, which were first identified in environmental samples from the Sargasso Sea in 1990 by Stephen Giovannoni's laboratory in the Department of Microbiology at Oregon State University and later found in oceans worldwide. P. ubique and its relatives may be the most abundant organisms in the ocean, and quite possibly the most abundant bacteria in the entire world. It can make up about 25% of all microbial plankton cells, and in the summer they may account for approximately half the cells present in temperate ocean surface water. The total abundance of P. ubique and relatives is estimated to be about 2 × 1028 microbes.It is rod or crescent shaped and one of the smallest self-replicating cells known, with a length of 0.37–0.89 µm and a diameter of only 0.12–0.20 µm. The Pelagibacter genome takes up about 30% of the cell's volume. It is gram negative. It recycles dissolved organic carbon. It undergoes regular seasonal cycles in abundance – in summer reaching ~50% of the cells in the temperate ocean surface waters. Thus it plays a major role in the Earth's carbon cycle.
Its discovery was the subject of "Oceans of Microbes", Episode 5 of "Intimate Strangers: Unseen Life on Earth" by PBS.Productivity (ecology)
In ecology, productivity refers to the rate of generation of biomass in an ecosystem. It is usually expressed in units of mass per unit surface (or volume) per unit time, for instance grams per square metre per day (g m−2 d−1). The mass unit may relate to dry matter or to the mass of carbon generated. Productivity of autotrophs such as plants is called primary productivity, while that of heterotrophs such as animals is called secondary productivity.Sanningasoq
Sanningasoq (old spelling: Sáningassoq) is a large oligotrophic twin lake in central-western Greenland, in the Qeqqata municipality. It is located approximately 9 km (5.6 mi) northeast of Kangerlussuaq. It is characteristic in that it is composed of two lakes connected via a narrow water passage through a broken isthmus. Its northwestern shore is at 67°05′15″N 50°39′50″W and its southeastern shore at 67°04′00″N 50°28′53″W.Streamlining theory
Genomic streamlining is a theory in evolutionary biology and microbial ecology that suggests that there is a reproductive benefit to prokaryotes having a smaller genome size with less non-coding DNA and fewer non-essential genes. There is a lot of variation in prokaryotic genome size, with the smallest free-living cell's genome being roughly ten times smaller than the largest prokaryote. Two of the bacterial taxa with the smallest genomes are Prochlorococcus and Pelagibacter ubique, both highly abundant marine bacteria commonly found in oligotrophic regions. Similar reduced genomes have been found in uncultured marine bacteria, suggesting that genomic streamlining is a common feature of bacterioplankton. This theory is typically used with reference to free-living organisms in oligotrophic environments.Sustainable gardening
Sustainable gardening includes the more specific sustainable landscapes, sustainable landscape design, sustainable landscaping, sustainable landscape architecture, resulting in sustainable sites. It comprises a disparate group of horticultural interests that can share the aims and objectives associated with the international post-1980s sustainable development and sustainability programs developed to address the fact that humans are now using natural biophysical resources faster than they can be replenished by nature.Included within this compass are those home gardeners, and members of the landscape and nursery industries, and municipal authorities, that integrate environmental, social, and economic factors to create a more sustainable future.
Organic gardening and the use of native plants are integral to sustainable gardening.Tasersuatsiaq
Tasersuatsiaq (old spelling: Taserssuatsiaq) is a lake in central-western Greenland, in the Qeqqata municipality. It is located southeast of Kangerlussuaq, with a depth of 80 m (262.5 ft), covering an area of 750ha. During the operating years of the American base at Bluie West Eight at Kangerlussuaq the lake was referred to as Lake Ferguson. The lake and the Roklubben Restaurant at its western shore are connected to Kangerlussuaq by a gravel road, one of the very few in Greenland. Tasersuatsiaq is a source of fresh water for Kangerlussuaq.Terriglobus roseus
Terriglobus roseus is a bacterium belonging to subdivision 1 of the Acidobacteria phylum, and is closely related to the genera Granulicella and Edaphobacter. T. roseus was the first species recognized in the genus Terriglobus in 2007. This bacterial species is extremely abundant and diverse in agricultural soils. T. roseus is an aerobic Gram-negative rod lacking motility. This bacteria can produce extracellular polymeric substances (EPS) to form a biofilm, or extracellular matrix, for means of protection, communication amongst neighboring cells, etc. Its type strain is KBS 63.As implied by its name, on solid media, the bacterial colonies produce a pink pigmentation, indicating the presence of carotenoids. T. roseus grows best at room temperature (23 °C) in a liquid media called R2B, containing peptone, casamino acids, yeast extract, glucose, soluble starch, sodium pyruvate and inorganic salts. Although T. roseus is found in soil and sediment environments, it is highly difficult to culture Acidobacteria in lab settings. Currently, there is no sufficient growth media that allows for T. roseus to grow in soil. This species optimal pH for growth is pH6, however this species can survive in acidic conditions as low as pH 5.