Glossary

Chemoautotrophs
Chemoautotrophs use endogenous light-independent reactions to obtain energy, these reactions involve inorganic molecules and an electron donor other than water and do not release oxygen.
Chemocline
A chemocline is a cline (slope) caused by a strong, vertical chemistry gradient within a body of water. A chemocline is similar to a thermocline.
Chemosynthesis
Synthesis of organic compounds by bacteria or other living organisms using energy derived from reactions involving inorganic chemicals, typically in the absence of sunlight.
El Niño
Is an abnormal weather pattern caused by the warming of the Pacific Ocean near the equator, off the coast of South America. The sun warms the water near the equator, which can make more clouds and, therefore, more rain. However, normally there are trade winds, which blow that warm water west. During El Niño, those trade winds weaken, or even reverse, which lets the warm water that is usually found in the western Pacific remain or flow east. This warm water displaces the cooler water that is normally found near the surface of the eastern Pacific, setting off atmospheric changes that affect weather patterns in many parts of the world.
Endosymbiosis
Symbiosis in which one of the symbiotic organisms lives inside the other
Extremophile
A microorganism, especially an archaean, that lives in conditions of extreme temperature, acidity, alkalinity, or chemical concentration
Epilimnion
The upper layer of water in a stratified lake
Ferrel Cell
In the Ferrel cell, air flows poleward and eastward near the surface and equatorward and westward at higher altitudes; this movement is the reverse of the airflow in the Hadley cell.
Halocline
A halocline (from Greek hals or halos 'salt' and klinein 'to slope') is a subtype of chemocline caused by a strong, vertical salinity gradient within a body of water (lake or ocean).
Halophile
An organism that needs high salt concentrations for growth.
Halotolerant
Halotolerance is tolerance to ionic stress, or the ability of an organism to grow at salt concentrations higher than those required for growth. Halotolerant organisms are able to survive at high salt concentrations but do not necessarilty require these conditions for growth.
Heliothermal lake
These lakes are usually saline, meromictic lakes, which means that when they stratify, only the upper layer of the water will mix. The layers are separated by a halocline, with the mixolimnion remaining fairly fresh and the lower monimolimnion containing a higher salt concentration. When this stratification falls within the photic zone, unusual events happen. Sunlight that reaches the monimolimnion heats the water. This heat cannot escape because the density of the saline lower layer is not significantly affected by increasing temperatures. The result is a heat trap at and below the halocline, where temperatures can easily reach 50°C and higher
Heterotrophic bacteria
Heterotrophic bacteria are a type of bacteria that take the sugars they need to survive and reproduce from their environment, rather than making the sugars themselves from carbon and hydrogen.
Heterotrophs
Heterotrophs (literally “feeders on others”) use organic molecules syn-thesized outside their body as a source of energy and carbon (consum-ers, detritovores, decomposers). They are saprophytes, obtaining their nutrients from dead organic matter. Most chemotrophs are autotrophic, but some are heterotrophs (chemoheterotrophs), which use inorganic oxidation for energy but use organic matter for carbon as well as sup-plemental energy. Photosynthetic bacteria have the biochemistry for either anoxygenic photosynthesis (non O2-producing) or oxygenic pho-tosynthesis (O2-producing). Most photosynthetic bacteria are auto-trophs that fix CO2 (photoautotrophs), but some rely on organic matter for their carbon (photoheterotrophs). Adaptive prokaryotes switch their modes of metabolism depending on environmental conditions
Holomictic lake
Holomictic lakes have a uniform temperature and density from top to bottom, which allows the lake waters to completely mix.
Homoacetogenesis
Homoacetogenesis is acetogenesis usinggaseous hydrogen and carbon dioxide
Hypolimnion
The layer of water in a stratified lake that lies below the chemocline or thermocline, and is noncirculating.
Intertropical Convergence Zone (ITCZ)
The Intertropical Convergence Zone (ITCZ), known by sailors as the doldrums or the calms because of its monotonous, windless weather, is the area where the northeast and southeast trade winds converge. It encircles Earth near the thermal equator, though its specific position varies seasonally. When it lies near the geographic Equator, it is called the near-equatorial trough. Where the ITCZ is drawn into and merges with a monsoonal circulation, it is sometimes referred to as a monsoon trough, a usage more common in Australia and parts of Asia
Lithoautotrophs
Lithoautotrophs depend upon inorganic compounds as electron donors for energy production.
La Niña
La Niña is a coupled ocean-atmosphere phenomenon that is the colder counterpart of El Niño, as part of the broader El Niño–Southern Oscillation (ENSO) climate pattern.
Lunette
A type of crescent-shaped dune composed of pelleted clay, quartz or gypsum, blown up along the edges or forming a local eroded high in a lake basin, especially in dry areas of Australia.
Meromixis
The property (of a lake) by which water below a certain depth does not circulate during overturn owing to its high density (usually the result of a high salt concentration)
Methanogen
Methanogens are microorganisms that produce methane as a metabolic byproduct in hypoxic conditions. They are prokaryotic and generally belong to the domain of archaea.
Mixolimnion
The upper layer of a meromictic lake; its upper waters are mixed by the wind and evaporation
Monimolimnion
The lower, dense water layer of a meromictic lake that does not mix with the waters above.
Sulphur oxidising bacteria
Sulphur oxidising bacteria (SOB) are aerobic, anaerobic or facultative, and most of them are obligate or facultative autotrophs, that can either use carbon dioxide or organic compounds as a source of carbon (mixotrophs)
Sulphur reducing bacteria
Sulphur reducing bacteria (SRB) get their energy by reducing elemental sulfur to hydrogen sulfide. They couple this reaction with the oxidation of acetate, succinate or other organic compounds. Several types of bacteria and many non-methanogenic archaea can reduce sulfur.
Thermocline
The temperature border at which warmer and cooler waters meet in an ocean, sea, lake, or other body of water.
Uniformitarianism
The doctrine suggesting that Earth's geologic processes acted in the same manner and with essentially the same intensity in the past as they do in the present and that such uniformity is sufficient to account for all geologic change.