A brine pool, sometimes called an underwater lake, deepwater or brine lake, is a volume of brine collected in a seafloor depression. These pools are dense bodies of water that have a salinity that is typically three to eight times greater than the surrounding ocean. Brine pools are commonly found below polar sea ice and in the deep ocean. This below-sea ice forms through a process called brine rejection. [1] For deep-sea brine pools, salt is necessary to increase the salinity gradient. The salt can come from one of two processes: the dissolution of large salt deposits through salt tectonics [2] or geothermally-heated brine issued from tectonic spreading centers. [3]
The brine often contains high concentrations of hydrogen sulfide and methane, which provide energy to chemosynthetic organisms that live near the pool. These creatures are often extremophiles and symbionts. [4] [5] Deep-sea and polar brine pools are toxic to marine animals due to their high salinity and anoxic properties, [1] which can ultimately lead to toxic shock and possibly death.
Brine pools are sometimes called sea floor "lakes" because the dense brine does not easily mix with overlying seawater, creating a distinct interface between water masses. The pools range in area from less than 1 square metre (11 sq ft) to as large as the 120-square-kilometre (46 sq mi) Orca Basin. [2] The high salinity raises the density of the brine, which creates a surface and shoreline for the pool. Depending on concentration, some minerals such as baryte (barium sulfate) precipitate out of the brine and form crystalline crusts around the edge of the pool. [6]
Because of the brine's high density and lack of mixing currents in the deep ocean, brine pools often become anoxic and deadly to respiring organisms. [7] Brine pools supporting chemosynthetic activity, however, form life on the pool's shores where bacteria and their symbionts grow near the highest concentrations of nutrient release. [8] Patchy, reddish layers can be observed floating above the dense brine interface due to high densities of halophilic archaea that are supported by these environments. [9] These shores are complex environments with significant shifts in salinity, oxygen concentration, pH, and temperature over a relatively small vertical scale. These transitions provide a variety of environmental niches. [10] [11]
Brine pools are created through three primary methods: brine rejection below sea ice, dissolution of salts into bottom water through salt tectonics, and geothermal heating of brine at tectonic boundaries and hot spots.
Due to the methods of their formation and lack of mixing, brine pools are anoxic and deadly to aerobic organisms, including most eukaryotes and multicellular organisms. When an organism enters a brine pool, it attempts to "breathe" the environment and experiences cerebral hypoxia due to the lack of oxygen and toxic shock from the hypersalinity. Organisms that cannot surface long enough to retreat to the rim quickly die. [12] When observed by submarines or remotely operated underwater vehicles (ROVs), brine pools are found to be eerily littered with dead fish, crabs, amphipods, and various other organisms that ventured too far into the brine. Dead organisms are then preserved in the brine for years without decay due to the anoxic nature of the pool. [8]
Despite the harsh conditions, life in the form of macrofauna such as bivalves can be found in a thin area along the rim of a brine pool. A novel genus and species of bivalves, known as Apachecorbula muriatica, has been found along the edge of the "Valdivia Deep" brine pool in the Red Sea. [13] There have also been recorded instances of macrofauna brine pools at the seawater interface. Inactive sulfur chimneys have been found with affiliated epifauna such as polychaetes and hydroids. Fauna like gastropods, capitellid polychaetes, and top snails have also been found to be associated with brine pools in the Red Sea. Such species typically feed on microbial symbionts or bacterial and detritus films. [14]
While organisms can typically flourish on the outskirts of a brine pool, they are not always safe from harm there. One possible reason for this is that underwater landslides can impact brine pools and cause waves of hypersaline brine to spill out into surrounding basins, thus negatively affecting the biological communities which live there. [15]
Despite their inhospitable nature, brine pools can also provide a home, allowing organisms to flourish. Deep-sea brine pools often coincide with cold seep activity, allowing for chemosynthetic life to thrive. Methane and hydrogen sulfide released by the seep is processed by bacteria, which have a symbiotic relationship with organisms such as seep mussels. [16] The seep mussels create two distinct zones: the inner zone, which is at the edge of the pool, provides the best physiological conditions and allows for maximum growth, while the outer zone is near the transition between the mussel bed and the surrounding seafloor, and this area provides the worst conditions, causing these mussels to have lower maximum sizes and densities. [17] This ecosystem is dependent on chemical energy and, relative to almost all other life on Earth, has no dependence on energy from the Sun. [18]
An important part of the study of extreme environments such as brine pools is the function and survival of microbes. Microbes help support the larger biological community around environments like brine pools and are key to understanding the survival of other extremophiles. Biofilms contribute to the creation of microbes and are considered the foundation by which other micro-organisms can survive in extreme environments. The research into the growth and function of artificial extremophile biofilms has been slow due to the difficulty in recreating the extreme deep-sea environments they are found in. [19]
Red Sea brine pool microbiology is among the most intensively studied using metagenomics and amplicon sequencing.
Metagenomic analysis is a powerful approach for characterizing microbial communities in a variety of environments. Previously, genetic analysis required having the microorganisms in culture, which is problematic since most microorganisms in nature have not been cultivated. [20] Metagenomics overcomes these problems by allowing researchers to directly sample and analyze and genetically characterize microbial communities sampled from the desired environment. [21] Metagenomic analyses has revealed previously-uncharacterized microbial communities in multiple brine pools. [22] Common procedures for characterizing marine microbial communities by metagenomic analysis includes sampling, filtration and extraction, DNA sequencing, and comparison to databases.[ citation needed ]
The taxonomic makeup of the main microbial communities found at Atlantis II and Discovery without including minor or unknown species to avoid ambiguity is summarized in the following list that is based on the data from primary articles. [23] [24] [25]
Domain | Microbes |
---|---|
Bacteria | [Order] Actinomycetales [25] |
[Family] Microbacteriaceae [23] | |
[Genus] Bacillus [24] | |
[Phylum] Bacteroidetes [25] | |
[Class] Flavobacteria [23] | |
[Phylum] Candidatus division od1 [23] | |
[Phylum] Chloroflexi [25] | |
[Class] Anaerolineae [23] | |
[Class] SAR202 clade [23] | |
[Phylum] Cyanobacteria [23] | |
[Phylum] Deinococcota [25] | |
[Genus] Meiothermus [24] | |
[Class] Deferribacteres [23] | |
[Phylum] Firmicutes [25] | |
[Order] Thermotoaea [25] | |
[Class] Candidatus Scalindua [23] | |
[Class] Candidatus Brocadiales l [23] | |
[Class] Alphaproteobacteria [23] [25] | |
[Genus] Phyllobacterium [24] | |
[Genus] Afipia [24] | |
[Genus] Bradyrhizobium [24] | |
[Order] SAR11(Pelagibacterales) [23] | |
[Class] Betaproteobacteria [23] [25] | |
[Genus] Rhodoferax [24] | |
[Genus] Malikia [24] | |
[Genus] Cupriavidus [24] | |
[Genus] Ralstonia [24] | |
[Class] Deltaproteobacteria [23] [25] | |
[Class] Gammaproteobacteria [25] | |
[Order] Alteromonadales [23] | |
[Order] Oceanospirillales [23] | |
[Genus] Acinetobacter [24] | |
[Genus] Alkanindiges [24] | |
[Genus] Stenotrophomonas [24] | |
Archaea | [Class] Group c3 [23] |
[Class] Marine benthic group a (MBG-A) [23] | |
[Class] Marine benthic group b (MBG-B) [23] | |
[Class] Marine group I (MGI) [23] | |
[Class] Misc crenarchaeotic group [23] | |
[Class] Psl12 [23] | |
[Order] Desulfurococcales [25] | |
[Order] Sulfolobales [25] | |
[Order] Thermoproteales [25] | |
[Phylum] Euryarchaeota [25] | |
[Class] Archaeoglobi [23] | |
[Order] Archaeoglobales [25] | |
[Order] Halobacteria [23] | |
[Order] Halobacteriales [25] | |
[Class] Methanomicrobia [23] | |
[Order] Methanobacteriales [25] | |
[Order] Methanocellales [25] | |
[Order] Methanococcales [25] | |
[Order] Methanomicrobiales [25] | |
[Order] Methanopyrales [25] | |
[Order] Methanosarcinales [25] | |
[Class] Thermoplasmata [23] | |
[Genus] Candidatus Korarchaeum cryptofilum [25] | |
[Genus] Candidatus Caldiarchaeum [25] |
The lack of mixing with the water column in combination with high salinity, anoxia, extremes in water temperature, and hydrostatic pressure results in microbial assemblages that are specific to these environments. [26]
The high salinity levels present challenges for the retention of water by cells and consequent effects on cell turgor and functioning. [26] Brine pools also exert ionic, kosmotropic, and chaotropic effects on the cells, which also causes additional challenges for the organisms to survive these extreme environments. [27] [28]
In addition, the lack of oxygen increases the difficulty of organisms to yield energy, as oxygen is the most energy-yielding electron acceptor. [29]
Organisms have developed different strategies to solve the challenges imposed by high levels of salinity. In order to decrease the risk of chaotropic effects on the cells, halophilic archaea have a "salt-in" approach and "compatible-solute" strategy, which increases intracellular ionic concentration (mostly K+) to decrease the osmotic pressure; thus, these organisms have adapted their entire metabolic machinery to maintain salt concentration inside of their cells. [30]
In some brine pools, high water temperatures and hydrostatic pressures result in piezophilic microorganisms that synthesize thermoprotective molecules (e.g. hydroxyketone) to prevent the denaturation of proteins and decrease the risk of desiccation. [31] [32] [33] [34]
Another important adaptation is the use of alternative electron acceptors to yield energy, such as iron, manganese, [35] sulfate, elemental sulfur, [36] carbon dioxide, nitrite, and nitrate. [37]
Animals have also been found living in these anaerobic brine pools, such as the first known metazoan from these environments described by Danovaro et al. (2010). [38] Many other taxa that from these extreme environments are still uncharacterized. [39] [40]
As the name suggests, brine pools, or deep hypersaline anoxic basins (DHABs), are characterized by a very high salt concentration and anoxic conditions. Sodium, chloride, magnesium, potassium, and calcium ion concentrations are all extremely high in brine pools. Due to low mixing rates between the above seawater and the brine water, brine-pool water becomes anoxic within the first ten centimeters or so. [41] While there are large variations in the geochemical composition of individual pools, [41] as well as extreme chemical stratification within the same pool, [42] conserved chemical trends are present. Deeper layers of DHABs will be saltier, hotter, more acidic, and more anaerobic than the preceding layers. [43] [44] The concentration of heavy metals (Fe, Mn, Si, Cu) and certain nutrients (NO2−, NH4+, NO3−, and PO4−) will tend to increase with depth, while the concentration of SO4− and both organic and inorganic carbon decrease with depth. [42] While these trends are all observed to some capacity in DHABs, the intensity and distance over which these trends take effect can vary in depth from one meter to tens of meters. [41]
The heavy stratification within DHABs has led to increased microbial metabolic diversity and varying cell concentrations between layers. The majority of cell biomass has been found at the interfaces between the distinct chemical layers (with the highest concentrations of cells located at the brine-surface interface). [45] Microbes exploit the sharp chemical gradients between the layers to make their metabolisms more thermodynamically favorable. [46]
Four heavily-studied DHABs are Urania, Bannock, L'Atalante, and Discovery. All four of these brine pools are located in the Mediterranean Sea, yet they all exhibit distinct chemical properties: Urania has the highest concentration of sulfuric acid observed (at c. 16 mM)—compared to normal sea water (2.6×10−6 mM) or the next highest [HS–] in the Bannock basin (c. 3 mM). [47] [45] Discovery has an extremely low concentration of Na+ (68 mM) and an extremely high concentration of Mg2+ (4,995 mM)—compared to the surrounding seawater with concentrations of 528 mM and 60 mM respectively. [45] [48] The L'Atalante basin has a high SO42- concentration compared to the other pools. This extreme variability in environmental conditions leads to each brine pool having a unique metabolic composition.
While it was initially thought that particulate organic matter (POM) was an important source of carbon for DHABs, due to their depth, the concentration of POM reaching the pools is not significant as originally thought. [41] The majority of fixed carbon is now thought to come from autotrophy, specifically methanogenesis. Direct measurements of methane production in DHABs have provided extensive molecular evidence of methanogenesis in these environments. [45] Proteomic analyses further support the presence of methanogenesis by identifying the enzyme RuBisCo in various DHABs. [49] Interestingly, it has been suggested that, instead of CO2 or acetoclastic methanogenesis, prokaryotes in DHABs use methylotrophic methanogenesis, as it allows for a higher energy yield [50] and the intermediates can be used for osmoprotectants. [51]
One of the key metabolic features of DHABs is the dissimilatory reduction of nitrogen. This is predominantly due to the thermodynamic favorability of nitrogen-based metabolisms in anaerobic environments. In Bannock basin and L'Atalante basin, anammox and denitrification pathways have been identified using a combination of transcriptomics and direct isotope tracking. [52] Other DHABs have been analyzed for anammox pathways using metatranscriptomic techniques with little positive results, which may be due to the limitations of transcriptomic sensitivity. In deeper DHAB layers, nitrogen fixation and ammonium assimilation has been observed. These reductive pathways require a lot of energy and are mainly performed by methanogens to synthesize osmoprotectants. [53]
Due to the high concentration of sulfate (especially in the Uranian Basin), sulfate reduction is extremely important in the biogeochemical cycling of DHABs. The highest rates of sulfate reduction tend to be found in the deepest DHAB layers, where redox potential is lowest. [46] Sulfate reducing bacteria have been found in the brines of Kebrit Deep, Nereus Deep, Erba Deep, Atlantis II Deep, and Discovery Deep. [54] Oxidative sulfur pathways help close the biogeochemical sulfur loops within the DHABs. There are three main sulfur oxidizing pathways which are likely found in DHABs:
A combination between the second and third pathway would allow for increased energetic yield. [55] In addition, some novel groups have been isolated from saline lakes which can anaerobically respire sulfur using acetate, pyruvate, formate, or hydrogen as a sole electron donors. [56]
There is a high concentration of bacteria present in brine pools that serve essential roles for the ecosystem, such as being part of symbiotic relationships or acting as a food source for several organisms in this habitat. Examples include tubeworms and clams having a symbiotic relationship with many of these bacteria to convert chemical energy from hydrogen sulfide, and in exchange providing them food to allow reproduction and development; [57] or mussels providing a safe habitat for bacteria that feed on methane while thriving due to the chemosynthetic, carbon-fixing symbionts that are inhabiting their gill tissues. [58] Thus, these symbiotic relationships with bacteria allow organisms to be abundant and have high biomass in these harsher environments. [59]
Bacteria can also act as epibiotic symbiont, which were found to play an important role in the adaptations of microorganisms to these environments, such as organisms from the flagellated group Euglenozoa that have been thriving in brine pools due to this relationship. [60]
One major idea involves harnessing the salinity of brine pools to use as a power source. This would be done using an osmotic engine which draws the high-salinity top water through the engine and pushes it down due to osmotic pressure. This would cause the brackish stream (which is less dense and has a lighter salinity) to be propelled away from the engine via buoyancy. The energy created by this exchange can be harnessed using a turbine to create a power output. [7]
It is possible to study liquid brine in order to harness its electrical conductivity to study if liquid water is present on Mars. [68] A HABIT (Habitability: Brines, Irradiation, and Temperature) instrument will be part of a 2020 campaign to monitor changing conditions on Mars. This device will include a BOTTLE (Brine Observation Transition to Liquid Experiment) experiment to quantify the formation of transient liquid brine as well as observe its stability over time under non-equilibrium conditions. [68]
A third idea involves using microorganisms in deep-sea brine pools to form natural-product drugs. [69] These microorganisms are important sources of bioactive molecules against various diseases due to the extreme environment they inhabit, giving potential to an increasing number of drugs in clinical trials. [70] In particular, a novel finding in a study used microorganisms from the Red Sea brine pools as potential anticancer drugs. [71] [72] [73]
Deep sea brine pools have also been a large interest in bioprospecting in the hope that unlikely environments might serve as sources of biomedical breakthroughs due to unexplored biodiversity. Some areas have been found to host antibacterial and anticancer activities in biosynthetic clusters. [74] Other novel antibiotic resistance enzymes have been found that are useful in various biomedical and industrial applications. [75]
A halophile is an extremophile that thrives in high salt concentrations. In chemical terms, halophile refers to a Lewis acidic species that has some ability to extract halides from other chemical species.
The purple sulfur bacteria (PSB) are part of a group of Pseudomonadota capable of photosynthesis, collectively referred to as purple bacteria. They are anaerobic or microaerophilic, and are often found in stratified water environments including hot springs, stagnant water bodies, as well as microbial mats in intertidal zones. Unlike plants, algae, and cyanobacteria, purple sulfur bacteria do not use water as their reducing agent, and therefore do not produce oxygen. Instead, they can use sulfur in the form of sulfide, or thiosulfate (as well, some species can use H2, Fe2+, or NO2−) as the electron donor in their photosynthetic pathways. The sulfur is oxidized to produce granules of elemental sulfur. This, in turn, may be oxidized to form sulfuric acid.
A salt lake or saline lake is a landlocked body of water that has a concentration of salts and other dissolved minerals significantly higher than most lakes. In some cases, salt lakes have a higher concentration of salt than sea water; such lakes can also be termed hypersaline lake, and may also be pink lakes on account of their color. An alkalic salt lake that has a high content of carbonate is sometimes termed a soda lake.
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.
Gammaproteobacteria is a class of bacteria in the phylum Pseudomonadota. It contains about 250 genera, which makes it the most genus-rich taxon of the Prokaryotes. Several medically, ecologically, and scientifically important groups of bacteria belong to this class. All members of this class are Gram-negative. It is the most phylogenetically and physiologically diverse class of the Pseudomonadota.
A chemocline is a type of cline, a layer of fluid with different properties, characterized by a strong, vertical chemistry gradient within a body of water. In bodies of water where chemoclines occur, the cline separates the upper and lower layers, resulting in different properties for those layers. The lower layer shows a change in the concentration of dissolved gases and solids compared to the upper layer.
Blood Falls is an outflow of an iron(III) oxide–tainted plume of saltwater, flowing from the tongue of Taylor Glacier onto the ice-covered surface of West Lake Bonney in the Taylor Valley of the McMurdo Dry Valleys in Victoria Land, East Antarctica.
L'Atalante basin is a hypersaline brine lake at the bottom of the Mediterranean Sea about 192 km (119 mi) west of the island of Crete. It is named for the French L'Atalante, one of the oceanographic research vessels involved in its discovery in 1993. L'Atalante and its neighbors the Urania and Discovery deep hyper saline anoxic basins (DHABs) are at most 35,000 years old. They were formed by Messinian evaporite salt deposits dissolving out of the Mediterranean Ridge and collecting in abyssal depressions about 3,000 m (9,800 ft) deep. L'Atalante is the smallest of the three; its surface begins at about 3,500 m (11,500 ft) below sea level.
A soda lake or alkaline lake is a lake on the strongly alkaline side of neutrality, typically with a pH value between 9 and 12. They are characterized by high concentrations of carbonate salts, typically sodium carbonate, giving rise to their alkalinity. In addition, many soda lakes also contain high concentrations of sodium chloride and other dissolved salts, making them saline or hypersaline lakes as well. High pH and salinity often coincide, because of how soda lakes develop. The resulting hypersaline and highly alkalic soda lakes are considered some of the most extreme aquatic environments on Earth.
The class Zetaproteobacteria is the sixth and most recently described class of the Pseudomonadota. Zetaproteobacteria can also refer to the group of organisms assigned to this class. The Zetaproteobacteria were originally represented by a single described species, Mariprofundus ferrooxydans, which is an iron-oxidizing neutrophilic chemolithoautotroph originally isolated from Kamaʻehuakanaloa Seamount in 1996 (post-eruption). Molecular cloning techniques focusing on the small subunit ribosomal RNA gene have also been used to identify a more diverse majority of the Zetaproteobacteria that have as yet been unculturable.
"Candidatus Scalindua" is a bacterial genus, and a proposed member of the order Planctomycetales. These bacteria lack peptidoglycan in their cell wall and have a compartmentalized cytoplasm. They are ammonium oxidizing bacteria found in marine environments.
Sulfurimonas is a bacterial genus within the class of Campylobacterota, known for reducing nitrate, oxidizing both sulfur and hydrogen, and containing Group IV hydrogenases. This genus consists of four species: Sulfurimonas autorophica, Sulfurimonas denitrificans, Sulfurimonas gotlandica, and Sulfurimonas paralvinellae. The genus' name is derived from "sulfur" in Latin and "monas" from Greek, together meaning a “sulfur-oxidizing rod”. The size of the bacteria varies between about 1.5-2.5 μm in length and 0.5-1.0 μm in width. Members of the genus Sulfurimonas are found in a variety of different environments which include deep sea-vents, marine sediments, and terrestrial habitats. Their ability to survive in extreme conditions is attributed to multiple copies of one enzyme. Phylogenetic analysis suggests that members of the genus Sulfurimonas have limited dispersal ability and its speciation was affected by geographical isolation rather than hydrothermal composition. Deep ocean currents affect the dispersal of Sulfurimonas spp., influencing its speciation. As shown in the MLSA report of deep-sea hydrothermal vents Campylobacterota, Sulfurimonas has a higher dispersal capability compared with deep sea hydrothermal vent thermophiles, indicating allopatric speciation.
Haloquadratum walsbyi is a species of Archaea in the genus Haloquadratum, known for its square shape and halophilic nature.
Okenane, the diagenetic end product of okenone, is a biomarker for Chromatiaceae, the purple sulfur bacteria. These anoxygenic phototrophs use light for energy and sulfide as their electron donor and sulfur source. Discovery of okenane in marine sediments implies a past euxinic environment, where water columns were anoxic and sulfidic. This is potentially tremendously important for reconstructing past oceanic conditions, but so far okenane has only been identified in one Paleoproterozoic rock sample from Northern Australia.
Sea Ice Microbial Communities (SIMCO) refer to groups of microorganisms living within and at the interfaces of sea ice at the poles. The ice matrix they inhabit has strong vertical gradients of salinity, light, temperature and nutrients. Sea ice chemistry is most influenced by the salinity of the brine which affects the pH and the concentration of dissolved nutrients and gases. The brine formed during the melting sea ice creates pores and channels in the sea ice in which these microbes can live. As a result of these gradients and dynamic conditions, a higher abundance of microbes are found in the lower layer of the ice, although some are found in the middle and upper layers. Despite this extreme variability in environmental conditions, the taxonomical community composition tends to remain consistent throughout the year, until the ice melts.
The hydrothermal vent microbial community includes all unicellular organisms that live and reproduce in a chemically distinct area around hydrothermal vents. These include organisms in the microbial mat, free floating cells, or bacteria in an endosymbiotic relationship with animals. Chemolithoautotrophic bacteria derive nutrients and energy from the geological activity at Hydrothermal vents to fix carbon into organic forms. Viruses are also a part of the hydrothermal vent microbial community and their influence on the microbial ecology in these ecosystems is a burgeoning field of research.
Microbialite is a benthic sedimentary deposit made of carbonate mud that is formed with the mediation of microbes. The constituent carbonate mud is a type of automicrite ; therefore, it precipitates in situ instead of being transported and deposited. Being 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.
An anchialine system is a landlocked body of water with a subterranean connection to the ocean. Depending on its formation, these systems can exist in one of two primary forms: pools or caves. The primary differentiating characteristics between pools and caves is the availability of light; cave systems are generally aphotic while pools are euphotic. The difference in light availability has a large influence on the biology of a given system. Anchialine systems are a feature of coastal aquifers which are density stratified, with water near the surface being fresh or brackish, and saline water intruding from the coast at depth. Depending on the site, it is sometimes possible to access the deeper saline water directly in the anchialine pool, or sometimes it may be accessible by cave diving.
The Red Sea and its extensions of the Gulf of Suez and the Gulf of Aqaba contain the largest recorded concentration of deep-sea brine pools on the planet. These pools have many features that make them uninhabitable to almost all organisms on the planet, yet certain communities of microbes thrive within these extreme environments that have temperatures ranging from 2.0 °C to 75 °C. The Red Sea brine pools have extreme salt concentrations and varying compositions of nutrients and other chemicals that directly affect their microbiomes. There are approximately 25 individual pools in the region, some of which are closely clustered together in groups, leading to their undetermined classification of names. The brine pools originate from hydrothermal vents, the shifting of tectonic plates, and the accumulation of water with properties that make it unsuitable for mixing, leading to its accumulation within faults and divots in the sea floor. Atlantis II Deep, Discovery Deep, and the Kebrit are the most investigated and researched brine pools within the Red Sea. Additionally, many microbial species form beneficial symbiotic relationships with organisms living and feeding in proximity to the pools. These relationships allow for the study of specialized adaptations of microbes to brine pool environments.
A sea ice brine pocket is an area of fluid sea water with a high salt concentration trapped in sea ice as it freezes. Due to the nature of their formation, brine pockets are most commonly found in areas below −2 °C (28 °F), where it is sufficiently cold for seawater to freeze and form sea ice. Though the high salinity and low light conditions of brine pockets create a challenging environment for marine mammals, brine pockets serve as a habitat for various microbes. Sampling and studying these pockets requires specialized equipment to accommodate the hypersaline conditions and subzero temperatures.
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