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107-521: The mesopelagic zone occupies about 60% of the planet's surface and about 20% of the ocean's volume, amounting to a large part of the total biosphere . It hosts a diverse biological community that includes bristlemouths , blobfish , bioluminescent jellyfish , giant squid , and a myriad of other unique organisms adapted to live in a low-light environment. It has long captivated the imagination of scientists, artists and writers; deep sea creatures are prominent in popular culture. The mesopelagic zone includes

214-507: A "pool" of water where oxygen concentrations fall from the normal range of 4–6 mg/L to below 2 mg/L. Surface ocean waters generally have oxygen concentrations close to equilibrium with the Earth's atmosphere . In general, colder waters hold more oxygen than warmer waters. As water moves out of the mixed layer into the thermocline , it is exposed to a rain of organic matter from above. Aerobic bacteria feed on this organic matter; oxygen

321-434: A South African purse seine fishery closed in the mid-1980s due to processing difficulties from the high oil content of fish. As the biomass in the mesopelagic is so abundant, there has been an increased interest to determine whether these populations could be of economic use in sectors other than direct human consumption. For example, it has been suggested that the high abundance of fish in this zone could potentially satisfy

428-417: A combination of anthropological factors (such as coal mining) in addition to natural factors. Mercury is a particularly important bioaccumulation contaminant because its concentration in the mesopelagic zone is increasing faster than in surface waters. Inorganic mercury occurs in anthropogenic atmospheric emissions in its gaseous elemental form, which then oxidizes and can be deposited in the ocean. Once there,

535-591: A dedicated effort called the Ocean Twilight Zone project that launched in August 2018. The deep scattering layer often characterizes the mesopelagic due to the high amount of biomass that exists in the region. Acoustic sound sent into the ocean bounces off particles and organisms in the water column and return a strong signal. The region was initially discovered by American researchers during World War II in 1942 during anti-submarine research with sonar . Sonar at

642-436: A demand for fishmeal and nutraceuticals . With a growing global population, the demand for fishmeal in support of a growing aquaculture industry is high. There is potential for an economically viable harvest. For example, 5 billion tons of mesopelagic biomass could result in the production of circa 1.25 billion tons of food for human consumption. Additionally, the demand for nutraceuticals is also rapidly growing, stemming from

749-656: A depth of 10,000 m (33,000 ft; 6.2 mi) in the Mariana Trench , the deepest spot in the Earth's oceans. In fact, single-celled life forms have been found in the deepest part of the Mariana Trench, by the Challenger Deep , at depths of 11,034 m (36,201 ft; 6.856 mi). Other researchers reported related studies that microorganisms thrive inside rocks up to 580 m (1,900 ft; 0.36 mi) below

856-414: A dynamic zone. The mesopelagic zone has some unique acoustic features. The Sound Fixing and Ranging (SOFAR) channel, where sound travels the slowest due to salinity and temperature variations, is located at the base of the mesopelagic zone at about 600–1,200m. It is a wave-guided zone where sound waves refract within the layer and propagate long distances. The channel got its name during World War II when

963-490: A food source for other organisms so it is important to monitor the different levels of marine snow to characterize the carbon cycling processes between the surface ocean and the mesopelagic. The Harbor Branch Oceanographic Institute has developed the Spatial PLankton Analysis Technique (SPLAT) to identify and map distribution patterns of bioluminescent plankton. The various bioluminescent species produce

1070-434: A fraction of POC is exported from the euphotic zone , an estimated 90% of that POC is respired in the mesopelagic zone. This is due to the microbial organisms that respire organic matter and remineralize the nutrients, while mesopelagic fish also package organic matter into quick-sinking parcels for deeper export. Another key process occurring in this zone is the diel vertical migration of certain species, which move between

1177-407: A gas, resulting in a net loss of nitrogen from the ocean. An organism's demand for oxygen is dependent on its metabolic rate . Metabolic rates can be affected by external factors such as the temperature of the water, and internal factors such as the species, life stage, size, and activity level of the organism. The body temperature of ectotherms (such as fishes and invertebrates ) fluctuates with

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1284-409: A general sense, biospheres are any closed, self-regulating systems containing ecosystems. This includes artificial biospheres such as Biosphere 2 and BIOS-3 , and potentially ones on other planets or moons . The term "biosphere" was coined in 1875 by geologist Eduard Suess , who defined it as the place on Earth's surface where life dwells. While the concept has a geological origin, it

1391-466: A key area of denitrification by prokaryotes, a heterotrophic pathways in which nitrate is converted into nitrogen gas, resulting in a loss to the ocean reservoir of reactive nitrogen. At the suboxic interface that occurs at the edge of the OMZ, nitrite and ammonium can be coupled to produce nitrogen gas through anammox , also removing nitrogen from the biologically available pool. Although some light penetrates

1498-482: A microscopic scale the processes causing ocean deoxygenation rely on microbial aerobic respiration. Aerobic respiration is a metabolic process that microorganisms like bacteria or archaea use to obtain energy by degrading organic matter, consuming oxygen, producing CO 2 and obtaining energy in the form of ATP. In the ocean surface photosynthetic microorganisms called phytoplankton use solar energy and CO 2 to build organic molecules (organic matter) releasing oxygen in

1605-408: A native Martian biosphere—as part of the topic of biospherics. Currently, the total number of living cells on the Earth is estimated to be 10 ; the total number since the beginning of Earth, as 10 , and the total number for the entire time of a habitable planet Earth as 10 . This is much larger than the total number of estimated stars (and Earth-like planets) in the observable universe as 10 ,

1712-860: A number which is more than all the grains of beach sand on planet Earth; but less than the total number of atoms estimated in the observable universe as 10 ; and the estimated total number of stars in an inflationary universe (observed and unobserved), as 10 . The earliest evidence for life on Earth includes biogenic graphite found in 3.7 billion-year-old metasedimentary rocks from Western Greenland and microbial mat fossils found in 3.48 billion-year-old sandstone from Western Australia . More recently, in 2015, "remains of biotic life " were found in 4.1 billion-year-old rocks in Western Australia. In 2017, putative fossilized microorganisms (or microfossils ) were announced to have been discovered in hydrothermal vent precipitates in

1819-401: A protein ( hemocyanin ) that readily binds oxygen. Another strategy used by some classes of bacteria in the oxygen minimum zones is to use nitrate rather than oxygen, thus drawing down the concentrations of this important nutrient. This process is called denitrification . The oxygen minimum zones thus play an important role in regulating the productivity and ecological community structure of

1926-859: A refuge. Zooplankton that exhibit daily vertical migrations to avoid predation and low oxygen conditions also excrete ammonium near the oxycline and contribute to increased anaerobic ammonium oxidation (anammox, which produces N 2 gas. As hypoxic regions expand vertically and horizontally, the habitable ranges for phytoplankton, zooplankton, and nekton increasingly overlap, increasing their susceptibility to predation and human exploitation. OMZs have changed over time due to effects from numerous global chemical and biological processes. To assess these changes, scientists utilize climate models and sediment samples to understand changes to dissolved oxygen in OMZs. Many recent studies of OMZs have focused on their fluctuations over time and how they may be currently changing as

2033-411: A result of climate change . Some research has aimed to understand how OMZs have changed over geological time scales . Throughout the history of Earth's oceans, OMZs have fluctuated on long time scales, becoming larger or smaller depending on multiple variables. The factors that change OMZs are the amount of oceanic primary production resulting in increased respiration at greater depths, changes in

2140-405: A small autonomous robot, Mesobot, weighing approximately 75 kg. Mesobot is equipped with high-definition cameras to track and record mesopelagic species on their daily migration over extended periods of time. The robot's thrusters were designed so that they do not disturb the life in the mesopelagic that it is observing. Traditional sample collection devices fail to preserve organisms captured in

2247-667: A stagnant pool of water with no direct connection to the ocean surface even though (as in the Eastern Tropical North Pacific) there may be relatively little organic matter falling from the surface. In OMZs oxygen concentration drops to levels <10 nM at the base of the oxycline and can remain anoxic for over 700 m depth. This lack of oxygen can be reinforced or increased due to physical processes changing oxygen supply such as eddy-driven advection, sluggish ventilation, increases in ocean stratification , and increases in ocean temperature which reduces oxygen solubility. At

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2354-407: A submersible chamber that can keep fish alive on the way up to the surface under a controlled atmosphere and pressure. A passive method to estimate mesopelagic fish abundance is by echosounding to locate the ' deep scattering layer ' through the backscatter received from these acoustic sounders. A 2015 study suggested that some areas have had a decline in abundance of mesopelagic fish, including off

2461-476: A unique flash that allows the SPLAT to distinguish each specie's flash characteristic and then map their 3-dimensional distribution patterns. Its intended use was not for investigating the mesopelagic zone, although it is capable of tracking movement patterns of bioluminescent species during their vertical migrations. It would be interesting to apply this mapping technique in the mesopelagic to obtain more information about

2568-399: A wide range of impacts on the marine world. One of the most critical issues is ingestion of plastic debris, specifically microplastics . Many mesopelagic fish species migrate to the surface waters to feast on their main prey species, zooplankton and phytoplankton , which are mixed with microplastics in the surface waters. Additionally, research has shown that even zooplankton are consuming

2675-429: Is active development for this zone to become a commercial fishery. There are currently thirty families of known mesopelagic fish. One dominant fish in the mesopelagic zone are lanternfish (Myctophidae), which include 245 species distributed among 33 different genera. They have prominent photophores along their ventral side. The Gonostomatidae, or bristlemouth, are also common mesopelagic fish. The bristlemouth could be

2782-596: Is an indication of the effect of both Charles Darwin and Matthew F. Maury on the Earth sciences . The biosphere's ecological context comes from the 1920s (see Vladimir I. Vernadsky ), preceding the 1935 introduction of the term " ecosystem " by Sir Arthur Tansley (see ecology history ). Vernadsky defined ecology as the science of the biosphere. It is an interdisciplinary concept for integrating astronomy , geophysics , meteorology , biogeography , evolution , geology , geochemistry , hydrology and, generally speaking, all life and Earth sciences. Geochemists define

2889-554: Is capable of reaching depths up to 2000 m and can estimate the amount of biomass and biodiversity in this mesopelagic ecosystem. Deep-See is equipped with cameras, sonars, sensors, water sample collection devices, and a real-time data transmission system. WHOI is collaborating with the Monterey Bay Aquarium Research Institute (MBARI), Stanford University, and the University of Texas Rio Grande Valley to develop

2996-401: Is common in krill and shrimp, so they can take advantage of the limited light. Some octopus and krill even have tubular eyes that look upwards in the water column. Most life processes, like growth rates and reproductive rates, are slower in the mesopelagic. Metabolic activity has been shown to decrease with increasing depth and decreasing temperature in colder-water environments. For example,

3103-418: Is controlled by the large-scale ocean circulation as well as local physical as well as biological processes. For example, wind blowing parallel to the coast causes Ekman transport that upwells nutrients from deep water. The increased nutrients support phytoplankton blooms, zooplankton grazing, and an overall productive food web at the surface. The byproducts of these blooms and the subsequent grazing sink in

3210-403: Is done experimentally by measuring activity and respiration rates under different temperature and oxygen conditions, or by collecting data from separate studies. Despite the low oxygen conditions, organisms have evolved to live in and around OMZs. For those organisms, like the vampire squid , special adaptations are needed to either make do with lesser amounts of oxygen or to extract oxygen from

3317-535: Is due to inaccurate incorporation of depth, species size distribution, and acoustic properties of the species. Norway's Institute of Marine Research has launched a research vessel named Dr. Fridtjof Nansen to investigate mesopelagic activity using sonar with their focus being on the sustainability of fishing operations. To overcome the challenges faced with acoustic sampling, WHOI is developing remote operated vehicles (ROVs) and robots (Deep-See, Mesobot, and Snowclops) that are capable of studying this zone more precisely in

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3424-503: Is generally scarce in the mesopelagic, so predators have to be efficient in capturing food. Gelatinous organisms are thought to play an important role in the ecology of the mesopelagic and are common predators. Though previously thought to be passive predators just drifting through the water column, jellyfish could be more active predators. One study found that the helmet jellyfish Periphylla periphylla exhibit social behavior and can find each other at depth and form groups. Such behavior

3531-483: Is high, the contribution of active transport by vertical migration has been estimated to be comparable to sinking particle export. Mean particle sinking rates are 10 to 100 m/day. Sinking rates have been measured in the project VERTIGO (Vertical Transport in the Global Ocean) using settling velocity sediment traps. The variability in sinking rates is due to differences in ballast, water temperature, food web structure and

3638-462: Is important in deoxygenated systems: an oxygen quantity which is dangerously low for one species might be more than enough for another species. Several indices to measure bioavailability have been suggested: Respiration Index, Oxygen Supply Index, and the Metabolic Index. The Respiration Index describes oxygen availability based on the free energy available in the reactants and products of

3745-417: Is the worldwide sum of all ecosystems . It can also be termed the zone of life on Earth . The biosphere (which is technically a spherical shell ) is virtually a closed system with regard to matter , with minimal inputs and outputs. Regarding energy , it is an open system, with photosynthesis capturing solar energy at a rate of around 100 terawatts . By the most general biophysiological definition,

3852-495: Is used as part of the bacterial metabolic process, lowering its concentration within the water. Therefore, the concentration of oxygen in deep water is dependent on the amount of oxygen it had when it was at the surface, minus depletion by deep sea organisms. The downward flux of organic matter decreases sharply with depth, with 80–90% being consumed in the top 1,000 m (3,300 ft). The deep ocean thus has higher oxygen because rates of oxygen consumption are low compared with

3959-485: The Nuvvuagittuq Belt of Quebec, Canada that were as old as 4.28 billion years, the oldest record of life on earth, suggesting "an almost instantaneous emergence of life" after ocean formation 4.4 billion years ago , and not long after the formation of the Earth 4.54 billion years ago. According to biologist Stephen Blair Hedges , "If life arose relatively quickly on Earth ... then it could be common in

4066-442: The ocean is at its lowest. This zone occurs at depths of about 200 to 1,500 m (700–4,900 ft), depending on local circumstances. OMZs are found worldwide, typically along the western coast of continents, in areas where an interplay of physical and biological processes concurrently lower the oxygen concentration (biological processes) and restrict the water from mixing with surrounding waters (physical processes), creating

4173-478: The stoichiometric equation for respiration. However, organisms have ways of altering their oxygen intake and carbon dioxide release, so the strict stoichiometric equation is not necessarily accurate. The Oxygen Supply Index accounts for oxygen solubility and partial pressure, along with the Q 10 of the organism, but does not account for behavioral or physiological changes in organisms to compensate for reduced oxygen availability. The Metabolic Index accounts for

4280-404: The universe ." Every part of the planet, from the polar ice caps to the equator , features life of some kind. Recent advances in microbiology have demonstrated that microbes live deep beneath the Earth's terrestrial surface and that the total mass of microbial life in so-called "uninhabitable zones" may, in biomass , exceed all animal and plant life on the surface. The actual thickness of

4387-406: The Earth's biosphere, including soil , hot springs , inside rocks at least 19 km (12 mi) deep underground, and at least 64 km (40 mi) high in the atmosphere. Marine life under many forms has been found in the deepest reaches of the world ocean while much of the deep sea remains to be explored. Under certain test conditions, microorganisms have been observed to survive

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4494-470: The Earth's crust. The rate at which the temperature increases depends on many factors, including the type of crust (continental vs. oceanic), rock type, geographic location, etc. The greatest known temperature at which microbial life can exist is 122 °C (252 °F) ( Methanopyrus kandleri Strain 116). It is likely that the limit of life in the " deep biosphere " is defined by temperature rather than absolute depth. On 20 August 2014, scientists confirmed

4601-514: The Earth's most abundant vertebrate , with numbers in the hundreds of trillions to quadrillions. Mesopelagic fish are difficult to study due to their unique anatomy. Many of these fish have swim bladders to help them control their buoyancy, which makes them hard to sample because those gas-filled chambers typically burst as the fish come up in nets and the fish die. Scientists in California have made progress on mesopelagic fish sampling by developing

4708-623: The US Navy proposed using it as a life saving tool. Shipwreck survivors could drop a small explosive timed to explode in the SOFAR channel and then listening stations could determine the position of the life raft. During the 1950s, the US Navy tried to use this zone to detect Soviet submarines by creating an array of hydrophones called the Sound Surveillance System (SOSUS.) Oceanographers later used this underwater surveillance system to figure out

4815-461: The biomass may be abundant, fish species at depth are generally smaller in size and slower to reproduce. Fishing with large trawl nets poses threats to a high percentage of bycatch as well as potential impacts to the carbon cycling processes. Additionally, ships trying to reach productive mesopelagic regions requires fairly long journeys offshore. In 1977, a Soviet fishery opened but closed less than 20 years later due to low commercial profits, while

4922-406: The biosphere as being the total sum of living organisms (the " biomass " or " biota " as referred to by biologists and ecologists). In this sense, the biosphere is but one of four separate components of the geochemical model, the other three being geosphere , hydrosphere , and atmosphere . When these four component spheres are combined into one system, it is known as the ecosphere . This term

5029-491: The biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere , cryosphere , hydrosphere , and atmosphere . The biosphere is postulated to have evolved , beginning with a process of biopoiesis (life created naturally from non-living matter, such as simple organic compounds) or biogenesis (life created from living matter), at least some 3.5 billion years ago. In

5136-835: The biosphere on Earth is difficult to measure. Birds typically fly at altitudes as high as 1,800 m (5,900 ft; 1.1 mi) and fish live as much as 8,372 m (27,467 ft; 5.202 mi) underwater in the Puerto Rico Trench . There are more extreme examples for life on the planet: Rüppell's vulture has been found at altitudes of 11,300 metres (37,100 feet; 7.0 miles); bar-headed geese migrate at altitudes of at least 8,300 m (27,200 ft; 5.2 mi); yaks live at elevations as high as 5,400 m (17,700 ft; 3.4 mi) above sea level; mountain goats live up to 3,050 m (10,010 ft; 1.90 mi). Herbivorous animals at these elevations depend on lichens, grasses, and herbs. Life forms live in every part of

5243-409: The coast of Southern California, using a long-term study dating back to the 1970s. Cold water species were especially vulnerable to decline. Mesopelagic fish are adapted to a low-light environment. Many fish are black or red, because these colors appear dark due to the limited light penetration at depth. Some fish have rows of photophores , small light-producing organs, on their underside to mimic

5350-504: The concentration of marine debris located there. In 2018, approximately 73% of approximately 200 fish sampled in the North Atlantic had consumed plastic. Bioaccumulation (a buildup of a certain substance in the adipose tissue ) and biomagnification (the process in which the concentration of the substance grows higher as you rise through the food chain) are growing issues in the mesopelagic zone. Mercury in fish can be traced back to

5457-409: The daily and shorter scales that a variety of animals move vertically through the zone and sinking of various debris. The mesopelagic zone plays a key role in the ocean's biological pump , which contributes to the oceanic carbon cycle . In the biological pump, organic carbon is produced in the surface euphotic zone where light promotes photosynthesis. A fraction of this production is exported out of

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5564-677: The deep sea when they die. It is estimated that the mesopelagic cycles between 5 and 12 billion tons of carbon dioxide from the atmosphere per year, and until recently, this estimate was not included in many climate models. It is difficult to quantify the effects of climate change on the mesopelagic zone as a whole, as climate change does not have uniform impacts geographically. Research suggests that in warming waters, as long as there are adequate nutrients and food for fish, then mesopelagic biomass could actually increase due to higher trophic efficiency and increased temperature-driven metabolism . However, because ocean warming will not be uniform throughout

5671-400: The diurnal vertical migrations that occur in this zone of the ocean. Biosphere The biosphere (from Ancient Greek βίος ( bíos )  'life' and σφαῖρα ( sphaîra )  'sphere'), also called the ecosphere (from Ancient Greek οἶκος ( oîkos )  'settlement, house' and σφαῖρα ( sphaîra )  'sphere'),

5778-424: The diversity in the deep oceans. The data collected, particularly through sonar observations showed that the biomass estimation in the mesopelagic was lower than previously thought. WHOI is currently working on a project to characterize and document the pelagic ecosystem. They have developed a device named Deep-See weighing approximately 700 kg, which is designed to be towed behind a research vessel. The Deep-See

5885-440: The energy requirement for growth and muscle formation. Other feeding adaptations include jaws that can unhinge, elastic throats, and massive, long teeth. Some predators develop bioluminescent lures, like the tasselled anglerfish , which can attract prey, while others respond to pressure or chemical cues instead of relying on vision. Marine debris , specifically in the plastic form, have been found in every ocean basin and have

5992-560: The euphotic zone and mesopelagic zone and actively transport particulate organic matter to the deep. In one study in the Equatorial Pacific, myctophids in the mesopelagic zone were estimated to actively transport 15–28% of the passive POC sinking to the deep, while a study near the Canary Islands estimated 53% of vertical carbon flux was due to active transport from a combination of zooplankton and micronekton. When primary productivity

6099-611: The euphotic zone, these microbes use up what oxygen is in the water as they break down the falling organic matter thus creating the lower oxygen conditions. Physical processes then constrain the mixing and isolate this low oxygen water from outside water. Vertical mixing is constrained due to the separation from the mixed layer by depth. Horizontal mixing is constrained by bathymetry and boundaries formed by interactions with sub-tropical gyres and other major current systems. Low oxygen water may spread (by advection) from under areas of high productivity up to these physical boundaries to create

6206-460: The existence of microorganisms living 800 m (2,600 ft; 0.50 mi) below the ice of Antarctica . Earth's biosphere is divided into several biomes , inhabited by fairly similar flora and fauna . On land, biomes are separated primarily by latitude . Terrestrial biomes lying within the Arctic and Antarctic Circles are relatively barren of plant and animal life. In contrast, most of

6313-415: The form of particulate and dissolved nutrients (from phytodetritus, dead organisms, fecal pellets, excretions, shed shells, scales, and other parts). This "rain" of organic matter (see the biological pump ) feeds the microbial loop and may lead to bacterial blooms in water below the euphotic zone due to the influx of nutrients. Since oxygen is not being produced as a byproduct of photosynthesis below

6420-416: The geographical range of many species could also occur with warming, with many of them shifting poleward. The combination of these factors could potentially mean that as global ocean basins continue to warm, there could be areas in the mesopelagic that increase in biodiversity and species richness, while declines in other areas, especially moving farther from the equator. There is a dearth of knowledge about

6527-458: The global mesopelagic zone, it is predicted that some areas may actually decrease in fish biomass, while others increase. Water column stratification will also likely increase with ocean warming and climate change. Increased ocean stratification reduces the introduction of nutrients from the deep ocean into the euphotic zone resulting in decreases in both net primary production and sinking particulate matter. Additional research suggests shifts in

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6634-569: The global ocean. For example, giant bacterial mats floating in the oxygen minimum zone off the west coast of South America may play a key role in the region's extremely rich fisheries, as bacterial mats the size of Uruguay have been found there. Decreased oxygen availability results in decreases in many zooplankton species’ egg production, food intake, respiration, and metabolic rates. Temperature and salinity in areas of decreased oxygen concentrations also affect oxygen availability. Higher temperatures and salinity lower oxygen solubility decrease

6741-448: The importance of viruses and microbes role in recycling organic matter from the surface ocean, known as the microbial loop . These many microbes can get their energy from different metabolic pathways. Some are autotrophs , heterotrophs , and a 2006 study even discovered chemoautotrophs. This chemoautotrophic Archaea crenarchaeon Candidatus can oxidize ammonium as their energy source without oxygen, which could significantly impact

6848-433: The last 50 years, and coastal waters have seen a tenfold increase in low-oxygen areas in the same time. Measurement of dissolved oxygen in coastal and open ocean waters for the past 50 years has revealed a marked decline in oxygen content. This decline is associated with expanding spatial extent, expanding vertical extent, and prolonged duration of oxygen-poor conditions in all regions of the global oceans. Examinations of

6955-423: The majority of the upper ocean will occur. Global warming increases ocean temperatures, especially in shallow coastal areas. When the water temperature increases, its ability to hold oxygen decreases, leading to oxygen concentrations going down in the water. This compounds the effects of eutrophication in coastal zones described above. Open ocean areas with no oxygen have grown more than 1.7 million square miles in

7062-524: The mesopelagic due to the large pressure change associated with surfacing. The Mesobot also has a unique sampling mechanism that is capable of keeping the organisms alive during their ascent. The first sea trial of this device is expected to be in 2019. Another mesopelagic robot developed by WHOI are the MINIONS. This device descends down the water column and takes images of the amount and size distribution of marine snow at various depths. These tiny particles are

7169-493: The mesopelagic is greater at higher latitudes and decreases towards the tropics, which is likely linked to the differing productivity levels in the surface waters. Viruses however are very abundant in the mesopelagic, with around 10 - 10 every cubic meter, which is fairly uniform throughout the mesopelagic zone. The mesopelagic zone hosts a diverse zooplankton community. Common zooplankton include copepods, krill, jellyfish, siphonophores, larvaceans, cephalopods, and pteropods. Food

7276-459: The mesopelagic shrimp-like mysid , Gnathophausia ingens , lives for 6.4 to 8 years, while similar benthic shrimp only live for 2 years. The mesopelagic is home to a significant portion of the world's total fish biomass. Mesopelagic fish are found globally, with exceptions in the Arctic Ocean. A 1980 study puts the mesopelagic fish biomass at about one billion tons. Then a 2008 study estimated

7383-423: The mesopelagic species that consume it. Many of the mesopelagic species, such as myctophids , that make their diel vertical migration to the surface waters, can transfer the neurotoxin when they are consumed by pelagic fish, birds and mammals. Historically, there have been few examples of efforts to commercialize the mesopelagic zone due to low economic value, technical feasibility and environmental impacts. While

7490-489: The mesopelagic zone move up into the epipelagic zone at night, and retreat to the mesopelagic zone during the day, which is known as diel vertical migration . These migrators can therefore avoid visual predators during the day and feed at night, while some of their predators also migrate up at night to follow the prey. There is so much biomass in this migration that sonar operators in World War II would regularly misinterpret

7597-513: The mesopelagic zone so researchers have begun to develop new technology to explore and sample this area. The Woods Hole Oceanographic Institution (WHOI), NASA , and the Norwegian Institute of Marine Research are all working on projects to gain a better understanding of this zone in the ocean and its influence on the global carbon cycle. Traditional sampling methods like nets have proved to be inadequate because they scare off creatures due to

7704-548: The mesopelagic zone, it is insufficient for photosynthesis . The biological community of the mesopelagic zone has adapted to a low-light environment. This is a very efficient ecosystem with many organisms recycling the organic matter sinking from the epipelagic zone resulting in very little organic carbon making it to deeper ocean waters. The general types of life forms found are daytime-visiting herbivores , detritivores feeding on dead organisms and fecal pellets, and carnivores feeding on those detritivores. Many organisms in

7811-428: The microplastics themselves. Mesopelagic fish play a key role in energy dynamics, meaning they provide food to a number of predators including birds, larger fish and marine mammals. The concentration of these plastics has the potential to increase, so more economically important species could become contaminated as well. Concentration of plastic debris in mesopelagic populations can vary depending on geographic location and

7918-524: The more populous biomes lie near the equator . Experimental biospheres, also called closed ecological systems , have been created to study ecosystems and the potential for supporting life outside the Earth. These include spacecraft and the following terrestrial laboratories: No biospheres have been detected beyond the Earth; therefore, the existence of extraterrestrial biospheres remains hypothetical. The rare Earth hypothesis suggests they should be very rare, save ones composed of microbial life only. On

8025-487: The nitrogen and carbon cycles. One study estimates these ammonium-oxidizing bacteria, which are only 5% of the microbial population, can annually capture 1.1 Gt of organic carbon. Microbial biomass and diversity typically decline exponentially with depth in the mesopelagic zone, tracking the general decline of food from above. The community composition varies with depths in the mesopelagic as different organisms are evolved for varying light conditions. Microbial biomass in

8132-400: The ocean due to climate change , with potential ramifications for ecosystems and humans. The global decrease in oceanic oxygen content is statistically significant and emerging beyond the envelope of natural fluctuations. This trend of oxygen loss is accelerating, with widespread and obvious losses occurring after the 1980s. The rate and total content of oxygen loss varies by region, with

8239-506: The ocean where no light can reach, aerobic respiration is the dominant process. When the oxygen in a parcel of water is consumed, the oxygen cannot be replaced without the water reaching the surface ocean. When oxygen concentrations drop to below <10 nM, microbial processes that are normally inhibited by oxygen can take place like denitrification and anammox . Both processes extract elemental nitrogen from nitrogen compounds and that elemental nitrogen which does not stay in solution escapes as

8346-448: The organic carbon reservoir in the mesopelagic. This pathway of carbon fixation has been estimated to be comparable in rate to the contribution by heterotrophic production in this ocean realm. The mesopelagic zone, an area of significant respiration and remineralization of organic particles, is generally nutrient-rich. This is in contrast to the overlying euphotic zone, which is often nutrient-limited. Areas of low oxygen such as OMZ's are

8453-398: The organism reaches maturity, metabolic demands switch from growth and development to maintenance, which requires far fewer resources. Smaller organisms have higher metabolisms per unit of mass, so smaller organisms will require more oxygen per unit mass, while larger organisms generally require more total oxygen. Higher activity levels also require more oxygen. This is why bioavailability

8560-562: The other hand, Earth analogs may be quite numerous, at least in the Milky Way galaxy , given the large number of planets. Three of the planets discovered orbiting TRAPPIST-1 could possibly contain biospheres. Given limited understanding of abiogenesis , it is currently unknown what percentage of these planets actually develop biospheres. Based on observations by the Kepler Space Telescope team, it has been calculated that provided

8667-408: The oxidized form can be converted to methylmercury , which is its organic form. Research suggests that current levels anthropogenic emissions will not equilibrate between the atmosphere and ocean for a period of decades to centuries, which means we can expect current mercury concentrations in the ocean to keep rising. Mercury is a potent neurotoxin , and poses health risks to the whole food web, beyond

8774-411: The oxygen supply due to poor ventilation, and amount of oxygen supplied through thermohaline circulation . While oxygen minimum zones (OMZs) occur naturally, they can be exacerbated by human impacts like climate change and land-based pollution from agriculture and sewage. The prediction of current climate models and climate change scenarios is that substantial warming and loss of oxygen throughout

8881-433: The partial pressure of oxygen. This decreased partial pressure increases organisms’ respiration rates, causing the oxygen demand of the organism to increase. In addition to affecting their vital functions, zooplankton alter their distribution in response to hypoxic or anoxic zones. Many species actively avoid low oxygen zones, while others take advantage of their predators’ low tolerance for hypoxia and use these areas as

8988-549: The popular human consumption of Omega-3 Fatty Acids in addition to the aquaculture industry that requires a specific marine oil for feed material. Lanternfish are of much interest to the aquaculture market, as they are especially high in fatty acids. The mesopelagic region plays an important role in the global carbon cycle , as it is the area where most of the surface organic matter is respired. Mesopelagic species also acquire carbon during their diel vertical migration to feed in surface waters, and they transport that carbon to

9095-421: The pressure wave formed by the towed net and the light produced by the bioluminescent species caught in the net. Mesopelagic activity was first investigated by use of sonar because the return bounces off of plankton and fish in the water. However, there are many challenges with acoustic survey methods and previous research has estimated errors in measured amounts of biomass of up to three orders of magnitude. This

9202-427: The probability of abiogenesis is higher than 1 to 1000, the closest alien biosphere should be within 100 light-years from the Earth. It is also possible that artificial biospheres will be created in the future, for example with the terraforming of Mars . Oxygen minimum zone The oxygen minimum zone ( OMZ ), sometimes referred to as the shadow zone , is the zone in which oxygen saturation in seawater in

9309-399: The process. A large fraction of the organic matter from photosynthesis becomes dissolved organic matter (DOM) that is consumed by bacteria during aerobic respiration in sunlit waters. Another fraction of organic matter sinks to the deep ocean forming aggregates called marine snow. These sinking aggregates are consumed via degradation of organic matter and respiration at depth. At depths in

9416-453: The processes being studied are changes in oxygen gas solubility as a result of rising ocean temperatures, as well as changes in the amount of respiration and photosynthesis occurring around OMZs. Many studies have concluded that OMZs are expanding in multiple locations, but fluctuations of modern OMZs are still not fully understood. Existing Earth system models project considerable reductions in oxygen and other physical-chemical variables in

9523-637: The region of sharp changes in temperature, salinity and density called the thermocline , halocline , and pycnocline respectively. The temperature variations are large; from over 20 °C (68 °F) at the upper layers to around 4 °C (39 °F) at the boundary with the bathyal zone . The variation in salinity is smaller, typically between 34.5 and 35 psu. The density ranges from 1023 to 1027 g/L of seawater. These changes in temperature, salinity, and density induce stratification which create ocean layers. These different water masses affect gradients and mixing of nutrients and dissolved gasses. This makes this

9630-523: The sea floor under 2,590 m (8,500 ft; 1.61 mi) of ocean off the coast of the northwestern United States , as well as 2,400 m (7,900 ft; 1.5 mi) beneath the seabed off Japan. Culturable thermophilic microbes have been extracted from cores drilled more than 5,000 m (16,000 ft; 3.1 mi) into the Earth's crust in Sweden , from rocks between 65–75 °C (149–167 °F). Temperature increases with increasing depth into

9737-419: The signal returned by this thick layer of plankton as a false sea floor. Estimates of the global biomass of mesopelagic fishes range from 1 gigatonne (Gt) based on net tows to 7–10 Gt based on measurements using active acoustics. Very little is known about the microbial community of the mesopelagic zone because it is a difficult part of the ocean to study. Recent work using DNA from seawater samples emphasized

9844-621: The sinking organic matter and lack of gas exchange, often creates an oxygen minimum zone (OMZ) in the mesopelagic. The mesopelagic OMZ is particularly severe in the eastern tropical Pacific Ocean and tropical Indian Ocean due to poor ventilation and high rates of organic carbon export to the mesopelagic. Oxygen concentrations in the mesopelagic are occasionally result in suboxic concentrations, making aerobic respiration difficult for organisms. In these anoxic regions, chemosynthesis may occur in which CO 2 and reduced compounds such as sulfide or ammonia are taken up to form organic carbon, contributing to

9951-564: The spatial extent of OMZs in the past through paleoceanographical methods clearly shows that the spatial extent of OMZs has expanded through time, and this expansion is coupled to ocean warming and reduced ventilation of thermocline waters. Research has attempted to model potential changes to OMZs as a result of rising global temperatures and human impact. This is challenging due to the many factors that could contribute to changes in OMZs. The factors used for modeling change in OMZs are numerous, and in some cases hard to measure or quantify. Some of

10058-535: The speed and direction of deep ocean currents by dropping SOFAR floats that could be detected with the SOSUS array. The mesopelagic zone is important for water mass formation, such as mode water . Mode water is a water mass that is typically defined by its vertically mixed properties. It often forms as deep mixed layers at the depth of the thermocline. The mode water in the mesopelagic has residency times on decadal or century scales. The longer overturning times contrast with

10165-429: The supply of cold, oxygen-rich deep waters from polar regions. In the surface layers, oxygen is supplied by photosynthesis of phytoplankton. Depths in between, however, have higher rates of oxygen consumption and lower rates of advective supply of oxygen-rich waters. In much of the ocean, mixing processes enable the resupply of oxygen to these waters (see upwelling ). A distribution of the open-ocean oxygen minimum zones

10272-412: The supply of oxygen in terms of solubility, partial pressure, and diffusivity of oxygen in water, and the organism's metabolic rate. The metabolic index is generally viewed as a closer approximation of oxygen bioavailability than the other indices. There are two thresholds of oxygen required by organisms: Since bioavailability is specific to each organism and temperature, calculation of these thresholds

10379-445: The surface mixed layer and into the mesopelagic zone. One pathway for carbon export from the euphotic layer is through sinking of particles, which can be accelerated through repackaging of organic matter in zooplankton fecal pellets, ballasted particles, and aggregates. In the mesopelagic zone, the biological pump is key to carbon cycling, as this zone is largely dominated by remineralization of particulate organic carbon (POC). When

10486-431: The surface ocean is usually oxygen-rich due to atmospheric gas exchange and photosynthesis, the mesopelagic zone is not in direct contact with the atmosphere, due to stratification at the base of the surface mixed layer. Organic matter is exported to the mesopelagic zone from the overlying euphotic layer, while the minimal light in the mesopelagic zone limits photosynthesis. The oxygen consumption due to respiration of most of

10593-534: The surrounding environment. Other fish have mirrored bodies which are angled to reflect the surrounding ocean low-light colors and protect the fish from being seen, while another adaptation is countershading where fish have light colors on the ventral side and dark colors on the dorsal side. Food is often limited and patchy in the mesopelagic, leading to dietary adaptations. Common adaptations fish may have include sensitive eyes and huge jaws for enhanced and opportunistic feeding. Fish are also generally small to reduce

10700-408: The temperature of the water. As the external temperature increases, ectotherm metabolisms increase as well, increasing their demand for oxygen. Different species have different basal metabolic rates and therefore different oxygen demands. Life stages of organisms also have different metabolic demands. In general, younger stages tend to grow in size and advance in developmental complexity quickly. As

10807-403: The time could not penetrate below this depth due to the large number of creatures obstructing sound waves. It is uncommon to detect deep scattering layers below 1000m. Until recently, sonar has been the predominant method for studying the mesopelagic. The Malaspina Circumnavigation Expedition was a Spanish-led scientific quest in 2011 to gain a better understanding of the state of the ocean and

10914-412: The types of phyto and zooplankton in different areas of the ocean. If the material sinks faster, then it gets respired less by bacteria, transporting more carbon from the surface layer to the deep ocean. Larger fecal pellets sink faster due to lower friction-surface/mass ratio. More viscous waters could slow the sinking rate of particles. Dissolved oxygen is a requirement for aerobic respiration, and while

11021-449: The vacuum of outer space . The total amount of soil and subsurface bacterial carbon is estimated as 5 × 10  g. The mass of prokaryote microorganisms—which includes bacteria and archaea, but not the nucleated eukaryote microorganisms —may be as much as 0.8 trillion tons of carbon (of the total biosphere mass , estimated at between 1 and 4 trillion tons). Barophilic marine microbes have been found at more than

11128-431: The water more efficiently. For example, the giant red mysid ( Gnathophausia ingens ) continues to live aerobically (using oxygen) in OMZs. They have highly developed gills with large surface area and thin blood-to-water diffusion distance that enables effective removal of oxygen from the water (up to 90% O 2 removal from inhaled water) and an efficient circulatory system with high capacity and high blood concentration of

11235-408: The world marine fish biomass at between 0.8 and 2 billion tons. A more recent study concluded mesopelagic fish could have a biomass amounting to 10 billion tons, equivalent to about 100 times the annual catch of traditional fisheries of about 100 million metric tons. However, there is a lot of uncertainty in this biomass estimate. This ocean realm could contain the largest fishery in the world and there

11342-408: Was coined during the 1960s and encompasses both biological and physical components of the planet. The Second International Conference on Closed Life Systems defined biospherics as the science and technology of analogs and models of Earth's biosphere; i.e., artificial Earth-like biospheres. Others may include the creation of artificial non-Earth biospheres—for example, human-centered biospheres or

11449-503: Was previously attributed to mating, but scientists speculate this could be a feeding strategy to allow a group of jellyfish to hunt together. Mesopelagic zooplankton have unique adaptations for the low light. Bioluminescence is a very common strategy in many zooplankton. This light production is thought to function as a form of communication between conspecifics, prey attraction, prey deterrence, and/or reproduction strategy. Another common adaption are enhanced light organs, or eyes, which

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