101-785: Longhurst is a surname. Notable people with the surname include: Alan Longhurst (1925–2023), British-born Canadian oceanographer Albert Henry Longhurst (1876–1955), Indianologist and archaeologist, Archaeological Commissioner of Ceylon Cyril Longhurst (1878–1948), ASI David Longhurst (1965–1990), English footballer Eva Longhurst , one of Ontario Provincial Confederation of Regions Party candidates, 1990 Ontario provincial election Garry Longhurst Henry Longhurst (1909–1978), renowned British golf writer and commentator Henry Longhurst (actor) (1891–1970), British actor Jane Longhurst , British school teacher murdered by Graham Coutts in 2003 John Longhurst (born 1940), organist for
202-408: A calcium carbonate (CaCO 3 ) protective coating. Once this carbon is fixed into soft or hard tissue, the organisms either stay in the euphotic zone to be recycled as part of the regenerative nutrient cycle or once they die, continue to the second phase of the biological pump and begin to sink to the ocean floor. The sinking particles will often form aggregates as they sink, which greatly increases
303-413: A day . Discarded appendicularian houses are highly abundant (thousands per m3 in surface waters) and are microbial hotspots with high concentrations of bacteria, ciliates, flagellates and phytoplankton. These discarded houses are therefore among the most important sources of aggregates directly produced by zooplankton in terms of carbon cycling potential. The composition of the phytoplankton community in
404-423: A dynamic part of the biological carbon pump. The efficiency of DOC production and export varies across oceanographic regions, being more prominent in the oligotrophic subtropical oceans. The overall efficiency of the biological carbon pump is mostly controlled by the export of POC. Most carbon incorporated in organic and inorganic biological matter is formed at the sea surface where it can then start sinking to
505-402: A global organisation of the biological seascape is by construction of a typology for seasonal cycles of pelagic production and consumption. The well-known Sverdrup critical depth concept for the induction of phytoplankton growth forced by local mixing and light is the starting point for the seasonal evolution of primary production, and this is very much related to regional oceanography. However,
606-403: A higher concentration of dissolved inorganic carbon than might be expected from average surface concentrations. Consequently, these two processes act together to pump carbon from the atmosphere into the ocean's interior. One consequence of this is that when deep water upwells in warmer, equatorial latitudes, it strongly outgasses carbon dioxide to the atmosphere because of the reduced solubility of
707-674: A job for less than a year in Wellington at the Fishery Department of New Zealand and worked on racial differences in snappers. Subsequently, he focused on the trophic structure and flux of energy through the pelagic ecosystems of the eastern Pacific Ocean (1963–1971), the Barents Sea (1973), the eastern Canadian Arctic (1983–1989) and the Northwest Atlantic Ocean (1978–1994). He coordinated the international EASTROPAC expeditions in
808-725: A personal perspective. After retirement in 1995, he and his wife Françoise opened and operated Galerie l'Acadie , a not-for-profit gallery of contemporary art in Cajarc, France. Longhurst died on 7 December 2023, at the age of 98. In 1988, Longhurst was elected a Fellow of the Royal Society of Canada . In 1991, he was awarded the Gold Medal by the Professional Institute of the Public Service of Canada for his cumulative influence in
909-576: A set of codes used to represent biogeochemical provinces in oceanographic research Longhirst [REDACTED] Surname list This page lists people with the surname Longhurst . If an internal link intending to refer to a specific person led you to this page, you may wish to change that link by adding the person's given name (s) to the link. Retrieved from " https://en.wikipedia.org/w/index.php?title=Longhurst&oldid=1246673225 " Category : Surnames Hidden categories: Articles with short description Short description
1010-524: A small number of large compartments (biomes), and the lower level comprises a large number of smaller compartments (provinces), each designated with a unique four-letter code . An initial proof-of-concept for the Ecological Geography of the Sea was demonstrated by estimating global primary production using satellite radiometer data partitioned into biogeochemical domains and provinces. This influential work
1111-426: A surface to deep alkalinity gradient which serves to raise the pH of surface waters, shifting the speciation of dissolved carbon to raise the partial pressure of dissolved CO 2 in surface waters, which actually raises atmospheric levels. In addition, the burial of CaCO 3 in sediments serves to lower overall oceanic alkalinity , tending to raise pH and thereby atmospheric CO 2 levels if not counterbalanced by
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#17328757023621212-469: Is determined by a combination of factors: seasonality; the composition of phytoplankton species; the fragmentation of particles by zooplankton; and the solubilization of particles by microbes. In addition, the efficiency of the biological pump is also dependent on the aggregation and disaggregation of organic-rich aggregates and interaction between POC aggregates and suspended "ballast" minerals. Ballast minerals (silicate and carbonate biominerals and dust) are
1313-515: Is different from Wikidata All set index articles Alan Longhurst Alan Reece Longhurst (5 March 1925 – 7 December 2023) was a British-born Canadian oceanographer who invented the Longhurst-Hardy Plankton Recorder, and is widely known for his contributions to the primary scientific literature, together with his numerous monographs, most notably the "Ecological Geography of the Sea". He led an effort that produced
1414-459: Is exported out of the euphotic zone, which attenuates exponentially towards the base of the mesopelagic zone and only about 1% of the surface production reaches the sea floor. The export efficiency of particulate organic carbon (POC) shows regional variability. For instance, in the North Atlantic, over 40% of net primary production is exported out of the euphotic zone as compared to only 10% in
1515-410: Is larger sinking particles that transport matter down to the sea floor while suspended particles and dissolved organics are mostly consumed by remineralisation. This happens in part due to the fact that organisms must typically ingest nutrients smaller than they are, often by orders of magnitude. With the microbial community making up 90% of marine biomass, it is particles smaller than the microbes (on
1616-510: Is not directly taken from the atmospheric budget, it is formed from dissolved forms of carbonate which are in equilibrium with CO 2 and then responsible for removing this carbon via sequestration. CO 2 + H 2 O → H 2 CO 3 → H + HCO 3 Ca + 2HCO 3 → CaCO 3 + CO 2 + H 2 O While this process does manage to fix a large amount of carbon, two units of alkalinity are sequestered for every unit of sequestered carbon. The formation and sinking of CaCO 3 therefore drives
1717-426: Is partially consumed by bacteria (black dots) and respired; the remaining refractory DOM is advected and mixed into the deep sea. DOM and aggregates exported into the deep water are consumed and respired, thus returning organic carbon into the enormous deep ocean reservoir of DIC. About 1% of the particles leaving the surface ocean reach the seabed and are consumed, respired, or buried in the sediments. There, carbon
1818-444: Is processed by microbes, zooplankton and their consumers into fecal pellets, organic aggregates ("marine snow") and other forms, which are thereafter exported to the mesopelagic (200–1000 m depth) and bathypelagic zones by sinking and vertical migration by zooplankton and fish. Although primary production includes both dissolved and particulate organic carbon (DOC and POC respectively), only POC leads to efficient carbon export to
1919-410: Is proposed as operating in the shallow waters of the continental shelves as a mechanism transporting carbon (dissolved or particulate) from the continental waters to the interior of the adjacent deep ocean. As originally formulated, the pump is thought to occur where the solubility pump interacts with cooler, and therefore denser water from the shelf floor which feeds down the continental slope into
2020-419: Is released from zooplankton individuals or populations. The fecal pellets of zooplankton can be important vehicles for the transfer of particulate organic carbon (POC) to the deep ocean, often making large contributions to the carbon sequestration. The size distribution of the copepod community indicates high numbers of small fecal pellets are produced in the epipelagic . However, small fecal pellets are rare in
2121-433: Is stored for millions of years. The net effect of these processes is to remove carbon in organic form from the surface and return it to DIC at greater depths, maintaining the surface-to-deep ocean gradient of DIC. Thermohaline circulation returns deep-ocean DIC to the atmosphere on millennial timescales. The first step in the biological pump is the synthesis of both organic and inorganic carbon compounds by phytoplankton in
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#17328757023622222-399: Is the larger contributor. Phytoplankton supports all life in the ocean as it converts inorganic compounds into organic constituents. This autotrophically produced biomass presents the foundation of the marine food web. In the diagram immediately below, the arrows indicate the various production (arrowhead pointing toward DOM pool) and removal processes of DOM (arrowhead pointing away), while
2323-436: Is the ocean's biologically driven sequestration of carbon from the atmosphere and land runoff to the ocean interior and seafloor sediments . In other words, it is a biologically mediated process which results in the sequestering of carbon in the deep ocean away from the atmosphere and the land. The biological pump is the biological component of the "marine carbon pump" which contains both a physical and biological component. It
2424-442: Is the part of the broader oceanic carbon cycle responsible for the cycling of organic matter formed mainly by phytoplankton during photosynthesis (soft-tissue pump), as well as the cycling of calcium carbonate (CaCO 3 ) formed into shells by certain organisms such as plankton and mollusks (carbonate pump). Budget calculations of the biological carbon pump are based on the ratio between sedimentation (carbon export to
2525-559: The Redfield ratio . Trace metals such as magnesium, cadmium, iron, calcium, barium and copper are orders of magnitude less prevalent in phytoplankton organic material, but necessary for certain metabolic processes and therefore can be limiting nutrients in photosynthesis due to their lower abundance in the water column. Oceanic primary production accounts for about half of the carbon fixation carried out on Earth. Approximately 50–60 Pg of carbon are fixed by marine phytoplankton each year despite
2626-516: The bathypelagic . The change in fecal pellet morphology, as well as size distribution, points to the repacking of surface fecal pellets in the mesopelagic and in situ production in the lower meso- and bathypelagic, which may be augmented by inputs of fecal pellets via zooplankton vertical migrations . This suggests the flux of carbon to the deeper layers within the Southern Ocean is strongly modulated by meso- and bathypelagic zooplankton, meaning that
2727-410: The biota . Heterotrophic organisms will utilize the materials produced by the autotrophic (and chemotrophic ) organisms and via respiration will remineralise the compounds from the organic form back to inorganic, making them available for primary producers again. For most areas of the ocean, the highest rates of carbon remineralisation occur at depths between 100–1,200 m (330–3,940 ft) in
2828-540: The euphotic zone to the ocean interior and subsequently to the underlying sediments. Thus, the biological pump takes carbon out of contact with the atmosphere for several thousand years or longer and maintains atmospheric CO 2 at significantly lower levels than would be the case if it did not exist. An ocean without a biological pump, which transfers roughly 11 Gt C yr into the ocean's interior, would result in atmospheric CO 2 levels ~400 ppm higher than present day. Passow and Carlson defined sedimentation out of
2929-741: The mixed layer (< 12 Gt C yr 14). Krill, copepods, zooplankton and microbes intercept phytoplankton in the surface ocean and sinking detrital particles at depth, consuming and respiring this POC to CO 2 ( dissolved inorganic carbon , DIC), such that only a small proportion of surface-produced carbon sinks to the deep ocean (i.e., depths > 1000 m). As krill and smaller zooplankton feed, they also physically fragment particles into small, slower- or non-sinking pieces (via sloppy feeding, coprorhexy if fragmenting faeces), retarding POC export. This releases dissolved organic carbon (DOC) either directly from cells or indirectly via bacterial solubilisation (yellow circle around DOC). Bacteria can then remineralise
3030-411: The "business as usual" CO 2 emission scenario. Marine ecosystems are a major sink for atmospheric CO 2 and take up similar amount of CO 2 as terrestrial ecosystems, currently accounting for the removal of nearly one third of anthropogenic CO 2 emissions from the atmosphere. The net transfer of CO 2 from the atmosphere to the oceans and then sediments , is mainly a direct consequence of
3131-1019: The 1960s and was the first Director of the Southwest Fisheries Science Center of the US National Marine Fisheries Service in La Jolla, California (1967–1971). Returning to England in 1971, he accepted a position as the Deputy Director of the Institute for Marine Environmental Research in Plymouth. Later, in Canada, he was Director of the Marine Ecology Laboratory at the Bedford Institute of Oceanography , Nova Scotia (1977–1979). His final administrative appointment
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3232-456: The 1970s Tony Longhurst (born 1957), Australian former racing driver and Australian Champion water skier William Henry Longhurst (1819–1904), English organist at Canterbury Cathedral See also [ edit ] Longhurst Plateau , narrow, snow-covered extension of the Antarctic polar plateau located just west of Mount Longhurst Hollinghurst Longphuirt Longhurst code ,
3333-794: The British army, graduating from the Royal Military Academy Sandhurst at the end of the war (1945). He then went to take part in the Allied occupation of Austria, ending up in Somalia and Abyssinia with the East African forces. After the war, he returned to London for a degree in entomology and then a doctoral degree in zoology (1952) at the Bedford College of the University of London (England) on
3434-475: The DOC to DIC (CO 2 , microbial gardening). The biological carbon pump is one of the chief determinants of the vertical distribution of carbon in the oceans and therefore of the surface partial pressure of CO 2 governing air-sea CO 2 exchange. It comprises phytoplankton cells, their consumers and the bacteria that assimilate their waste and plays a central role in the global carbon cycle by delivering carbon from
3535-459: The Earth's carbon cycle . It is also intimately linked to the cycling of other elements and compounds. The ocean plays a fundamental role in Earth's carbon cycle, helping to regulate atmospheric CO 2 concentration. The biological pump is a set of processes that transfer organic carbon from the surface to the deep ocean, and is at the heart of the ocean carbon cycle . The biological pump depends on
3636-554: The Mormon Tabernacle Choir for 30 years Kate Longhurst , English footballer Mark Longhurst , UK television newsreader and journalist Martha Longhurst , UK TV Coronation Street character Neil Longhurst (born 1984), English cricketer Robert Longhurst (born 1949), American sculptor from Schenectady, New York Robyn Longhurst , New Zealand professor of human geography Sue Longhurst , English actress, most famous for appearing in several X-rated comedies in
3737-445: The Sea" is a book on the regional geography of the world ocean for ecologists. According to Longhurst, regional oceanographic processes are paramount in moulding the characteristics of regional ecosystems. A central argument of this book is that spatial bounds to ocean ecosystems can be set by reference to features of the physical circulation of the oceans rather than to the distribution of individual species. The root of this approach to
3838-565: The South Pacific, and this is driven in part by the composition of the phytoplankton community including cell size and composition (see below). Exported organic carbon is remineralized, that is, respired back to CO 2 in the oceanic water column at depth, mainly by heterotrophic microbes and zooplankton. Thus, the biological carbon pump maintains a vertical gradient in the concentration of dissolved inorganic carbon (DIC), with higher values at increased ocean depth. This deep-ocean DIC returns to
3939-484: The accumulation or loss of phytoplankton biomass is influenced by secondary processes, such as variation in the size of the herbivore population at the start of the bloom. In extending the Sverdrup model to all parts of the ocean, a typology of plankton cycles is necessary that describes a continuum from strongly seasonal regions with seasonal recharge of photic zone nutrients to weakly seasonal regions where nutrient renewal of
4040-412: The atmosphere for several thousand years or longer. An ocean without a biological pump would result in atmospheric carbon dioxide levels about 400 ppm higher than the present day. The element carbon plays a central role in climate and life on Earth. It is capable of moving among and between the geosphere , cryosphere , atmosphere , biosphere and hydrosphere . This flow of carbon is referred to as
4141-411: The atmosphere on millennial timescales through thermohaline circulation . In 2001, Hugh et al. expressed the efficiency of the biological pump as the amount of carbon exported from the surface layer (export production) divided by the total amount produced by photosynthesis (overall production). Modelling studies by Buesseler and Boyd revealed that the overall transfer efficiency of the biological pump
Longhurst - Misplaced Pages Continue
4242-432: The atmosphere to the deep sea, where it is concentrated and sequestered for centuries. Photosynthesis by phytoplankton lowers the partial pressure of CO 2 in the upper ocean, thereby facilitating the absorption of CO 2 from the atmosphere by generating a steeper CO 2 gradient. It also results in the formation of particulate organic carbon (POC) in the euphotic layer of the epipelagic zone (0–200 m depth). The POC
4343-466: The atmosphere. Budget calculations of the biological carbon pump are based on the ratio between sedimentation (carbon export) and remineralization (release to the atmosphere). It has been estimated that sinking particles export up to 25% of the carbon captured by phytoplankton in the surface ocean to deeper water layers. About 20% of this export (5% of surface values) is buried in the ocean sediments mainly due to their mineral ballast. During
4444-474: The biological carbon pump fixes inorganic carbon (CO 2 ) into particulate organic carbon in the form of sugar (C 6 H 12 O 6 ), the carbonate pump fixes inorganic bicarbonate and causes a net release of CO 2 . In this way, the carbonate pump could be termed the carbonate counter pump. It works counter to the biological pump by counteracting the CO 2 flux into the biological pump. The continental shelf pump
4545-577: The biological pump. The biological pump is responsible for transforming dissolved inorganic carbon (DIC) into organic biomass and pumping it in particulate or dissolved form into the deep ocean. Inorganic nutrients and carbon dioxide are fixed during photosynthesis by phytoplankton, which both release dissolved organic matter (DOM) and are consumed by herbivorous zooplankton. Larger zooplankton - such as copepods - egest fecal pellets which can be reingested and sink or collect with other organic detritus into larger, more-rapidly-sinking aggregates. DOM
4646-469: The biological pump. This is particularly the case with copepods and krill , and is especially important in oligotrophic waters of the open ocean. Through sloppy feeding, excretion, egestion, and leaching of fecal pellets, zooplankton release dissolved organic matter (DOM) which controls DOM cycling and supports the microbial loop. Absorption efficiency, respiration, and prey size all further complicate how zooplankton are able to transform and deliver carbon to
4747-442: The combined effect of the solubility and the biological pump. While the solubility pump serves to concentrate dissolved inorganic carbon (CO 2 plus bicarbonate and carbonate ions) in the deep oceans, the biological carbon pump (a key natural process and a major component of the global carbon cycle that regulates atmospheric CO 2 levels) transfers both organic and inorganic carbon fixed by primary producers (phytoplankton) in
4848-520: The dashed arrows represent dominant biological processes involved in the transfer of DOM. Due to these processes, the fraction of labile DOM decreases rapidly with depth, whereas the refractory character of the DOM pool considerably increases during its export to the deep ocean. DOM, dissolved organic matter. The marine biological pump depends on a number of key pools, components and processes that influence its functioning. There are four main pools of carbon in
4949-609: The deep ocean. Excretion and sloppy feeding (the physical breakdown of food source) make up 80% and 20% of crustacean zooplankton-mediated DOM release respectively. In the same study, fecal pellet leaching was found to be an insignificant contributor. For protozoan grazers, DOM is released primarily through excretion and egestion and gelatinous zooplankton can also release DOM through the production of mucus. Leaching of fecal pellets can extend from hours to days after initial egestion and its effects can vary depending on food concentration and quality. Various factors can affect how much DOM
5050-526: The deeper layers, suggesting they are not transferred efficiently to depth. This means small fecal pellets make only minor contributions to fecal pellet fluxes in the meso- and bathypelagic, particularly in terms of carbon. In a study is focussed on the Scotia Sea , which contains some of the most productive regions in the Southern Ocean, the dominant fecal pellets in the upper mesopelagic were cylindrical and elliptical, while ovoid fecal pellets were dominant in
5151-551: The development of Canadian oceanography. In 1997, he received the A.C. Redfield Lifetime Achievement Award from the Association for the Sciences of Limnology and Oceanography "in recognition of sustained excellence in the study of marine food webs and biogeography, and of outstanding leadership in the development of international collaboration and in the administration of world-renowned oceanographic programs". "Ecological Geography of
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#17328757023625252-556: The direct effects of ballast minerals on sinking velocity and degradation rates in sinking aggregates are still unclear. A 2008 study demonstrated copepod fecal pellets produced on a diet of diatoms or coccolithophorids show higher sinking velocities as compared to pellets produced on a nanoflagellate diet. Carbon-specific respiration rates in pellets, however, were similar and independent of mineral content. These results suggest differences in mineral composition do not lead to differential protection of POC against microbial degradation, but
5353-737: The ecology and taxonomy of Notostraca , a small group of living‐fossil, fresh‐water crustaceans. Early in his career, Longhurst studied the ecology of benthic communities and demersal fish on the continental shelf of the Gulf of Guinea (1954–1963) during service at the West African Fisheries Research Institute in Freetown, Sierra Leone and the Federal Fisheries Service in Lagos, Nigeria. In the middle of this early period, he took
5454-480: The energy stored in organic molecules and recycling matter within the system to be reused as nutrients by other organisms . What fraction does escape remineralisation varies depending on the location. For example, in the North Sea, values of carbon deposition are ~1% of primary production while that value is <0.5% in the open oceans on average. Therefore, most of nutrients remain in the water column, recycled by
5555-486: The enhanced sinking velocities may result in up to 10-fold higher carbon preservation in pellets containing biogenic minerals as compared to that of pellets without biogenic minerals Minerals seem to enhance the flocculation of phytoplankton aggregates and may even act as a catalyst in aggregate formation. However, it has also been shown that incorporation of minerals can cause aggregates to fragment into smaller and denser aggregates. This can potentially lower
5656-500: The euphotic zone and a significant portion is remineralized in midwater processes during particle sinking. The portion of carbon that leaves the surface mixed layer of the ocean is sometimes considered "sequestered", and essentially removed from contact with the atmosphere for many centuries. However, work also finds that, in regions such as the Southern Ocean , much of this carbon can quickly (within decades) come back into contact with
5757-422: The euphotic zone is processed by microbes, zooplankton and their consumers into organic aggregates (marine snow), which is thereafter exported to the mesopelagic (200–1000 m depth) and bathypelagic zones by sinking and vertical migration by zooplankton and fish. Export flux is defined as the sedimentation out of the surface layer (at approximately 100 m depth) and sequestration flux is the sedimentation out of
5858-851: The euphotic zone largely determines the quantity and quality of organic matter that sinks to depth. The main functional groups of marine phytoplankton that contribute to export production include nitrogen fixers ( diazotrophic cyanobacteria ), silicifiers (diatoms) and calcifiers (coccolithophores). Each of these phytoplankton groups differ in the size and composition of their cell walls and coverings, which influence their sinking velocities. For example, autotrophic picoplankton (0.2–2 μm in diameter)—which include taxa such as cyanobacteria (e.g., Prochlorococcus spp. and Synechococcus spp.) and prasinophytes (various genera of eukaryotes <2 μm)—are believed to contribute much less to carbon export from surface layers due to their small size, slow sinking velocities (<0.5 m/day) and rapid turnover in
5959-421: The fact that they account for less than 1% of the total photosynthetic biomass on Earth. The majority of this carbon fixation (~80%) is carried out in the open ocean while the remaining amount occurs in the very productive upwelling regions of the ocean. Despite these productive regions producing 2 to 3 times as much fixed carbon per area, the open ocean accounts for greater than 90% of the ocean area and therefore
6060-423: The first estimate of global primary production in the oceans using satellite imagery, and also quantified vertical carbon flux through the planktonic ecosystem via the biological pump . In later life he offered several critical reviews of several aspects of fishery management science and climate change science. Alan Longhurst was born in Plymouth, England, the son of a naval dental surgeon. He spent four years in
6161-524: The first of which is the production of fixed carbon by planktonic phototrophs in the euphotic (sunlit) surface region of the ocean. In these surface waters, phytoplankton use carbon dioxide (CO 2 ), nitrogen (N), phosphorus (P), and other trace elements ( barium , iron , zinc , etc.) during photosynthesis to make carbohydrates , lipids , and proteins . Some plankton, (e.g. coccolithophores and foraminifera ) combine calcium (Ca) and dissolved carbonates ( carbonic acid and bicarbonate ) to form
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#17328757023626262-423: The form of dissolved inorganic carbon (DIC) from the ocean's surface to its interior. It involves physical and chemical processes only, and does not involve biological processes. The solubility pump is driven by the coincidence of two processes in the ocean: Since deep water (that is, seawater in the ocean's interior) is formed under the same surface conditions that promote carbon dioxide solubility, it contains
6363-400: The form of marine snow aggregates (>0.5 mm) composed of phytoplankton, detritus, inorganic mineral grains, and fecal pellets in the ocean. Formation and sinking of these aggregates drive the biological carbon pump via export and sedimentation of organic matter from the surface mixed layer to the deep ocean and sediments. The fraction of organic matter that leaves the upper mixed layer of
6464-654: The fraction of primary produced organic matter that survives degradation in the euphotic zone and that is exported from surface water to the ocean interior, where it is mineralized to inorganic carbon , with the result that carbon is transported against the gradient of dissolved inorganic carbon (DIC) from the surface to the deep ocean. This transfer occurs through physical mixing and transport of dissolved and particulate organic carbon (POC), vertical migrations of organisms ( zooplankton , fish ) and through gravitational settling of particulate organic carbon. The biological pump can be divided into three distinct phases,
6565-493: The fundamental issues of pelagic ecology and biogeography, which distil to whether, at some level of probability, a deduction may be made about the characteristic features of any region. Here, the definition of the region is crucial since it determines the scale of the biological seascape. By placing the typology of seasonal plankton cycles into the context of regional oceanography, characteristic features of ecology can be discerned at two hierarchical scales. The higher level comprises
6666-412: The gas. The carbonate pump is sometimes referred to as the "hard tissue" component of the biological pump. Some surface marine organisms, like coccolithophores , produce hard structures out of calcium carbonate, a form of particulate inorganic carbon, by fixing bicarbonate. This fixation of DIC is an important part of the oceanic carbon cycle. Ca + 2 HCO 3 → CaCO 3 + CO 2 + H 2 O While
6767-438: The global particulate organic carbon (POC) fluxes were associated with carbonate , and suggested carbonate was a more efficient ballast mineral as compared to opal and terrigenous material. They hypothesized that the higher density of calcium carbonate compared to that of opal and the higher abundance of calcium carbonate relative to terrigenous material might be the reason for the efficient ballasting by calcium carbonate. However,
6868-440: The interactions between minerals and organic aggregates affect the degradation and sinking velocity of the aggregates and, hence, carbon sequestration in the ocean. Remineralisation refers to the breakdown or transformation of organic matter (those molecules derived from a biological source) into its simplest inorganic forms. These transformations form a crucial link within ecosystems as they are responsible for liberating
6969-504: The major constituents of particles that leave the ocean surface via sinking. They are typically denser than seawater and most organic matter, thus, providing a large part of the density differential needed for sinking of the particles. Aggregation of particles increases vertical flux by transforming small suspended particles into larger, rapidly-sinking ones. It plays an important role in the sedimentation of phytodetritus from surface layer phytoplankton blooms. As illustrated by Turner in 2015,
7070-400: The marine carbon cycle bring atmospheric carbon dioxide (CO 2 ) into the ocean interior and distribute it through the oceans. These three pumps are: (1) the solubility pump, (2) the carbonate pump, and (3) the biological pump. The total active pool of carbon at the Earth's surface for durations of less than 10,000 years is roughly 40,000 gigatons C (Gt C, a gigaton is one billion tons, or
7171-462: The mesopelagic zone (at approximately 1000 m depth). A portion of the POC is respired back to CO 2 in the oceanic water column at depth, mostly by heterotrophic microbes and zooplankton, thus maintaining a vertical gradient in concentration of dissolved inorganic carbon (DIC). This deep-ocean DIC returns to the atmosphere on millennial timescales through thermohaline circulation . Between 1% and 40% of
7272-418: The microbial loop. In contrast, larger phytoplankton cells such as diatoms (2–500 μm in diameter) are very efficient in transporting carbon to depth by forming rapidly sinking aggregates. They are unique among phytoplankton, because they require Si in the form of silicic acid (Si(OH)4) for growth and production of their frustules, which are made of biogenic silica (bSiO2) and act as ballast. According to
7373-494: The neighbouring deep ocean. The shallowness of the continental shelf restricts the convection of cooling water, so the cooling can be greater for continental shelf waters than for neighbouring open ocean waters. These cooler waters promote the solubility pump and lead to an increased storage of dissolved inorganic carbon . This extra carbon storage is further augmented by the increased biological production characteristic of shelves. The dense, carbon-rich shelf waters then sink to
7474-569: The new input of alkalinity from weathering. The portion of carbon that is permanently buried at the sea floor becomes part of the geologic record. Calcium carbonate often forms remarkable deposits that can then be raised onto land through tectonic motion as in the case with the White Cliffs of Dover in Southern England. These cliffs are made almost entirely of the plates of buried coccolithophores . Three main processes (or pumps) that make up
7575-443: The ocean floor) and remineralization (release of carbon to the atmosphere). The biological pump is not so much the result of a single process, but rather the sum of a number of processes each of which can influence biological pumping. Overall, the pump transfers about 10.2 gigatonnes of carbon every year into the ocean's interior and a total of 1300 gigatonnes carbon over an average 127 years. This takes carbon out of contact with
7676-468: The ocean floor. However, through processes such as coagulation and expulsion in predator fecal pellets, these cells form aggregates. These aggregates, known as marine snow , have sinking rates orders of magnitude greater than individual cells and complete their journey to the deep in a matter of days. In the diagram on the right, phytoplankton fix CO 2 in the euphotic zone using solar energy and produce particulate organic carbon (POC). POC formed in
7777-434: The ocean floor. The deep ocean gets most of its nutrients from the higher water column when they sink down in the form of marine snow. This is made up of dead or dying animals and microbes, fecal matter, sand and other inorganic material. A single phytoplankton cell has a sinking rate around one metre per day. Given that the average depth of the ocean is about four kilometres, it can take over ten years for these cells to reach
7878-427: The ocean interior, whereas the DOC fraction in surface waters is mostly recycled by bacteria. However, a more biologically resistant DOC fraction produced in the euphotic zone (accounting for 15–20% of net community productivity), is not immediately mineralized by microbes and accumulates in the ocean surface as biologically semi-labile DOC . This semi-labile DOC undergoes net export to the deep ocean, thus constituting
7979-414: The ocean is, among other factors, determined by the sinking velocity and microbial remineralisation rate of these aggregates. Recent observations have shown that the fluxes of ballast minerals (calcium carbonate, opal, and lithogenic material) and the organic carbon fluxes are closely correlated in the bathypelagic zones of the ocean. This has led to the hypothesis that organic carbon export is determined by
8080-478: The ocean. Particulate inorganic carbon (PIC) usually takes the form of calcium carbonate (CaCO 3 ), and plays a key part in the ocean carbon cycle. This biologically fixed carbon is used as a protective coating for many planktonic species (coccolithophores, foraminifera) as well as larger marine organisms (mollusk shells). Calcium carbonate is also excreted at high rates during osmoregulation by fish, and can form in whiting events . While this form of carbon
8181-569: The order of 10 ) that will be taken up for remineralisation. Marine phytoplankton perform half of all photosynthesis on Earth and directly influence global biogeochemical cycles and the climate, yet how they will respond to future global change is unknown. Carbon dioxide is one of the principal drivers of global change and has been identified as one of the major challenges in the 21st century. Carbon dioxide (CO 2 ) generated during anthropogenic activities such as deforestation and burning of fossil fuels for energy generation rapidly dissolves in
8282-677: The particulate organic carbon (POC) flux, in 2007 Richardson and Jackson suggested that all phytoplankton, including picoplankton cells, contribute equally to POC export. They proposed alternative pathways for picoplankton carbon cycling, which rely on aggregation as a mechanism for both direct sinking (the export of picoplankton as POC) and mesozooplankton- or large filter feeder-mediated sinking of picoplankton-based production. In addition to linking primary producers to higher trophic levels in marine food webs, zooplankton also play an important role as "recyclers" of carbon and other nutrients that significantly impact marine biogeochemical cycles, including
8383-457: The photic zone is slow or episodic and where productivity is largely fuelled by internal nutrient regeneration. Along this continuum, phytoplankton and zooplankton exhibit characteristic features of ecological structure and function that arise as outcomes of systemic behaviour. A full exposition of this organisational scheme into a rational partition of the global ocean was a landmark in many respects. In essence, this ecological geography addresses
8484-571: The planktonic ecosystem. It was reviewed in Nature , Science , Limnology and Oceanography , and Trends in Ecology and Evolution , amongst others. The second edition (2007) included considerations of the strong coupling between benthic and pelagic processes that occur over continental shelves, and between plankton and larger pelagic organisms. Biological pump The biological pump (or ocean carbon biological pump or marine biological carbon pump )
8585-427: The presence of ballast minerals within settling aggregates. Mineral ballasting is associated with about 60% of the flux of particulate organic carbon (POC) in the high-latitude North Atlantic, and with about 40% of the flux in the Southern Ocean. Strong correlations exist also in the deep ocean between the presence of ballast minerals and the flux of POC. This suggests ballast minerals enhance POC flux by increasing
8686-409: The primary production is exported out of the euphotic zone, which attenuates exponentially towards the base of the mesopelagic zone and only about 1% of the surface production reaches the sea floor. Of the 50–60 Pg of carbon fixed annually, roughly 10% leaves the surface mixed layer of the oceans, while less than 0.5% of eventually reaches the sea floor. Most is retained in regenerated production in
8787-441: The reports of Miklasz and Denny, the sinking velocities of diatoms can range from 0.4 to 35 m/day. Analogously, coccolithophores are covered with calcium carbonate plates called 'coccoliths', which are central to aggregation and ballasting, producing sinking velocities of nearly 5 m/day. Although it has been assumed that picophytoplankton , characterizing vast oligotrophic areas of the ocean, do not contribute substantially to
8888-468: The sediment and may remain there for millions of years. It is this sequestered carbon that is responsible for ultimately lowering atmospheric CO 2 . Biology, physics and gravity interact to pump organic carbon into the deep sea. The processes of fixation of inorganic carbon in organic matter during photosynthesis, its transformation by food web processes (trophodynamics), physical mixing, transport and gravitational settling are referred to collectively as
8989-762: The shelf floor and enter the sub-surface layer of the open ocean via isopycnal mixing. As the sea level rises in response to global warming, the surface area of the shelf seas will grow and in consequence the strength of the shelf sea pump should increase. In the diagram on the right, phytoplankton convert CO 2 , which has dissolved from the atmosphere into the surface oceans (90 Gt yr ), into particulate organic carbon (POC) during primary production (~ 50 Gt C yr ). Phytoplankton are then consumed by copepods , krill and other small zooplankton grazers, which in turn are preyed upon by higher trophic levels . Any unconsumed phytoplankton form aggregates, and along with zooplankton faecal pellets, sink rapidly and are exported out of
9090-470: The sink rate of ballasted aggregates. Ballast minerals could additionally provide aggregated organic matter some protection from degradation. It has been proposed that organic carbon is better preserved in sinking particles due to increased aggregate density and sinking velocity when ballast minerals are present and/or via protection of the organic matter due to quantitative association to ballast minerals. In 2002, Klaas and Archer observed that about 83% of
9191-452: The sinking process, these organic particles are hotspots of microbial activity and represent important loci for organic matter mineralization and nutrient redistribution in the water column. Observations have shown that fluxes of ballast minerals (calcium carbonate, opal, and lithogenic material) and organic carbon fluxes are closely correlated in the bathypelagic zones of the ocean. A large fraction of particulate organic matter occurs in
9292-452: The sinking rate. It is this aggregation that gives particles a better chance of escaping predation and decomposition in the water column and eventually making it to the sea floor. The fixed carbon that is decomposed by bacteria either on the way down or once on the sea floor then enters the final phase of the pump and is remineralized to be used again in primary production . The particles that escape these processes entirely are sequestered in
9393-407: The sinking velocity of the aggregated organic material due to the reduced aggregate sizes, and, thus, lower the total export of organic matter. Conversely, if the incorporation of minerals increases the aggregate density, its size-specific sinking velocity may also increase, which could potentially increase the carbon export. Therefore, there is still a need for better quantitative investigations of how
9494-416: The surface layer (at approximately 100 m depth) as the "export flux" and that out of the mesopelagic zone (at approximately 1000 m depth) as the "sequestration flux". Once carbon is transported below the mesopelagic zone, it remains in the deep sea for 100 years or longer, hence the term "sequestration" flux. According to the modelling results of Buesseler and Boyd between 1% and 40% of the primary production
9595-413: The surface ocean and lowers seawater pH, while CO 2 remaining in the atmosphere increases global temperatures and leads to increased ocean thermal stratification . While CO 2 concentration in the atmosphere is estimated to be about 270 ppm before the industrial revolution, it has currently increased to about 400 ppm and is expected to reach 800–1000 ppm by the end of this century according to
9696-479: The uppermost, sunlit layers of the ocean. Organic compounds in the form of sugars, carbohydrates, lipids, and proteins are synthesized during the process of photosynthesis : CO 2 + H 2 O + light → CH 2 O + O 2 In addition to carbon, organic matter found in phytoplankton is composed of nitrogen, phosphorus and various trace metals . The ratio of carbon to nitrogen and phosphorus varies from place to place, but has an average ratio near 106C:16N:1P, known as
9797-618: The vertical flux of sinking particles is mainly due to a combination of fecal pellets, marine snow and direct sedimentation of phytoplankton blooms, which are typically composed of diatoms, coccolithophorids, dinoflagellates and other plankton. Marine snow comprises macroscopic organic aggregates >500 μm in size and originates from clumps of aggregated phytoplankton (phytodetritus), discarded appendicularian houses, fecal matter and other miscellaneous detrital particles, Appendicularians secrete mucous feeding structures or "houses" to collect food particles and discard and renew them up to 40 times
9898-405: The water column, decreasing down to about 1,200 m (3,900 ft) where remineralisation rates remain pretty constant at 0.1 μmol kg yr . This provides the most nutrients available for primary producers within the photic zone, though it leaves the upper surface waters starved of inorganic nutrients. Most remineralisation is done with dissolved organic carbon (DOC). Studies have shown that it
9999-442: The weight of approximately 6 million blue whales ), and about 95% (~38,000 Gt C) is stored in the ocean, mostly as dissolved inorganic carbon . The speciation of dissolved inorganic carbon in the marine carbon cycle is a primary controller of acid-base chemistry in the oceans. The biological pump is accompanied by a physico-chemical counterpart known as the solubility pump . This pump transports significant amounts of carbon in
10100-677: Was as Director-General of that Institute (1980–1986). He later turned down the position of Assistant Deputy Minister of Science at the national headquarters of the Department of Fisheries and Oceans (Government of Canada) in favour of going "back to the bench" as a research scientist. Longhurst has published more than 80 research papers and his most recent books are " Ecological Geography of the Sea " (1st edition 1998, 2nd edition 2007) and " Mismanagement of Marine Fisheries " (2010). He has also written on " Doubt and Certainty in Climate Science " from
10201-455: Was published in 1995 with co-authors Shubha Sathyendranath , Trevor Platt , and Carla Caverhill, and stands as the most highly cited paper in the Journal of Plankton Research . Parenthetically, the first paper in the first issue of the first volume of this journal which appeared in 1979 was also authored by Longhurst. The first edition of the Ecological Geography of the Sea (1998) dealt only with
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