Zooplankton are the heterotrophic component of the planktonic community (the " zoo- " prefix comes from Ancient Greek : ζῷον , romanized : zôion , lit. 'animal'), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequently, they drift or are carried along by currents in the ocean , or by currents in seas , lakes or rivers .
130-628: Zooplankton can be contrasted with phytoplankton ( cyanobacteria and microalgae ), which are the plant-like component of the plankton community (the " phyto- " prefix comes from Ancient Greek: φῠτόν , romanized: phutón , lit. 'plant', although taxonomically not plants ). Zooplankton are heterotrophic (other-feeding), whereas phytoplankton are autotrophic (self-feeding), often generating biological energy and macromolecules through chlorophyllic carbon fixation using sunlight — in other words, zooplankton cannot manufacture their own food, while phytoplankton can. As
260-554: A cell wall , as found in plants and many algae . Although the traditional practice of grouping protozoa with animals is no longer considered valid, the term continues to be used in a loose way to identify single-celled organisms that can move independently and feed by heterotrophy . Marine protozoans include zooflagellates , foraminiferans , radiolarians and some dinoflagellates . Radiolarians are unicellular predatory protists encased in elaborate globular shells usually made of silica and pierced with holes. Their name comes from
390-508: A better view of their global distribution. The term phytoplankton encompasses all photoautotrophic microorganisms in aquatic food webs . However, unlike terrestrial communities , where most autotrophs are plants , phytoplankton are a diverse group, incorporating protistan eukaryotes and both eubacterial and archaebacterial prokaryotes . There are about 5,000 known species of marine phytoplankton. How such diversity evolved despite scarce resources (restricting niche differentiation )
520-435: A body of water or cultured, though the former method is seldom used. Phytoplankton is used as a foodstock for the production of rotifers , which are in turn used to feed other organisms. Phytoplankton is also used to feed many varieties of aquacultured molluscs , including pearl oysters and giant clams . A 2018 study estimated the nutritional value of natural phytoplankton in terms of carbohydrate, protein and lipid across
650-583: A calcium carbonate shell called a coccosphere that is sensitive to ocean acidification. Because of their short generation times, evidence suggests some phytoplankton can adapt to changes in pH induced by increased carbon dioxide on rapid time-scales (months to years). Phytoplankton serve as the base of the aquatic food web, providing an essential ecological function for all aquatic life. Under future conditions of anthropogenic warming and ocean acidification, changes in phytoplankton mortality due to changes in rates of zooplankton grazing may be significant. One of
780-663: A central role in determining the magnitude of ectothermic temperature-size responses, but it is hard to disentangle the relative effects of oxygen and temperature from field data because these two variables are often strongly inter-related in the surface ocean. Zooplankton can be broken down into size classes which are diverse in their morphology, diet, feeding strategies, etc. both within classes and between classes: Microzooplankton are defined as heterotrophic and mixotrophic plankton. They primarily consist of phagotrophic protists , including ciliates, dinoflagellates, and mesozooplankton nauplii . Microzooplankton are major grazers of
910-643: A critical role in supporting the ocean's biological pump through various forms of carbon export , including the production of fecal pellets, mucous feeding webs, molts, and carcasses. Fecal pellets are estimated to be a large contributor to this export, with copepod size rather than abundance expected to determine how much carbon actually reaches the ocean floor. The importance of fecal pellets can vary both by time and location. For example, zooplankton bloom events can produce larger quantities of fecal pellets, resulting in greater measures of carbon export. Additionally, as fecal pellets sink, they are reworked by microbes in
1040-525: A culture medium. This water must be sterilized , usually by either high temperatures in an autoclave or by exposure to ultraviolet radiation , to prevent biological contamination of the culture. Various fertilizers are added to the culture medium to facilitate the growth of plankton. A culture must be aerated or agitated in some way to keep plankton suspended, as well as to provide dissolved carbon dioxide for photosynthesis . In addition to constant aeration, most cultures are manually mixed or stirred on
1170-413: A decrease in productivity as the waters are no longer receiving nutrient-rich water. Without these nutrients, the rest of the trophic pyramid cannot be sustained, and the rich upwelling ecosystem will collapse. Coastal upwelling has a major influence over the affected region's local climate. This effect is magnified if the ocean current is already cool. As the cold, nutrient-rich water moves upwards and
1300-414: A decreasing population, especially in species that do not breed often under normal circumstances or become reproductively mature late in life. Another problem is that the decrease in the population of a species due to fisheries can lead to a decrease in genetic diversity, resulting in a decrease in biodiversity of a species. If the species diversity is decreased significantly, this could cause problems for
1430-400: A delay in the reconstruction of this upwelling community. The possibility of such an ecosystem collapse is the very danger of fisheries in upwelling regions. Fisheries may target a variety of different species, and therefore they are a direct threat to many species in the ecosystem, however they pose the highest threat to the intermediate pelagic fish . Since these fish form the crux of
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#17328697521111560-880: A focused effort be placed on the development of instrumentation that can link changes in phytoplankton biomass or optical properties with grazing. Grazing is a central, rate-setting process in ocean ecosystems and a driver of marine biogeochemical cycling . In all ocean ecosystems, grazing by heterotrophic protists constitutes the single largest loss factor of marine primary production and alters particle size distributions. Grazing affects all pathways of export production, rendering grazing important both for surface and deep carbon processes. Predicting central paradigms of ocean ecosystem function, including responses to environmental change requires accurate representation of grazing in global biogeochemical, ecosystem and cross-biome-comparison models. Several large-scale analyses have concluded that phytoplankton losses, which are dominated by grazing are
1690-778: A fundamental principle to understand marine ecology, biogeochemistry and phytoplankton evolution. However, the Redfield ratio is not a universal value and it may diverge due to the changes in exogenous nutrient delivery and microbial metabolisms in the ocean, such as nitrogen fixation , denitrification and anammox . The dynamic stoichiometry shown in unicellular algae reflects their capability to store nutrients in an internal pool, shift between enzymes with various nutrient requirements and alter osmolyte composition. Different cellular components have their own unique stoichiometry characteristics, for instance, resource (light or nutrients) acquisition machinery such as proteins and chlorophyll contain
1820-611: A gel matrix, which can increase massively in size during blooms . As a result, Phaeocystis is an important contributor to the marine carbon and sulfur cycles . A number of forams are mixotrophic. These have unicellular algae as endosymbionts , from diverse lineages such as the green algae , red algae , golden algae , diatoms , and dinoflagellates . Mixotrophic foraminifers are particularly common in nutrient-poor oceanic waters. Some forams are kleptoplastic , retaining chloroplasts from ingested algae to conduct photosynthesis . By trophic orientation, dinoflagellates are all over
1950-727: A geographical region, so are zooplankton. However, species of zooplankton are not dispersed uniformly or randomly within a region of the ocean. As with phytoplankton, 'patches' of zooplankton species exist throughout the ocean. Though few physical barriers exist above the mesopelagic , specific species of zooplankton are strictly restricted by salinity and temperature gradients, while other species can withstand wide temperature and salinity gradients. Zooplankton patchiness can also be influenced by biological factors, as well as other physical factors. Biological factors include breeding, predation, concentration of phytoplankton, and vertical migration. The physical factor that influences zooplankton distribution
2080-495: A high concentration of nitrogen but low in phosphorus. Meanwhile, growth machinery such as ribosomal RNA contains high nitrogen and phosphorus concentrations. Based on allocation of resources, phytoplankton is classified into three different growth strategies, namely survivalist, bloomer and generalist. Survivalist phytoplankton has a high ratio of N:P (>30) and contains an abundance of resource-acquisition machinery to sustain growth under scarce resources. Bloomer phytoplankton has
2210-430: A high number of commercial fishers and fisheries. On one hand, this is another benefit of the upwelling process as it serves as a viable source of food and income for so many people and nations besides marine animals. However, just as in any ecosystem, the consequences of over-fishing from a population could be detrimental to that population and the ecosystem as a whole. In upwelling ecosystems, every species present plays
2340-602: A lot about past environments and climates. Dinoflagellates are a phylum of unicellular flagellates with about 2,000 marine species. Some dinoflagellates are predatory , and thus belong to the zooplankton community. Their name comes from the Greek "dinos" meaning whirling and the Latin "flagellum" meaning a whip or lash . This refers to the two whip-like attachments (flagella) used for forward movement. Most dinoflagellates are protected with red-brown, cellulose armour. Excavates may be
2470-565: A low N:P ratio (<10), contains a high proportion of growth machinery, and is adapted to exponential growth. Generalist phytoplankton has similar N:P to the Redfield ratio and contain relatively equal resource-acquisition and growth machinery. The NAAMES study was a five-year scientific research program conducted between 2015 and 2019 by scientists from Oregon State University and NASA to investigated aspects of phytoplankton dynamics in ocean ecosystems, and how such dynamics influence atmospheric aerosols , clouds, and climate (NAAMES stands for
2600-538: A mix of internal plastids and external sources. Many marine microzooplankton are mixotrophic, which means they could also be classified as phytoplankton. Zooplankton ( / ˈ z oʊ . ə p l æ ŋ k t ən / ; / ˌ z oʊ . ə ˈ p l æ ŋ k t ən / ) are heterotrophic (sometimes detritivorous ) plankton . The word zooplankton is derived from Ancient Greek : ζῷον , romanized : zôion , lit. 'animal'; and πλᾰγκτός , planktós , 'wanderer; drifter'. Zooplankton
2730-803: A north and south split. The split in this system occurs at Point Conception , California due to weak upwelling in the South and strong upwelling in the north. The Canary Current is an eastern boundary current of the North Atlantic Gyre and is also separated due to the presence of the Canary Islands . Finally, the Humboldt Current or the Peru Current flows west along the coast of South America from Peru to Chile and extends up to 1,000 kilometers offshore. These four eastern boundary currents comprise
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#17328697521112860-435: A nutritional supplement for captive invertebrates in aquaria . Culture sizes range from small-scale laboratory cultures of less than 1L to several tens of thousands of litres for commercial aquaculture. Regardless of the size of the culture, certain conditions must be provided for efficient growth of plankton. The majority of cultured plankton is marine, and seawater of a specific gravity of 1.010 to 1.026 may be used as
2990-635: A potentially important source of food for benthic organisms . Phytoplankton Phytoplankton ( / ˌ f aɪ t oʊ ˈ p l æ ŋ k t ə n / ) are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems . The name comes from the Greek words φυτόν ( phyton ), meaning ' plant ', and πλαγκτός ( planktos ), meaning 'wanderer' or 'drifter'. Phytoplankton obtain their energy through photosynthesis , as trees and other plants do on land. This means phytoplankton must have light from
3120-505: A rate of about 5–10 meters per day, but the rate and proximity of upwelling to the coast can be changed due to the strength and distance of the wind. Deep waters are rich in nutrients, including nitrate , phosphate and silicic acid , themselves the result of decomposition of sinking organic matter (dead/detrital plankton) from surface waters. When brought to the surface, these nutrients are utilized by phytoplankton , along with dissolved CO 2 ( carbon dioxide ) and light energy from
3250-491: A regular basis. Light must be provided for the growth of phytoplankton. The colour temperature of illumination should be approximately 6,500 K, but values from 4,000 K to upwards of 20,000 K have been used successfully. The duration of light exposure should be approximately 16 hours daily; this is the most efficient artificial day length. Marine phytoplankton perform half of the global photosynthetic CO 2 fixation (net global primary production of ~50 Pg C per year) and half of
3380-409: A result, zooplankton are primarily found in surface waters where food resources (phytoplankton or other zooplankton) are abundant. Zooplankton can also act as a disease reservoir . Crustacean zooplankton have been found to house the bacterium Vibrio cholerae , which causes cholera , by allowing the cholera vibrios to attach to their chitinous exoskeletons . This symbiotic relationship enhances
3510-904: A result, zooplankton must acquire nutrients by feeding on other organisms such as phytoplankton, which are generally smaller than zooplankton. Most zooplankton are microscopic but some (such as jellyfish ) are macroscopic , meaning they can be seen with the naked eye . Many protozoans (single-celled protists that prey on other microscopic life) are zooplankton, including zooflagellates , foraminiferans , radiolarians , some dinoflagellates and marine microanimals . Macroscopic zooplankton include pelagic cnidarians , ctenophores , molluscs , arthropods and tunicates , as well as planktonic arrow worms and bristle worms . The distinction between autotrophy and heterotrophy often breaks down in very small organisms. Recent studies of marine microplankton have indicated over half of microscopic plankton are mixotrophs , which can obtain energy and carbon from
3640-529: A significant flow of water northwards. This is actually a type of coastal upwelling. Since there are no continents in a band of open latitudes between South America and the tip of the Antarctic Peninsula, some of this water is drawn up from great depths. In many numerical models and observational syntheses, the Southern Ocean upwelling represents the primary means by which deep dense water is brought to
3770-493: A species increases rapidly under conditions favorable to growth can produce harmful algal blooms (HABs). Phytoplankton are a key food item in both aquaculture and mariculture . Both utilize phytoplankton as food for the animals being farmed. In mariculture, the phytoplankton is naturally occurring and is introduced into enclosures with the normal circulation of seawater. In aquaculture, phytoplankton must be obtained and introduced directly. The plankton can either be collected from
3900-436: A vital role in the functioning of that ecosystem. If one species is significantly depleted, that will have an effect throughout the rest of the trophic levels. For example, if a popular prey species is targeted by fisheries, fishermen may collect hundreds of thousands of individuals of this species just by casting their nets into the upwelling waters. As these fish are depleted, the food source for those who preyed on these fish
4030-557: A wasp-waist richness pattern. In this type of pattern, the high and low trophic levels are well-represented by high species diversity. However, the intermediate trophic level is only represented by one or two species. This trophic layer, which consists of small, pelagic fish usually makes up about only three to four percent of the species diversity of all fish species present. The lower trophic layers are very well-represented with about 500 species of copepods , 2500 species of gastropods , and 2500 species of crustaceans on average. At
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4160-405: A year, meaning they respond to climate changes between years. Sparse, monthly sampling will still indicate vacillations. Protozoans are protists that feed on organic matter such as other microorganisms or organic tissues and debris. Historically, the protozoa were regarded as "one-celled animals", because they often possess animal -like behaviours, such as motility and predation , and lack
4290-600: Is a categorization spanning a range of organism sizes including small protozoans and large metazoans . It includes holoplanktonic organisms whose complete life cycle lies within the plankton, as well as meroplanktonic organisms that spend part of their lives in the plankton before graduating to either the nekton or a sessile , benthic existence. Although zooplankton are primarily transported by ambient water currents, many have locomotion , used to avoid predators (as in diel vertical migration ) or to increase prey encounter rate. Just as any species can be limited within
4420-465: Is a notable exception). While almost all phytoplankton species are obligate photoautotrophs , there are some that are mixotrophic and other, non-pigmented species that are actually heterotrophic (the latter are often viewed as zooplankton ). Of these, the best known are dinoflagellate genera such as Noctiluca and Dinophysis , that obtain organic carbon by ingesting other organisms or detrital material. Phytoplankton live in
4550-405: Is being exported via zooplankton fecal pellet production. Carcasses are also gaining recognition as being important contributors to carbon export. Jelly falls – the mass sinking of gelatinous zooplankton carcasses – occur across the world as a result of large blooms. Because of their large size, these gelatinous zooplankton are expected to hold a larger carbon content, making their sinking carcasses
4680-500: Is declining, leading to higher light penetration and potentially more primary production; however, there are conflicting predictions for the effects of variable mixing patterns and changes in nutrient supply and for productivity trends in polar zones. The effect of human-caused climate change on phytoplankton biodiversity is not well understood. Should greenhouse gas emissions continue rising to high levels by 2100, some phytoplankton models predict an increase in species richness , or
4810-430: Is depleted. Therefore, the predators of the targeted fish will begin to die off, and there will not be as many of them to feed the predators above them. This system continues throughout the entire food chain , resulting in a possible collapse of the ecosystem. It is possible that the ecosystem may be restored over time, but not all species can recover from events such as these. Even if the species can adapt, there may be
4940-492: Is driven by — the Redfield ratio of macronutrients generally available throughout the surface oceans. Phytoplankton also rely on trace metals such as iron (Fe), manganese (Mn), zinc (Zn), cobalt (Co), cadmium (Cd) and copper (Cu) as essential micronutrients, influencing their growth and community composition. Limitations in these metals can lead to co-limitations and shifts in phytoplankton community structure. Across large areas of
5070-889: Is evaluating the contributions of phytoplankton to carbon fixation and forecasting how this production may change in response to perturbations. Predicting the effects of climate change on primary productivity is complicated by phytoplankton bloom cycles that are affected by both bottom-up control (for example, availability of essential nutrients and vertical mixing) and top-down control (for example, grazing and viruses). Increases in solar radiation, temperature and freshwater inputs to surface waters strengthen ocean stratification and consequently reduce transport of nutrients from deep water to surface waters, which reduces primary productivity. Conversely, rising CO 2 levels can increase phytoplankton primary production, but only when nutrients are not limiting. Some studies indicate that overall global oceanic phytoplankton density has decreased in
5200-656: Is evidence from DNA analysis that dinoflagellate symbiosis with radiolarians evolved independently from other dinoflagellate symbioses, such as with foraminifera . A mixotroph is an organism that can use a mix of different sources of energy and carbon , instead of having a single trophic mode on the continuum from complete autotrophy at one end to heterotrophy at the other. It is estimated that mixotrophs comprise more than half of all microscopic plankton. There are two types of eukaryotic mixotrophs: those with their own chloroplasts , and those with endosymbionts —and others that acquire them through kleptoplasty or by enslaving
5330-511: Is loss from zooplankton in the form of respired CO 2 . The relative sizes of zooplankton and prey also mediate how much carbon is released via sloppy feeding. Smaller prey are ingested whole, whereas larger prey may be fed on more “sloppily”, that is more biomatter is released through inefficient consumption. There is also evidence that diet composition can impact nutrient release, with carnivorous diets releasing more dissolved organic carbon (DOC) and ammonium than omnivorous diets. Zooplankton play
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5460-425: Is of utmost importance to secondary producers such as copepods, fish and shrimp, because it determines the nutritional quality and influences energy flow through the marine food chains . Climate change may greatly restructure phytoplankton communities leading to cascading consequences for marine food webs , thereby altering the amount of carbon transported to the ocean interior. The figure gives an overview of
5590-447: Is predicted to co-occur with ocean acidification and warming, due to increased stratification of the water column and reduced mixing of nutrients from the deep water to the surface. The compartments influenced by phytoplankton include the atmospheric gas composition, inorganic nutrients, and trace element fluxes as well as the transfer and cycling of organic matter via biological processes (see figure). The photosynthetically fixed carbon
5720-451: Is rapidly recycled and reused in the surface ocean, while a certain fraction of this biomass is exported as sinking particles to the deep ocean, where it is subject to ongoing transformation processes, e.g., remineralization. Phytoplankton contribute to not only a basic pelagic marine food web but also to the microbial loop. Phytoplankton are the base of the marine food web and because they do not rely on other organisms for food, they make up
5850-402: Is recycled back to the marine environment. Low feeding rates typically lead to high AE and small, dense pellets, while high feeding rates typically lead to low AE and larger pellets with more organic content. Another contributing factor to DOM release is respiration rate. Physical factors such as oxygen availability, pH, and light conditions may affect overall oxygen consumption and how much carbon
5980-452: Is released from zooplankton individuals or populations. Absorption efficiency (AE) is the proportion of food absorbed by plankton that determines how available the consumed organic materials are in meeting the required physiological demands. Depending on the feeding rate and prey composition, variations in AE may lead to variations in fecal pellet production, and thus regulates how much organic material
6110-607: Is sensitive to changes in temperature due to the thermal dependence of physiological processes. The plankton is mainly composed of ectotherms which are organisms that do not generate sufficient metabolic heat to elevate their body temperature, so their metabolic processes depends on external temperature. Consequently, ectotherms grow more slowly and reach maturity at a larger body size in colder environments, which has long puzzled biologists because classic theories of life-history evolution predict smaller adult sizes in environments delaying growth. This pattern of body size variation, known as
6240-529: Is the eastern boundary of the South Atlantic subtropical gyre and can be divided into a northern and southern sub-system with upwelling occurring in both areas. The subsystems are divided by an area of permanent upwelling off of Luderitz , which is the strongest upwelling zone in the world. The California Current System (CCS) is an eastern boundary current of the North Pacific that is also characterized by
6370-471: Is unclear. In terms of numbers, the most important groups of phytoplankton include the diatoms , cyanobacteria and dinoflagellates , although many other groups of algae are represented. One group, the coccolithophorids , is responsible (in part) for the release of significant amounts of dimethyl sulfide (DMS) into the atmosphere . DMS is oxidized to form sulfate which, in areas where ambient aerosol particle concentrations are low, can contribute to
6500-783: The Canary Current (off Northwest Africa ), the Benguela Current (off southern Africa ), the California Current (off California and Oregon ), the Humboldt Current (off Peru and Chile ), and the Somali Current (off Somalia and Oman ). All of these currents support major fisheries. The four major eastern boundary currents in which coastal upwelling primarily occurs are the Canary Current, Benguela Current, California Current, and Humboldt Current. The Benguela Current
6630-530: The El Nino-Southern Oscillation (ENSO) event. The Peruvian upwelling system is particularly vulnerable to ENSO events, and can cause extreme interannual variability in productivity. Changes in bathymetry can affect the strength of an upwelling. For example, a submarine ridge that extends out from the coast will produce more favorable upwelling conditions than neighboring regions. Upwelling typically begins at such ridges and remains strongest at
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#17328697521116760-659: The Portuguese Man o' War ; crustaceans such as cladocerans , copepods , ostracods , isopods , amphipods , mysids and krill ; chaetognaths (arrow worms); molluscs such as pteropods ; and chordates such as salps and juvenile fish. This wide phylogenetic range includes a similarly wide range in feeding behavior: filter feeding , predation and symbiosis with autotrophic phytoplankton as seen in corals. Zooplankton feed on bacterioplankton , phytoplankton, other zooplankton (sometimes cannibalistically ), detritus (or marine snow ) and even nektonic organisms . As
6890-449: The diatoms ). Most phytoplankton are too small to be individually seen with the unaided eye . However, when present in high enough numbers, some varieties may be noticeable as colored patches on the water surface due to the presence of chlorophyll within their cells and accessory pigments (such as phycobiliproteins or xanthophylls ) in some species. Phytoplankton are photosynthesizing microscopic protists and bacteria that inhabit
7020-422: The diatoms ). Many other organism groups formally named as phytoplankton, including coccolithophores and dinoflagellates , are now no longer included as they are not only phototrophic but can also eat. These organisms are now more correctly termed mixoplankton . This recognition has important consequences for how we view the functioning of the planktonic food web. Phytoplankton obtain energy through
7150-561: The marine food web , gelatinous organisms with a body plan largely based on water that offers little nutritional value or interest for other organisms apart from a few specialised predators such as the ocean sunfish and the leatherback sea turtle . That view has recently been challenged. Jellyfish, and more gelatinous zooplankton in general, which include salps and ctenophores , are very diverse, fragile with no hard parts, difficult to see and monitor, subject to rapid population swings and often live inconveniently far from shore or deep in
7280-543: The 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 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
7410-449: The photic zone of the ocean, where photosynthesis is possible. During photosynthesis, they assimilate carbon dioxide and release oxygen. If solar radiation is too high, phytoplankton may fall victim to photodegradation . Phytoplankton species feature a large variety of photosynthetic pigments which species-specifically enables them to absorb different wavelengths of the variable underwater light. This implies different species can use
7540-433: The process of photosynthesis and must therefore live in the well-lit surface layer (termed the euphotic zone ) of an ocean , sea , lake , or other body of water. Phytoplankton account for about half of all photosynthetic activity on Earth. Their cumulative energy fixation in carbon compounds ( primary production ) is the basis for the vast majority of oceanic and also many freshwater food webs ( chemosynthesis
7670-410: The sun , to produce organic compounds , through the process of photosynthesis . Upwelling regions therefore result in very high levels of primary production (the amount of carbon fixed by phytoplankton ) in comparison to other areas of the ocean. They account for about 50% of global marine productivity. High primary production propagates up the food chain because phytoplankton are at the base of
7800-410: The Latin for "hole bearers". Their shells, often called tests , are chambered (forams add more chambers as they grow). The shells are usually made of calcite, but are sometimes made of agglutinated sediment particles or chiton , and (rarely) silica. Most forams are benthic, but about 40 species are planktic. They are widely researched with well-established fossil records which allow scientists to infer
7930-520: The Latin for "radius". They catch prey by extending parts of their body through the holes. As with the silica frustules of diatoms, radiolarian shells can sink to the ocean floor when radiolarians die and become preserved as part of the ocean sediment . These remains, as microfossils , provide valuable information about past oceanic conditions. Like radiolarians, foraminiferans ( forams for short) are single-celled predatory protists, also protected with shells that have holes in them. Their name comes from
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#17328697521118060-599: The North Atlantic Aerosols and Marine Ecosystems Study). The study focused on the sub-arctic region of the North Atlantic Ocean, which is the site of one of Earth's largest recurring phytoplankton blooms. The long history of research in this location, as well as relative ease of accessibility, made the North Atlantic an ideal location to test prevailing scientific hypotheses in an effort to better understand
8190-486: The ability of phytoplankton to store carbon that was emitted by human activities. Human (anthropogenic) changes to phytoplankton impact both natural and economic processes. Upwelling Upwelling is an oceanographic phenomenon that involves wind -driven motion of dense, cooler, and usually nutrient-rich water from deep water towards the ocean surface. It replaces the warmer and usually nutrient-depleted surface water . The nutrient-rich upwelled water stimulates
8320-551: The apex and near-apex trophic levels, there are usually about 100 species of marine mammals and about 50 species of marine birds. The vital intermediate trophic species however are small pelagic fish that usually feed on phytoplankton . In most upwelling systems, these species are either anchovies or sardines, and usually only one is present, although two or three species may be present occasionally. These fish are an important food source for predators, such as large pelagic fish, marine mammals, and marine birds. Although they are not at
8450-432: The bacterium's ability to survive in an aquatic environment, as the exoskeleton provides the bacterium with carbon and nitrogen. Body size has been defined as a "master trait" for plankton as it is a morphological characteristic shared by organisms across taxonomy that characterises the functions performed by organisms in ecosystems. It has a paramount effect on growth, reproduction, feeding strategies and mortality. One of
8580-404: The base of marine and freshwater food webs and are key players in the global carbon cycle . They account for about half of global photosynthetic activity and at least half of the oxygen production, despite amounting to only about 1% of the global plant biomass. Phytoplankton are very diverse, comprising photosynthesizing bacteria ( cyanobacteria ) and various unicellular protist groups (notably
8710-405: The base of the trophic pyramid, they are the vital species that connect the entire marine ecosystem and keep the productivity of upwelling zones so high A major threat to both this crucial intermediate trophic level and the entire upwelling trophic ecosystem is the problem of commercial fishing . Since upwelling regions are the most productive and species rich areas in the world, they attract
8840-503: The catch. Besides directly causing the collapse of the ecosystem due to their absence, this can create problems in the ecosystem through a variety of other methods as well. The animals higher in the trophic levels may not completely starve to death and die off, but the decreased food supply could still hurt the populations. If animals do not get enough food, it will decrease their reproductive viability meaning that they will not breed as often or as successfully as usual. This can lead to
8970-468: The ciliate abundance was mixotrophic, and up to 65% of the amoeboid, foram and radiolarian biomass was mixotrophic. Phaeocystis species are endosymbionts to acantharian radiolarians. Phaeocystis is an important algal genus found as part of the marine phytoplankton around the world. It has a polymorphic life cycle, ranging from free-living cells to large colonies. It has the ability to form floating colonies, where hundreds of cells are embedded in
9100-491: The contribution of jellyfish to the energy budgets of predators may be much greater than assumed because of rapid digestion, low capture costs, availability, and selective feeding on the more energy-rich components. Feeding on jellyfish may make marine predators susceptible to ingestion of plastics." According to a 2017 study, narcomedusae consume the greatest diversity of mesopelagic prey, followed by physonect siphonophores , ctenophores and cephalopods . The importance of
9230-456: The cryptophytes by itself, and instead relies on ingesting ciliates such as the red Myrionecta rubra , which sequester their chloroplasts from a specific cryptophyte clade (Geminigera/Plagioselmis/Teleaulax)". Free-living species in the crustacean class Copepoda are typically 1 to 2 mm long with teardrop-shaped bodies. Like all crustaceans, their bodies are divided into three sections: head, thorax, and abdomen, with two pairs of antennae;
9360-446: The dilution technique, an elegant method of measuring microzooplankton herbivory rate, has been developed for almost four decades (Landry and Hassett 1982). The number of observations of microzooplankton herbivory rate is around 1600 globally, far less than that of primary productivity (> 50,000). This makes validating and optimizing the grazing function of microzooplankton difficult in ocean ecosystem models. Mesozooplankton are one of
9490-578: The direction of the wind, and the friction between that layer and the layer beneath it causes the successive layers to move in the same direction. This results in a spiral of water moving down the water column. Then, it is the Coriolis forces that dictate which way the water will move; in the Northern hemisphere, the water is transported to the right of the direction of the wind. In the Southern Hemisphere,
9620-544: The entire phototrophic cell. The distinction between plants and animals often breaks down in very small organisms. Possible combinations are photo- and chemotrophy , litho- and organotrophy , auto- and heterotrophy or other combinations of these. Mixotrophs can be either eukaryotic or prokaryotic . They can take advantage of different environmental conditions. Many marine microzooplankton are mixotrophic, which means they could also be classified as phytoplankton. Recent studies of marine microzooplankton found 30–45% of
9750-400: The entire trophic process of upwelling ecosystems, they are highly represented throughout the ecosystem (even if there is only one species present). Unfortunately, these fish tend to be the most popular targets of fisheries as about 64 percent of their entire catch consists of pelagic fish. Among those, the six main species that usually form the intermediate trophic layer represent over half of
9880-565: The equator, upwelling still occurs just north and south of the equator. This results in a divergence, with denser, nutrient-rich water being upwelled from below, and results in the remarkable fact that the equatorial region in the Pacific can be detected from space as a broad line of high phytoplankton concentration. Large-scale upwelling is also found in the Southern Ocean . Here, strong westerly (eastward) winds blow around Antarctica , driving
10010-492: The first pair is often long and prominent. They have a tough exoskeleton made of calcium carbonate and usually have a single red eye in the centre of their transparent head. About 13,000 species of copepods are known, of which about 10,200 are marine. They are usually among the more dominant members of the zooplankton. In addition to copepods the crustacean classes ostracods , branchiopods and malacostracans also have planktonic members. Barnacles are planktonic only during
10140-498: The first trophic level. Organisms such as zooplankton feed on these phytoplankton which are in turn fed on by other organisms and so forth until the fourth trophic level is reached with apex predators. Approximately 90% of total carbon is lost between trophic levels due to respiration, detritus, and dissolved organic matter. This makes the remineralization process and nutrient cycling performed by phytoplankton and bacteria important in maintaining efficiency. Phytoplankton blooms in which
10270-410: The general effects are the same. In the overall process of upwelling, winds blow across the sea surface at a particular direction, which causes a wind-water interaction. As a result of the wind, the water has transported a net of 90 degrees from the direction of the wind due to Coriolis forces and Ekman transport. Ekman transport causes the surface layer of water to move at about a 45-degree angle from
10400-513: The global population of phytoplankton is an area of active research. Changes in the vertical stratification of the water column, the rate of temperature-dependent biological reactions, and the atmospheric supply of nutrients are expected to have important effects on future phytoplankton productivity. The effects of anthropogenic ocean acidification on phytoplankton growth and community structure has also received considerable attention. The cells of coccolithophore phytoplankton are typically covered in
10530-443: The growth and reproduction of primary producers such as phytoplankton . The biomass of phytoplankton and the presence of cool water in those regions allow upwelling zones to be identified by cool sea surface temperatures (SST) and high concentrations of chlorophyll a . The increased availability of nutrients in upwelling regions results in high levels of primary production and thus fishery production. Approximately 25% of
10660-436: The key mediators of the biological pump . Understanding the response of phytoplankton to changing environmental conditions is a prerequisite to predict future atmospheric concentrations of CO 2 . Temperature, irradiance and nutrient concentrations, along with CO 2 are the chief environmental factors that influence the physiology and stoichiometry of phytoplankton. The stoichiometry or elemental composition of phytoplankton
10790-452: The larger size classes of zooplankton. In most regions, mesozooplankton are dominated by copepods , such as Calanus finmarchicus and Calanus helgolandicus . Mesozooplankton are an important prey for fish. As plankton are rarely fished, it has been argued that mesoplankton abundance and species composition can be used to study marine ecosystems' response to climate change. This is because they have life cycles that generally last less than
10920-460: The larval stage. Ichthyoplankton are the eggs and larvae of fish ("ichthyo" comes from the Greek word for fish ). They are planktonic because they cannot swim effectively under their own power, but must drift with the ocean currents. Fish eggs cannot swim at all, and are unambiguously planktonic. Early stage larvae swim poorly, but later stage larvae swim better and cease to be planktonic as they grow into juvenile fish . Fish larvae are part of
11050-415: The majority of organic carbon loss from marine primary production . However, zooplankton grazing remains one of the key unknowns in global predictive models of carbon flux, the marine food web structure and ecosystem characteristics, because empirical grazing measurements are sparse, resulting in poor parameterisation of grazing functions. To overcome this critical knowledge gap, it has been suggested that
11180-597: The majority of coastal upwelling zones in the oceans. Upwelling at the equator is associated with the Intertropical Convergence Zone (ITCZ) which actually moves, and consequently, is often located just north or south of the equator. Easterly (westward) trade winds blow from the Northeast and Southeast and converge along the equator blowing West to form the ITCZ. Although there are no Coriolis forces present along
11310-493: The many food chains in the ocean – remarkable due to the small number of links – is that of phytoplankton sustaining krill (a crustacean similar to a tiny shrimp), which in turn sustain baleen whales . The El Niño-Southern Oscillation (ENSO) cycles in the Equatorial Pacific area can affect phytoplankton. Biochemical and physical changes during ENSO cycles modify the phytoplankton community structure. Also, changes in
11440-592: The more dominant phytoplankton and reflect a larger portion of the biomass . In the early twentieth century, Alfred C. Redfield found the similarity of the phytoplankton's elemental composition to the major dissolved nutrients in the deep ocean. Redfield proposed that the ratio of carbon to nitrogen to phosphorus (106:16:1) in the ocean was controlled by the phytoplankton's requirements, as phytoplankton subsequently release nitrogen and phosphorus as they are remineralized. This so-called " Redfield ratio " in describing stoichiometry of phytoplankton and seawater has become
11570-410: The most basal flagellate lineage. Dinoflagellates often live in symbiosis with other organisms. Many nassellarian radiolarians house dinoflagellate symbionts within their tests. The nassellarian provides ammonium and carbon dioxide for the dinoflagellate, while the dinoflagellate provides the nassellarian with a mucous membrane useful for hunting and protection against harmful invaders. There
11700-419: The most is mixing of the water column ( upwelling and downwelling along the coast and in the open ocean) that affects nutrient availability and, in turn, phytoplankton production. Through their consumption and processing of phytoplankton and other food sources, zooplankton play a role in aquatic food webs , as a resource for consumers on higher trophic levels (including fish), and as a conduit for packaging
11830-494: The number of different species within a given area. This increase in plankton diversity is traced to warming ocean temperatures. In addition to species richness changes, the locations where phytoplankton are distributed are expected to shift towards the Earth's poles. Such movement may disrupt ecosystems, because phytoplankton are consumed by zooplankton, which in turn sustain fisheries. This shift in phytoplankton location may also diminish
11960-433: The ocean circulation suggest that broad-scale upwelling occurs in the tropics, as pressure driven flows converge water toward the low latitudes where it is diffusively warmed from above. The required diffusion coefficients, however, appear to be larger than are observed in the real ocean. Nonetheless, some diffusive upwelling does probably occur. Upwelling intensity depends on wind strength and seasonal variability, as well as
12090-476: The ocean interior, upwelling associated with eddies, topographically-associated upwelling, and broad-diffusive upwelling in the ocean interior. Coastal upwelling is the best known type of upwelling, and the most closely related to human activities as it supports some of the most productive fisheries in the world. Coastal upwelling will occur if the wind direction is parallel to the coastline and generates wind-driven currents. The wind-driven currents are diverted to
12220-504: The ocean. Controversy about manipulating the ecosystem and the efficiency of iron fertilization has slowed such experiments. The ocean science community still has a divided attitude toward the study of iron fertilization as a potential marine Carbon Dioxide Removal (mCDR) approach. Phytoplankton depend on B vitamins for survival. Areas in the ocean have been identified as having a major lack of some B Vitamins, and correspondingly, phytoplankton. The effects of anthropogenic warming on
12350-437: The ocean. It is difficult for scientists to detect and analyse jellyfish in the guts of predators, since they turn to mush when eaten and are rapidly digested. But jellyfish bloom in vast numbers, and it has been shown they form major components in the diets of tuna , spearfish and swordfish as well as various birds and invertebrates such as octopus , sea cucumbers , crabs and amphipods . "Despite their low energy density,
12480-495: The oceanic food chain. The food chain follows the course of: Coastal upwelling exists year-round in some regions, known as major coastal upwelling systems , and only in certain months of the year in other regions, known as seasonal coastal upwelling systems . Many of these upwelling systems are associated with relatively high carbon productivity and hence are classified as Large Marine Ecosystems . Worldwide, there are five major coastal currents associated with upwelling areas:
12610-457: The oceans such as the Southern Ocean , phytoplankton are often limited by the lack of the micronutrient iron . This has led to some scientists advocating iron fertilization as a means to counteract the accumulation of human-produced carbon dioxide (CO 2 ) in the atmosphere . Large-scale experiments have added iron (usually as salts such as ferrous sulfate ) to the oceans to promote phytoplankton growth and draw atmospheric CO 2 into
12740-407: The oldest manifestations of the biogeography of traits was proposed over 170 years ago, namely Bergmann's rule , in which field observations showed that larger species tend to be found at higher, colder latitudes. In the oceans, size is critical in determining trophic links in planktonic ecosystems and is thus a critical factor in regulating the efficiency of the biological carbon pump . Body size
12870-529: The organic material in the biological pump . Since they are typically small, zooplankton can respond rapidly to increases in phytoplankton abundance, for instance, during the spring bloom . Zooplankton are also a key link in the biomagnification of pollutants such as mercury . Ecologically important protozoan zooplankton groups include the foraminiferans , radiolarians and dinoflagellates (the last of these are often mixotrophic ). Important metazoan zooplankton include cnidarians such as jellyfish and
13000-422: The oxygen production despite amounting to only ~1% of global plant biomass. In comparison with terrestrial plants, marine phytoplankton are distributed over a larger surface area, are exposed to less seasonal variation and have markedly faster turnover rates than trees (days versus decades). Therefore, phytoplankton respond rapidly on a global scale to climate variations. These characteristics are important when one
13130-434: The past century, but these conclusions have been questioned because of the limited availability of long-term phytoplankton data, methodological differences in data generation and the large annual and decadal variability in phytoplankton production. Moreover, other studies suggest a global increase in oceanic phytoplankton production and changes in specific regions or specific phytoplankton groups. The global Sea Ice Index
13260-565: The place. Some dinoflagellates are known to be photosynthetic , but a large fraction of these are in fact mixotrophic , combining photosynthesis with ingestion of prey ( phagotrophy ). Some species are endosymbionts of marine animals and other protists, and play an important part in the biology of coral reefs . Others predate other protozoa, and a few forms are parasitic. Many dinoflagellates are mixotrophic and could also be classified as phytoplankton. The toxic dinoflagellate Dinophysis acuta acquire chloroplasts from its prey. "It cannot catch
13390-638: The plankton community. As the primary consumers of marine phytoplankton, microzooplankton consume ~ 59–75% daily of the marine primary production , much larger than mesozooplankton. That said, macrozooplankton can sometimes have greater consumption rates in eutrophic ecosystems because the larger phytoplankton can be dominant there. Microzooplankton are also pivotal regenerators of nutrients which fuel primary production and food sources for metazoans. Despite their ecological importance, microzooplankton remain understudied. Routine oceanographic observations seldom monitor microzooplankton biomass or herbivory rate, although
13520-487: The poles. Phytoplankton release dissolved organic carbon (DOC) into the ocean. Since phytoplankton are the basis of marine food webs , they serve as prey for zooplankton , fish larvae and other heterotrophic organisms. They can also be degraded by bacteria or by viral lysis . Although some phytoplankton cells, such as dinoflagellates , are able to migrate vertically, they are still incapable of actively moving against currents, so they slowly sink and ultimately fertilize
13650-839: The population of cloud condensation nuclei , mostly leading to increased cloud cover and cloud albedo according to the so-called CLAW hypothesis . Different types of phytoplankton support different trophic levels within varying ecosystems. In oligotrophic oceanic regions such as the Sargasso Sea or the South Pacific Gyre , phytoplankton is dominated by the small sized cells, called picoplankton and nanoplankton (also referred to as picoflagellates and nanoflagellates), mostly composed of cyanobacteria ( Prochlorococcus , Synechococcus ) and picoeucaryotes such as Micromonas . Within more productive ecosystems, dominated by upwelling or high terrestrial inputs, larger dinoflagellates are
13780-444: The process of upwelling. However, during El Niño events, trade winds are weaker, causing decreased upwelling in the equatorial regions as the divergence of water north and south of the equator is not as strong or as prevalent. The coastal upwelling zones diminish as well since they are wind driven systems, and the wind is no longer a very strong driving force in these areas. As a result, global upwelling drastically decreases, causing
13910-413: The putative explanation for annual cycles in phytoplankton biomass, accumulation rates and export 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 the biological pump . This is particularly important in
14040-434: The ridge even after developing in other locations. The most productive and fertile ocean areas, upwelling regions are important sources of marine productivity. They attract hundreds of species throughout the trophic levels; these systems' diversity has been a focal point for marine research . While studying the trophic levels and patterns typical of upwelling regions, researchers have discovered that upwelling systems exhibit
14170-608: The right of the winds in the Northern Hemisphere and to the left in the Southern Hemisphere due to the Coriolis effect . The result is a net movement of surface water at right angles to the direction of the wind, known as the Ekman transport (See also Ekman Spiral ). When Ekman transport is occurring away from the coast, surface waters moving away are replaced by deeper, colder, and denser water. Normally, this upwelling process occurs at
14300-570: The role of phytoplankton aerosol emissions on Earth's energy budget. NAAMES was designed to target specific phases of the annual phytoplankton cycle: minimum, climax and the intermediary decreasing and increasing biomass, in order to resolve debates on the timing of bloom formations and the patterns driving annual bloom re-creation. The NAAMES project also investigated the quantity, size, and composition of aerosols generated by primary production in order to understand how phytoplankton bloom cycles affect cloud formations and climate. Phytoplankton are
14430-433: 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
14560-565: The sea surface temperature gets cooler, the air immediately above it also cools down and is likely to condensate, forming sea fog and stratus clouds . This also inhibits the formation of higher altitude clouds, showers and thunderstorms and results in rainfall over the ocean leaving the land dry. In year-round upwelling systems (like that of the western coasts of Southern Africa and South America), temperatures are generally cooler and precipitation scarce. Seasonal upwelling systems are often paired with seasonal downwelling systems (like that of
14690-488: The seafloor with dead cells and detritus . Phytoplankton are crucially dependent on a number of nutrients . These are primarily macronutrients such as nitrate , phosphate or silicic acid , which are required in relatively large quantities for growth. Their availability in the surface ocean is governed by the balance between the so-called biological pump and upwelling of deep, nutrient-rich waters. The stoichiometric nutrient composition of phytoplankton drives — and
14820-454: The so-called "jelly web" is only beginning to be understood, but it seems medusae, ctenophores and siphonophores can be key predators in deep pelagic food webs with ecological impacts similar to predator fish and squid. Traditionally gelatinous predators were thought ineffectual providers of marine trophic pathways, but they appear to have substantial and integral roles in deep pelagic food webs . Grazing by single-celled zooplankton accounts for
14950-441: The species in an environment that is so variable and quick-changing; they may not be able to adapt, which could result in a collapse of the population or ecosystem. Another threat to the productivity and ecosystems of upwelling regions is El Niño-Southern Oscillation (ENSO) system, or more specifically El Niño events. During the normal period and La Niña events, the easterly trade winds are still strong, which continues to drive
15080-432: The structure of the phytoplankton, such as a significant reduction in biomass and phytoplankton density, particularly during El Nino phases can occur. The sensitivity of phytoplankton to environmental changes is why they are often used as indicators of estuarine and coastal ecological condition and health. To study these events satellite ocean color observations are used to observe these changes. Satellite images help to have
15210-406: The sun, so they live in the well-lit surface layers ( euphotic zone ) of oceans and lakes. In comparison with terrestrial plants, phytoplankton are distributed over a larger surface area, are exposed to less seasonal variation and have markedly faster turnover rates than trees (days versus decades). As a result, phytoplankton respond rapidly on a global scale to climate variations. Phytoplankton form
15340-509: The surface. In some regions of Antarctica, wind-driven upwelling near the coast pulls relatively warm Circumpolar deep water onto the continental shelf, where it can enhance ice shelf melt and influence ice sheet stability. Shallower, wind-driven upwelling is also found in off the west coasts of North and South America, northwest and southwest Africa, and southwest and south Australia , all associated with oceanic subtropical high pressure circulations (see coastal upwelling above). Some models of
15470-452: The temperature contrast is greatly seasonably variable, creating periods of strong upwelling in the spring and summer, to weak or no upwelling in the winter. For example, off the coast of Oregon, there are four or five strong upwelling events separated by periods of little to no upwelling during the six-month season of upwelling. In contrast, tropical latitudes have a more constant temperature contrast, creating constant upwelling throughout
15600-506: The temperature-size rule (TSR), has been observed for a wide range of ectotherms, including single-celled and multicellular species, invertebrates and vertebrates. The processes underlying the inverse relationship between body size and temperature remain to be identified. Despite temperature playing a major role in shaping latitudinal variations in organism size, these patterns may also rely on complex interactions between physical, chemical and biological factors. For instance, oxygen supply plays
15730-447: The total global marine fish catches come from five upwellings, which occupy only 5% of the total ocean area. Upwellings that are driven by coastal currents or diverging open ocean have the greatest impact on nutrient-enriched waters and global fishery yields. The three main drivers that work together to cause upwelling are wind , Coriolis effect , and Ekman transport . They operate differently for different types of upwelling, but
15860-501: The upper sunlit layer of marine and fresh water bodies of water on Earth. Paralleling plants on land, phytoplankton undertake primary production in water, creating organic compounds from carbon dioxide dissolved in the water. Phytoplankton form the base of — and sustain — the aquatic food web , and are crucial players in the Earth's carbon cycle . Phytoplankton are very diverse, comprising photosynthesizing bacteria ( cyanobacteria ) and various unicellular protist groups (notably
15990-446: The various environmental factors that together affect phytoplankton productivity . All of these factors are expected to undergo significant changes in the future ocean due to global change. Global warming simulations predict oceanic temperature increase; dramatic changes in oceanic stratification , circulation and changes in cloud cover and sea ice, resulting in an increased light supply to the ocean surface. Also, reduced nutrient supply
16120-428: The vertical structure of the water , variations in the bottom bathymetry , and instabilities in the currents . In some areas, upwelling is a seasonal event leading to periodic bursts of productivity similar to spring blooms in coastal waters. Wind-induced upwelling is generated by temperature differences between the warm, light air above the land and the cooler denser air over the sea. In temperate latitudes ,
16250-407: The water column, which can thus alter the carbon composition of the pellet. This affects how much carbon is recycled in the euphotic zone and how much reaches depth. Fecal pellet contribution to carbon export is likely underestimated; however, new advances in quantifying this production are currently being developed, including the use of isotopic signatures of amino acids to characterize how much carbon
16380-417: The water is transported to the left of the wind. If this net movement of water is divergent, then upwelling of deep water occurs to replace the water that was lost. The major upwellings in the ocean are associated with the divergence of currents that bring deeper, colder, nutrient rich waters to the surface. There are at least five types of upwelling: coastal upwelling, large-scale wind-driven upwelling in
16510-471: The wavelength of light different efficiently and the light is not a single ecological resource but a multitude of resources depending on its spectral composition. By that it was found that changes in the spectrum of light alone can alter natural phytoplankton communities even if the same intensity is available. For growth, phytoplankton cells additionally depend on nutrients, which enter the ocean by rivers, continental weathering, and glacial ice meltwater on
16640-402: The world ocean using ocean-colour data from satellites, and found the calorific value of phytoplankton to vary considerably across different oceanic regions and between different time of the year. The production of phytoplankton under artificial conditions is itself a form of aquaculture. Phytoplankton is cultured for a variety of purposes, including foodstock for other aquacultured organisms,
16770-406: The year. The Peruvian upwelling, for instance, occurs throughout most of the year, resulting in one of the world's largest marine fisheries for sardines and anchovies . In anomalous years when the trade winds weaken or reverse, the water that is upwelled is much warmer and low in nutrients, resulting in a sharp reduction in the biomass and phytoplankton productivity. This event is known as
16900-411: The zooplankton that eat smaller plankton, while fish eggs carry their own food supply. Both eggs and larvae are themselves eaten by larger animals. Gelatinous zooplankton include ctenophores , medusae , salps , and Chaetognatha in coastal waters. Jellyfish are slow swimmers, and most species form part of the plankton. Traditionally jellyfish have been viewed as trophic dead ends, minor players in
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