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88-515: Plankton are the diverse collection of organisms that drift in water (or air ) but are unable to actively propel themselves against currents (or wind ). The individual organisms constituting plankton are called plankters . In the ocean, they provide a crucial source of food to many small and large aquatic organisms, such as bivalves , fish , and baleen whales . Marine plankton include bacteria , archaea , algae , protozoa , microscopic fungi , and drifting or floating animals that inhabit
176-405: A jellyfish , the parts collaborating to provide the functions of the colonial organism. The evolutionary biologists David Queller and Joan Strassmann state that "organismality", the qualities or attributes that define an entity as an organism, has evolved socially as groups of simpler units (from cells upwards) came to cooperate without conflicts. They propose that cooperation should be used as
264-435: A top-down or bottom-up approach . Essentially, this research is focused on understanding whether changes in the food web are driven by nutrients at the bottom of the food web or predators at the top. The general conclusion is that the bottom-up approach seemed to be more predictive of food web behavior. This indicates that plankton have more sway in determining the success of the primary consumer species that prey on them than do
352-430: A buffer that prevents the collapse of ecosystems during times with little to no light. Plankton are also often described in terms of size. Usually the following divisions are used: However, some of these terms may be used with very different boundaries, especially on the larger end. The existence and importance of nano- and even smaller plankton was only discovered during the 1980s, but they are thought to make up
440-569: A few enzymes and molecules like those in living organisms, they have no metabolism of their own; they cannot synthesize the organic compounds from which they are formed. In this sense, they are similar to inanimate matter. Viruses have their own genes , and they evolve . Thus, an argument that viruses should be classed as living organisms is their ability to undergo evolution and replicate through self-assembly. However, some scientists argue that viruses neither evolve nor self-reproduce. Instead, viruses are evolved by their host cells, meaning that there
528-474: A few months, famously can enter suspended animation during dry or hostile conditions and survive for decades. This allows them to be ubiquitous in terrestrial environments despite needing water to grow and reproduce. Many microscopic crustacean groups like copepods and amphipods (of which sandhoppers are members) and seed shrimp are known to go dormant when dry and live in transient bodies of water too Gelatinous zooplankton are fragile animals that live in
616-398: A group could be viewed as a superorganism , optimized by group adaptation . Another view is that attributes like autonomy, genetic homogeneity and genetic uniqueness should be examined separately rather than demanding that an organism should have all of them; if so, there are multiple dimensions to biological individuality, resulting in several types of organism. A unicellular organism
704-408: A nektic (swimming) or benthic (sea floor) existence. Examples of meroplankton include the larvae of sea urchins , starfish , crustaceans , marine worms , and most fish . The amount and distribution of plankton depends on available nutrients, the state of water and a large amount of other plankton. The study of plankton is termed planktology and a planktonic individual is referred to as
792-407: A plankter. The adjective planktonic is widely used in both the scientific and popular literature, and is a generally accepted term. However, from the standpoint of prescriptive grammar, the less-commonly used planktic is more strictly the correct adjective. When deriving English words from their Greek or Latin roots, the gender-specific ending (in this case, "-on" which indicates the word is neuter)
880-430: A process known as fishing down the food web . However, more recent work finds no relation between economic value and trophic level; and that mean trophic levels in catches, surveys and stock assessments have not in fact declined, suggesting that fishing down the food web is not a global phenomenon. However Pauly et al . note that trophic levels peaked at 3.4 in 1970 in the northwest and west-central Atlantic, followed by
968-416: A process known as volatilisation . When airborne, these microbes can be transported long distances to coastal regions. If they hit land they can have an effect on animal, vegetation and human health. Marine aerosols that contain viruses can travel hundreds of kilometers from their source and remain in liquid form as long as the humidity is high enough (over 70%). These aerosols are able to remain suspended in
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#17329305902491056-648: A process of recombination (a primitive form of sexual interaction ). Trophic level The trophic level of an organism is the position it occupies in a food web . Within a food web, a food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves. The trophic level of an organism is the number of steps it is from the start of the chain. A food web starts at trophic level 1 with primary producers such as plants, can move to herbivores at level 2, carnivores at level 3 or higher, and typically finish with apex predators at level 4 or 5. The path along
1144-415: A process which depends on typically inadequate zooplankton density, starving many larvae. In time fish larvae become able to swim against currents, at which point they cease to be plankton and become juvenile fish . Holoplankton are organisms that are planktic for their entire life cycle. Holoplankton can be contrasted with meroplankton , which are planktic organisms that spend part of their life cycle in
1232-495: A reduced level (because of reduced light). Despite significant macronutrient concentrations, some ocean regions are unproductive (so-called HNLC regions ). The micronutrient iron is deficient in these regions, and adding it can lead to the formation of phytoplankton algal blooms . Iron primarily reaches the ocean through the deposition of dust on the sea surface. Paradoxically, oceanic areas adjacent to unproductive, arid land thus typically have abundant phytoplankton (e.g.,
1320-411: A subsequent decline to 2.9 in 1994. They report a shift away from long-lived, piscivorous, high-trophic-level bottom fishes, such as cod and haddock, to short-lived, planktivorous, low-trophic-level invertebrates (e.g., shrimp) and small, pelagic fish (e.g., herring). This shift from high-trophic-level fishes to low-trophic-level invertebrates and fishes is a response to changes in the relative abundance of
1408-404: A wide variety of aquatic organisms that have both planktonic and benthic stages in their life cycles. Much of the meroplankton consists of larval stages of larger organisms. Meroplankton can be contrasted with holoplankton , which are planktonic organisms that stay in the pelagic zone as plankton throughout their entire life cycle. After some time in the plankton, many meroplankton graduate to
1496-445: Is a microorganism such as a protist , bacterium , or archaean , composed of a single cell , which may contain functional structures called organelles . A multicellular organism such as an animal , plant , fungus , or alga is composed of many cells, often specialised. A colonial organism such as a siphonophore is a being which functions as an individual but is composed of communicating individuals. A superorganism
1584-401: Is a teleonomic or goal-seeking behaviour that enables them to correct errors of many kinds so as to achieve whatever result they are designed for. Such behaviour is reminiscent of intelligent action by organisms; intelligence is seen as an embodied form of cognition . All organisms that exist today possess a self-replicating informational molecule (genome), and such an informational molecule
1672-741: Is a colony, such as of ants , consisting of many individuals working together as a single functional or social unit . A mutualism is a partnership of two or more species which each provide some of the needs of the other. A lichen consists of fungi and algae or cyanobacteria , with a bacterial microbiome ; together, they are able to flourish as a kind of organism, the components having different functions, in habitats such as dry rocks where neither could grow alone. The evolutionary biologists David Queller and Joan Strassmann state that "organismality" has evolved socially, as groups of simpler units (from cells upwards) came to cooperate without conflicts. They propose that cooperation should be used as
1760-409: Is also well-recognized in extensive and semi-intensive pond fish farming. Plankton population-based pond management strategies for fish rearing have been practiced by traditional fish farmers for decades, illustrating the importance of plankton even in man-made environments. Of all animal fecal matter, it is whale feces that is the 'trophy' in terms of increasing nutrient availability. Phytoplankton are
1848-535: Is an argument for viewing viruses as cellular organisms. Some researchers perceive viruses not as virions alone, which they believe are just spores of an organism, but as a virocell - an ontologically mature viral organism that has cellular structure. Such virus is a result of infection of a cell and shows all major physiological properties of other organisms: metabolism , growth, and reproduction , therefore, life in its effective presence. The philosopher Jack A. Wilson examines some boundary cases to demonstrate that
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#17329305902491936-411: Is because plankton are defined by their ecological niche and level of motility rather than by any phylogenetic or taxonomic classification. The "plankton" category differentiates these organisms from those that float on the water's surface, called neuston , those that can swim against a current, called nekton , and those that live on the deep sea floor, called benthos . The name plankton
2024-459: Is because there is a consistent increase in the nitrogen isotopic composition at each trophic level caused by fractionations that occur with the synthesis of biomolecules; the magnitude of this increase in nitrogen isotopic composition is approximately 3–4‰. In fisheries, the mean trophic level for the fisheries catch across an entire area or ecosystem is calculated for year y as: where Y i y {\displaystyle Y_{iy}}
2112-428: Is called tritrophic interaction. Ecologists often restrict their research to two trophic levels as a way of simplifying the analysis; however, this can be misleading if tritrophic interactions (such as plant–herbivore–predator) are not easily understood by simply adding pairwise interactions (plant-herbivore plus herbivore–predator, for example). Significant interactions can occur between the first trophic level (plant) and
2200-446: Is defined in a medical dictionary as any living thing that functions as an individual . Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have been proposed to define what an organism is. Among the most common is that an organism has autonomous reproduction , growth , and metabolism . This would exclude viruses , despite
2288-444: Is in contrast to nekton organisms, such as fish , squid and marine mammals , which can swim against the ambient flow and control their position in the environment. Within the plankton, holoplankton spend their entire life cycle as plankton (e.g. most algae , copepods , salps , and some jellyfish ). By contrast, meroplankton are only planktic for part of their lives (usually the larval stage), and then graduate to either
2376-568: Is inadequate in biology; that the concept of individuality is problematic; and from a philosophical point of view, question whether such a definition is necessary. Problematic cases include colonial organisms : for instance, a colony of eusocial insects fulfills criteria such as adaptive organisation and germ-soma specialisation. If so, the same argument, or a criterion of high co-operation and low conflict, would include some mutualistic (e.g. lichens) and sexual partnerships (e.g. anglerfish ) as organisms. If group selection occurs, then
2464-472: Is likely intrinsic to life. Thus, the earliest organisms also presumably possessed a self-replicating informational molecule ( genome ), perhaps RNA or an informational molecule more primitive than RNA. The specific nucleotide sequences in all currently extant organisms contain information that functions to promote survival, reproduction , and the ability to acquire resources necessary for reproduction, and sequences with such functions probably emerged early in
2552-501: Is made up of numerous microbes , including viruses , about 1000 different species of bacteria , around 40,000 varieties of fungi , and hundreds of species of protists , algae , mosses and liverworts that live some part of their life cycle as aeroplankton, often as spores , pollen , and wind-scattered seeds . Additionally, peripatetic microorganisms are swept into the air from terrestrial dust storms, and an even larger amount of airborne marine microorganisms are propelled high into
2640-406: 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. The growth of phytoplankton populations is dependent on light levels and nutrient availability. The chief factor limiting growth varies from region to region in
2728-496: Is normally dropped, using only the root of the word in the derivation. Plankton are primarily divided into broad functional (or trophic level ) groups: Recognition of the importance of mixotrophy as an ecological strategy is increasing, as well as the wider role this may play in marine biogeochemistry . Studies have shown that mixotrophs are much more important for marine ecology than previously assumed and comprise more than half of all microscopic plankton. Their presence acts as
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2816-402: Is respiration rate. Physical factors such as oxygen availability, pH, and light conditions may affect overall oxygen consumption and how much carbon 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
2904-414: Is stable (zero) over periods of time when changes in trophic levels are matched by appropriate changes in the catch in the opposite direction. The index increases if catches increase for any reason, e.g. higher fish biomass, or geographic expansion. Such decreases explain the "backward-bending" plots of trophic level versus catch originally observed by Pauly and others in 1998. One aspect of trophic levels
2992-437: Is the annual catch of the species or group i in year y , and T L i {\displaystyle \ TL_{i}\ } is the trophic level for species i as defined above. Fish at higher trophic levels usually have a higher economic value, which can result in overfishing at the higher trophic levels. Earlier reports found precipitous declines in mean trophic level of fisheries catch, in
3080-669: Is the availability of light. All plankton ecosystems are driven by the input of solar energy (but see chemosynthesis ), confining primary production to surface waters, and to geographical regions and seasons having abundant light. A secondary variable is nutrient availability. Although large areas of the tropical and sub-tropical oceans have abundant light, they experience relatively low primary production because they offer limited nutrients such as nitrate , phosphate and silicate . This results from large-scale ocean circulation and water column stratification . In such regions, primary production usually occurs at greater depth, although at
3168-420: Is the mean trophic level of the catch at year y , Y 0 {\displaystyle Y_{0}} is the catch, T L 0 {\displaystyle TL_{0}} the mean trophic level of the catch at the start of the series being analyzed, and T E {\displaystyle TE} is the transfer efficiency of biomass or energy between trophic levels. The FiB index
3256-463: The Portuguese Man o' War , which are buoyant. Pseudoplankton are often found in the guts of filtering zooplankters . Tychoplankton are organisms, such as free-living or attached benthic organisms and other non-planktonic organisms, that are carried into the plankton through a disturbance of their benthic habitat, or by winds and currents. This can occur by direct turbulence or by disruption of
3344-431: The benthic zone . Examples of holoplankton include some diatoms , radiolarians , some dinoflagellates , foraminifera , amphipods , krill , copepods , and salps , as well as some gastropod mollusk species. Holoplankton dwell in the pelagic zone as opposed to the benthic zone . Holoplankton include both phytoplankton and zooplankton and vary in size. The most common plankton are protists . Meroplankton are
3432-590: The biological pump , is one reason that oceans constitute the largest carbon sink on Earth . However, it has been shown to be influenced by increments of temperature. In 2019, a study indicated that at ongoing rates of seawater acidification , Antarctic phytoplanktons could become smaller and less effective at storing carbon before the end of the century. It might be possible to increase the ocean's uptake of carbon dioxide ( CO 2 ) generated through human activities by increasing plankton production through iron fertilization – introducing amounts of iron into
3520-425: The nekton or adopt a benthic (often sessile ) lifestyle on the seafloor . The larval stages of benthic invertebrates make up a significant proportion of planktonic communities. The planktonic larval stage is particularly crucial to many benthic invertebrates in order to disperse their young. Depending on the particular species and the environmental conditions, larval or juvenile-stage meroplankton may remain in
3608-463: The saltwater of oceans and the brackish waters of estuaries . Freshwater plankton are similar to marine plankton, but are found in lakes and rivers. Mostly, plankton just drift where currents take them, though some, like jellyfish , swim slowly but not fast enough to generally overcome the influence of currents. Although plankton are usually thought of as inhabiting water, there are also airborne versions that live part of their lives drifting in
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3696-642: The "defining trait" of an organism. Samuel Díaz‐Muñoz and colleagues (2016) accept Queller and Strassmann's view that organismality can be measured wholly by degrees of cooperation and of conflict. They state that this situates organisms in evolutionary time, so that organismality is context dependent. They suggest that highly integrated life forms, which are not context dependent, may evolve through context-dependent stages towards complete unification. Viruses are not typically considered to be organisms, because they are incapable of autonomous reproduction , growth , metabolism , or homeostasis . Although viruses have
3784-466: The "defining trait" of an organism. This would treat many types of collaboration, including the fungus / alga partnership of different species in a lichen , or the permanent sexual partnership of an anglerfish , as an organism. The term "organism" (from the Ancient Greek ὀργανισμός , derived from órganon , meaning instrument, implement, tool, organ of sense or apprehension) first appeared in
3872-452: The English language in the 1660s with the now-obsolete meaning of an organic structure or organization. It is related to the verb "organize". In his 1790 Critique of Judgment , Immanuel Kant defined an organism as "both an organized and a self-organizing being". Among the criteria that have been proposed for being an organism are: Other scientists think that the concept of the organism
3960-848: The atmosphere for about 31 days. Evidence suggests that bacteria can remain viable after being transported inland through aerosols. Some reached as far as 200 meters at 30 meters above sea level. The process which transfers this material to the atmosphere causes further enrichment in both bacteria and viruses in comparison to either the SML or sub-surface waters (up to three orders of magnitude in some locations). Many animals live in terrestrial environments by thriving in transient often microscopic bodies of water and moisture, these include rotifers and gastrotrichs which lay resilient eggs capable of surviving years in dry environments, and some of which can go dormant themselves. Nematodes are usually microscopic with this lifestyle. Water bears, despite only having lifespans of
4048-464: The atmosphere in sea spray. Aeroplankton deposits hundreds of millions of airborne viruses and tens of millions of bacteria every day on every square meter around the planet. The sea surface microlayer , compared to the sub-surface waters, contains elevated concentration of bacteria and viruses . These materials can be transferred from the sea-surface to the atmosphere in the form of wind-generated aqueous aerosols due to their high vapour tension and
4136-410: The atmosphere. These aeroplankton include plant spores , pollen and wind-scattered seeds . They may also include microorganisms swept into the air from terrestrial dust storms and oceanic plankton swept into the air by sea spray . Though many planktonic species are microscopic in size, plankton includes organisms over a wide range of sizes, including large organisms such as jellyfish. This
4224-483: The average trophic level of human beings at 2.21, similar to pigs or anchovies. This is only an average, and plainly both modern and ancient human eating habits are complex and vary greatly. For example, a traditional Inuit living on a diet consisting primarily of seals would have a trophic level of nearly 5. In general, each trophic level relates to the one below it by absorbing some of the energy it consumes, and in this way can be regarded as resting on, or supported by,
4312-532: The biomass at any one moment may be low; for example, phytoplankton (producer) biomass can be low compared to the zooplankton (consumer) biomass in the same area of ocean. The efficiency with which energy or biomass is transferred from one trophic level to the next is called the ecological efficiency . Consumers at each level convert on average only about 10% of the chemical energy in their food to their own organic tissue (the ten-per cent law ). For this reason, food chains rarely extend for more than 5 or 6 levels. At
4400-506: The bobcat eats rabbits, but the mountain lion eats both bobcats and rabbits. Animals can also eat each other; the bullfrog eats crayfish and crayfish eat young bullfrogs. The feeding habits of a juvenile animal, and, as a consequence, its trophic level, can change as it grows up. The fisheries scientist Daniel Pauly sets the values of trophic levels to one in plants and detritus, two in herbivores and detritivores (primary consumers), three in secondary consumers, and so on. The definition of
4488-511: The case of marine ecosystems, the trophic level of most fish and other marine consumers takes a value between 2.0 and 5.0. The upper value, 5.0, is unusual, even for large fish, though it occurs in apex predators of marine mammals, such as polar bears and orcas. In addition to observational studies of animal behavior, and quantification of animal stomach contents, trophic level can be quantified through stable isotope analysis of animal tissues such as muscle , skin , hair , bone collagen . This
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#17329305902494576-765: The chain can form either a one-way flow or a part of a wider food "web". Ecological communities with higher biodiversity form more complex trophic paths. The word trophic derives from the Greek τροφή (trophē) referring to food or nourishment. The concept of trophic level was developed by Raymond Lindeman (1942), based on the terminology of August Thienemann (1926): "producers", "consumers", and "reducers" (modified to "decomposers" by Lindeman). The three basic ways in which organisms get food are as producers, consumers, and decomposers. Trophic levels can be represented by numbers, starting at level 1 with plants. Further trophic levels are numbered subsequently according to how far
4664-678: The concept of organism is not sharply defined. In his view, sponges , lichens , siphonophores , slime moulds , and eusocial colonies such as those of ants or naked molerats , all lie in the boundary zone between being definite colonies and definite organisms (or superorganisms). Scientists and bio-engineers are experimenting with different types of synthetic organism , from chimaeras composed of cells from two or more species, cyborgs including electromechanical limbs, hybrots containing both electronic and biological elements, and other combinations of systems that have variously evolved and been designed. An evolved organism takes its form by
4752-509: The eastern Atlantic Ocean , where trade winds bring dust from the Sahara Desert in north Africa ). While plankton are most abundant in surface waters, they live throughout the water column. At depths where no primary production occurs, zooplankton and bacterioplankton instead consume organic material sinking from more productive surface waters above. This flux of sinking material, so-called marine snow , can be especially high following
4840-530: The end of a food chain. Thus food chains start with primary producers and end with decay and decomposers. Since decomposers recycle nutrients, leaving them so they can be reused by primary producers, they are sometimes regarded as occupying their own trophic level. The trophic level of a species may vary if it has a choice of diet. Virtually all plants and phytoplankton are purely phototrophic and are at exactly level 1.0. Many worms are at around 2.1; insects 2.2; jellyfish 3.0; birds 3.6. A 2013 study estimates
4928-422: The evolution of life. It is also likely that survival sequences present early in the evolution of organisms included sequences that facilitate the avoidance of damage to the self-replicating molecule and promote the capability to repair such damages that do occur. Repair of some of the genome damages in these early organisms may have involved the capacity to use undamaged information from another similar genome by
5016-433: The exception being intermittent mass extinction events. Food webs largely define ecosystems, and the trophic levels define the position of organisms within the webs. But these trophic levels are not always simple integers, because organisms often feed at more than one trophic level. For example, some carnivores also eat plants, and some plants are carnivores. A large carnivore may eat both smaller carnivores and herbivores;
5104-433: The fact that they evolve like organisms. Other problematic cases include colonial organisms ; a colony of eusocial insects is organised adaptively, and has germ-soma specialisation , with some insects reproducing, others not, like cells in an animal's body. The body of a siphonophore , a jelly-like marine animal, is composed of organism-like zooids , but the whole structure looks and functions much like an animal such as
5192-436: The fish predation rate in their environment. Depending on the predation rate, they could express regular or chaotic behavior. A negative effect that fish larvae can have on planktonic algal blooms is that the larvae will prolong the blooming event by diminishing available zooplankton numbers; this in turn permits excessive phytoplankton growth allowing the bloom to flourish . The importance of both phytoplankton and zooplankton
5280-472: The food provided by the chiton from the zooplankton, but also from the protection from acidic environments. Once the copepods have been ingested by a human host, the chitinous exterior protects the bacteria from the stomach acids in the stomach and proceed to the intestines. Once there, the bacteria bind with the surface of the small intestine and the host will start developing symptoms, including extreme diarrhea, within five days. Organism An organism
5368-474: The freshwaters of lakes and rivers. Aeroplankton are tiny lifeforms that float and drift in the air, carried by the current of the wind ; they are the atmospheric analogue to oceanic plankton. Most of the living things that make up aeroplankton are very small to microscopic in size, and many can be difficult to identify because of their tiny size. Scientists can collect them for study in traps and sweep nets from aircraft , kites or balloons. Aeroplankton
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#17329305902495456-434: 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 impacts on future phytoplankton productivity. Additionally, changes in the mortality of phytoplankton due to rates of zooplankton grazing may be significant. Zooplankton are
5544-704: The initial prey item for almost all fish larvae as they switch from their yolk sacs to external feeding. Fish rely on the density and distribution of zooplankton to match that of new larvae, which can otherwise starve. Natural factors (e.g., current variations, temperature changes) and man-made factors (e.g. river dams, ocean acidification , rising temperatures) can strongly affect zooplankton populations, which can in turn strongly affect fish larval survival, and therefore breeding success. It has been shown that plankton can be patchy in marine environments where there aren't significant fish populations and additionally, where fish are abundant, zooplankton dynamics are influenced by
5632-499: The largest proportion of all plankton in number and diversity. The microplankton and smaller groups are microorganisms and operate at low Reynolds numbers , where the viscosity of water is more important than its mass or inertia. Marine plankton includes marine bacteria and archaea , algae , protozoa and drifting or floating animals that inhabit the saltwater of oceans and the brackish waters of estuaries. Freshwater plankton are similar to marine plankton, but are found inland in
5720-409: The lowest trophic level (the bottom of the food chain), plants convert about 1% of the sunlight they receive into chemical energy. It follows from this that the total energy originally present in the incident sunlight that is finally embodied in a tertiary consumer is about 0.001% Both the number of trophic levels and the complexity of relationships between them evolve as life diversifies through time,
5808-530: The next lower trophic level. Food chains can be diagrammed to illustrate the amount of energy that moves from one feeding level to the next in a food chain. This is called an energy pyramid . The energy transferred between levels can also be thought of as approximating to a transfer in biomass , so energy pyramids can also be viewed as biomass pyramids, picturing the amount of biomass that results at higher levels from biomass consumed at lower levels. However, when primary producers grow rapidly and are consumed rapidly,
5896-447: 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 juveniles . Fish larvae are part of the zooplankton that eat smaller plankton, while fish eggs carry their food supply. Both eggs and larvae are themselves eaten by larger animals. Fish can produce high numbers of eggs which are often released into
5984-463: The ocean's carbon cycle . Fish larvae mainly eat zooplankton, which in turn eat phytoplankton Primarily by grazing on phytoplankton, zooplankton provide carbon to the planktic foodweb , either respiring it to provide metabolic energy, or upon death as biomass or detritus . Organic material tends to be denser than seawater , so it sinks into open ocean ecosystems away from the coastlines, transporting carbon along with it. This process, called
6072-481: The ocean. However, this technique may not be practical at a large scale. Ocean oxygen depletion and resultant methane production (caused by the excess production remineralising at depth) is one potential drawback. Phytoplankton absorb energy from the Sun and nutrients from the water to produce their own nourishment or energy. In the process of photosynthesis , phytoplankton release molecular oxygen ( O 2 ) into
6160-407: The open ocean and the deep sea and are less available to the casual ocean observer. Ichthyoplankton are the eggs and larvae of fish. They are mostly found in the sunlit zone of the water column , less than 200 metres deep, which is sometimes called the epipelagic or photic zone . Ichthyoplankton are planktonic , meaning they cannot swim effectively under their own power, but must drift with
6248-606: The open water column. Fish eggs typically have a diameter of about 1 millimetre (0.039 in). The newly hatched young of oviparous fish are called larvae . They are usually poorly formed, carry a large yolk sac (for nourishment), and are very different in appearance from juvenile and adult specimens. The larval period in oviparous fish is relatively short (usually only several weeks), and larvae rapidly grow and change appearance and structure (a process termed metamorphosis ) to become juveniles. During this transition larvae must switch from their yolk sac to feeding on zooplankton prey,
6336-424: The organism is along the food chain. In real-world ecosystems , there is more than one food chain for most organisms, since most organisms eat more than one kind of food or are eaten by more than one type of predator. A diagram that sets out the intricate network of intersecting and overlapping food chains for an ecosystem is called its food web . Decomposers are often left off food webs, but if included, they mark
6424-415: The oxygen in the atmosphere is produced in the oceans from phytoplankton performing photosynthesis, meaning that the majority of the oxygen available for us and other organisms that respire aerobically is produced by plankton. Plankton also make up the base of the marine food web, providing food for all the trophic levels above. Recent studies have analyzed the marine food web to see if the system runs on
6512-501: The partially understood mechanisms of evolutionary developmental biology , in which the genome directs an elaborated series of interactions to produce successively more elaborate structures. The existence of chimaeras and hybrids demonstrates that these mechanisms are "intelligently" robust in the face of radically altered circumstances at all levels from molecular to organismal. Synthetic organisms already take diverse forms, and their diversity will increase. What they all have in common
6600-452: The pelagic zone for durations ranging from hours to months. Pseudoplankton are organisms that attach themselves to planktonic organisms or other floating objects, such as drifting wood, buoyant shells of organisms such as Spirula , or man-made flotsam . Examples include goose barnacles and the bryozoan Jellyella . By themselves these animals cannot float , which contrasts them with true planktonic organisms, such as Velella and
6688-630: The 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 absorption efficiency may lead to variations in fecal pellet production, and thus regulates how much organic material is recycled back to the marine environment. Low feeding rates typically lead to high absorption efficiency and small, dense pellets, while high feeding rates typically lead to low absorption efficiency and larger pellets with more organic content. Another contributing factor to dissolved organic matter (DOM) release
6776-432: The powerhouse of open ocean primary production and they can acquire many nutrients from whale feces. In the marine food web, phytoplankton are at the base of the food web and are consumed by zooplankton & krill, which are preyed upon by larger and larger marine organisms, including whales, so it can be said that whale poop fuels the entire food web. Plankton have many direct and indirect effects on humans. Around 70% of
6864-481: The preferred catch. They consider that this is part of the global fishery collapse, which finds an echo in the overfished Mediterranean Sea. Humans have a mean trophic level of about 2.21, about the same as a pig or an anchovy. Since biomass transfer efficiencies are only about 10%, it follows that the rate of biological production is much greater at lower trophic levels than it is at higher levels. Fisheries catch, at least, to begin with, will tend to increase as
6952-414: The secondary consumers that prey on the primary consumers. In some cases, plankton act as an intermediate host for deadly parasites in humans. One such case is that of cholera , an infection caused by several pathogenic strains of Vibrio cholerae . These species have been shown to have a symbiotic relationship with chitinous zooplankton species like copepods . These bacteria benefit not only from
7040-535: The substrate and subsequent entrainment in the water column. Tychoplankton are, therefore, a primary subdivision for sorting planktonic organisms by duration of lifecycle spent in the plankton, as neither their entire lives nor particular reproductive portions are confined to planktonic existence. Tychoplankton are sometimes called accidental plankton . Apart from aeroplankton, plankton inhabits oceans, seas, lakes and ponds. Local abundance varies horizontally, vertically and seasonally. The primary cause of this variability
7128-406: The termination of spring blooms . The local distribution of plankton can be affected by wind-driven Langmuir circulation and the biological effects of this physical process. As well as representing the lower levels of a food chain that supports commercially important fisheries , plankton ecosystems play a role in the biogeochemical cycles of many important chemical elements , including
7216-512: The trophic level declines. At this point the fisheries will target species lower in the food web. In 2000, this led Pauly and others to construct a "Fisheries in Balance" index, usually called the FiB index. The FiB index is defined, for any year y , by where Y y {\displaystyle Y_{y}} is the catch at year y , T L y {\displaystyle TL_{y}}
7304-445: The trophic level, TL, for any consumer species is: where T L j {\displaystyle TL_{j}} is the fractional trophic level of the prey j , and D C i j {\displaystyle DC_{ij}} represents the fraction of j in the diet of i . That is, the consumer trophic level is one plus the weighted average of how much different trophic levels contribute to its food. In
7392-423: The water as a waste byproduct. It is estimated that about 50% of the world's oxygen is produced via phytoplankton photosynthesis. The rest is produced via photosynthesis on land by plants . Furthermore, phytoplankton photosynthesis has controlled the atmospheric CO 2 / O 2 balance since the early Precambrian Eon. The absorption efficiency (AE) of plankton is the proportion of food absorbed by
7480-520: The water column in the ocean. Their delicate bodies have no hard parts and are easily damaged or destroyed. Gelatinous zooplankton are often transparent. All jellyfish are gelatinous zooplankton, but not all gelatinous zooplankton are jellyfish. The most commonly encountered organisms include ctenophores , medusae , salps , and Chaetognatha in coastal waters. However, almost all marine phyla, including Annelida , Mollusca and Arthropoda , contain gelatinous species, but many of those odd species live in
7568-688: The world's oceans. On a broad scale, growth of phytoplankton in the oligotrophic tropical and subtropical gyres is generally limited by nutrient supply, while light often limits phytoplankton growth in subarctic gyres. Environmental variability at multiple scales influences the nutrient and light available for phytoplankton, and as these organisms form the base of the marine food web, this variability in phytoplankton growth influences higher trophic levels. For example, at interannual scales phytoplankton levels temporarily plummet during El Niño periods, influencing populations of zooplankton, fishes, sea birds, and marine mammals . The effects of anthropogenic warming on
7656-459: Was co-evolution of viruses and host cells. If host cells did not exist, viral evolution would be impossible. As for reproduction, viruses rely on hosts' machinery to replicate. The discovery of viruses with genes coding for energy metabolism and protein synthesis fuelled the debate about whether viruses are living organisms, but the genes have a cellular origin. Most likely, they were acquired through horizontal gene transfer from viral hosts. There
7744-484: Was coined by German marine biologist Victor Hensen in 1887 from shortening the word halyplankton from Greek ᾰ̔́λς háls "sea" and πλανάω planáō to "drift" or "wander". While some forms are capable of independent movement and can swim hundreds of meters vertically in a single day (a behavior called diel vertical migration ), their horizontal position is primarily determined by the surrounding water movement, and plankton typically flow with ocean currents . This
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