Plankton is the first and most important layer of the oceanic food chain. The combined weight of all plankton outweighs that of all other sea animals.
Zooplankton is the tiny animals found near the surface in aquatic environments. Tiny fish and snails also eat zooplankton.
Zooplankton incorporates the Greek word Zion, meaning “animal.” Some species of zooplankton are born as plankton and remain so for their entire lives.
These organisms are known as zooplankton and include such tiny species as cope pods, periods, and emphasis. Zooplankton may be classified according to their size or by the length of time they are planktonic (largely immobile).
Microplankton : Organisms 2-20 µm in size which includes some cope pods and other zooplankton. Zooplankton : Organisms 200 µm-2 mm in size, which includes larval crustaceans.
Micronewton : Organisms 20-200 mm in size, which includes some euphausiids and cephalopods. Megaloplankton : Planktonic organisms greater than 200 mm in size, which includes jellyfish and sales.
Zooplankton : Organisms that have a planktonic stage, but mature out of it, such as some fish and crustaceans. Rather than getting nutrition from sunlight and nutrients via photosynthesis like phytoplankton, they must consume other organisms in order to survive.
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 the Portuguese Man o' War ; crustaceans such as cope pods, strands, isopods, amphibious, mys ids and krill ; Chaetognatha (arrow worms); mollusks such as Pteropus ; and chordates such as sales 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. Just as any species can be limited within 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. Biological factors include breeding, predation, concentration of phytoplankton, and vertical migration.
The physical factor that influences zooplankton distribution the most is mixing of the water column (upwelling and down welling 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 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.
This symbiotic relationship enhances the bacterium's ability to survive in an aquatic environment, as the exoskeleton provides the bacterium with carbon and nitrogen. Historically, the protozoa were regarded as “one-celled animals”, because they often possess animal -like behaviors, such as motility and predation, and lack 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. Radiolarians are unicellular predatory protists encased in elaborate globular shells usually made of silica and pierced with holes.
They catch prey by extending parts of their body through the holes. As with the silica frustules of diatoms, radiocarbon shells can sink to the ocean floor when radiolarians die and become preserved as part of the ocean sediment.
Cutaway schematic diagram of a spherical radiocarbon shell They are widely researched with well established fossil records which allow scientists to infer a lot about past environments and climates.
Dinoflagellates Dinoflagellates are part of the algae group, and form a phylum of unicellular flagellates with about 2,000 marine species. This refers to the two whip-like attachments (flagella) used for forward movement.
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.
Many marine microzooplankton are mixotrophic, which means they could also be classified as phytoplankton. Recent studies of marine microzooplankton found 30–45% of the climate abundance was mixotrophic, and up to 65% of the amoebic, form and radiocarbon biomass was mixotrophic.
Protists that retain chloroplasts and sometimes other organelles from one algal species or very closely related algal species Diaphysis acuminataDinophysis SPP. Protists or zooplankton with algal endosymbiosis of only one algal species or very closely related algal species Noctilucent scintillas Meta zooplankton with algal endosymbiosis Most mixotrophic Riparian (Alcántara, Polycystic, and Foraminifera)Green Noctilucent scintillas a Chloroplast (or plastic) retention = sequestration = enslavement.
Some plastid-retaining species also retain other organelles and prey cytoplasm. Phagocytes species are endosymbiosis to contrarian radiolarians.
Phagocytes 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 a gel matrix, which can increase massively in size during blooms. As a result, Phagocytes is an important contributor to the marine carbon and sulfur cycles.
White Phagocytes algal foam washing up on a beach 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 endosymbiosis of marine animals and other protists, and play an important part in the biology of coral reefs. The toxic dinoflagellate Diaphysis acute acquire chloroplasts from its prey.
“It cannot catch the bryophytes by itself, and instead relies on ingesting climates such as the red Marionette Aubrey, which sequester their chloroplasts from a specific bryophyte clade (Geminigera/Plagioselmis/Teleplay)”. Cope pods are typically 1 to 2 mm long with a teardrop-shaped bodies.
Like all crustaceans, their bodies are divided into three sections: head, thorax, and abdomen, with two pairs of antennae; 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 center of their transparent head.
Gelatinous zooplankton Gelatinous zooplankton include ctenophores, medusae, sales, 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 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 specialized predators such as the ocean sunfish and the leather back sea turtle. Jellyfish, and more gelatinous zooplankton in general, which includes alps 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 the ocean.
It is difficult for scientists to detect and analyze 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 amphibious.
According to a 2017 study, narcomedusae consume the greatest diversity of mesopelagic prey, followed by physonectsiphonophores, ctenophores and cephalopods. The importance of 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. Pelagic food web and the biological pump.
Links among the ocean's biological pump and pelagic food web and the ability to sample these components remotely from ships, satellites, and autonomous vehicles. Light blue waters are the euphoric zone, while the darker blue waters represent the twilight zone.
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 oligotrophic waters of the open ocean.
Through sloppy feeding, excretion, election, 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.
Adapted from Miller et al. (2005), Saga et al. (2009) and Steinberg et al. (2017). Excretion and sloppy feeding (the physical breakdown of food source) make up 80% and 20% of crustacean zooplankton -mediated DOM release respectively. In the same study, fecal pellet leaching was found to be an insignificant contributor.
For protozoan grazers, DOM is released primarily through excretion and election and gelatinous zooplankton can also release DOM through the production of mucus. Leaching of fecal pellets can extend from hours to days after initial election and its effects can vary depending on food concentration and quality.
Various factors can affect how much DOM 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 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 is loss from zooplankton in the form of respired CO2.
The relative sizes of zooplankton and prey also mediate how much carbon is released via sloppy feeding. Zooplankton plays 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 cope pod 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 microbial reworked by microbes in the water column, which can thus alter the carbon composition of the pellet.
This affects how much carbon is recycled in the euphoric zone and how many 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 is being exported via zooplankton fecal pellet production.
Because of their large size, these gelatinous zooplankton are expected to hold a larger carbon content, making their sinking carcasses a potentially important source of food for benthic organisms. New Jersey, USA: Prentice Hall College.
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