Krill

Animal: Animal Group: Description of animal group || krill Krill is a general term used to describe about 85 species of free-swimming, open-ocean crustaceans known as euphausiids. Antarctic krill (//Euphausia superba//) would have to be one of the most abundant and successful animal species on Earth. Scientists estimate there are about 500 million tonnes of Antarctic krill in the Southern Ocean. The biomass of this one species may be the largest of any multi-cellular animal species on the planet. **More than anything else, krill are the engine that powers the Antarctic ecosystem.** They are a small semi-transparent crustacean like a shrimp, about 4-5 cm (2") in length when fully grown, they can live for up to 6 years which is quite remarkable considering the wide variety of animals that feed on them in huge quantities. Krill belong to the animals that make up the zooplankton. The "zoo" means that they are animals, the "plankton" means that they float in the upper reaches of the water column and are at the mercy of the ocean currents, being able to change their position in the water column, but not able to swim against the current or migrate in the normal sense. || Observation Describe your animal (Colour, size, body parts) || In the water, krill have an exotic appearance, with a translucent, reddish shell and large black eyes. Krill spend most of their 5-7 year life span in huge schools or "swarms," living in concentrations so dense and vast that they cover kilometers in every direction with as many as 30,000 krill per cubic meter. Estimates of the total weight of Antarctic krill range from 50 to 500 million metric tonnes. || Describe how your animal behaves (moves, flies, runs) || In winter, they have to use other food sources such as the algae which grows on the underside of the pack ice, detritus on the sea-floor or the other animals in the water. Krill can survive for long periods (up to 200 days) without food and can shrink in length as they starve. Most of the time the schools stay deep in the water during daylight hours and only rise to the surface at night. It is not known why swarms are occasionally seen at the surface during broad daylight. || Where it lives || Krill swim in water off the coast, out in the open ocean, and around polar ice. Most krill feed and mate close to the surface, but a few species live at depths of up to 16,404 feet (5,000 meters). Antarctic krill are found thronging the surface waters of the [|Southern Ocean]; they have a circumpolar distribution, with the highest concentrations located in the [|Atlantic] sector. The northern boundary of the Southern Ocean with its Atlantic, [|Pacific Ocean] and [|Indian Ocean] sectors is defined more or less by the Antarctic convergence, a circumpolar front where the cold Antarctic surface water submerges below the warmer [|subantarctic] waters. This front runs roughly at 55° South; from there to the continent, the Southern Ocean covers 32 million square kilometers. This is 65 times the size of the [|North Sea]. In the winter season, more than three quarters of this area become covered by ice, whereas 24 million square kilometers become ice free in summer. The water temperatures range between −1.3 and 3 [|°C]. The waters of the Southern Ocean form a system of currents. Whenever there is a [|West Wind Drift], the surface strata travels around Antarctica in an easterly direction. Near the continent, the [|East Wind Drift] runs counterclockwise. At the front between both, large [|eddies] develop, for example, in the [|Weddell Sea]. The krill schools drift with these water masses, to establish one single stock all around Antarctica, with gene exchange over the whole area. Currently, there is little knowledge of the precise migration patterns since individual krill cannot yet be tagged to track their movements. Antarctic krill are found thronging the surface waters of the [|Southern Ocean]; they have a circumpolar distribution, with the highest concentrations located in the [|Atlantic] sector. The northern boundary of the Southern Ocean with its Atlantic, [|Pacific Ocean] and [|Indian Ocean] sectors is defined more or less by the Antarctic convergence, a circumpolar front where the cold Antarctic surface water submerges below the warmer [|subantarctic] waters. This front runs roughly at 55° South; from there to the continent, the Southern Ocean covers 32 million square kilometers. This is 65 times the size of the [|North Sea]. In the winter season, more than three quarters of this area become covered by ice, whereas 24 million square kilometers become ice free in summer. The water temperatures range between −1.3 and 3 [|°C]. The waters of the Southern Ocean form a system of currents. Whenever there is a [|West Wind Drift], the surface strata travels around Antarctica in an easterly direction. Near the continent, the [|East Wind Drift] runs counterclockwise. At the front between both, large [|eddies] develop, for example, in the [|Weddell Sea]. The krill schools drift with these water masses, to establish one single stock all around Antarctica, with gene exchange over the whole area. Currently, there is little knowledge of the precise migration patterns since individual krill cannot yet be tagged to track their movements. Antarctic krill are found thronging the surface waters of the [|Southern Ocean]; they have a circumpolar distribution, with the highest concentrations located in the [|Atlantic] sector. The northern boundary of the Southern Ocean with its Atlantic, [|Pacific Ocean] and [|Indian Ocean] sectors is defined more or less by the Antarctic convergence, a circumpolar front where the cold Antarctic surface water submerges below the warmer [|subantarctic] waters. This front runs roughly at 55° South; from there to the continent, the Southern Ocean covers 32 million square kilometers. This is 65 times the size of the [|North Sea]. In the winter season, more than three quarters of this area become covered by ice, whereas 24 million square kilometers become ice free in summer. The water temperatures range between −1.3 and 3 [|°C]. The waters of the Southern Ocean form a system of currents. Whenever there is a [|West Wind Drift], the surface strata travels around Antarctica in an easterly direction. Near the continent, the [|East Wind Drift] runs counterclockwise. At the front between both, large [|eddies] develop, for example, in the [|Weddell Sea]. The krill schools drift with these water masses, to establish one single stock all around Antarctica, with gene exchange over the whole area. Currently, there is little knowledge of the precise migration patterns since individual krill cannot yet be tagged to track their movements. || What it eats How it eats || Krill feed on microscopic phytoplankton ("phyto" - plant) that are extremely abundant in Antarctic waters due to the great **upwellings of deep waters at the Antarctic convergence**. These upwellings bring with them great amounts of dissolved nutrients, especially nitrate and phosphate that fertilize the microscopic but hugely abundant phytoplankton in the same way that a farmer puts fertiliser on the fields. Add to this the 24 hour intense sunlight of the summer months and the scene is set for a super-abundance of life. Antarctic krill are mainly herbivorous, feeding mostly on the phytoplankton (microscopic suspended plants) of the Southern Ocean and, to a lesser extent, planktonic animals (zooplankton). In winter, they have to use other food sources such as the algae which grows on the underside of the pack ice, detritus on the sea-floor or the other animals in the water. Krill can survive for long periods (up to 200 days) without food and can shrink in length as they starve. || How does it have babies? How does it care for its babies? How long do they live? || Female Antarctic krill lay up to 10,000 eggs at a time, sometimes several times a season. They are a small semi-transparent crustacean like a shrimp, about 4-5 cm (2") in length when fully grown, they can live for up to 6 years. In the water, krill have an exotic appearance, with a translucent, reddish shell and large black eyes. Krill spend most of their 5-7 year life span in huge schools or "swarms," living in concentrations so dense and vast that they cover kilometers in every direction with as many as 30,000 krill per cubic meter. Estimates of the total weight of Antarctic krill range from 50 to 500 million metric tonnes. || What does it do during the day and night? ||  Krill feed on microscopic phytoplankton ("phyto" - plant) that are extremely abundant in Antarctic waters due to the great **upwellings of deep waters at the Antarctic convergence**. These upwellings bring with them great amounts of dissolved nutrients, especially nitrate and phosphate that fertilize the microscopic but hugely abundant phytoplankton in the same way that a farmer puts fertiliser on the fields. Add to this the 24 hour intense sunlight of the summer months and the scene is set for a super-abundance of life. Most of the time the schools stay deep in the water during daylight hours and only rise to the surface at night. It is not known why swarms are occasionally seen at the surface during broad daylight. || How has it changed over time in Antarctica? ||  Krill are unusual in that they are so super-abundant and large when compared to other phytoplankton feeders in other oceans. This means that many large animals such as seals, penguins, whales and myriad birds are able to **tap the food chain close to the production of the phytoplankton before energy is lost**, so the Antarctic supports a large population of large animals. || Increasingly, krill's natural predators, such as penguins and seals, must now compete for their prey with industrial fishing vessels that often trawl in coves and near-shore waters, close to rookeries and feeding grounds. Recent field research shows that the demand for krill by land-based species has begun to exceed supply in certain areas of the southwest Atlantic. Some scientists warn that the potential now exists for localized depletion of krill at levels that could seriously impact the entire southern marine ecosystem. These concerns have been made more urgent by global warming and by new technology that allows krill to be caught and pumped continuously out of the water and onto a vessel, where it can be processed immediately to prevent spoilage. || Antarctic krill are tiny, little-known crustaceans that serve as the "bread and butter" for hundreds of species. For many marine mammals and seabirds, from the blue whale to the albatross, krill are by far the most important food in their diet. There have been attempts to catch krill commercially and great factory ships have been sent down to the Antarctic by some nations to catch and can krill quickly. Fortunately for the krill and the Antarctic ecosystem, krill go off very quickly after being caught, the Antarctic is a long way away and consumer interest remains fairly low (krill aren't very nice for people to eat!). Krill is harvested by the Japanese (and a small amount by Russia) at around 100,000 tonnes per annum. ||    || Type in the content of your page here.
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 * Source 2: || [-   %20http://www.coolantarctica.com/Antarctica%20fact%20file/wildlife/krill.htm|http://www.krillcount.org/krill.htm - http://www.coolantarctica.com/Antarctica%20fact%20file/wildlife/krill.htm] ||
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 * **Threats:** || The Antarctic Peninsula, a key breeding ground for the krill, is one of the places in the world where there has been the greatest rise in temperatures due to global warming. This region has warmed by 2.5°C in the last 50 years (much more than the mean global rate), with a striking consequential decrease in winter sea-ice cover.
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