Where are Krill?
Antarctic Krill (Euphausia superba) are found all around the continent of Antarctica. They are a semi-transparent, shrimp-like creatures that feed upon diatoms, small unicellular phytoplankton that are encase in silica, a form of glass. Antarctic krill are also one of the largest species of krill among the 85 species that are known today. They can live up to seven years and at any given time, their numbers could range anywhere from 10,000 to 30,000 individual members per cubic meter (Hamner et. al. 1983, Behavior of Antarctic krill). This is a good thing considering one humpback whale is known to eat over four tons of krill a day (National Geographic, Krill). Antarctic krill have also adapted to one of the most extreme environments on earth. Ask these questions to yourself, would you want to live in Antarctica? Would you be able to? The krill have evolved to survive in what most species would deem as their extreme lower limit. Not only are the krill surviving and reproducing, but they are surviving and reproducing at incredible rates. Part of the reason why krill are so successful at living in the antarctic is because how stable the upper water level is temperature wise year round. Think of it like a house plant. It is able to grow year round and survive because the temperature within your house is fairly constant unless you are trying to save on your power bill. Please remember though, krill are not houseplants.
What are Krill?
Krill fall under the category of zoo plankton because they are able to change their position within a water column, but they cannot swim against a current or migrate in the traditional sense (Cool Antarctica). The krill's main source of food comes from the algae blooms that occur beneath the Antarctic ice. They are also known to eat each other on occasion. The krill use their highly developed front legs as a form of filter feeding as they swim through the water and as they graze upon the bottom of the Antarctic ice on more algae (National Geographic, Krill).
Krill can clear over one square foot of ice over a 10 minute period. With the abundance of Antarctic ice, it is no wonder there is a superabundance of krill and why this species is the primary food source of so many other animals. There is so much of it that there is plenty of krill to go around between the many different animals. Many species of seals, birds, and whale eat primarily krill and have even been specifically adapted to that food source. Over the last 30 years, though, researchers have said there has been an 80% decrease in krill population (Kawaguchi et. al., 2011, Will krill fare well...), because of rising ocean temperatures that lead to their ice-habitat retreating and shrinking their living space, and ocean acidification that may have physiological effects on the krill and can harm embryonic development, which means less krill reach adulthood each year.
Good overview!
ReplyDeleteGood background info.
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