kril

Krill, sometimes spelled kril, are small shrimp-like marine crustaceans that form a cornerstone of ocean ecosystems. They belong to the order Euphausiacea within the class Malacostraca. About 80 described species are grouped into several genera; the best known is the Antarctic krill Euphausia superba. Individual krill typically measure about 1 to 2 centimeters, though some species can reach larger sizes.

Krill occur in all oceans, with high densities in polar and subpolar waters. Antarctic krill inhabit the Southern Ocean. They are planktivores, feeding on phytoplankton and detrital material, and their vertical movement connects surface waters with deeper layers, contributing to carbon transport as they migrate up at night and down by day.

Ecological role: Krill are a primary food source for baleen whales, seals, penguins, fish, squid, and seabirds. Their abundance and distribution influence the productivity of higher trophic levels and the overall structure of marine food webs.

Life cycle and biology: Krill reproduce by releasing eggs into the water; the eggs hatch into free-swimming nauplius larvae, followed by additional larval stages before reaching adulthood. Growth and maturation occur over months to years, varying by species. Some krill species can live several years.

Human use and management: Krill are harvested for animal feeds, aquaculture diets, and nutritional supplements such as krill oil. The Antarctic krill fishery is the most extensive and is managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), with quotas and conservation measures. Environmental concerns include climate change and ocean warming, which affect krill distribution and abundance and, in turn, their predators.