Antarctic Ecosystem Environmental Contamination, Climate Change and Human Impact

In the Southern Ocean, the marginal ice zone is the nursery ground for E. superba (by far the dominant herbivore), which channels organic matter produced by nanoplankton and diatoms to cephalopods, fish, seabirds, seals and baleen whales. Krill has a number of unique characteristics – its life cycle closely matches seasonal cycles of primary productivity, adults are larger than other pelagic herbivorous crustaceans (up to 6.2 cm long), they have an unusually high metabolic rate and swimming speed, adapt to whatever food is available, and survive notwithstanding the low food supply in winter. A salient characteristic of euphausiids, especially of E. superba, is the formation of dense aggregations which vary considerably in area (from a few to 1,000 m2 and sometimes even many square kilometres), density (from 0.5 to several kg m–3) and depth (usually in the upper 100–200 m of the water column;). In view of these characteristics and its central position in the Antarctic pelagic food chain, krill has been of extreme interest to man since the onset of sealing in the 18th century. Despite intensive research, however, secondary productivity by krill and its total biomass in the Southern Ocean are still unknown. Estimates based on its annual consumption by predators (40, 100, 40, 25 and 15x106 tonnes (t) by reduced whale stocks, seals, squid, birds and fish respectively; Knox 1994) give an idea of annual krill production and of its role in transferring metals and POPs to higher levels of the Antarctic pelagic food chain