Desarrollo de la Antártica

THE DEVELOPMENT OF LIVING RESOURCES OF ANTARCTIC: KRILL R. B. Thomson Antarctic Division, Department of Scientific and Industrial Research. Christ– church. New Zealand. The massive circulation of ocean waters around the Antarctic conti– nent is subjected to the cooling effects of melting ice causing upper layers to sink and the warmer water from considerable depths to rise in the form of upweIling on a gigantic scale. This rising water is especially rich in inorganic nutrients such as sulphate, magnesium, potassium, iron, manganese, nitrogen and phosphorus, plus traces uf ol1ganic substances so essential for growtlh. In sunlit areas of the ocean particularly as provided by the long summer in Antarctica, photosynrhesis provides a very high rate oi productivity for phytoplankton. Phytoplankton represents the first link in the primary food chain from inorganic to organic material. It is rich in protein and usualIy a substantial proportion of fatty mate– rial is presento Krill feed almost excIusively on phytoplankton, hence their abun– dance, aided by the comparatively small losses from primary pro– duction to adultJhood. Krill is represented by sorne ninety species and the most numerOilS is the Eup,hausia superba Dano, which in quantity is the most im– portant member of the zooplankton found in Antarctic waters. This small crustacean with an average length of 5.5 cm has two antennae, five pairs of hairy legs for swimming and for m.e as food strainers, and is red-orange on top and bright green underneath. It has seven pairs of Hght organs along its body which gIows when alarmed. Spawning, which starts in late November and continues throughout the austral summer is concentrated in waters near tlhe Antarctic con– vergence at around 50-55 degrees south. Following copulation the male swims off to die and the female having passed her ripened eggs into her fertilized pouch now sheds more than 11,000 eggs which sink to depths of up ro 2,000 metres where they drift south with the bot– tom current towards the Antarctic continent. In spring of the follo– wing year the young rise to within 50 metres of the surface and soon start to drift northwards where they rearo maturity at the age of two prior to spawning and dying. The krill travel noruh and south between the Antarctic conver-