METABOLISM OF ANTARCTIC MICRONEKTONIC CRUSTACEA AS A FUNCTION OF DEPTH OF OCCURRENCE AND SEASON

Oxygen comsumption rates were determined on 21 species of crustaceans typical of the Southern Ocean micronektonic crustacean assemblage duri ng spring (November), fall (March), and winter (June-August). Specimen s were collected in the Scotia-Weddell Sea region in the vicinity of 6 0-degrees-S, 40-degrees-W in the upper 1000 m of the water column. Res piration (y, mul O2mg-1 wet mass h-1) declined with depth of occurrenc e (x, m) according to the equation y = 0.125 x-0.172 +/- 0.052 (p < 0. 05) despite the isothermal character of the water column, suggesting t hat lower metabolic rates are a temperature-independent adaptation to life in the deep sea. Three species of Crustacea showed a lowered meta bolism during the winter season: the krill Euphausia superba and the 2 hyperiid amphipods Cyllopus lucasii and Vibilia stebbingi. Critical o xygen partial pressure (Pc) varied between 29 and 52 mm Hg, well below the lowest PO2 found in the water column. It is suggested that the lo ng nights of the Antarctic winter decrease the effectiveness of visual predation in the epipelagic zone, allowing lowered metabolic rates to be a viable overwintering strategy for some species.