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During three 'Polarstern' cruises to the ice-covered Greenland Sea (spring 1997, summer 1994, autumn 1995) studies on the under-ice habitat (morphology, hydrography, ice-algal biomass) and on the macrofaunal, autochthonous under-ice amphipods (species diversity, abundance) were carried out in order to describe environmental controls and seasonal patterns in this community. In spring, the ice underside was rather smooth and whitish, while in summer melting structures and sloughed-off ice-algal threads were observed, in autumn detritus clumps accumulated in depressions at the ice underside. Only in summer, a thin layer of warm (up to -0.6 [degrees] C) and less saline (as low as S = 6.3) water was found at the ice-water interface above Polar Water. Integrated ice-algal biomass was highest during autumn (2.6 mg chl a [m.sup.-2]) and lowest during summer (1.2 mg chl a [m.sup.-2]). Four species of under-ice amphipods occurred in spring and summer (Apherusa glacialis, Onisimus glacialis, O. nanseni, Gammarus wilkitzkii), but only the last species was observed at the ice underside in autumn. A. glacialis and G. wilkitzkii were equally abundant in spring; A. glacialis dominated in summer. The highest total abundance of amphipods occurred during summer (31.9 ind. [m.sup.-2]), compared to lower abundances in spring and autumn (5.3 and 1.1 ind. [m.sup.-2], respectively). A factor analysis revealed seasonal patterns in the data set, which mainly influences. A. glacialis, and species-specific relations between several environmental factors and the distribution of under-ice amphipods. Abundance of A. glacialis was closely related to the under-ice hydrography and ice-legal biomass, whereas the other amphipod species were more influenced by the under-ice morphology. It is therefore stated that the observed thinning of the Arctic sea ice and the resulting increased meltwater input and change in morphology of floes will have a profoundly adverse effect on the under-ice amphipods.

The rapid digestion rate in scavenging lysianassoid amphipods (Eurythenes gryllus) conforms to the batch reactor feeding model. Digestion rates varies with the nature of the bait. The rapid digestion and assimilation rates in E. gryllus allows additional feeding during unpredictable food supply. Digestion and assimilation rates with timed exposure to bait was studied at various depths in the Canada Basin of the Arctic Ocean and Sohm Abyssal Plains in the Atlantic Ocean.

The deep-sea amphipod Eurythenes gryllus, captured with and without baits in the Canada Basin of the Arctic Ocean, show extended meal intervals by gut size. Allometric regression of body length and wet weight, by estimating the meal sizes for instars segregated by body length, shows no sex-linked differences in the length-weight relationships. Size of meals was < 50% of empty-gut body weight for the 1-5th instars, more than 60% for mature males above 8th instar and > 75% for mature females above 14/15th instar. Ingested plus stored body lipid energy sustains 1-6 months of respiration in juveniles, 14-22 months in mature females and 9-14 months in mature males.