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The ability of Tween 20 and whey protein isolate (WPI) to influence lipid oxidation was investigated by evaluating the effects of emulsifier concentration and physical location on iron-catalyzed oxidation of emulsified Menhaden oil. Addition of Tween 20 or WPI to the aqueous phase of a 0.5 wt% Tween 20 stabilized emulsion increased lipid oxidation as determined by both thiobarbituric acid reactive substances (TBARS) and lipid peroxides. Tween 20 (2.0 wt%) and WPI (0.05-1.0 wt%) combinations inhibited TBARS formation 23-60%. Oxidation of a WPI-stabilized emulsion decreased with decreasing pH (3-7) but in a Tween 20 stabilized emulsion oxidation increased with decreasing pH. The low oxidation rate for the WPIstabilized emulsion at pH 3 was increased when Tween 20 displaced WPI from the droplet interface. Results indicate that the oxidative stability of emulsifed Menhaden oil could be increased by controlling emulsifier type, location and concentration.

Proximate (protein, lipid, carbohydrate and chitin) and elemental (carbon and nitrogen) composition were determined for 18 species of Antarctic micronektonic Crustacea, representing the majority of species found in the Antarctic water column. Individuals used in the analyses were captured during fall and winter; for 8 species data were collected in both seasons. Seven of the 8 species showed some evidence that combustion of body stores were an aid to surviving the winter months; comparison with data from other investigators suggests that most of the species inhabiting shallow and mid-depths exhibit some degree of combustion of body stores during winter. Three types of overwintering stratey e s are proposed for Antarctic zooplankton and micronekton. Type 1, exhibited by some calanoid copepods, is characterized by accumulation of large lipid deposits and a true dormancy, or diapause, during winter. Type 2, exhibited by euphausiids and hyperiid amphipods, is characterized by a marked reduction in metabolic rate, combustion of body substance, opportunistic feeding, but no true dormancy. Type 3, 'business as usual' is exhibited by decapods and gammarid amphipods; it is characterized by an absence of a winter reduction in metabolic rate, combustion of body stores in some species but a lack of combustion or accumulation of energy in others, and opportunistic feeding. Overwintering scenarios computed for Euphausia superba suggest that the impact of the winter season is most severe in the smaller size classes.KEY WORDS: Proximate composition . Antarctic . Pelagic Crustacea . Overwinter INTRODUCTIONThe micronektonic crustacean assemblage of the Antarctic pelagial is a unique blend of cosmopolitan deep-living species and high-latitude endemics (Nagata 1986, Iwasaki & Nemoto 1987, Lancraft et al. 1989. In the Atlantic sector, most of the cosmopolitan species disappear from the water column at the Weddell-Scotia confluence, a physical boundary that defines the northern limit of winter sea ice and separates the low and high Antarctic ecosystems (Lancraft et al. 1989). Species living south of the confluence must contend with the seasonal advance and retreat of pack ice and its influence on water column irradiance; all species must deal with highly pulsed seasonal production and uniformly cold temperatures in the upper 1000 m of the water column. In the Weddell Sea region primary production varies from 560 mg C m-2 d-l during spring in the vicinity of the ice edge at 60°S, 40" W (Smith & Sakshaug 1990) to 25 mg C m-2 d-' during winter (June-August) in the same region (W. 0 .Extreme seasonality in primary production has its most severe impact on herbivorous Crustacea and, as a consequence, shapes their Me histories. Many species of the best-studied pelagic Crustacea, the calanoid copepods, accumulate large quantities of lipid during the productive season and enter a state of true dormancy, or diapause, during the non-productive season, resuming normal feeding activity at the onset of phytoplankton growth (Sargent & Hen...

Oxygen consun~ption rates were determined on 21 species of crustaceans typical of the Southern Ocean micronektonic crustacean assemblage during spring (November), fall (March), and winter (June-August). Specimens were collected in the Scotia-Weddell Sea region in the vicinity of 60" S, 40" W in the upper 1000 m of the water column. Respiration (y, p1 O2 m g ' wet mass h-') declined with depth of occurrence ( X , m) according to the equation y = 0.125 x -~-~~~'~~~~ (p < 0.05) despite the isothermal character of the water column, suggesting that lower metabolic rates are a temperatureindependent adaptation to life in the deep sea. Three species of Crustacea showed a lowered metabolism during the winter season: the krill Euphausia superba and the 2 hyperiid amphipods Cyllopus lucasii and Vibilia stebbingi. Critical oxygen partial pressure (Pc) varied between 29 and 52 mm Hg, well below the lowest PO, found in the water column. It is suggested that the long 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.

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