Proximate composition and overwintering strategies of Antarctic micronektonic Crustacea

Abstract

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...

Acoustic insights into the zooplankton dynamics of the eastern Weddell Sea

“…In order to survive the dark season when photosynthetic primary production is insufficient to balance the metabolic losses of heterotrophs, polar zooplankton have developed several overwintering strategies. These strategies, comprising inter alia opportunistic feeding on varying sources, combustion of body substance and degrowth, and dormancy or diapause, can differ between groups, species and even developmental stages (Clarke and Peck, 1991;Bathmann et al, 1993;Torres et al, 1994;Hagen and Schnack-Schiel, 1996;Meyer, 2012;Auerswald et al, 2015). Many crustaceans for instance, in particular the polar species, are able to store energy in the form of lipid reserves.…”

Diet variability and reproductive performance of macaroni penguins Eudyptes chrysolophus at Bird Island, South Georgia

“…The energy content of Euphausia superba was calculated using a mean value for males and females (Clarke 1980). A single energy value was used for each of: euphausiids other than E. superba, based on Thysanoessa macura (Torres et al 1994); amphipods, based on Themisto gaudichaudii (Ciancio et al 2007); and cephalopods, based on a mean value for muscular squid (Clarke et al 1985) ( Table 2). The energy content of fish was calculated based on the species composition for each year, with energy values for key species given in Table 2.…”

Lipids as trophic markers in Antarctic krill. II. Lipid composition of the body and digestive gland of Euphausia superba in controlled conditions

“…In fact, numerous factors, including sex and maturity stages, have been shown to strongly affect the lipid class and FA composition (Clarke 1980, Kolokowska 1991, Pond et al 1995, Virtue et al 1996. These effects might predominate over the potential of diet to influence lipid content and composition, and this could explain why only small or no differences have been observed between krill exposed to different diets in the field (Torres et al 1994, Cripps & Hill 1998, or fed on different controlled regimes in the laboratory . In particular, the essential role of long chain PUFA, such as EPA and DHA, in major biological processes causes them to be highly conserved by marine organisms (Sargent & Henderson 1995) and may interfere with their potential suitability as dietary markers (Hagen et al 2001.…”