Dark-Season Survival Strategies of Coastal Zone Zooplankton in the Canadian Arctic

Abstract

ABSTRACT. For herbivorous zooplankton, surviving the arctic winter requires that sufficient energy be stored in summer to enable ten months or more of possible starvation. Energy and materials for reproduction may also be totally derived from stored lipid and bodily protein. The predominant storage products are wax esters, often visible as translucent droplets or a fusiform inclusion in the tissues. Lipid may constitute more than 50% of dry weight at the end of summer. Reproduction is synchronized with season and environmental conditions to enable offspring to exploit the brief period of intense primary production. So far as we know, fertilization occurs only once in the copepods studied here, which make up more than 98% of the total zooplankton by numbers, and males are short lived, but in one species (Calanus hyperboreus) females may survive into a second productive season, thereby storing sufficient reserves to spawn a second time. Several planktonic species, including larval invertebrates, start growth early by utilizing algae that develop on the under-ice surface several months before the pelagic phytoplankton bloom. The minimum water temperature (-13°C) is constant and much warmer than the atmosphere, so overwintering should be less stressful for aquatic species than for terrestrial forms. Additional adaptations used by zooplankton in winter include seeking deeper water to escape predation, reducing swimming costs by regulating buoyancy, and further lowering metabolic rates by limiting synthesis of enzymes and increasing the fraction of lipid used in respiration. Key words: copepods, zooplankton, phytoplankton, ice-algae, fast ice, lipid, overwintering, survival strategies, growth, reproduction &SUMfi. Afin de survivre it l'hiver arctique, le zooplancton herbivore doit stocker suffisamment d'knergie en kt6 pour faire face it 10 mois ou plus de famine potentielle. Il se peut aussi que l'knergie et les mat6riaux servant it la reproduction soient tirks en totalit6 des lipides emmagasinks et des protkines du tissu corporel. Les produits stockks les plus importants sont les esters cireux, souvent visibles sous la forme de gouttelettes translucides ou d'une inclusion fusiforme dans les tissus. Les lipides peuvent constituer plus de 50 p. cent du poids sec ii la fin de l'ktk. La reproduction est synchroni& avec les saisons et les conditions environnementales de façon B pennettre it la progkniture de profiter de la courte pkriode de production primaire intense. Dans l'ktat de nos connaissances actuelles, la fertilisation a lieu une seule fois chez les copkpodes qui nous intkressent, et qui constituent plus de 98 p. cent du zooplancton total sur le plan numerique. Les &les ont une dur& de vie relativement courte, mais dans l'esp&ce Calanus hyperboreus, les femelles peuvent vivre assez longtemps pour entrer dans une deuxihme phase de reproduction, stockant ainsi suffisamment de &serves pour frayer une seconde fois. Plusieurs e s p h s planctoniques, y compris des invertkbrks larvaires, commencent it croître de bonne...

Penetration of Pacific zooplankton into the western Arctic Ocean tracked with molecular population genetics

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Trophodynamics and seasonal cycle of the copepod Pseudocalanus acuspes in the Central Baltic Sea (Bornholm Basin): evidence from lipid composition

“…in Arctic regions (e.g. Pertsova 1981;McLaren et al 1989;Norrbin et al 1990;Norrbin 1991;Conover and Siferd 1993), with highest reproductive activities in spring, a successive accumulation of resting copepodite stages starting in early summer and a potential interposition of minor summer generations. This is supported by the corresponding lipid-storing strategies of P. acuspes.…”

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