Lipids and life strategy of Arctic Calanus

Abstract

The three Arctic Calanus species, C. finmarchicus, C. glacialis and C. hyperboreus, are the most important herbivores in Arctic seas in terms of species biomass. They play a key role in the lipid-based energy flux in the Arctic, converting low-energy carbohydrates and proteins in ice algae and phytoplankton into high-energy wax esters. In this paper we review the overwintering strategy, seasonal migration, stage development, life span, feeding strategy, body size, lipid biochemistry and the geographic distribution of the three dominant Calanus species in Arctic waters. We then relate these parameters to other biotic and abiotic factors, such as the timing of the Arctic phytoplankton and ice algae bloom, sea ice cover and climate variability. We also present new data on fatty acid and fatty alcohol content in the three Calanus species in addition to reviewing the available literature on these topics. These data are analysed for species homogeneity and geographic grouping. The dominance of diatom fatty acid trophic markers in the lipids of Calanus underpins the importance of diatoms as Arctic primary producers, even if dinoflagellates and Phaeocystis pouchetii can also be important food sources for the calanoid copepods. We conclude that the Arctic Calanus species are herbivores, engineered to feed on the Arctic bloom, and that the timing of the bloom is the most important factor in determining the life strategies of the individual species.

Lipid and fatty acid/alcohol compositions of the subarctic copepods Neocalanus cristatus and Eucalanus bungii from various depths in the Oyashio region, western North Pacific

“…Saito and Kotani (2000) reported even a predominance of this 20:1(n − 11) isomer as alcohol moiety in both N. cristatus and N. flemingeri. In contrast to these Pacific species, the 20:1(n−11) isomer is almost absent from the North Atlantic, Arctic and Antarctic herbivorous Calanus and Calanoides species, instead the 20:1(n − 9) is a major alcohol (Kattner et al, 1994;Falk-Petersen et al, 2009). In these species the 20:1(n−11) isomer is almost completely elongated to the 22:1(n−11) fatty acid and then reduced to the corresponding alcohol .…”

“…The wax ester storage is especially pronounced in herbivorous zooplankton and related to the fatty acid and alcohol compositions, i.e., the biosynthesis and accumulation of the 20:1 and 22:1 moieties exclusively produced by herbivorous calanoid copepods (Kattner and Krause, 1989;Kattner and Hagen, 1995;Falk-Petersen et al, 2009). The energy content of the stored lipid is maximized by increasing the chain length of the constituent fatty acids and alcohols (Albers et al, 1996;Scott et al, 2002).…”

Composition of wax esters is linked to diapause behavior of Calanus finmarchicus in a sea loch environment

“…Fatty acids derived from diatoms, and specifically 20:5(n-3), are major components of wax esters of highlatitude calanoid copepods (Falk-Petersen et al 2009;Pond et al in press) and were also dominant in the lipids of C. finmarchicus from Loch Etive. A recent study of lateautumn populations of C. finmarchicus collected from the Newfoundland shelf and slope waters has similarly established that copepods diapausing at greater depths contain more lipid, with higher amounts of diatom biomarkers than those at shallower depths (Pepin et al 2011).…”

Sensitivity to ocean acidification parallels natural pCO 2 gradients experienced by Arctic copepods under winter sea ice

“…7). Due to their large body size, high lipid content, and dominant biomass, calanoid copepods, in particular, are an important high-quality food source for many pelagic Arctic fish (8,9); hence, their responses to OA have important implications for Arctic ecosystems. Copepods have a mainly chitinous exoskeleton, so they are not as vulnerable to calcium carbonate undersaturation as other calcifying Arctic organisms, such as pteropods (10).…”