Grazing, egg production, and biochemical evidence of differences in the life strategies of Calanus finmarchicus, C. glacialis and C. hyperboreus in Disko Bay, western Greenland

Abstract

This is the first high temporal-resolution study in Disko Bay covering population dynamics, grazing, reproduction, and biochemical composition of 3 dominating copepod species (Calanus finmarchicus, C. glacialis and C. hyperboreus) from late winter to midsummer in 2008. C. finmarchicus and C. glacialis ascended to the surface layer at the onset of the spring phytoplankton bloom, followed by C. hyperboreus 2 wk later. C. finmarchicus spawning occurred during the bloom and postbloom period, partially fueled by wax esters. C. glacialis commenced spawning before the bloom, yet it was greatly stimulated when food became available. However, feeding and reproduction was terminated after the main bloom despite the presence of food. In terms of feeding, this was also the strategy for C. hyperboreus. Between pre-bloom and post-bloom, C. finmarchicus showed an increase in carbon, nitrogen, and phospholipid content but a decrease in total lipid content. This was likely the result of protein synthesis, oocyte maturation, and spawning fueled by wax esters and by feeding. C. glacialis showed a similar pattern, although with an increasing total lipid content from pre-bloom to post-bloom, and an increasing wax ester and decreasing phospholipid content after reproduction was terminated. C. hyperboreus showed greatly increased content of carbon, nitrogen, and all lipid classes between the pre-and post-bloom periods. Hence, C. finmarchicus commenced feeding and spawning at the onset of the bloom and continued throughout the remaining study period. Both C. glacialis and C. hyperboreus females refueled their storage lipids (wax esters) during the bloom and post-bloom period, suggesting that they may spawn in an additional year. KEY WORDS:Calanus spp. · Distribution · Egg production · Fecal pellet production · Carbon conversion factors · Lipids · Spring bloom Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 429: [125][126][127][128][129][130][131][132][133][134][135][136][137][138][139][140][141][142][143][144] 2011 ice cover (Hansen et al. 2006) influences the timing of the diatom-dominated spring bloom ). Local ice melting and runoff from the glacier at Ilulissat creates a strong stratification and an outflow of low-saline water leaving the bay (Nielsen & Hansen 1995, Buch 2000. Future increase in temperature will reduce the extent of the ice cover, promote stratification, and probably make the timing and duration of the bloom more predictable. However, wind is also an important factor in determining the onset of the bloom. Lack of sea ice can, in situations with prevailing winds, destabilize the water column and hence postpone the bloom (Melle & Skjoldal 1998).Copepods of the genus Calanus are the primary herbivores in Arctic pelagic ecosystems during spring and summer (Hirche & Mumm 1992, Nielsen & Hansen 1995, Thibault et al. 1999. Calanus spp. is an important prey item for many species of fish, birds, and whales (Dale & Kaartvedt 2000, Kitaysky & Golubova 2000. C. finmar...

Oceanographic regime shift during 1997 in Disko Bay, Western Greenland

“…The three Calanus species differ in their phenology and in their nutritional value to larger consumers (Swalethorp et al 2011). Changes in their relative proportions will alter the efficiency of energy transfer through the marine food web.…”

“…Changes in the hydrography of the region, such as the timing of the ice break and the composition of bottom waters, will alter plankton phenology and have consequences for the rest of the food web in the bay; a trophic mismatch may result. The origin of the ''new'' bottom water and its higher temperature may favor the smallest, less nutritious, Calanus species, C. finmarchicus, at the expense of the larger, much more lipid rich, true arctic species, C. glacialis and C. hyperboreus (Swalethorp et al 2011). A trophic mismatch at this bottleneck of the lipid transfer at the base of the food web will result in lower food quality and less reproduction success for the copepods (Madsen et al 2001;Hansen et al 2003;Madsen et al 2008) and influence the feeding conditions and breeding success at higher trophic levels Karnovsky et al 2010).…”

“…Calanus spp. time their release from hibernation in bottom waters and ascend to forage upon the emerging phytoplankton , representing a perfect trophic match (Swalethorp et al 2011). The trigger for this ascent is currently unknown, and three Calanus species with different nutritional value and phenology are present in bottom waters awaiting the spring phytoplankton bloom (Swalethorp et al 2011).…”

“…time their release from hibernation in bottom waters and ascend to forage upon the emerging phytoplankton , representing a perfect trophic match (Swalethorp et al 2011). The trigger for this ascent is currently unknown, and three Calanus species with different nutritional value and phenology are present in bottom waters awaiting the spring phytoplankton bloom (Swalethorp et al 2011). Changes in the hydrography of the region, such as the timing of the ice break and the composition of bottom waters, will alter plankton phenology and have consequences for the rest of the food web in the bay; a trophic mismatch may result.…”

Copepod Life Strategy and Population Viability in Response to Prey Timing and Temperature: Testing a New Model across Latitude, Time, and the Size Spectrum

“…Calanoid copepods range in adult body size by more than two orders of magnitude, from <10 to >1000 µg C. Lipid content is likewise quite variable (Kattner and Hagen, 2009), even among congeneric species in a single environment (Swalethorp et al, 2011). Many but not all species enter a seasonal period of diapause in deep water, in which they do not feed and basal metabolism is reduced to ∼1/4 of what it is during active periods .…”