High-latitude marine ecosystems are characterized by substantial climate-driven environmental variability that defines the phenologies of the ecosystem. Large calanoid copepods of the genera Calanus and Neocalanus dominate the biomass but smaller calanoid and cyclopoid copepods are dominant numerically. Species of Calanus and Neocalanus have life cycles with strong seasonality, ranging from multiple generations per year for species such as Calanus finmarchicus in the southern part of their range to multi-annual life cycles for Arctic species such as Calanus glacialis and Calanus hyperboreus. These large calanoid copepods use ice algae, phytoplankton, and microzooplankton to reproduce and grow during spring and summer, storing lipid reserves to survive the winter often at depth.
Other smaller micro- and meso- zooplankton similarly use spring production but remain active for longer periods. The small polar cod still largely dominate the pelagic fish assemblage of subarctic and Arctic seas in many areas, but other forage fish such as capelin and sand lance also are important.
The large copepods form essential foodweb links between phytoplankton, microzooplankton, and planktivorous fish, seabirds and mammals such as the large baleen whales. These upper trophic level consumers use the seasonal pulse of zooplankton production and occurrence to feed, grow, and store energy for reproduction and wintering. Many of them have pronounced seasonal migrations in high latitude ecosystems in which they come to feed during the productive summer season on the large zooplankton including calanoid copepods, krill and amphipods. Polar cod is major prey for seabirds, seals, and toothed whales and may influence up to 75% of the energy transfer between the zooplankton and higher trophic levels in some areas.
Ongoing climate change will have a significant impact on environmental seasonality and associated plankton phenology, production, and distribution that can cascade to the upper trophic level consumers. Many studies have already documented northward shifts in distributions or abundances of plankton, fish and other groups in response to warming in northern high-latitude ecosystems.
in this theme session, presentations are invited on how climate variability and change influence the distribution of zooplankton and fish, and the roles of both these groups in their wider high-latitude ecosystems. Topics encouraged include:
Photo: R.R. Hopcroft and Cornelia Jaspers