Life history traits of copepods in a changing Arctic : seasonal patterns in the physiology of Calanus glacialis

The Arctic experiences rapid environmental changes and to date, we cannot predict to what extent calanoid copepods can adapt to shifts in environmental conditions. On the Arctic shelf, the large species Calanus glacialis accumulates energy reserves in surface waters during the productive season and overwinters in diapause in deep waters. This thesis aims to investigate the physiology of C. glacialis in a comprehensive approach during activity and diapause in relation to environmental factors. This study revealed clear seasonal patterns in the physiology of C. glacialis. Enzymatic activities and extracellular pH (pHe) were high during the productive season, while catabolic activities were high and pHe low in winter. The usage of internal energy reserves was high in the end of overwintering. The timing of diapause is adjusted to the prevailing environmental conditions, which suggests that C. glacialis may be able to adjust to future climate driven changes in the environment

A year-round study on digestive enzymes in the Arctic copepod Calanus glacialis: implications for its capability to adjust to changing environmental conditions

The biomass of zooplankton communities in Arctic shelf regions is dominated by the calanoid copepod Calanus glacialis . This species spends the winter in deep water, and then, metabolic rates are low. In late winter, it migrates to the surface where the spring generation develops. To date, it is not fully understood what regulates the activity of the copepods and how it coincides with food availability. To fill this gap, we sampled C. glacialis, mainly copepodite stage V, in a high-Arctic fjord in monthly intervals for 1 year and determined proteinase and lipase/esterase activities in relation to food availability and depth distribution of the copepods. By substrate SDSPAGE(sodium dodecyl sulfate-polyacrylamide gel electrophoresis),we tackled changes in specific isoforms. We found a clear seasonal enzyme activity pattern. Activities in winter were reduced by at least 75 % as compared to spring. Substrate SDS-PAGE showed high heterogeneity of lipolytic enzymes, which could reflect extensive accumulation and metabolization of internal lipids. Only one band of proteolytic activity was found, and it intensified with the onset of the algal blooms. In late winter/spring, we sampled females and CIV, which also showed high digestive enzyme activities in surface water and low activities in deep water. High enzyme activities were related to the ice algal and phytoplankton blooms in spring. In autumn, the copepods descended although food was still available. C. glacialis could thus benefit from an early ice breakup and early algal blooms, but not from long-lasting phytoplankton availabilit

Saisonale Veränderungen in der Physiologie von Calanus glacialis in einer sich wandelnden Arktis

The Arctic experiences rapid environmental changes and to date, we cannot predict to what extent calanoid copepods can adapt to shifts in environmental conditions. On the Arctic shelf, the large species Calanus glacialis accumulates energy reserves in surface waters during the productive season and overwinters in diapause in deep waters. This thesis aims to investigate the physiology of C. glacialis in a comprehensive approach during activity and diapause in relation to environmental factors. This study revealed clear seasonal patterns in the physiology of C. glacialis. Enzymatic activities and extracellular pH (pHe) were high during the productive season, while catabolic activities were high and pHe low in winter. The usage of internal energy reserves was high in the end of overwintering. The timing of diapause is adjusted to the prevailing environmental conditions, which suggests that C. glacialis may be able to adjust to future climate driven changes in the environment