Spatial distribution of digestive enzyme activities of Calanus finmarchicus and C.hyperboreus in Fram Strait/Greenland Sea

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Abstract
Digestive enzymes of copepodite V (CV) Calanus finmarchicus and C.hyperboreus from two different depths were compared during MIZEX 1984 (June/July) at stations in the ice and open water. CV of both species from 500–200 m showed reduced enzyme activity, indicating that they were in a resting stage. In moulting experiments at the end of June using CV from 100–0 m moulting was delayed and began only after 3 weeks in C.finmarchicus and after 3 months in C.hyperboreus. These results suggest that the deep CV populations are the seed of the new overwintering stock. In surface CV C.finmarchicus and C. hyperboreus enzyme activities were generally much higher than in deep CV. In neither species were enzyme activities correlated with chlorophyll concentrations. Activities in C.finmarchicus reflected overall phytoplankton distribution and were highest in the marginal ice zone, whereas they decreased under the ice except for polynya stations on the East Greenland Shelf. In surface C.hyperboreus digestive enzymes were not correlated with those of C.finmarchicus, pointing to different diets or regulatory mechanisms. Enzyme activity was lowest in the marginal ice zone and increased under the ice. High activities were found at polynya stations and other close pack ice. The utilization of ice algae by C.hyperboreus could explain these discrepancies in digestive enzyme activities of both species.