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

Digestive enzymes of copepodite V (CV) Calanus finmarchicusand C.hyperboreus from two different depths were compared duringMIZEX 1984 (June/July) at stations in the ice and open water.CV of both species from 500–200 m showed reduced enzymeactivity, indicating that they were in a resting stage. In moultingexperiments at the end of June using CV from 100–0 m moultingwas delayed and began only after 3 weeks in C.finmarchicus andafter 3 months in C.hyperboreus. These results suggest thatthe deep CV populations are the seed of the new overwinteringstock. In surface CV C.finmarchicus and C. hyperboreus enzymeactivities were generally much higher than in deep CV. In neitherspecies were enzyme activities correlated with chlorophyll concentrations.Activities in C.finmarchicus reflected overall phytoplanktondistribution and were highest in the marginal ice zone, whereasthey decreased under the ice except for polynya stations onthe East Greenland Shelf. In surface C.hyperboreus digestiveenzymes were not correlated with those of C.finmarchicus, pointingto different diets or regulatory mechanisms. Enzyme activitywas lowest in the marginal ice zone and increased under theice. High activities were found at polynya stations and otherclose pack ice. The utilization of ice algae by C.hyperboreuscould explain these discrepancies in digestive enzyme activitiesof both species.