Trans-Atlantic Study of Calanus: Latitudinal Differences in population dynamics: Mesocosm Studies

The hatched nauplii, from the two sites, will be raised in triplicates, in parallel mesocosm in the northern site during the first year, and in the southern site during the next year. The mesocosms will be run for the period from March to June/July. The Ho hypothesis will thus be that there is no differences in growth pattern, developmental and mortality schedules among the two geographical distinct populations of C. finmarchicus.

Cylindric mesocosms (50 m3) arranged around a platform nearby Karvika Research Station in Tromso, will be filled with FSW, and stocked with Calanus eggs, and a composite natural phytoplankton community, generated from spores in sediment samples form the area. After Day 30 additional stocks of flagellates will be added in order ensure a high quality diet for the intensive growth period during the copepodite stages (see Berggreen et al. 1988; Hansen et al. 1994).

Light conditions in the mesocosms will be set equal to 10 m of depth by maintaining a light filtering net on to of each mesocosm. The food conditions, temperature and salinity will be monitored daily. Parameters like temperature, chlorophyll, particulare organic carbon (Infra Red Gas Analyser), C/N, species composition of phytoplankton and microzooplankton will be monitored weekly.

Copepod samples will be obtained weekly by a plankton net (100 and 180 mm mesh), staged, weighed and stored for later lipid analysis. Sex differentiation, signs of diapause entry and the degree of moulting success to a second generation will be studied by gonad examination of the cohorts under study.