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Calanus feeding and reproduction in the Irminger (article in press)

Grazing rates and egg production rates of Calanus finmarchicus are reported from 60 open ocean stations spanning from the Irminger Sea to the Azores. Calanus finmarchicus is one of the most important components of the zooplankton in the North Atlantic, where it may constitute up 80% of the copepod biomass.

Over the large spatial scales, the egg production rates were positively related to ingestion rates and phytoplankton biomass, while negatively related to mean surface layer temperature and essentially independent of body size. Only a relatively small part of the variance could be explained by ingestion rate and chlorophyll a in the simple linear models (respectively, 34% and 30%). One reason might be that the estimates of ingestion rates only consider ingestion of phytoplankton food, and similarly the chlorophyll a measurements are only a measure of the quantity of potential phytoplankton food, and they do not take into account other food parameters which may influence egg production rates, such as food quality (particle size and species composition) and heterotrophic feeding (see Harris, 1996, for review).

To catch live animals in order to measure egg production rates of C. finmarchicus, separate vertical hauls (0–100 m) were made with a WP-2 net (0.25m2 mouth area, 200 micron mesh size, R.V. Ami Fridriksson) or a Juday net (2m sq. mouth area, 375 micron mesh size, R.V. G.O. Sars) fitted with a non-filtering cod-end. One female was added to a chamber and whenever possible 20 replicates were done per station. The egg production chambers were incubated for 24 h in the dark at ambient surface water temperatures.

Phytoplankton ingestion by female C. finmarchicus was estimated from gut fluorescence multiplied by the gut clearance rate (Mackas and Bohrer, 1976). The gut clearance rates were estimated from the temperature as k=0.0124 x e ^(0.07675 x T), where k is the gut clearance rate and T is temperature (average in 0–100 m) (Dam and Peterson, 1988; Bamstedt et al., 2000).

The samples were collected as part of the two campaigns within the MAR-ECO Project, and the data will be available through EUROCEANS Vital Rates Database for ecosystems end-to-end modeling.  

Reference:
A. Gislason, E. Gaard, H. Debes, T. Falkenhaug. Abundance, feeding and reproduction of Calanus finmarchicus in the Irminger Sea and on the northern Mid-Atlantic Ridge in June, Deep-Sea Research II, doi:10.1016/j.dsr2.2007.09.008

RELEVENT LINKS:
- EUR-OCEANS Vital Rates Database
-
Copepod datasets targeted and included in the Vital Rates Database
- Calanus populations spawn during Norwegian Sea spring bloom, doi:10.1016/j.dsr2.2007.08.027
- Spatial demography of Calanus finmarchicus in the Irmin... Progress In Oceanography
- MAR-ECO Project Website - http://www.mar-eco.no/

- EUROCEANS film ‘Calanus in Spitzberg’ (ESP, DE, ENG, FR)



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