A direct estimate of Calanus finmarchicus biomass in the Norwegian Sea

No abstracts are to be cited without prior reference to the author.

A full life-cycle model for Calanus finmarchicus embedded in the physical-biological model system NORWCOM.E2E has been evaluated for the Norwegian Sea for the period 1995-2007. The inter annual zooplankton biomass variability was large, up to a factor of three for the period 1995-2007, and there was a negative trend toward the end of the time series. In the model, this negative trend is explained by bottom-up processes, and not related to increased predation pressure by fish. The mean annual production was found to be 22.6 million tons (MT) carbon (= 150 MT wet weight), with a maximum in 1997 (34.5 MT carbon) and a minimum in 2004 (13 MT carbon). The model showed a delay in the maximum of biomass and timing of the spring bloom compared to available observations, but for nearly all months for all years, the observations lay between the maximum and minimum values within a time- and space window of 10 days and ± 2 grid cells of the model. The sampling pattern was proved to be of great significance to the results in the model, producing biomass estimates for individual years varying by a factor of three.