Dynamics of the lipid content and biomass of Calanus finmarchicus (copepodite V) in a Norwegian Fjord.

Calanus finmarchicus is the dominant zooplankton species in the North Atlantic. This zooplankton is also of interest for commercial harvesting due to its high abundance and biochemical contents. In the present study, copepodite stage V of C. finmarchicus was sampled at different depths from January to June in 2009, 2010 and 2011 in the Trondheimsfjord (63°29'N 10°18'E). The fatty acid composition was analyzed in individual copepods and in the seston. It was found that the fatty acid profile of copepods was related to the fatty acid profile of potential food sources. This study indicates that the onset of vertical migration of stage V, which was observed in May, has a strong link to the production of phytoplankton and lipid accumulation in C. finmarchicus. The content of 14:0 and 16:0 fatty acids in the specimens did not increase from February to May in surface waters. This suggests that these fatty acids in the diet were used as precursors for the biosynthesis of 20:1n-9 and 22:1n-11 fatty acids and fatty alcohols. A potential harvesting season of C. finmarchicus could be when the species is abundant in surface waters; the content of n-3 fatty acids will vary throughout this season. The peak abundance of C. finmarchicus in the spring varied substantially between the years studied.

Properties of Calanus finmarchicus biomass during frozen storage after heat inactivation of autolytic enzymes.

Calanus finmarchicus is a marine zooplankton of interest for the aquaculture industry, as well as for nutraceuticals and the cosmetic industry. The chemical composition of C. finmarchicus rapidly changes postmortem due to autolytic processes; in particular phospholipids rapidly degrade to give free fatty acids. The aim of this study was to inactivate autolytic enzymes in C. finmarchicus by applying heat (72°C, 5-30min) through mixing with boiling, fresh water, and further to explore the effects of heat (70°C, 15min) combined with long time storage (-20°C, 12months) of treated and untreated material. Heat treatment (5min) inactivated all tested enzymes and maintained the initial amount of phospholipids, total lipids and crude protein. Storage of untreated material led to complete degradation of all phospholipids, whereas heat treatment resulted in a stable product containing the initial amount of phospholipids and astaxanthin.