Calanus finmarchicus along the northern Mid-Atlantic Ridge: variation in fatty acid and alcohol profiles and stable isotope values, 15N and 13C
Fatty acid and alcohol profiles and stable nitrogen and carbon isotope values, δ 15 N and δ 13 C, of Calanus finmarchicus CV were studied in June 2004 to estimate their trophic status along the northern Mid-Atlantic Ridge i.e. the Reykjanes Ridge (RR), extending from Iceland in the north to the productive region of the Sub-Polar Front (SPF) in the south. Two main groups of stations were defined in the study area based on fatty acid (FA) and fatty alcohol compositions, the stations in the RR area constituted one group and the stations in the frontal area constituted another. The sum of relative amounts of the dietary FAs was significantly higher in the RR area than in the frontal area. Conversely, the long-chained FAs, 20:1 and 22:1, were found in significantly lower relative amounts in the RR area than in the frontal area, thus indicating later ascent of the animals in the frontal area. Further support of this is provided by the fatty alcohols ratio 20:1/22:1 which differed significantly between the two areas. The δ 15 N values were significantly higher in the frontal area compared to the RR area indicating higher trophic position and/or different pelagic-POM baseline in these areas.