The effect of upwelling filaments and island-induced eddies on indices of feeding, respiration and growth in copepods

Vertical (0–200 m) and horizontal distribution of two calanoid copepod species, Scolecithrix danae and Scottocalanus sp., were studied in relation to physical structures in the transition zone off Northwest Africa during the summer of 1999. Zooplankton biomass and indices of feeding (gut fluorescence, GF), respiration (electron transfer system activity, ETS) and structural growth (aminoacyl-tRNA synthetases activity, AARS) were assessed across (1) upwelling filaments, (2) a cyclonic eddy and (3) three anticyclonic island-induced eddies in the waters south of the Canary Islands. Hydrography was an important influence on the populations studied, enhancing their development by advecting chlorophyll enriched cold waters towards the open ocean. S. danae had highest rates in anticyclonic eddies at the limit of the upwelled waters. However, GF was more than two-fold higher inside the filaments than in the surrounding waters. Scottocalanus sp. occurred only inside the upwelling area and within upwelling filaments that advected them toward oceanic waters. The frontal zone south of Gran Canaria showed the highest AARS activities for both species.