Large-scale patterns of diel vertical migration in the North Atlantic

Samples historically collected and analysed by the Continuous Plankton Recorder (CPR) survey in the North Atlantic were used to examine large-scale spatial patterns in both the normal diel vertical migration (normal DVM) behaviour and the mean body size within epi-pelagic copepod communities. Normal DVM was most marked in the northwest Atlantic and less marked in the northeast Atlantic and in shallow coastal areas such as around the U.K. and on the Grand Banks of Newfoundland. These patterns of normal DVM were strongly correlated with patterns of mean body size, with normal DVM being more marked in those areas where larger species predominated. In both the northwest and northeast Atlantic, marked seasonal changes occurred in the migrating biomass. In the northwest Atlantic, Euchaeta norvegica and Calanus finmarchicus were the most important contributors to the total migrating biomass, while in the northeast Atlantic the most important contributors were E. norvegica, Metridia lucens and Pleuromamma robusta.