Geographical distribution and seasonal and diel changes in the diversity of calanoid copepods in the North Atlantic and North Sea

This paper examines spatial distribution in the pelagic diversity of calanoid copepods in the North Atlantic and the North Sea, taking into account changes at seasonal and diel scales. Based on 40 yr of sampling by the Continuous Plankton Recorder (CPR) survey, the diversity (as number of taxa) was estimated on a regular grid for each month and time of day. Principal components analysis (PCA) allowed spatial decomposition of diversity, detection of major seasonal and diel patterns, the location of regions where these occur, and finally the modelling of temporal changes at seasonal land diel scales. The results underline the importance of hydrography and topography in the regulation of pelagic diversity, By considering these abiotic factors and the characteristics of seasonal and diel changes in diversity, a partition of the North Atlantic and the North Sea is proposed. This demonstrates the importance of the warm North Atlantic Current and the continental slope currents and undercurrents along the European Continental Shelf. It is suggested that modification in the path or intensity of these currents could imply marked changes in the structure and functioning of ecosystems west and north of the British Isles.