Oceanic forcing of the dynamics at the continental margin west of Ireland and the effect on zooplankton distributions

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Historical records from the Continuous Plankton Recorder survey in the Northeast Atlantic span from the 1960s to the present day. The Continuous Plankton Recorder is towed behind ships of opportunity (usually merchant vessels) and the samples are analysed and collated by the Sir AlisterHardy Foundation of Ocean Science in Plymouth, UK. This study has analysed these data for trends in zooplankton abundance and examined the effects of the regional oceanographic forcings upon significant keystone species. The hydrographic conditions to the west of Ireland have been studied, in particular the North Atlantic Current (NAC) and the Shelf Edge Current and the seasonal and interannual variations in their flows. These flows are strongly correlated with the North Atlantic Oscillation (NAO) and efforts are made to elucidate these links through direct measurements of the currentfield. A number of direct and indirect measurements were used to observe these variations: Sea Surface Height from satellite altimetry; direct current meter measurements; remote sensed sea surface temperature and wind stress curl data to measure the effect of the NAO on the NAC through variations in storminess. Through the direct measurement of these oceanographic variables and the abundances of key indicator species and assemblages, this study aims to show the effect of climate change upon the zooplankton to the west of Ireland, an area of great importance, both for oceanography with a branch of the thermohaline circulation passing through the region and for fisheries with a number of large, economically important nurseries in the area.