INVESTIGATIONS IN THE EUPHOTIC ZONE OF THE TROPICAL NORTH-ATLANTIC - PROGRAM AND HYDROGRAPHY DURING THE NECTAR CRUISES

In 1977 a multidisciplinary study of the euphotic zone of permanently stratified waters was started by the Netherlands Institute for Sea Research. The programme, North Equatorial Current Trans Atlantic Research (NECTAR), involves investigations of the carbon budget in the upper 300 m of the oligotrophic Atlantic Ocean. The sampling programme at 6 driftstations of 24 to 48 hours along 20° N in the autumns of 1977 and 1978 is described. Particular attention was paid to the measurement of primary production with the 14C method as compared with diurnal variations in biologically affected parameters. Another main scientific objective was the significance of vertical profiles of irradiance, O2, POC, DOC, CO2, nutrients, ETS, ATP, bacterioplankton, chlorophyll and zooplankton. The hydrographic data of the NECTAR cruises are presented and compared with the general hydrography of the area described in recent literature. Discrepancies from the latter comprise a more southerly extension of North Atlantic Water in the upper 100 m and a pronounced influence of South Atlantic Central Water in subsurface waters down to 500 m between 23° W and 32° W. © 1979.