Physical oceanography, inorganic nutrients, dissolved and particulate organic carbon and nitrogen during FLUXES-1 cruise to the Cape Verde Frontal Zone in 2017

The Cape Verde Frontal Zone (CVFZ) is a highly dynamic region located in the southern boundary of the Canary Current Eastern Boundary Upwelling Ecosystem. Due to the interaction of the Cape Verde Front with the Mauritanian coastal upwelling, the area features large vertical and horizontal export fluxes of organic matter. Full-depth profiles were recorded during FLUXES I cruise, with four consecutive transects defining a box embracing the giant filament of Cape Blanc and the Cape Verde front. Fifteen levels were sampled in medium and long stations (down to 4000 dbar) and 10 levels in short stations (down to 2000 dbar) where inorganic nutrients (NO3, NO2, Si(OH)4 and PO4), dissolved organic carbon/total dissolved nitrogen (DOC/TDN), and suspended particulate organic carbon and nitrogen (POC and PON) were sampled. Micromolar concentrations of nutrient salts were determined simultaneously by segmented flow analysis in an Alliance Futura autoanalyser. The determination of suspended POC and PON was carried out by high temperature catalytic oxidation at 900 °C in a Perkin Elmer 2400 elemental analyser. DOC and TDN were analysed by high temperature catalytic oxidation at 680 °C with a Shimadzu TOC-V analyser connected in line with a TNM1 measuring unit. Alongside with water samples conductivity, temperature and depth (CTD; SeaBird SBE911 plus), and dissolved oxygen (SeaBird SBE43), fluorescence of chlorophyll (SeaPoint SCF), and turbidity (SeaPoint STM) were measured. CTD conductivity was calibrated with water samples taken from the rosette and analysed on board with a Guildline 8410-A Portasal salinometer. Samples for dissolved oxygen (O2) determination were analysed on board by the Winkler potentiometric method. The chlorophyll (Chl) fluorescence sensor was calibrated with water samples taken at 4 depths in the photic layer which were estimated fluorometrically by means of a Turner Designs bench fluorometer 10-AU.