Guinea Upwelling Tracer Release Experiment - Cruise No. M80/2 - November 26 - December 22, 2009 - Mindelo (Cape Verde) - Dakar (Senegal) (English)

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METEOR cruise M80/2 conducted chemical, physical and biological oceanographic research in the northeastern tropical Atlantic in order to obtain a better understanding of the variability of tropical oxygen minimum zones within the framework of the SFB 754 (Climate - Biogeochemical interactions in the tropical Oceans). The main goal of the leg M80/2 was to resurvey the purposeful tracer release patch about 1.5 years after its injection in April 2008. Secondary objectives include 1) Water mass variability and oxygen/nutrient distributions in the survey region by transient tracer and oxygen data. 2) A trace metal program focused on understanding the controls on the solubility and cycling of aluminum, iron and titanium and the speciation of dissolved cobalt. 3) A molecular genetic approach was used to investigate the contribution of diazotrophs to the oceanic nitrogen cycle and in particular the fixation of molecular nitrogen. 4) The depth distribution of NH2OH was measured at selected stations, and ten incubation experiments on N2O/NH2OH production/consumption mechanisms were conducted. 5) One program focused on the nitrification and nutrient regeneration in the water column, i.e. the cycling of N-nutrients as mediated by microbes. Experiments were carried to quantify rates of remineralisation/respiration by heterotrophic archaea/bacteria by means of 13C/15N/18O-tracer incubations. 6) One project focused on the pelagic community response to changes in nutrient stoichiometry by conducting two mesocosm growth experiments and by conducting station work along transects.