Spatial distribution (vertical and horizontal) and partitioning of dissolved and particulate nutrients (C, N and P) in the Campos Basin, Southern Brazil

•This study contains new information about the hydrochemistry of the Campos Basin, at depths reaching up to 2300 m.•Surface waters (biogenic layer) show oligotrophic conditions in contrast to enriched deep waters (biolytic layer).•Horizontal nutrients distribution showed higher values closer to continent.•N limitation for primary producer was found, but dissolved organic and particulate materials indicate strong P depletion.

Tropical oceans are characterized by low amounts of dissolved nutrients and high amounts of particulates in the biogenic layer and by increased dissolved nutrients and reduced particulates in the water masses of the biolytic layer. In this study, the hydrochemistry of the area included in the Campos Basin was evaluated at 72 sampling sites and six depths (surface, a second depth and the cores of deep water masses – up to 2300 m) during the summer and winter seasons of 2009. The vertical distribution of dissolved and particulate nutrients had patterns typical of permanently stratified tropical waters, and greater values were found on the continental shelf than on the slope, as expected. These results confirm that the continent is an important source of the materials found in the studied water masses. Additionally, the spatial variations observed are likely related to the South Atlantic Central Water (SACW) intrusion into the continental shelf in the Cabo Frio region and to eddies formation in the Cabo de São Tomé region, where higher concentrations of dissolved and particulate nutrients were found. Despite the N:P ratio indicates limitation of primary producers by inorganic nitrogen, the particulated and dissolved organic N:P indicate a strong depletion of P relative to N, suggesting preferential degradation of that.