Biogeochemical characteristics of coastal waters adjacent to small river–mangrove systems, East Brazil

Abstract

This study addresses the composition of biogenic matter and the metabolic activity of coastal waters of the eastern Brazilian shelf, bordered by small river–mangrove systems. Oceanic Brazil Current waters induce oligotrophic and near to homogeneous conditions of chemical constituents along the inner shelf. The impact of small river–mangrove systems upon coastal waters is minor and of local nature. Bottom topography, coral reef habitats, and local upwelling also induce minor local spatial variability of dissolved inorganic and organic nutrients and O₂ and CO₂ saturation levels in the coastal waters. Metabolic activity during the daylight period, inferred from O₂ and CO₂ saturation levels, varied from slightly autotrophic to heterotrophic.