Downward fluxes of particulate organic matter in coastal and oceanic areas off Chile: The role of the OMZ and functional groups of the plankton

Vertical fluxes of particles have been estimated during the last decade in coastal and oceanic systems off central-southern Chile. Free-drifting, cylindrical sediment traps have been deployed below the mixing layer from coastal areas, while automatic, cone-shaped sediment traps have been anchored in deep oceanic areas. Vertical fluxes toward 2300 m depth off Coquimbo were dominated by calcium carbonate (~70 mg m-2 d-1) instead of particulate organic carbon (POC ~7 mg m-2 d-1), where foraminifers (Neogloboquadrina pachyderma) and faecal pellets of Euphausia mucronata and Oikopleura spp, played important roles as vehicles for carbonate and carbon, respectively. In coastal upwelling systems, (i. e. Concepción), the dominant vertical flux was POC, mainly driven by euphausiids faecal strings and diatoms of the genera Thalassiosira, Chaetoceros and Skeletonema. Bacterial degradation of exported POC towards deeper layer of the ocean seems not to be significantly affected by the oxic versus hypoxic levels of dissolved oxygen characteristics of different water masses.