Primary productivity and sizes of pools of organic carbon in the mixed layer of the ocean

We estimated primary productivity and distributions of carbon in the phytoplankton, micro-zooplankton, and suspended and dissolved matter in various areas of the World Ocean to increase our information about the organic carbon cycle in the surface layer of the sea. Primary productivity ranged from about 0.1 gC m^–2 day^–1 in the Gulf of Mexico to 9 gC m^–2 day^–1 in nutrient-rich water off Peru. Phytoplankton carbon ranged from less than 10 g/l in the former to 750 g/l in the latter and in nutrient-rich water off southwest Africa. Micro-zooplankton carbon usually was less than 50 g/l in all waters, and was dominated by ciliates, copepodids, and copepod nauplii in all areas. Concentrations of particulate carbon ranged from 12 g/l off the east coast of South America to 850 g/l off southwest Africa. Concentrations of dissolved organic carbon varied between 0.5 and 1.5 mg/l in all areas except off Peru, where maximum values of 4.5 mg/l were observed. Turnover rates of carbon by small standing crops of micro-flagellates (1 to 5 longest dimension) and dinoflagellates in nutrient-poor waters were lower than those by large standing crops of diatoms and micro-flagellates in nutrient-rich waters. Concentrations of phytoplankton usually accounted for 20 to 55% and micro-zooplankton for 2 to 30% of the particulate carbon in the surface layer of the sea. Concentrations of dissolved organic carbon were not related to concentrations of particulate carbon in most waters except off Peru, where they appear to be directly related.