Primary production was measured with the in situ 14C method of Steeman-Nielsen (Steemann-Nielsen, E. 1952. The use of radio-active carbon 14C for measuring organic production in the sea. Journal du Conseil International pour l'Exploration de la Mer. 18:3, 117-140). Samples were dispensed in 250 ml transparent polycarbonate bottles (three light and one dark for each depth); and each one was inoculated with 5 µCi 14-C-NaHCO3 and incubated at the collection depths for 2 hours. Fractionation was carried out by filtration through 0.2 µm, 1.2 µm and 3.0 µm polycarbonate Millipore filters. Filters were placed in scintillation vials, acidified with 0.5 N HCl and counted in a liquid scintillation counter.