PRIMARY PRODUCTION, WATER COLUMN CHANGES, AND THE DEMISE OF A PHAEOCYSTIS BLOOM AT THE MARINE LIGHT-MIXED LAYERS SITE (59-DEGREES-N, 21-DEGREES-W) IN THE NORTHEAST ATLANTIC-OCEAN

Primary production in incubations is compared with daily changes in wa ter column oxygen inventories and particulate organic carbon (POC, and estimated from the beam attenuation coefficient) at a station in the northeast Atlantic (the Marine Light-Mixed Layers (MLML) site) in the spring of 1991. Drifters were followed over three periods. The first i s characterized by a bloom of Phaeocystis pouchetii. Prior to the seco nd and third deployments, there were storms that mixed the water colum n to >150 m over a period of 3 days, and consequently, the Phaeocystis bloom dissipated. After deployment of the third drifter, the water co lumn restratified, followed by high rates of primary production. All i ncubation experiments for carbon assimilation were greater than that c alculated from changes in oxygen or POC. The C-14 estimates agreed wit h the prediction of a bio-optical model for primary production. During the early days of the cruise, C-14 estimates were high, while water c olumn changes indicated negative net community production. In addition to the usual overestimate of net primary production by the C-14 estim ates, the differences are ascribed to mixing losses for the first part of the cruise, and to grazing losses after restratification.