A GONYAULAX-DIGITALE RED WATER BLOOM IN THE BEDFORD BASIN, NOVA-SCOTIA, CANADA

A red water bloom, dominated by the dinoflagellate Gonyaulax digitale (4.25 x 10(5) cells L-1, 43% of total phytoplankton cell concentration) was recorded for the first time from the Canadian Atlantic coasts. The magnitude of this bloom (42 mug Chl a L-1) was higher than that of the major spring bloom in these waters. The dinoflagellate in the bloom was succeeded by Skeletonema costatum and a naviculoid diatom. Photosynthetic rates of the red water population were low (alpha(B): 1.87 x 10(-3) to 5.02 x 10(-3) [mug C (mug Chl a)-1 h-1 (mumol m-2 s-1)], P(m)B: < 3.5 [mug C (mug Chl a)-1 h-1] for the dinoflagellate, initially dominant in the phytoplankton assemblage, compared to those of the diatom that replaced it in the later phase. Photosynthetic carbon assimilation rates (P(m)B) and alpha(B) of the phytoplankton assemblage were negatively correlated with the proportion of G. digitale.