Phytoplankton pigments and biomass in the northeastern Sea of Okhotsk from March 23 to April 14, 1998

Studies were carried out in the northeastern Sea of Okhotsk, in the zone of interaction of the West Kamchatka and Compensating Currents at the beginning of spring seasonal succession from March 23 to April 14,1998. Samples for analysis of pigmentary and species compositions of phytoplankton were taken from the sea surface layer, depth 0.5 m. To reduce influence of micropatchiness on phytoplankon distribution at each station subsamples 0.7-1 l were collected every 50-100 m. These subsamples were used to make integral samples 4.5-8.0 l. Phytoplankton biomass and concentration of chlorophyll a varied from 18.7 to 490.9 mg/m**3 and from 0.129 to 2.422 mg/m**3, respectively. Total concentration of phytoplankton pigments varied from 0.622 to 6.679 mg/m**3. In samples studied 51 species of microalgae from 5 orders were found. In terms of the number of species, Bacillariophyta (31 species) and Dinophyta (15 species) prevailed. Diatomaceous algae make up more than 80% of the total phytoplankton biomass in waters of the Compensating Current, from 50 to 80% in intermediate waters, and less than 50% in waters of the West Kamchatka Current. Phytoplankton populations consisting primarily of diatoms were characterized by very low chlorophyll a to biomass ratio (0.1 %). It is three times lower than the ratio observed in phytoplankton populations that were close by species composition and size composition in this area in the late April-early May 1996.