Spatial and temporal variability of the phytoplankton community structure in the North Water Polynya, investigated using pigment biomarkers

Phytoplankton taxonomic pigments were measured by high-performance liquid chromatography (HPLC) during a 3-month survey (April-June 1998) in the North Water (NOW) Polynya (Canadian Arctic) to investigate changes in phytoplankton biomass and composition and the physical-chemical factors that influence these changes. A phytoplankton bloom with high chlorophyll a (Chl a) concentrations (up to 17.45 mg(.)m(-3) at 15 m) occurred in mid-May along the Greenland coast in the southeastern part of the NOW Polynya. The initiation of the phytoplankton bloom was linked to shallow mixed-layer depths. The contribution of the different phytoplankton groups to Chl a inferred using a factorization program (CHEMTAX) indicated that the bloom was diatom-dominated (maximum 94% diatoms). The phytoplankton community structure was influenced by the water mass characteristics and the surface circulation pattern. Autotrophic flagellates dominated in April and May along the Canadian coast, where cold Arctic waters with relatively deep mixed layers were found. In contrast, diatoms dominated in May along the Greenland coast in warmer water masses of Atlantic origin and during June in the whole polynya, except in the southernmost part.