Temporal and spatial patterns in the surface-water biomass of phytoplankton in the North Water

Temperature, salinity, and in vivo fluorescence of surface seawater in the North Water were recorded continuously, using a CTD+fluorometer, in August 1997, April–July 1998 and August–October 1999. The phytoplankton bloom started in the polynya on the Greenland side in April. In April and May, high phytoplankton biomass coincided with saline water on the Greenland side, while biomass was low on the Ellesmere Island (Canada) side where a deep mixed layer prevailed. High phytoplankton biomass extended over the whole polynya in June, when surface temperature increased due to solar heating and salinity decreased due to freshwater input. The initiation of the bloom was about 2 months earlier on the Greenland than the Canadian side. In July and August, phytoplankton biomass became low in the southern survey area, indicating that the phytoplankton bloom had ended. In September, relatively saline and warm water occurred in the southeastern part of the study area where, consistent with the change in water properties, high concentrations of chlorophyll a were observed again. These results imply that both the earlier start of the algal bloom in spring and the eventual increase in phytoplankton biomass in summer contribute to the high annual primary production along the Greenland side, thus influencing the structure and biological productivity of the entire North Water ecosystem.