Grazing of phytoplankton by microzooplankton in the Barents Sea during early summer

Phytoplankton growth rates and grazing losses to microzooplankton were determined in surface waters of the central Barents Sea during a cruise in June/July 1999. Five stations were occupied which had been studied repeatedly over the past 15–20 years. Dilution experiments using chlorophyll a (chl a) as a tracer were used to estimate daily rates in three size fractions; image-analyzed fluorescence microscopy provided quantitative estimates of standing stocks of auto- and heterotrophic nano- and microplankton. Phytoplankton contributed the largest share of protistan biomass, followed by bacteria and microzooplankton. On average, nanophytoplankton (