The short-term temporal variation in the phytoplankton and mesozooplankton cycles was studied in a coastal area off east Gran Canaria Island. A small phytoplankton bloom, split into two peaks, appeared during late winter (end of February and March), coinciding with the lowest temperatures in the water column. A clear inverse relationship was observed between the biomasses in mesozooplankton and phytoplankton during the bloom period. The peaks in primary production and phytoplankton biomass were

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... uncoupled in time, suggesting that biomass could depend on consumer control (grazing), and primary production on resource control (nutrients). Mesozooplankton grazing represented less than 20% of the primary production, an indication that small zooplankton and protozoans controlled the phytoplankton populations, dominated by picoplanktonic cells (>60% of the primary production). The ratio between depth-integrated primary production and community respiration (P/R) covaried with primary production (P), showing that changes in P control the trophic status of the system. At P > 400 mgC m -2 day -1 the P/R ratio is >1, switching the system from heterotrophy to autotrophy, a situation that takes place during the phytoplankton growth period.