Diel periodicity in Synechococcus and grazing by heterotrophic nanoflagellates: Analysis of food vacuole contents

Dolan, John R., Karel Šimek

Limnol. Oceanogr., 44(6), 1999, 1565-1570 | DOI: 10.4319/lo.1999.44.6.1565

ABSTRACT: The relationship between heterotrophic nanoflagellates (HFLAG) and the autotrophic prokaryote Synechococcus was examined in the bay of Villefranche (NW Mediterranean) in June 1998. We determined Synechococcus concentrations, % of dividing Synechococcus cells, concentrations of HFLAG, and numbers of Synechococcus cells inside HFLAG food vacuoles in samples taken every 2-3 h over 62 h (n = 28). Synechococcus cells in division ranged from 10 to 30%, with peak values in late afternoon-early evening hours. Numbers of Synechococcus in HFLAG food vacuoles (0.06-0.34 Synechococcus HFLAG-1) were not related to concentrations of total Synechococcus, or nondividing Synechococcus but were negatively related to % of dividing Synechococcus. The data suggest there may be a relationship between vulnerability to predation and average Synechococcus cell size. HFLAG community grazing pressure, estimated from food vacuole content and HFLAG abundances, ranged from about 0.2% Synechococcus stock removed h-1 at midnight to 1%

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