Phytoplankton growth and microzooplankton grazing in the Homa Lagoon (İzmir Bay, Turkey)

 Phytoplankton
growth and microzooplankton grazing were investigated at one station in the
Homa Lagoon from February to January in 2006-2007. Our results showed
significant seasonal variations in phytoplankton dynamics. Microzooplankton was
mainly composed of dinoflagellates and tintinnid ciliates and nauplii.
Microzooplankton grazing increased with increasing of temperature. Grazing rate
was maximum levels in spring and summer. Microphytoplankton, which dominated
the total algal biomass and production, were characterized by the proliferation
of several chain-forming diatoms. Small heterotrophic flagellates and aloricate
ciliates were the main controllers of phytoplankton.
Phytoplankton represented a significant for micrograzers, which grazing
represented 20–120% of diatom and cynabacteria algal production during
2006-2007. Microzooplankton has, however, a relatively high impact on
microphytoplankton, as > 45% of microalgal production was consumed
throughout the year. These results suggest that the low grazing was one of the
factors contributing to the development of the spring bloom. All of seasonal bases, the phytoplankton production were grazed by
microzooplankton in summer, autumn and winter–spring seasons have been changing
between 20%-120%. The seasonal variation in the
microzooplankton grazing pressure seems to result from the dominant size class of
the phytoplankton community of this lagoon diatom and cynabacteria.