Phytoplankton growth and microzooplankton grazing in the Homa Lagoon (Izmir 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.