SS2.01 Effects of Biotic Interactions on the Structure and Function of Microbial Food Webs
Date: Wednesday, June 12, 2002
Location: Poster Session - VCC
YangEJ, Dept. of Oceanography, Inha University, Inchon, Republic Of Korea,
Choi, J, K, Dept. of Oceanography, Inha University, Inchon, Republic Of Korea,
Grazing impact and community structure of microzooplankton during summer-fall phytoplankton blooms in coastal waters of Inchon, Yellow sea.
Grazing impacts, abundance and carbon biomass of microzooplankton during the summer-fall phytoplankton blooms was investigated on two day interval in August-september 2001 at a site in the coastal area of Inchon. Microzooplankton grazing impacts on phytoplankton were estimated at 25 – 27 ℃ in the laboratory using the dilution technique. During this study, chlorophyll-a concentrations varied widely from 1.32 to 19.35 ug/l (average : 5.4 0.99 ug/l) , and showed two peak of summer (August) and fall bloom (September). Size fractionated chlorophyll-a concentration showed that the net-phytoplankton comprised over 70 % of total chlorophyll-a contents during the phytoplankton bloom, while nano- and picophytoplankton comprised over 70 % during the non-phytoplankton bloom. Abundance and carbon biomass of microzooplankton ranged from 3,600 to 29,000 cells/l and 23.6 to 251.7 ugC/l , respectively. Carbon biomass of microzooplankton was lowest in the summer peak, and was highest after the fall phytoplankton bloom. Community of microzooplankton was composed of 3 group of heterotrophic ciliates, heterotrohpic dinoflagellates and copepod naupliis. Heterotrophic ciliates were dominated after summer phytoplankton blooms, and contributed over 70 % of the total microzooplankton carbon biomass. Heterotrophic dinoflagellates were dominated after fall phytoplankton bloom, contributed over 80 % of the total microzooplankton carbon biomass. Copepod naupliis were mainly dominated before summer phytoplankton bloom. The relative contribution of each component of the microzooplankton was showed differences between before and after phytoplankton blooms. Grazing rates of microzooplankton on phytoplankton varied from 0.12 to 0.94 /day, with the lowest values during summer and fall blooming, and the highest values after summer and fall phytoplankton blooming. The grazing impact of microzooplankton correspond to a daily loss of about 19.1 to 62.1 % of the initial phytoplankton standing stock and about 33 to >100 % of the potential productions of phytoplankton. During this study, microzooplankton represented important consumer in decay of phytoplankton bloom and could potentially control the growth of phytoplankton.