PARENT SESSION
Contributed Oral Session 98: Marine Ecology: Feeding Strategies and Food Webs
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 518 C, Level 5, Palais des congrès de Montréal
Seasonal and geographical variations in abundance, biomass, production rate and grazing impact of microzooplankton in eutrophic northern Hiroshima Bay, the Inland Sea of Japan.
GODHANTARAMAN, NALLAMUTHU*,, HOSHIKA, AKIRA , UYE, SHIN-ICHI,
ABSTRACT- In order to elucidate the ecological roles of microzooplankton in eutrophic northern Hiroshima Bay, the Inland Sea of Japan coastal waters, we measured their abundance and biomass, and estimated their production rate and grazing impact, monthly from June 2000 to May 2001. There were remarkable seasonal variations in abundance and biomass of microzooplankton: being high in spring-summer and low in fall-winter. Over the study area and study period, tintinnids were overwhelmingly dominant in terms of abundance (mean: 71.4%), followed, in order, by copepod nauplii (14.4%) and naked ciliates (14.2%). In terms of biomass, tintinnids, copepod nauplii and naked ciliates accounted for 51.2 29.8 and 19.0% respectively. Geographically, the abundance and biomass of microzooplankton were highest of the innermost station and decreased offshore. Tintinnids occurred homogenously over the area, whereas naked ciliates tended to occur more abundantly at inshore stations and copepod nauplii at offshore stations. The biomass of microzooplankton showed a significant positive relationship with chlorophyll a concentration (both total and <10 mm fraction) indicating that the microzooplankton growth is controlled by food supply. The grazing impact of microzooplankton as expressed by daily removal of phytoplankton biomass was lower at inshore stations (annual mean: 2.0%) than offshore stations (5.8%). These results demonstrated that in the northern Hiroshima Bay, the trophodynamic role of microzooplankton as nanoplankton grazers are less important in the innermost highly eutrophic area compared to offshore less eutrophic area.
Key words: Microzooplankton, biomass, production, eutrophic waters