Seasonal changes in the species composition of tintinnid ciliates were examined based on time-series samples taken at 2 week intervals over a 3 year period in Hiroshima Bay, the Seto Inland Sea of Japan. The maximum abundance of total tintinnids over the entire period was 5.7 X 10 3 individuals 1"'. Among 32 species identified, a consistent seasonal occurrence was recognized in 22 species. The relationships between various environmental factors and the abundance of each species of tintinnids were analyzed using principal component analysis. From this analysis, the abundance of many tintinnids was revealed to be associated with temperature, the <20 prni size fraction of chlorophyll a and water column stability, but not with the >20 u.m size fraction of chlorophyll a, nor with salinity. From these results, tintinnid species were divided into five association types: species whose abundance increased with increasing temperature, decreasing temperature, nanophytoplankton abundance, increasing water column mixing, or increasing water stratification coupled with low temperature.

No abstract

No abstract

No abstract

The distribution of the main microbial loop components (bacteria, heterotrophic nanoflagellates (HNF), ciliates) was investigated at three sites: the inner, central and outer regions of Hiroshima Bay, Seto Inland Sea, Japan, in summer (June and August 1996 and July 1997). At the inner region site, lower salinity and higher concentrations of nutrients and chlorophyll a were observed than in the other regions. Bacterial, HNF and ciliate biomasses ranging from 32.6 to 170.1 µg C/L, from 1.5 to 84.8 µg C/L and from 0.1 to 91.7 µg C/L, respectively, were generally highest at the inner region site. The ciliate assemblages were mostly dominated by mixotrophic aloricate ciliates in the surface and near‐surface layers. The relationship between the biomass of aloricate ciliates and their prey organisms showed significant linear correlations at the three sites. The slope of the regression line was lowest and the X‐axis intercept of the line was highest at the inner region site, possibly suggesting relatively low energy transfer efficiency between them in this site. Hence, high biomass of less than 20 µm phytoplankton, bacteria and HNF may not be efficiently utilized by ciliates in the inner region of Hiroshima Bay, compared with the situation in other regions of the bay.