SEASONAL-VARIATION IN THE SPECIES COMPOSITION OF TINTINNID CILIATES IN HIROSHIMA BAY, THE SETO INLAND SEA-OF-JAPAN

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 ma ximum abundance of total tintinnids over the entire period was 5.7 x 1 0(3) individuals l(-1). Among 32 species identified, a consistent seas onal occurrence was recognized in 22 species. The relationships betwee n various environmental factors and the abundance of each species of t intinnids were analyzed using principal component analysis. From this analysis, the abundance of many tintinnids was revealed to be associat ed with temperature, the <20 mu m size fraction of chlorophyll a and w ater column stability, but not with the >20 mu m size fraction of chlo rophyll a, nor with salinity From these results, tintinnid species wer e divided into five association types: species whose abundance increas ed with increasing temperature, decreasing temperature, nanophytoplank ton abundance, increasing water column mixing, or increasing water str atification coupled with low temperature.