Abstract:Studies on the abundance and biomass of planktonic ciliates were conducted in the Bohai Bay during spring (May), summer (July) and autumn (September) of 2015. Fifteen stations were investigated in each season. One-liter sample of seawater from the surface layer was collected and fixed in 1% acid Lugol’s iodine solution. Water samples were pre-concentrated using the Utermöhl method and observed using an Olympus IX71 inverted microscope. The dimensions of the ciliates were measured and the cell volume of each species was estimated using appropriate geometric shapes. The carbon/volume ratio used to calculate the biomass was 0.19 pg C/µm3. The classification of tintinnids was based on previous literatures about taxonomy. The abundance and biomass of ciliates and the community structure varied in the three seasons. The average abundance of ciliates in the spring, summer and autumn was (1016± 868) ind./L, (2011±1327) ind./L and (2456±1776) ind./L respectively. The average biomass of ciliates in the spring, summer and autumn was (1.91±2.53) μg·C/L, (5.78±4.45) μg·C/L and (3.11±2.40) μg·C/L respectively. Tintinnids accounted for (26.7±23.3)% of the total ciliate abundance, and the value was the highest in the summer (43.4%±25.1%) and the lowest in the autumn (12.3%±8.1%). Aloricate ciliates and tintinnids exhibited different distribution patterns. The abundance and biomass of aloricate ciliates were higher in the coastal and offshore areas, while tintinnids tended to accumulate in the coastal area. Twenty five tintinnid species were identified that belonged to 8 genera, 15 of which were in genus Tintinnopsis. The most dominant species were Tintinnopsis baltica, Tintinnopsis beroidea and Tintinnidium primitivum in the spring. The most dominant species were Tintinnopsis tocantinensis, Tintinnidium primitivum and Tintinnopsis amoyensis in the summer. The most dominant specie was Tintinnidium primitivum in the autumn. The lorica oral diameter of the tintinnid community was larger in the summer [(35.9±8.2) μm] and autumn [(34.8±5.2) μm] than in the spring [(31.5±2.5) μm]. The Shannon index and Pielou index of the tintinnid community were both higher in the summer than in the spring and autumn. Our study may provide basic data for the future research on both the planktonic ecosystem and the development of the fishery industry.
