Planktonic ciliates in Southampton Water: quantitative taxonomic studies

The species-specific abundance and biomass of marine planktonic ciliates were determined at monthly intervals at two stations in Southampton Water between June 1986 and June 1987. The two stations, an outer one at Calshot and an inner one at north-west Netley, were subject to differing marine and terrestrial influences. A total of 55 ciliate taxa were recorded during the sampling period; of these 34 taxa were identified to genus and 16 to species. The heterotrophic ciliate community at both stations was dominated by aloricate taxa which comprised >90% of the community abundance and biomass during some months. The loricate tintinnids were also common, especially at Calshot, during winter months. Oligotrichs dominated the aloricate community at both stations with haptorids prominent at north-west Netley. At Calshot,Strotnbidiumsp. dominated the heterotrophic community abundance and biomass throughout the study period, whileAskenasiasp.,Strobilidiumsp. andTintinnopsissp. were also common.Strombidiumsp. also contributed most to heterotrophic community abundance at north-west Netley.Balanionsp. andTintinnopsissp. were also abundant. However,Cydotrichiumsp. andDidiniuntsp. dominated community biomass at this station. Most taxa exhibited a seasonal cycle with low winter and high spring and summer abundances. Some taxa reached abundances of >2000 l1However, maximum abundance of one species ofTintinnopsiswas found during winter months. The autotrophic ciliate,Mesodinium rubrum, was also recorded at both stations achieving densities >105l1at north-west Netley during ‘bloom’ conditions.