Periphytic ciliate colonization: annual cycle and responses to environmental conditions

Glass slides were used as artificial substrates for collecting periphytic ciliates from scallop-farming waters of Jiaozhou Bay near Qingdao (China) over a period of 1 yr. A total of 37 ciliate species, about half of which belong to the orders Hypotrichida and Cyrtophorida, were identified using living observation and silver impregnation methods. Peaks of ciliate abundance and biomass occurred in November, mainly due to the suctorian Corynophrya lyngbyi, while sessile peritrichs (especially Pseudovorticella sinensis, Zoothamnium duplicatum and Z. plumula) dominated the ciliate communities during August. Vagile ciliates had low abundance and biomass despite accounting for a large proportion of the species richness. Almost no typical periphytic ciliates were detected in the winter months (from January to March). Twelve dominant species showed clear succession over the year and were found to correlate with a variety of environmental variables. Univariate and multivariate analyses were performed in order to explore the relationship between ciliate community and environmental conditions (temperature, salinity, pH, dissolved inorganic nitrogen, soluble reactive phosphate, dissolved oxygen, chlorophyll a, turbidity). Diversity and evenness indices were found to be relatively independent of physico-chemical factors, whereas species richness and the ratio of biomass to abundance were strongly related to nutrients. Multivariate analyses revealed that temperature, nutrients and salinity may best explain the changes in community structure of ciliates colonizing the glass slides.