Ciliate community structures correlates with environmental variables: investigation on agricultural and natural soils.

Ciliated protozoa are ubiquitous eukaryotic microorganisms, which constitutes an essential component of aquatic and soil ecosystems. Ciliates are very sensitive to any change in their habitat, fluctuations in their communities can affect the food web and energy transfer within the ecosystem. Thus, monitoring the structure of ciliate communities can represent a valuable tool to assess ecosystem quality and functioning. Currently, few studies have been addressed to the analysis of soil ciliate communities and in particular, from agricultural soils under organic and conventional management. In our study, the first one to be performed in Italy, the ciliate communities in three fields under organic and one field under conventional management located in a hill area (300-550 m asl) of the provinces of Macerata and Ancona (Marche), were investigated by means of qualitative method. Furthermore, six more sites representative of natural and semi-natural soils were sampled for comparison. Soil samples were taken twice in autumn and spring. Chemical-physical parameters were analysed for all sampled sites. Our surveys showed a total of 68 species belonging to 9 classes, 19 orders, 45 genera from all sites under study with the dominance of the ciliates genus: Colpoda, Gonostomum, Oxytricha, and Halteria. The species richness ranged from 37 to 14 and it is higher in agricultural sites as compared with the natural habitats. Principal Component Analysis (PCA) was able to discriminate between agricultural (organic and conventional) and natural sites. Furthermore, Canonical Correspondence Analysis (CCA) and Generalized Procrustes Analysis (GPA) showed strict correlations between environmental variables and distribution of ciliate species. Altogether, these results highlight the importance of environmental variables in shaping the ciliate communities in the investigated soil types.