Diversity and bioindicative value of soil ciliate communities: Opportunities, challenges, and case studies in Italy.

This report aims to provide an overview of the outcomes and the challenges encountered in using ciliated protozoa as indicator of soil health in the framework of several projects conducted in Italy since 2009. Ciliates (and, in general, protistan microorganisms) in spite of the key roles they play in the soil microbial loop, constitute a neglected component of the soil biodiversity, which is rarely included in soil biomonitoring plans. Ciliates are important bacterial feeders and thus, they significantly contribute to channel nutrients up to the soil food web. In this scenario, soil biomonitoring projects including ciliates offer precious opportunities to better assess their potential as bioindicators of soil health. The specific aims of our surveys were i) to investigate for the first time in Italy, ciliates diversity and the spatial and temporal distribution of their communities in different soil ecosystems; ii) to evaluate the capacity of ciliates to discriminate between different types of land uses and farming management practices; and iii) to assess relationships among ciliates and abiotic parameters. Ciliate communities were studied by means of classical qualitative and quantitative methods. More than 250 sites were sampled (mostly twice or more) in northern and central Italy. Sampling sites were representative of natural sites (forests, marshes, prairies), agroecosystems (arable fields, meadows, vineyards, truffle cultivations, olive and fruit orchards), as well as, industrial sites. Overall, the results of our surveys confirmed the bioindicative potential of soil ciliate communities in discriminating between different natural sites and agroecosystems, and, at least preliminarily, between different management systems. Furthermore, these studies have contributed to disclose soil ciliate diversity studies in Italy, to update Italian checklist, to identify more than 25 novel genus/species and in final to highlight that ciliates should be effectively included in soil biomonitoring plans.