Sampling sufficiency for analyzing taxonomic relatedness of periphytic ciliate communities using an artificial substratum in coastal waters

Taxonomic relatedness measures of ciliated protozoan communities have successively been used as useful indicators for assessing water quality in marine ecosystems with a number of desirable properties. Sampling sufficiency for analyzing taxonomic relatedness indices of periphytic ciliate communities was studied in coastal waters of the Yellow Sea, northern China, from May to June, 2010. Samples were collected at two depths of 1 m and 3 m using an artificial substratum (glass slides), and were analyzed based on different sampling strategies (slide replicates). For achieving a dissimilarity of < 10%, more slide replicates were required with shortening community ages: 3–10 slide replicates were sufficient for the young (1–7 days) communities while 2–4 slide replicates were for the mature (10–28 days). The standard errors of four taxonomic relatedness indices due to the sample sizes were increased only in the young communities with shortening colonization times. For achieving a standard error of < 10%, 1 slide replicate was generally sufficient for the mature communities, whereas 4–10 were required for the young. These findings suggested that low slide replicates were required for measuring taxonomic relatedness indices compared to analyzing the community patterns, and that these indices were more sensitive to the sample sizes of a young community than a mature one of periphytic ciliates in marine ecosystems.