Spatial variation in taxonomic distinctness of ciliated protozoan communities at genus-level resolution and relationships to marine water quality in Jiaozhou Bay,northern China

Taxonomic distinctness of ciliated protozoan communities at genus-level resolution was studied over a 12-month period (June 2007–May 2008) in Jiaozhou Bay, northern China. Samples were collected biweekly from three different depths at each of five sites. A range of physico-chemical parameters were also measured in order to determine water quality. Multivariate and univariate analyses showed that (1) spatial patterns of ciliated protozoan communities were significantly different among the five sampling sites (P < 0.05); (2) there were no significant differences among the three depths at each site (P > 0.05); (3) the taxonomic patterns of ciliate communities at genus-level resolution were significantly correlated with the spatial variation of environmental variables, in particular nitrate nitrogen (NO₃-N), sum of NO₃-N and nitrite nitrogen (NO _n -N), and soluble reactive phosphate (SRP); (4) the Margalef’s index did not show a significant correlation with chemical parameters although it was higher for the less eutrophic than the more eutrophic sites (P > 0.05); (5) the average taxonomic distinctness (Δ⁺) and variation in taxonomic distinctness (Λ⁺) of the ciliate communities at genus-level resolution were significantly negatively correlated with the combination of NO _n -N and SRP; (6) the paired taxonomic biodiversity indices (Δ⁺ and Λ⁺) showed a clear decreasing trend of departure from the expected taxonomic breadth in response to water quality. These results suggest that spatial patterns and taxonomic distinctness (especially the paired Δ⁺ and Λ⁺) of ciliated protozoan communities at genus-level resolution can be used as potential indicators for assessing marine water quality while minimizing costs in terms of the time and resources needed for sample analysis.