Identifying indicator redundancy of biofilm-dwelling protozoa for bioassessment in marine ecosystems.

A multivariate peeling method of data analysis was applied to determine indicator redundancy and for identifying indicator units (IUs) among biofilm-dwelling ciliate communities used for bioassessment of marine water quality. Samples were taken monthly over a 1-year period at four stations in coastal waters of the Yellow Sea: one heavily polluted, one moderately polluted, one intermittently polluted, and one unpolluted. Four IUs (IU1-4) were identified consisting of 22, 13, 14, and 17 species, respectively, out of a total of 144 species. The IUs showed significant correlation with temporal and spatial variations in environmental variables. The redundancy levels of IUs were interchangeable in time and space. However, IU1 and IU2 generally dominated the communities in moderately and intermittently polluted areas during cool (e.g., early spring, late autumn, and winter) and warm (late spring and early autumn) seasons; IU3 dominated in warm seasons (e.g., late spring to autumn) in the heavily polluted area; and IU4 mainly dominated the samples in the unpolluted and moderately polluted areas during the late summer and early autumn. Furthermore, different trophic-functional groupings were represented within the four IUs and these were generally associated with water quality status. These findings suggest that there is high indicator redundancy in marine biofilm-dwelling ciliate communities subjected to different levels of water quality.