Comparison of the effect of different input data on the STAR_ICMi index in 8 rivers. Observed is the real score counting all the individuals; the error bars on the observed value are calculated using the bootstrap approach and represent 95% confidence intervals. Estimate is the index value when the abundance of the most abundant taxa was estimated using the geometric series (see Appendix 1 for examples); rank, class and presence is the index value when the real input data were reduced to rank, classes and presence respectively.