The influence of data transformations on biological monitoring studies using macroinvertebrates

The relative merits of untransformed root-transformed, root root-transforme d and binary data for the discrimination of sites of varying water quality was investigated using macroinvertebrate data from the river Trent system i n England. The influence of these four data treatments was investigated usi ng the CLUSTER, ANOSIM and SIMPER programmes of the PRIMER computer softwar e package. In general, the results showed that relative abundance is import ant in distinguishing between the more heavily polluted sites, which have p oor faunas. In contrast, the down-weighting of abundant taxa, through the u se of data transformations or binary data allows for a more effective discr imination of richer sites. The root root-transformation can be recommended over the other data treatments as it offers a good compromise between untra nsformed and binary data, and as it allows for the effective discrimination of sites over a wide range of water qualities. (C) 1998 Elsevier Science L td. All rights reserved.