Relationships between taxonomic resolution, macrobenthic community patterns and disturbance

Although analyses of macrobenthic infaunal communities traditionally require identification of the organisms to the species level, there is still only a limited number of studies which have examined the use of higher-level taxa in monitoring surveys.These generally indicate that identification of organisms to the lowest possible taxon may not always be necessary to enable description of spatial patterns in routine environmental and pollution monitoring programs.In other fields of marine ecology, such as studies of biodiversity, comparative investigations over large geographical areas, and the development of rapid-assessment techniques, the use of identification to higher taxonomic levels is often necessary.Detailed comparative studies of faunal patterns at various taxonomic levels are therefore important.This study uses multivariate analyses of macrofauna and environmental data from 20 separate investigations in the Skagerrak and North Sea to examine faunal patterns at different taxonomic levels.Data are analysed at the levels of species, genus, family, order, class and phylum.Transformation of data is also considered since degree of tlansforrnation is as important in determining the outcome of subsequent analyses as the taxonomic level to whlch organisms are Identified.Correlations between the underlying similarity matrices at the species level and higher taxonomic levels show highest values in polluted areas, lower values in less disturbed areas and lowest values in pnstine areas, indicating that the faunal patterns for the various taxonomlc levels become more similar as the degree of disturbance increases.For those areas where time-senes data are available it is shown that, as contamination increases, correlations between the faunal patterns at all taxonomlc levels, but especially the highest levels, and the environmental variables tend to increase, and after several years of contamination all the correlations are high, independent of taxonomic level.Again, the faunal patterns at the different taxonomic levels tend to become more s~milar as a result of increased pollution For all 20 investigations, highest correlations between faunal patterns (i.e. the underlying similarity matrices) and environmental variables were mainly found at the levels of species, genus and family, and often there was a distinct drop in correlation value between family and order In most cases, ~ndependent of the level of pollution, there is only a minor reduction in correlation between species and family, suggesting that identification to the level of family may be satisfactory in many routine monitonng surveys.The debate about the level of taxonomic resolution required for routine environmental monitoring becomes relatively unimportant if the effects of choosing different transformations are not also considered.