RELATIONSHIPS BETWEEN TAXONOMIC RESOLUTION, MACROBENTHIC COMMUNITY PATTERNS AND DISTURBANCE

Although analyses of macrobenthic infaunal communities traditionally r equire 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 alwa ys be necessary to enable description of spatial patterns in routine e nvironmental and pollution monitoring programs. In other fields of mar ine ecology, such as studies of biodiversity, comparative investigatio ns over large geographical areas, and the development of rapid-assessm ent techniques, the use of identification to higher taxonomic levels i s often necessary. Detailed comparative studies of faunal patterns at various taxonomic levels are therefore important. This study uses mult ivariate analyses of macrofauna and environmental data from 20 separat e investigations in the Skagerrak and North Sea to examine faunal patt erns at different taxonomic levels. Data are analysed at the levels of species, genus, family, order, class and phylum. Transformation of da ta is also considered since degree of transformation is as important i n determining the outcome of subsequent analyses as the taxonomic leve l to which organisms are identified. Correlations between the underlyi ng similarity matrices at the species level and higher taxonomic level s show highest values in polluted areas, lower values in less disturbe d areas and lowest values in pristine areas, indicating that the fauna l patterns for the various taxonomic levels become more similar as the degree of disturbance increases. For those areas where time-series da ta are available it is shown that, as contamination increases, correla tions between the faunal patterns at all taxonomic levels, but especia lly the highest levels, and the environmental variables tend to increa se, and after several years of contamination all the correlations are high, independent of taxonomic level, Again, the faunal patterns at th e different taxonomic levels tend to become more similar as a result o f 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, g enus and family, and often there was a distinct drop in correlation va lue between family and order. In most cases, independent of the level of pollution, there is only a minor reduction in correlation between s pecies and family, suggesting that identification to the level of fami ly may be satisfactory in many routine monitoring surveys. The debate about the level of taxonomic resolution required for routine environme ntal monitoring becomes relatively unimportant if the effects of choos ing different transformations are not also considered.