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.

Although surveys of soft-bottom macrofauna are an important tool in marine pollution monitoring, the high costs involved have often been criticised. Species identification is time-consuming, and one solution is to identify organisms to a taxonomic level higher than species. This study, using data from a survey in the vicinity of the Valhall oil field in the Norwegian sector of the North Sea, examines the effects of using abundances of different taxonomic levels, and of using different data transformations (used to adjust the relative weightings of rare and abundant taxa) in subsequent multivariate analyses of faunal patterns, and relates the environmental variables to the observed faunal patterns from the different analyses. The study area has a constant water depth, homogeneous bottom sedlment and a uniform benthic community. At the time of the survey the platform had been active for 9 yr, and strong gradients in environmental contaminants and related faunal changes were found. Data from 27 stations around the oil platform were analysed at the levels of species, genus, family, order, class and phylum, using a range of data transformations and multivariate techniques. The data matrix contained 156 species grouped into 138 genera, 102 families, 4 2 orders, 18 classes and 10 phyla. Matrices derived from species, genus and family abundances constructed using the same transformation are very similar, and even at higher taxonomic levels the gradient of change in community structure is still detectable. As the taxonomic level increases the effects of transformations become stronger, so although both taxonomic resolution and transformation affect the results of analyses, the effects of each are different and, to a large extent, unrelated. The highest correlations between matrices derived from measured environmental variables and biotic matrices are between environmental variables related to drihng activity and mildly transformed family abundances, suggesting that analyses of higher taxonomic levels are more likely to reflect a contamination gradient than are analyses based on species abundances. Before any general recommendations regarding taxonomic levels are given for future macrobenthic surveys, there is an obvious need for studies of weak, intermediate and strong gradients in various types of contamination in homogeneous and heterogeneous environments, using the same sampling and analysis methods.

Sublittoral macrofauna was sampled along a putative pollution gradient at 6 sites in Frierfjord/Langesundfjord. Norway, during the GEEP Mlorkshop. Data were subjected to a variety of multivariate statistical analyses which discriminate between sites on their faunistic attributes, and univariate measures of community stress were determined. Multivariate analyses produced generally slmilar results. Univariate stress measures in combination ranked the sites in order of increasing disturbance. Measured levels of pollutants in the sediments correlated poorly with the multivariate 2-D configurations and with the univariate measures of disturbance. It was concluded that water depth was the overriding factor controlling community structure, and that this masked any possible effects of pollution. The 3 deepest sites d~splayed the most obvious signs of stress, and this was attributed to seasonal anoxia in the deeper parts of Langesundfjord. In order to establish cause and effect relations between measured levels of pollutants (copper and hydrocarbons) and community responses, boxcores of sublittoral sedlment were subjected to 4 levels of contamination in a mesocosm experiment. Although some of the 'classical' intuitive methods indicated possible con~munity responses, the objective methods largely failed to reveal clear-cut differences in community structure between treatment levels. The relative merits of the 'classical' and objective approaches are discussed.

Sublittoral meiofauna was sampled for the GEEP Workshop along a putative pollution gradient at 6 sites in FrierfjordlLangesundfjord, Norway. Data were subjected to mutivariate statistical analyses which discriminate between sites on their faunlstic attributes, and univariate measures of community stress were determined. Most mulhvariate techniques produced similar results. The copepod component of the meiofauna discriminated between sites better than the nematodes at the species level, but nematodes were more robust to analyses based on data aggregated to higher taxonomic levels. It is concluded that pollution monitoring at the community level using higher taxonomic groupings of meiofauna is viable, and renders such studies much less time-consuming and more cost-effective than more standard procedures. Appropriate taxonomic levels for the 2 major meiofaunal taxa (nematodes and copepods) and for the total meiofauna are discussed. There is a paucity of validated univariate measures of community perturbation available for use with meiofauna. Traditional diversity measures were rather uninformative, but the community at one site was identified as being adversely affected by pollution.

In a prevlous note, Warwick & Clarke (1995; Mar Ecol Prog Ser 129:301-305) used 2 indices, A and A ' , to demonstrate a continuous decrease in taxonomic distinctness of marine macrofaunal assemblages along a gradient of ~ncreasincr environmental contamination, in a situation where species diversity remained constant, In the vicinity of 1 oilfield in the Norwegian sector of the North Sea. These indices are tested here uslng species abundance data from 3 other oilfields in the Norwegian sector, each sampled on 3 different occasions No consistent pattern of decreasing taxonomic distinctness with increasing env~ronmental contamination 1s evident.