Analysis of community attributes of the benthic macrofauna of Frierfjord/Langesundfjord and in a mesocosm experiment

Abstract

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.