Environment- and scale-dependent changes in the functioning of invertebrate communities associated with Fucus vesiculosus

The functional trait approach focuses on the diversity of species characteristics, and can reveal much more about community functioning and trophic structure, compared to classical biodiversity concepts. In this study, we assessed large- and small-scale patterns in the functional traits of invertebrate communities associated with the marine macroalga Fucus vesiculosus. Large-scale comparisons were done across coastal areas representing different water quality (good, moderate, and poor) and small-scale comparisons across communities from sites with different exposures (sheltered, exposed) within the areas. Functional richness differed between areas of different water quality, with higher richness generally observed in areas with clearer waters. On a smaller scale, functional richness and dispersion were highest at sheltered sites, whereas the effect of exposure on functional divergence varied between study areas. Community trait composition differed among areas of different water quality with opportunistic traits becoming more prevalent in areas in poorer state. For example, community-weighted body sizes differed between areas and the smallest body sizes were observed in areas with moderate or poor water quality. The results illustrate how faunal traits within the same habitat type can differ geographically and how the functioning of communities may change due to anthropogenic pressures and natural drivers at different scales.