Data from: Biodiversity-ecosystem functioning relationships in fish communities: biomass is related to evenness and the environment, not to species richness

The relationship between biodiversity and ecosystem functioning (BEF) is a
topic of considerable interest to scientists and managers because a better
understanding of its underlying mechanisms may help us mitigate the
consequences of biodiversity loss on ecosystems. Our current knowledge of
BEF relies heavily on theoretical and experimental studies, typically
conducted on a narrow range of spatio-temporal scales, environmental
conditions and trophic levels. Hence, whether a relationship holds in the
natural environment is poorly understood, especially in exploited marine
ecosystems. Using large-scale observations of marine fish communities, we
applied a structural equation modelling framework to investigate the
existence and significance of BEF relationships across North western
European seas. We find that ecosystem functioning, here represented by
spatial patterns in total fish biomass, is unrelated to species richness –
the most commonly used diversity metric in BEF studies. Instead, community
evenness, differences in species composition, and abiotic variables are
significant drivers. In particular, we find that high fish biomass is
associated with fish assemblages dominated by a few generalist species
with high trophic level, who are able to exploit both the benthic and
pelagic energy pathway. Our study provides a better understanding of the
mechanisms behind marine ecosystem functioning and allows for the
integration of biodiversity into management considerations.