Current and projected rates of extinction provide impetus to investigate the conse-\udquences of biodiversity loss for ecosystem processes. Yet our understanding of present day biodiver-\udsity–ecosystem functioning relations contrasts markedly with our understanding of the responses of\udspecies to changes that have occurred in the geological record. Of the experiments that have explic-\uditly tested the relationship between biodiversity and ecosystem functioning, few have attempted to\udreconcile whether the underlying process that gives rise to the observed response is affected by bio-\uddiversity in the same way as the observed response. In the present study, we use benthic macrofau-\udnal invertebrates to examine and distinguish the effects of species richness and species identity on\udbioturbation intensity, a key mechanism that has been important on evolutionary timescales regulat-\uding ecosystem functioning in the marine benthos. Our study identifies significant effects of species\udrichness that reflect species-specific impacts on particle reworking that, in turn, lead to elevated lev-\udels of nutrient generation. However, our findings also suggest that the consideration of only bioturba-\udtion intensity forms an incomplete evaluation of bioturbation effects because the way in which spe-\udcies interact with the benthic environment does not necessarily reflect organism traits only associated\udwith particle transport. Our study emphasises the need for caution when extrapolating from assumed\udknowledge of organism traits to how changes in species composition associated with ecological crises\udmay impact ecosystem function. Nonetheless, the empirically derived mechanistic effects of bioturba-\udtion on ecosystem functioning documented here are sufficiently general to seek correlations between\uddiversity and function in natural systems, including those from the palaeoecological record.
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