Stressors Increase the Impacts of Coastal Macrofauna Biodiversity Loss on Ecosystem Multifunctionality

Abstract There is substantial evidence that biodiversity underpins ecosystem functioning, but it unclear how these relationships change with multiple stressors in complex real-world settings. Coastal zones are affected by numerous (for example, sediment input and nutrient runoff from land) the cumulative effects of may result pronounced unexpected changes functioning ecosystems. To investigate turbidity elevated nutrients on coastal biodiversity-ecosystem relationships, we performed a large-scale field experiment manipulating situ porewater ammonium concentrations measured functions related to carbon fixation mineralisation 15 estuaries varying levels turbidity. The results indicated benthic macrofauna diversity (species richness, abundance, functional richness) declined increased there were clear thresholds light at seafloor relation function relationships. Multifunctionality indices (an integrated index all functions) moderately turbid (daily mean PAR < 420 µmol m −2 s −1 ) decreased loss biodiversity. Functioning low-turbidity > however remained relatively constant, suggesting they more resilient against nutrient-induced loss. Our demonstrate ecosystems already stressed alter performance (turbidity) be prone overall if reduced another stressor (nutrient enrichment), highlighting potential snowballing change.