Stressors increase the impacts of coastal macrofauna biodiversity loss on ecosystem multifunctionality

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There is substantial evidence that biodiversity underpins ecosystem functioning, but it is unclear how these relationships change with multiple stressors in complex real-world settings. Coastal zones are affected by numerous stressors (e.g. sediment input and nutrient runoff from land) and the cumulative effects of these stressors may result in pronounced and unexpected changes in the functioning of ecosystems.

To investigate the cumulative effects of turbidity and elevated nutrients on coastal biodiversity-ecosystem functioning relationships, we performed a large-scale field experiment manipulating in situ sediment porewater ammonium concentrations and measured multiple ecosystem functions in 15 estuaries with varying levels of turbidity.

The results showed that the benthic macrofauna diversity declined with increased porewater ammonium concentrations and there were clear changes in biodiversity-ecosystem function relationships with turbidity. Our results demonstrate that ecosystems already stressed by stressors that alter functional performance (turbidity), may be more prone to loss of overall functioning if biodiversity is reduced by another stressor (nutrient enrichment), highlighting the potential snowballing effects of cumulative change.