The microbiome mediates the interaction between predation and heavy metals

Gut microbiota communities are fundamental ecological components in the aquatic food web. Their potential to mediate how organisms respond to multiple environmental stressors remains understudied. Here we explored how manipulations of the gut microbiome of Daphnia pulex, a keystone species in aquatic communities, influenced life history (size at maturity, age at maturity, somatic growth rate and clutch size), morphology (induced defence) and body condition (lipid status deposits) responses to combined anthropogenic (copper) and natural (predation risk) stress. Data from a factorial experiment revealed that the effect of predation risk on traits was often mediated by copper (predation risk and copper interact). These patterns align with theory linking predation risk and copper contamination via digestive physiology. We also found that each stressor, and their combination, was associated with the same community composition of the D. pulex microbiome. However, antibiotic manipulation of the microbiome reversed 7/12 the trait responses across life history, morphology and body condition. This was associated with dramatically different communities to control conditions, with clear and unique patterns of microbiome community composition for each stressor and their combination. Our study revealed that microbiome community composition is highly correlated with the response of organisms to multiple, simultaneous stressors. (C) 2021 Published by Elsevier B.V.

Automated summary

The study revealed that gut microbiome composition of Daphnia pulex is highly correlated with the organism's response to multiple stressors. Predation risk and copper contamination interact to influence traits through digestive physiology. Antibiotic manipulation of the microbiome can reverse trait responses across life history, morphology, and body condition.