Experimental evidence root‐associated microbes mediate seagrass response to environmental stress

Below-ground microbiota play an important role in mediating environmental conditions with consequences for plant performance. Micro-organisms involved plant–soil interactions may be associated roots or bulk soil; however, the relative influence of these below-ground microbial assemblages on performance is poorly known, particularly marine plants. We separately manipulated root and sediment seagrass Zostera muelleri a fully factorial experiment to determine how determined response (e.g. growth) nutrient enrichment, major stressor systems. Under ambient conditions, growth was maintained regardless assemblage disruption. high stress, seagrasses disrupted had reduced growth, whereas intact microbiota. Disruption bulk-sediment did not affect growth. Nutrient elevation correlated enhanced abundances several putatively beneficial taxa sulphide-oxidising Beggiatoaceae denitrifying Geofilum rubicundum) roots. Synthesis. Our results suggest that under micro-organisms influencing performance, but more stressful positive plant–root micro-organism strengthened. These are among first experimentally between plants root-associated key drivers human-induced changes. This suggests as terrestrial systems, resilience depends stress-mitigating functions their disturbance those plant–microbiota can deleterious Improving our understanding plant–micro-organism critical functioning threatened developing effective restoration strategies them.