Low-salinity transitions drive abrupt microbial response to sea-level change

The salinisation of many coastal ecosystems is underway and is expected to continue into the future because of sea-level rise and storm intensification brought about by the changing climate. However, the response of soil microbes to increasing salinity conditions within coastal environments is poorly understood, despite their importance for nutrient cascading, carbon sequestration and wider ecosystem functioning. Here, we demonstrate deterioration in the productivity of a top-tier microbial group (testate amoebae) with increasing coastal salinity, which we show to be consistent across phylogenetic groups, salinity gradients, environment types and latitude. Our results show that microbial changes occur in the very early stages of marine inundation, presaging more radical changes in soil and ecosystem function and providing an early warning of coastal salinisation that could be used to improve coastal planning and adaptation.

Automated summary

The salinisation of coastal ecosystems is ongoing and expected to continue due to climate change effects. Despite the importance of soil microbes for ecosystem functioning, their response to increased salinity in coastal environments is not well understood. Our research demonstrates a decline in the productivity of a key microbial group with rising coastal salinity, indicating early warning signs of coastal salinisation and potential impacts on soil and ecosystem function.