Lethal microbial blooms delayed freshwater ecosystem recovery following the end-Permian extinction

Harmful algal and bacterial blooms linked to deforestation, soil loss and global warming are increasingly frequent in lakes and rivers. We demonstrate that climate changes and deforestation can drive recurrent microbial blooms, inhibiting the recovery of freshwater ecosystems for hundreds of millennia. From the stratigraphic successions of the Sydney Basin, Australia, our fossil, sedimentary and geochemical data reveal bloom events following forest ecosystem collapse during the most severe mass extinction in Earth's history, the end-Permian event (EPE; c. 252.2 Ma). Microbial communities proliferated in lowland fresh and brackish waterbodies, with algal concentrations typical of modern blooms. These initiated before any trace of post-extinction recovery vegetation but recurred episodically for >100 kyrs. During the following 3 Myrs, algae and bacteria thrived within short-lived, poorly-oxygenated, and likely toxic lakes and rivers. Comparisons to global deep-time records indicate that microbial blooms are persistent freshwater ecological stressors during warming-driven extinction events. Harmful algal and bacterial blooms are increasingly frequent in lakes and rivers. From the Sydney Basin, Australia, this study uses fossil, sedimentary and geochemical data to reveal bloom events following forest ecosystem collapse during the end-Permian event and that blooms have consistently followed warming-related extinction events, inhibiting the recovery of freshwater ecosystems for millennia.

Automated summary

The study shows that harmful algal and bacterial blooms are increasingly frequent in lakes and rivers due to deforestation, soil loss, and global warming. These blooms have consistently followed warming-related extinction events, inhibiting the recovery of freshwater ecosystems for millennia.