Rivers are warming and losing oxygen faster than oceans, according to a Penn State-led study published in the journal Nature Climate Change. The study shows that of nearly 800 rivers, warming occurred in 87% and oxygen loss occurred in 70%.
For anyone curious, "the great dying" is thought to have killed over 95% of aquatic species in part because Oxygen levels in the ocean dropped considerably. Approximately 75% of species on land at the time died. It is thought to be the most devastating mass extinction in Earth's history.
this is already happening in Australia. our river systems have been heavily abused due to mining and agriculture. we're having more and more of these fish dying events.