Findings from a “natural laboratory” in seas off Papua New Guinea suggest that acidifying oceans will severely hit coral reefs by the end of the century.Carbon dioxide bubbles into the water from the slopes of a dormant volcano here, making it slightly more acidic.
Coral is badly affected, not growing at all in the most CO2-rich zone.
Writing in journal Nature Climate Change, the scientists say this “lab” mimics conditions that will be widespread if CO2 emissions continue.
The closer to the vents, the lower the pH. So the researchers were able to exactly stratify the ecosystems around the vents by pH levels. As pH dropped and became more acidic, the types of coral seen also dropped until at 7.8 – the ocean is normally a pH of 8.1 – there was only one simple type of coral left.
At 7.7, there were no corals at all and a completely different ecosystem, dominated by grasses. But the hard shelled mollusks – who have a hard time creating their shells at low pH – normally seen with these grasses were missing.
And this was a reef not affected by overfishing or pollution, so it probably understates the ecosystem change.
There is a very good chance that these levels of ocean acidification will be seen in the lifetimes of people alive today. They would witness the death of coral reefs.