It seems crazy that twelve people have walked on the moon and only three have made it seven miles down to the deepest part of the oceans – the Mariana Trench1. Our ocean floor has been mapped to a resolution of 5km (this is why it is so hard to detect plane wreckage in the oceans). We have maps of the surfaces of Mars, Venus and the Moon at much higher resolutions. And yet our oceans host 50-80% of all life on Earth. They are precious, mysterious and vulnerable.
Throughout the Earth’s history there have been a number of mass extinctions. We all know about the dinosaurs. However, the greatest mass extinction happened 252 million years ago, marking the end of the Permian period2. Marine species took the greatest hit, with 96% becoming extinct, especially those with calcium carbonate skeletons who rely on stable CO2 levels. 70% of terrestrial vertebrate species died out and it is the only known mass extinction of insects. It took life on Earth millions of years to resurrect itself.
In April, an article in Science was published by a group from the University of Otago in Dunedin, New Zealand3. The team leader, Matthew Clarkson, and his colleagues studied rocks in the United Arab Emirates, which were submerged in the oceans at that time. Using boron isotope data, they analysed the pH of seawater during this period. Boron exists in water in two states, depending on how acid or alkaline the water is, and so it is a good pH indicator for the period. They found chemical evidence that the oceans went from alkaline to acidic over the course of a few thousand years, which is very fast in geological terms.
Clarkson and his team suggest that during the first phase of extinction, the oceans could buffer any changes in atmospheric CO2, and so pH levels remained stable. However, during the second phase of extinction, a rapid and massive injection of CO2 caused a sudden rise in ocean acidity and so a huge loss of calcified marine biota.
The Siberian Traps4 are thought to be the source of the CO2. This was one of the Earth’s largest volcanic events, lasting for about 1 million years. It covers a landmass equal to Western Europe.
Why does this matter? Well, a consequence of increased CO2 levels in our atmosphere today means that our oceans are again at great risk of increased acidification5. The loss of coral reef communities globally is well charted and will continue.
The threat to our oceans doesn’t end with acidification. In the last 50 years we have eaten 90% of the big fish6. The natural systems cannot replenish at the rate in which we are trawling the seas. In your lifetime it is possible that the Arctic ocean may be ice-free… no more polar bears, amongst other species.
As young scientists you have the potential to make a difference within this burgeoning field. You can use your skills to explore, your insight to inform and your creativity to propose innovative ways forward.
2. Knoll et al. Science 273, (5274): 452-457 (1996)
3. Clarkson, M. O. et al. Science 348, 229–232 (2015)
5. Barker, S. & Ridgwell, A. (2012) Ocean Acidification. Nature Education Knowledge 3(10):21
6. Ransom A. Myers & Boris Worm Nature 423, 280-283 (15 May 2003)