This guest post is from Elliot Scanes, a PhD candidate from Western Sydney University who runs cool experiments to understand the impact of climate change on our molluscs. Elliot has a great Instagram research account with Dr Vicky Cole called seao2, so give them a follow to keep up to date with their work.
Ocean Acidification – The Ocean’s other problem with CO2
by Elliot Scanes
Humans are currently emitting CO2 faster than has occurred on Earth for millions of years. Currently, atmospheric CO2 concentrations are at their highest point in 800,000 years and don’t look like slowing any time soon. Inevitable global warming as a consequence of the excess CO2 and other pollutants causing the “greenhouse effect” is well established among scientists (despite what politicians might say). This warming of the earth will eventually also cause warming of the oceans, most notably affecting species ranges. But this is not the only way excess CO2 is going to change the world’s oceans. The oceans have already absorbed 40% of the CO2 emitted by humans, and will keep continuing to do so. As CO2 dissolves in seawater, it forms carbonic acid, which, in turn causes the oceans to acidify. So far, oceanic pH (the measure of acidity) has fallen 0.1 units, and is predicted to fall 0.3 – 0.4 pH units by 2100 unless drastic global action is taken to curb emissions.
Collecting Sydney rock oysters (Saccostrea glomerata) for experiments in Port Stephens.
Opening flat oysters (Ostrea angasai).
This small decrease in pH may seem insignificant, however pH is measured on a natural logarithmic scale (for those mathematicians) which means that each unit is an order of magnitude larger than the previous. A 0.3 unit drop in pH means that calcium carbonate, the mineral that all shelled animals shells are composed of, is now soluble in seawater. Predictably, scientists are most concerned about the shelled animals of the ocean like molluscs, crustaceans and cnidarian (corals). Investigations by our lab at Western Sydney University have shown that under these scenarios Sydney rock oysters will have difficulty forming their shell, especially in their juvenile stages. These difficulties waste vital energy, which is especially important in an environment where you always need an edge on your competitor. Similar studies have found comparable effects in sea urchins, corals, scallops and almost every shelled animal in the ocean that you can think of. Continue reading