To most of us, how climate change works and its effects on the terrestrial biosphere, are pretty well understood. However, how are these changes going to affect our oceans and the organisms within it? This question is almost never spoken about when the topic arises, despite the obvious impact it could have on our lives.
As Attenborough famously said “Our planet is a blue planet, with over 80% of its surface covered in oceans”. Consequently, understanding how the increases in carbon dioxide are affecting the oceans seems to me to be the largest slice of the problem.
The bit we all know is that as we produce more carbon dioxide through the burning of fossil fuels, the amount of heat escaping our atmosphere is being reduced. This is causing the planet, in general, to warm up. This is what gave rise to the original name of “Global Warming”. Today we understand that although on average the world is warming up, weather patterns are becoming more erratic, unpredictable and devastating. But how does the same atmospheric carbon dioxide cause changes in the ocean?
The atmosphere and the oceans are in equilibrium with respect to exchanges in gases. Therefore, as carbon dioxide concentrations increase in the atmosphere, they increase in our oceans proportionately. Dissolved carbon dioxide is a weak acid and this is driving “ocean acidification” which is another term commonly used in conjunction with coral reefs.
The oceans have been absorbing the bulk of the carbon dioxide we produce and up to now, this has been a bit of a lifeline for the planet. However, studies indicate that the oceanic absorption of carbon dioxide is reaching saturation state. Whilst this is bad news it actually gets worse. As the average global temperature rises the seas begin to warm. Sea ice, which typically reflects heat, melts and warming speeds up further. This increase in oceanic temperature drives down the carbon saturation limit which decreases the amount of gas the water can hold on to. We are already seeing this effect around the world with newly discovered methane seeps bubbling up from marine sediments below.
As it turns out, corals and other marine calcifiers are helping us out because they use this dissolved carbon dioxide to make their external skeletons. This process removes the carbon dioxide from the ocean and allows it to absorb more from the atmosphere. There is one marine calcifier which has really peaked scientific interest in the last 10 years and the fate of this organism could help to unravel our oceans future.
Coccolithophores are single cell algae which calcify. They produce beautiful wheel like structures on the cell membrane which is used to defend it from predation. Over its lifetime the algae produce many of these structures which fall off the cell membrane and sink to the sediments below. This acts as a valuable export of carbon from our oceans.
The bad news is that ocean acidification will limit the ability of corals and coccolithophores to produce these defensive structures and consequently deteriorate the ability of future oceans to continue absorbing carbon dioxide. As algae they also form the base of the food webs which comes as a bit of a double whammy. Acidification will also prevent future oceans from absorbing any more carbon dioxide and that might elevate the rate of atmospheric build up which will increase warming.
The good news is that coccolithophores have inhabited the oceans for millions of years and over this huge geological timescale have been through worse episodes throughout our planets history. Also, they are not the only marine algae available so it is possible that the impact may be limited to certain specialised species.
Further good news comes from scientific research which is investigating how mitigating the acidification might help to form pockets of ocean where these organisms can continue to grow. In these areas the oceans would still be able to absorb carbon dioxide and might help to stem the impact of the negative consequences predicted by the intergovernmental panel on climate change (IPCC).
But this is not just something for scientists to resolve. Climate is something that concerns us all and therefore it is imperative that society do our part to help reduce our carbon footprint. At home, LED light bulbs combined with turning off lights when you leave a room are simple measures which can lower your power consumption. Reuse and recycling of goods can really help as its estimated that around 30% of greenhouse gases are produced from the provisioning of them. Instead of drinking bottled water you could switch to a reusable bottle. A lot of emissions come from the transportation of bottled water which is very energy intensive.
These are but a few small changes in our lives which can have a larger impact than we give it credit for. As with all these things; It doesn’t need to cost the earth, but it just might save it!