Can coral create rain?

By Tim Brown, class of 2016

As I’m typing this, a group of researchers from QUT are cruising along the Great Barrier Reef. But they aren’t surveying fish or looking at coral. They are simultaneously sampling the water beneath them and the air above them for a small molecule called dimethyl sulphide (or DMS).

So, why do they care about DMS? Well, they think coral influences the weather on land in northern Queensland and DMS could be the key.

What exactly is DMS?

Depending on who you are, DMS is associated with different things. Brewers would know it as the chemical responsible for the aroma of cooked or creamed corn in beer. Sailors knew it as the “smell of the shore”. Although, for many people it’s regarded as the “smell of the sea”.

This is because a major source of DMS is marine algae. These algae are often found in high densities close to shore. They are also in high densities in plankton blooms which are usually associated with lots of krill. Some seabirds with keen noses actually use DMS to locate these banquets.

Another place with a lot of DMS producing algae: coral reefs. In fact, the algae living inside the coral produces DMS.
Where’s that DMS coming from? Image credit: John Cobb via Unsplash

Making it rain more than Steph Curry

After the DMS rises from the sea, it’s quickly reunited with water. In the atmosphere, DMS is converted into various sulphur compounds which absorb any surrounding water vapour. As more and more water gathers around these particles, a cloud begins to form.

If enough water is absorbed, it will start to rain. So theoretically, the more DMS released, the more clouds and the more rain.

The man who proposed the Gaia hypothesis, James Lovelock, actually thinks DMS may help prevent wild swings in the climate. See, when UV radiation and air temperatures rise, the top ocean layer gets hotter. When the marine algae in this layer heat up, they produce more DMS, which results in more clouds. The sun’s heat is then reflected by these clouds rather than absorbed by the dark ocean. As the temperature drops back down, DMS and cloud production drops too, allowing the sun’s heat back in.

Back to the reef

The algae within the coral of the Great Barrier Reef is believed to be a major source of DMS. If this is true, it may play a crucial role in controlling the climate back on land.

By measuring DMS levels above and below the surface, the researchers from QUT are hoping to gain a better understanding of how coral affects rainfall and cloud cover in northern Queensland.

Of course, the big question is: what happens if all the coral dies?

Further reading:
https://culturingscience.wordpress.com/2010/07/19/dms/
http://www.whoi.edu/oceanus/viewArticle.do?id=45946