Written by Sofia Perez

Edited by Manu Madhavan

In a world where the news and scientific literature is dominated by a discussion about carbon dioxide, I’ve decided to shine a light on a neglected member of the atmospheric gas community: dimethyl sulphide. In particular, let’s focus on a paper published by Sonya L. Fiddes, Matthew T. Woodhouse, Todd P. Lane, and Robyn Schofield that was in April 2021 called Coral-reef-derived dimethyl sulphide and the climatic consequences of the destruction of coral reefs.

To begin with  though, we need to know what dimethyl sulfide actually is. If you break it down by atoms, it’s a sulfur which shares electrons between two carbon atoms, one on each side. Each of these carbon atoms shares electrons among three hydrogens. Overall, dimethyl sulfide is a sulfur atom, two carbon atoms, and six hydrogens. Its role in the environment is as a “naturally-occurring aerosol precursor gas,”- which means that in the atmosphere, it quickly gets converted into several sulfur compounds that act as aerosols, allowing water vapour to condense around them and form clouds. This trait of dimethyl sulfide “plays an important role in the global sulfur budget, aerosol formation, and climate”. 

All of this is thought to be thanks to marine algae and phytoplankton, who are believed to convert dimethyl sulfoniopropionate into dimethyl sulfide when they’re stressed by the ultraviolet radiation of the sun. According to this Woods Hole Oceanographic Institute article, “The DMS flushes out chemically reactive molecules that cause cellular damage, in much the same way that our bodies use antioxidants to bind to free radicals.”

In the aforementioned 2021 study, however, researchers propose an interesting addition to this group of DMS-producing creatures: corals and their symbionts, who the study suggests produce a “comparable amount of DMS, which is unaccounted for in models”. In fact, the paper even suggests that DMS produced from coral reefs might have an influence on regional climate. Naturally, this evokes a sense of concern given the threat coral reefs are currently under due to climate change, acidification, biodiversity loss, etc., which only reiterates the importance of conserving them.  

In this study, researchers used something called a global climate model, which helps scientists understand how the earth’s climate works, in this case, particularly regarding tiny particles in the air called aerosols. Overall, the researchers were looking for clues as to how DMS from coral reefs can affect the climate and found that it makes a slight difference of about 1.7% of all DMS produced globally. They then looked into how this additional DMS affects different regions worldwide. This was done by comparing the difference between “nudged” and “free-running” ensemble simulations with and without coral-reef-derived DMS. What this means is that the researchers were comparing two different types of computer simulations in order to understand the impact of coral reef-derived DMS on regional climate. “Nudged” simulations mean they were using real-world observations of certain variables, such as wind and temperature, to guide the simulation. On the other hand, a “free-running” simulation means the simulation was not influenced by these real-world observations and was allowed to run on its own. “Ensemble simulations” just indicate that several simulations with different conditions were run. To measure the effectiveness of the DMS produced by coral reefs on regional climate, they compared the results of these simulations with and without coral reef-derived DMS. 

The conclusion was that these simulations provided no “robust evidence that coral-reef-derived DMS influences global and regional climate”. That said, there is still value to be derived from this study, which addresses a topic that still evokes much uncertainty, namely, how the aerosols in the atmosphere affect convection. This is the name for the physical movement of a fluid or gas. In the atmosphere, this is the process by which heat is transferred from the surface of the Earth to the atmosphere, causing the air to heat up and rise. As the air rises, it expands and cools, forming clouds and precipitation. The cooled air eventually sinks back to the surface, completing the cycle. This process is integral to shaping climate, but it’s difficult to understand how it is affected by aerosols, so more research is needed. 

Studying atmospheric gases and understanding their sources and effects is a vital step in developing strategies to approach climate change. Additionally, while research from this study has demonstrated little evidence to suggest the production of dimethyl sulfide from coral reefs is significant, it’s important to remember that they are still facing many threats, including climate change, pollution, and overfishing. This only reiterates what scientists keep repeating: investing in scientific research on atmospheric gases and coral reefs is an investment in our collective future.

Sources

Dodd, Scott. “DMS: The Climate Gas You’ve Never Heard Of.” Https://Www.whoi.edu/, 17 July 2008, http://www.whoi.edu/oceanus/feature/dms–the-climate-gas-youve-never-heard-of/. Accessed 19 Jan. 2023.

Fiddes, Sonya L., et al. “Coral-Reef-Derived Dimethyl Sulfide and the Climatic Impact of the Loss of Coral Reefs.” Atmospheric Chemistry and Physics, vol. 21, no. 8, 20 Apr. 2021, pp. 5883–5903, acp.copernicus.org/articles/21/5883/2021/, 10.5194/acp-21-5883-2021. Accessed 19 Jan. 2023.

Nevitt, G. A. “The Neuroecology of Dimethyl Sulfide: A Global-Climate Regulator Turned Marine Infochemical.” Integrative and Comparative Biology, vol. 51, no. 5, 31 Aug. 2011, pp. 819–825, 10.1093/icb/icr093. Accessed 19 Jan. 2023.Wang, Shanlin, et al. “Influence of Dimethyl Sulfide on the Carbon Cycle and Biological Production.” Biogeochemistry, vol. 138, no. 1, 27 Feb. 2018, pp. 49–68, 10.1007/s10533-018-0430-5. Accessed 6 Mar. 2022.