By Claire Robinson
A recently discovered biological process involving global oceanic dimethyl sulfide (DMS) can reverse the anthropogenic warming of the Earth’s atmosphere.
Known as the CLAW hypothesis, DMS has been linked to production of cloud-condensation nuclei (CCN) in the atmosphere, which produce clouds and reflect the Sun’s radiation back into space.1 The CLAW acronym stands for the 4 authors’ last names who developed this hypothesis: Charlson, Lovelock, Andreae, and Warren. The underlying theme of the CLAW hypothesis is that organisms are able to biologically alleviate stressors in their living environment. This negative feedback process could potentially stabilize atmospheric temperatures.
The characteristic smell of the sea is very distinctive. That salty, beachy, unique scent is actually DMS. DMS is a biologically produced compound, produced from multiple species of microscopic plants that photosynthesize, called phytoplankton. DMS is formed by the decomposition of dimethylsulfoniopropionate (DMSP); in other words, when DMSP is broken down, DMS is produced.1,3 DMSP is broken down either by bacterial metabolism or in phytoplankton by enzymes called DMSP-lyases.3
The application of this process can be monumental. If we can understand and harness this particular feedback process to our advantage, we might be able to say in the future: “DMS saved the world.”
Recent papers have found that there are multiple pathways for DMS in the environment. In reality, most DMS produced is redeposited back into the ocean, leaving only 3% to exit into the atmosphere.3 Other pathways for DMS include photooxidation and microbial consumption.3 However, this isn’t stopping some researchers who are using alternative theories and methods to use DMS to our advantage.
An example is the Southern Ocean Iron Enrichment Experiment (SOFeX) that occurred in 2002. Biogeochemist Oliver Wingenter and others fertilized portions of the Southern Ocean with iron sulfate (FeSO4) and observed changes in concentrations of trace gases, including DMS. DMS was observed at five times normal concentrations during the experiment.4 Other scientists disagree with the idea of iron fertilization, or nutrient fertilization altogether.5,6
Climate change is one of the hottest topics in the media right now. President Barack Obama recently released his final version of the Clean Power Plan, which will hopefully begin to address the threat of climate change on our planet. “There is such a thing as being too late when it comes to climate change,” says Obama.7 The reality is that climate change is real, it’s happening now, and we need to educate ourselves about it. A good place to start is our ocean.
Seventy percent of the Earth’s surface is ocean, and the oceans have been regulating climate on a global scale through coupled interactions throughout history. DMS is a perfect example of an oceanic-atmospheric coupled interaction.
Dr. Rob Condon, an oceanographer from the University of North Carolina Wilmington, states: “Everyone has an opinion; thus the issue of climate change is debated and denied based on perception, not the evidence.” What most scientists can agree on is that climate change is happening in our generation, and the oceans are affecting climate tremendously. The data speaks for itself, and action on climate change requires trusting scientists and also trusting the media’s communication of that data.
Further studies must be done to understand in full detail the role of DMS in the oceans and also in the atmosphere. What has been discovered so far about DMS is astounding, and it has easily become one of the most influential compounds in the ocean.
1Charlson, R. J., J. E. Lovelock, M. O. Andreae, and S. G Warren. 1987. Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate. Nature 326: 655-661.
2Trenberth, K. E. The Role of the Oceans and Climate. Oco.noaa.gov. Accessed 15 September 2015.
3Gypens, N., A. V. Borges, G. Speeckaert, and C. Lancelot. 2014. The dimethylsulfide cycle in the eutrophied southern North Sea: A model study integrating phytoplankton and bacterial processes. PLoS ONE 9(1): e85862.
4Wingenter, O. W., K. B. Haase, P. Strutton, G. Friederich, S. Meinardi, D. R. Blake, and F. S. Rowland. 2004. Changing concentrations of CO, CH4, C5H8, CH3Br, CH3I, and dimethyl sulfide during the Southern Ocean iron enrichment experiments. PNAS 101(23): 8537-8541.
5Chisholm, S. W., P. G. Falkowski, and J. T. Cullen. 2001. Dis-crediting ocean fertilization. Science 294(5542): 309-310.
6Fuhrman, J. A. and D. G. Capone. 1991. Possible biogeochemical consequences of ocean fertilization. Association for the Sciences of Limnology and Oceanography 36(8): 1951-1959.
7The White House. “President Obama Announces the Clean Power Plan.” Online video clip. Youtube.com. 3 August 2015. Web. Accessed 16 September 2015.