Sam Dupont -
13.00, 2 of Maj
Interview by: Karl
Location of interview: Zoom
Sam Dupont calls himself an “eco-physiologist”. He works with trying to understand why marine organisms are where they are. With the help of experiments in the lab and in the field, he tries to figure out how humans will impact marine life. More specifically, Sam focuses on ocean acidification. If we continue to release CO2 like we do now, it is projected that the overall pH will decrease by 0.3-0.4 (0.4 is a dubbeling of the amount of protons, since the scale is logarithmic). However, Sam stresses that the release of carbon dioxide not only changes the pH of the ocean, it fundamentally changes its chemistry. Since a third of all the carbon dioxide released is picked up by the oceans, in addition to acidity the carbon levels, and the levels of carbonate and bicarbonate is affected too. All this will lead to a decline in biodiversity and a decline in the services that are provided by the ocean. One example of this, Sam mentions, is the oyster industry in the US, which was partly crushed by acidification.
It is regarded as common knowledge that acidity is a problem for biodiversity since organisms have a harder time boulding shells and skeletons when the water is acidic. Sam argues that this is not the whole story. Actually, many organisms with shells have adapted to live in waters with very low pH. Instead, the main problem is that organisms have to spend much more energy keeping their internal pH stable if the pH around them decreases. However, Sam points out that some organisms will probably be better off in a sea with higher acidity. For instance, toxic algae are projected to withstand acidity better, making it possible for a rapid increase in the amount of booth algae and toxins, becoming an environmental problem of itself.
One thing that is understudied when it comes to ocean acidification according to Sam is local variation. In the open ocean, the variation is low, hence requiring fewer data points. In the coastal region however, there is a need for much more data than is currently generated. This is because the variation over times is much higher, thanks to the presence of marine life that photosynthesize and respire.
There is both daily and seasonal variation. Since photosynthetic organisms photosynthesize during the day and respire during the night, the pH will increase during the day and decrease at night. In addition, pH will increase during winter since there is less biological activity and CO2 is less soluble in cold water. For instance, at the facility that Sam is doing his research in the pH varies between 7,6 and 8,6. It is projected that these variations will increase with higher CO2-levels, and this is a problem because it would mean that there is a higher risk that the pH will go below the threshold of survival for the organisms living there.
Sam highlights the need to measure pH in combination with other metrics, such as temperature, salinity, alkalinity and CO2 levels. Alkalinity is a measurement of the carbonate/ bicarbonate of the water, and it acts like a buffer for changes in acidity. High alkalinity means that CO2 will not make the water as acid as it would have been if it had low alkalinity.
Sam argues that with more data on acidity, he can create detailed maps and recommendations for policymakers. The UN had said that they want a predictable ocean, but Sam thinks that it is enough to be able to tell which activity is creating the most impact (e.i. overfishing, pollution). In addition, Sam thinks it is good that there is a sustainable development goal regarding acidification (14.3), but that policymakers are not doing enough.