Could Hydrogen Peroxide production by UV-B in Planktonic Microorganisms Cause Sea Warming and Ice Melting?
By Jordan Smith
Hydrogen Peroxide is an extremely common household item that most people recognize and possibly have used before. But what most people do not know is that hydrogen peroxide can be produced inside marine planktonic microorganisms and as a result affect marine ecosystems, decrease ice thickness, and alter climate!
Is this really something we should be worried about? Under ultraviolent-B radiation (UV-B) oxidation of water (H2O) by dioxygen (O2) yields hydrogen peroxide (H2O2) but hydrogen peroxide is a potent microbicide so as soon as it is produced inside the cell it must be removed through catalase activity. This decomposition of hydrogen peroxide produces an extreme amount of heat that is 13 times greater than that which is produced in ATP hydrolysis. Making this reaction by far the most exothermic in nature1.
All this heat must go somewhere! A paper published by Dr. Cosme Moreno in 2012 showed the importance of this heat produced from over activated hydrogen peroxide catalase. Dr. Moreno estimated that with a 0.07 W/m2 increase (which is 30% of the UV-B increase of the Arctic) being transformed to heat at the water-ice interface, in an area the size of a spherical 8 km in diameter during a week could produce a little more than a megaton of energy. Which is 80 times larger than the atomic bomb used in the Second World War.
With an increasing amount of UV-B radiation reaching the earth and penetrating deeper through the ice, the radiation will reach more organisms. This will create a negative feedback loop. For instance, in high latitude regions, marine microorganisms, which have been encased in floating ice during winter, are released in spring to the interface between the water and ice. There they absorb UV-B radiation, produce hydrogen peroxide, use catalase to remove the hydrogen peroxide, and in turn produce heat which causes them to become less dense and rise. This density effect from the heat produced inside the cell will lead to the accumulation of these organisms at the water-air or water-ice interfaces leading to increased absorption, heat production, and sea ice melting.
The heat produced at the water-air interface is largely transferred to the air and contributes to the heat flux to the atmosphere. Though this flux has largely been ignored it has the capacity to significantly change atmospheric circulation and sea surface warming when viewed on a time scale of a decade. Moving forward more research needs to be conducted on this biogeochemical process, which has been shown to cause significant effects on marine ecosystems and climate.
Moreno. C. M. (2012). Hydrogen peroxide production driven by UV-B in planktonic microorganisms: a photocatalytic factor in sea warming and ice melting in regions with ozone depletion. Biogeochemistry. 107:1-8.