Like most people here, I'm reading the tsunami of increasingly dismal news about rising temperatures, disappearing polar ice, unforeseen droughts and storms. Climate change effects on the oceans are increasingly grim. After a disastrous 2016, another bleaching event seems to be underway on the Great Barrier Reef. Of wider concern is ocean acidification, which can directly affect all marine food chains, since all of them include things like corals, plankton, or mollusks that incorporate calcium carbonate into their bodies. Climate chance in the oceans will thus radically change not only weather patterns but also food supplies for millions. And we need to start worrying about methane and CO2 releases from growing ocean dead zones, as well as from the permafrost.
There is one point in all this that I hadn't seen much discussed but which I think might be rather important. Oceanic phytoplankton is the source of about 50% of the oxygen we breathe. What is rising ocean acidification going to do to THAT?
Compared to the flood of information and comment about sea levels, storms and drought, there has been comparatively little discussion about what could happen to our air supply. Obviously, it's a complex issue. Like any plant community, 'phytoplankton' includes many different species with different tolerances to acidic levels. The few studies I've encountered are in the "probably not that much but we don't really know" category (Here) Still, if you have a vegetable garden and you switch from giving it water to vinegar, you can probably expect that your future harvests will be rather less that what you're accustomed to.
Recently however, there has been a spike of social media buzz over a study that brings a bit more urgency to the question. It is a study by Yadigar Sekerci and Sergei Petrovskii published in The Bulletin of Mathematical Biology, entitled: Mathematical Modelling of Plankton–Oxygen Dynamics Under the Climate Change. The article is highly mathematical and unfortunately behind a paywall. A brief popular summary can be found HERE.
Sekercii and Petrovskii modeled theoretical physico-chemical connections between zooplankton, phytoplankton, oxygen concentrations, productivity, and how all these are affected by temperature. Their main result predicts oxygen depletion when the oxygen production rate in the ocean becomes either too high or too low. Since this rate, like most biological rates, is affected by temperature, the authors conclude that global warming will push the planktonic ecosystem out of the theoretical "safe" zone and eventually cause the system to shut down. They make no guesses about how many years before rising global temperatures might shut off half our existing oxygen supply.
But although they were careful to stress the uncertainties in their model, and its theoretical nature, it seems they couldn't resist one little prediction about our probable future…
In this paper, however, we have shown that the danger to be
stifled is probably more real than to be drowned