Of course, ocean acidification is not a manifestation of climate change, but rather a concurrent manifestation of rising levels of carbon dioxide. However, many instructors address it in climate courses because it’s pertinent to the level of carbon dioxide emissions reductions that should be pursued in relation to reductions of other greenhouse gas. Despite receiving extensive attention in scientific and policy forums in recent years, the “other CO2 problem” there remains huge questions about the ultimate impacts of carbon dioxide on ocean species.
One of the primary questions in this context, and one that shines a ray of hope in this context, is whether ocean species may be able to acclimatize to falling pH levels. Unfortunately, experiments to date, especially for longer-lived organisms, have usually been conducted on too short of a timeline to ascertain whether species may, indeed, be able to acclimate, adapt or evolve under these environmental conditions. A new study published in the Proceedings of the National Academy of Sciences may help to answer some of these questions. The study focused on two examples of rapid carbon release in the geological record, in the Eocene Thermal Maximum and the Paleocene Eocene Thermal Maximum (PETM), and used two benthic foraminifers (protozoa that usually form an external shell, usually made of calcium carbonate) as a model group. The study reconstructed the calcification response of of survivor species to determine for evidence of ability to acclimatize or adapt to acidification.
The study concluded that two foraminifera species, O. umbonatus and N. truempyi, survived the PETM, suggesting that the former species adapted to carbonate-corrosive condition in pore waters and the latter species to low-carbonate ion bottom waters. While this is certainly good news, the study also points to “preferential survival of species adapted to to calcify under low carbonate saturation.” This conclusion necessarily leads to the question of whether ocean acidification may lead to fundamental changes in species assemblage in marine ecosystems, which may still have far-reaching implications for the marine environment.
This article would be a good jumping-off point for discussion of ocean acidification science issues, as well as the abiding issue of how policymakers should respond under conditions of high risk and high uncertainty.