Forecast Fish and Marine Mammal Population Responses to Ocean Acidification in the North Pacific Ocean and Bering Sea
September 19, 2018
Approximately 30-50% of global anthropogenic CO2 emissions are absorbed by the world’s oceans (Feely et al. 2004, Sabine et al. 2004). Increased CO2 uptake by the oceans is expected to reduce surface ocean pH by 0.3 – 0.5 units over the next century, which would be the largest change in pH to occur in the last 20-200 million years (Feely et al. 2004). Ocean acidification reduces the calcium carbonate (CaCO3) saturation point. Dramatic reductions in calcium carbonate saturation have been observed in the North Pacific since the industrial revolution (Feely et al. 2004).
Ocean acidification likely will impact the ability of marine calcifiers, such as corals and mollusks, to make shells and skeletons from calcium carbonate. This will occur principally because of a reduction in the availability of the chemical constituents needed for calcified shells and plates. In addition, ocean acidification may elicit broad physiological responses from non-calcifying organisms through less obvious pathways. For example, changes in ocean pH may affect the availability of nutrients to phytoplankton, the bioavailability of marine toxins to bacteria and phytoplankton, and internal CO2 concentrations of marine animals (UK Royal Society 2005). Ocean acidification may indirectly affect fish and marine mammal species through reduced abundance of marine calcifiers at the base of the food web. Changes in ocean pH also may affect reproductive success of commercially important species by reducing demersal egg adhesion or the fertilization success of eggs broadcast into the ocean. Coldwater corals provide shelter for structure-oriented species such as rockfish. The numerous pathways for effects (both direct and indirect) imply that ocean acidification may have important impacts on many marine species.