Many marine organisms are affected by ocean acidification, particularly those with shells and skeletons built from calcium carbonate; e.g., corals, oysters, clams, mussels, snails, and phytoplankton and zooplankton—the tiny plants and animals that form the base of the marine food web. These “marine calcifiers” face two potential problems associated with ocean acidification. The first one is that their shells and skeletons may dissolve as the ocean pH decreases; as CO2 is dissolved in seawater it becomes more corrosive, and the water chemistry undergoes major changes, such that fewer carbonate ions, the primary building blocks of marine organisms, are accessible for uptake to shells and skeletons. To build their shells or skeletons, marine organisms generally undergo an internal chemical process that converts bicarbonate to carbonate in the form of calcium carbonate. Exactly how ocean acidification slows calcification or shell formation is not yet completely understood, but various mechanisms are being studied. Most investigations of this corrosive environment focus on the evolutionary defense mechanisms that organisms must have in order to build and maintain their calcium carbonate shells and skeletons in an increasingly acidified environment. In such environments, these organisms can be subject to greater energy expenditure and environmental stressors such as ocean temperature increases, low oxygen accessibility, disease, and habitat loss.
Bharatha Rathna P. & Santhanam P., 2019. A study on the impact of acidification on the morphometry, photosynthesis, and biochemical composition of phytoplankton. In: Santhanam P., Begum A. & Pachiappan P. (Eds.), Basic and Applied Phytoplankton Biology, pp. 239-249. Springer, Singapore. Chapter (restricted access).
