A key emerging issue in marine biology has been the recent predictions of changes in oceanic chemistry as a result of rising anthropogenic carbon dioxide in the atmosphere. Current geochemical models predict oceanic pH will reduce and undersaturation in aragonite will occur over the next 100 years. “Ocean acidification” appears to have begun. The average pH of the ocean has declined by 0.1 units since pre-industrial times, and is projected to decrease by 0.77 units by 2100. Such large scale changes have not been recorded in the past 300 million years and are likely to have significant effects on the living ocean.
Organisms in shallow waters are likely to be the first affected by ocean acidification. Lowered pH can reduce the productivity of algae and heterotrophic organisms, as well as affecting the metabolism of zooplankton, benthic species and fish. In many species, it is likely that lower pH will also reduce reproductive success disrupting recruitment processes and eventually changing species distribution and abundance. Lowered aragonite concentration may have serious consequences for shell producing pteropods and coccolithophores, which are a primary food source for higher marine organisms. All these effects may resonate through to deeper waters since disruption to productivity at the surface could alter the supply of food material to the seafloor.
You can read more about ocean acidification in the reviews below.