Ocean acidification is an emerging global environmental problem that is currently widely researched in order to predict and prevent its detrimental outcomes on marine life.

What is Ocean Acidification?
When carbon dioxide is absorbed by seawater, the pH levelof seawater is lowered, and there are also decreases in carbonate ion concentration and saturation states of biologically important calcium carbonate minerals. This chemical process is known as ocean acidification and poses a threat to marine life, as calcium carbonate minerals are essential building blocks of the skeletons and shells of many sea creatures. It is estimated that by the end of this century, the acidity of the surface waters of the ocean could be 150% higher than today.

What are the biological impacts?
Various marine organisms are affected. Some benefit from higher carbon dioxide levels, such as photosynthetic algae and seagrasses. However, others will suffer from lower calcium carbonate saturation, such as oysters, clams, sea urchins, shallow water and deep sea corals, and calcareous plankton.

Pteropods, or sea butterflies, will lose their shells – when placed in seawater with pH and carbonate levels projected for the year 2100, their shells dissolve within 45 days.

Shellfish are also affected. Oysters are currently experiencing a reproductive failure, and low pH may be a cause, however more research is required to confirm this.

Rising carbon dioxide levels and decreasing pH in oceans affects many organisms that produce calcium carbonate shells or skeletons, and this includes corals. Research suggests that by the end of this century, coral reefs will be eroding faster than they can be rebuilt, which will have a detrimental effect on these ecosystems and the millions of species that rely on coral reef habitats.

Source: https://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F