Ocean acificication is a low but sure process going on in our oceans.
CO2 is emmited into the atmosphere in a number of ways, many of them naturally, and with balances. Humans have come along and thrown off this millenium-old system with emissions that are not countered, leading to increased CO2 in our atmosphere. The ocean is a carbon sink, which means it absorbs and stores carbon.
As more and more CO2 is absorbed into the atmosphere, it also absorbs into the ocean as mentioned above. Increases in CO2 concentration in the ocean lead to the PH of the water decreasing, or becoming an acid over time. Currently, the Ph of the ocean is around 8, but at the current rate of change, as soon as 2100 we could see that dip below 7, which is considered an acid.
As ocean acidification unfolds and our oceans creep closer to becoming an acid, many things begin to happen. At the start, shellfish shells are unable to form from calcium due to the acids stopping them from building up. This effects not only local ecosystems, but also effects the food industry by no longer being able to find these animals to sell. This also has an effect on costal communities as fishing jobs are wiped out. Another major concern in regards to ocean acidification and CO2 saturation is when the ocean becomes fully saturated and becomes a carbon source instead of a sink. This means it is putting out more CO2 from evaporation and other ways than what is absorbing. When this happens, CO2 content in the atmosphere will raise at an even higher rate since there will be even less to help absorb it. If changes are not made soon, these effects could be irreversible.