With the absorption and decomposition of carbon dioxide in ocean water beyond the desired level, there will be

Extra dissolved carbon dioxide in seawater can spur the growth of phytoplankton that use it for photosynthesis.

Excess carbon dioxide does not lower ocean temperature.

It does not raise the salinity of the water.

A direct rise in sea level is driven by thermal expansion and ice melt, not by dissolved carbon dioxide.

Beyond a point, absorbed carbon dioxide also acidifies the ocean, harming shell-forming life.

Ocean acidification threatens coral reefs and shellfish by dissolving carbonate.