For Bill Mook, coastal acidification is one thing his oyster hatchery cannot afford to ignore.Mook Sea Farm depends on seawater from the Gulf of Maine pumped into a Quonset hut-style building where tiny oysters are grown in tanks. Mook sells these tiny oysters to other oyster farmers or transfers them to his oyster farm on the Damariscotta River where they grow large enough to sell to restaurants and markets on the East Coast.The global ocean has soaked up one third of human-caused carbon dioxide (CO2) emissions since the start of the Industrial Era, increasing the CO2 and acidity of seawater. Increased seawater acidity reduces available carbonate, the building blocks used by shellfish to grow their shells. Rain washing fertilizer and other nutrients into nearshore waters can also increase ocean acidity.