Overview Increased atmospheric carbon dioxide (CO₂) levels, caused by the burning of fossil fuels and deforestation, is the primary driver of a process termed ocean acidification, where the addition of CO₂ to the surface ocean acts to increase seawater acidity and lower pH. Why It Matters Carbon dioxide gas dissolves so readily in seawater that approximately one quarter of human caused CO₂ emissions become sequestered in the ocean. Once in the ocean, CO₂ combines with water to form a weak acid, resulting in a change in the chemistry of the sea. As the CO₂ increases, the pH decreases; indicating increasing acidificication. A Compounding Crisis While increased atmospheric CO₂ is the primary driver of coastal and ocean acidification in surface ocean waters, the coastal oceans and estuaries experience additional processes – both natural and anthropogenic (human-caused) – that play a role in changing water chemistry.
Natural input of nutrients to the ocean via rivers, groundwater, and atmospheric deposition promotes algae growth in estuarine waters, making these estuaries areas of high productivity. In a process known as eutrophication, additional input of nutrients to the estuary and coastal ocean (due to use of fertilizer, wastewater treatment, and changing land use) fuels additional growth of algae during the productive spring and summer seasons.