{"id":167,"date":"2026-09-08T12:45:20","date_gmt":"2026-09-08T12:45:20","guid":{"rendered":"https:\/\/oceandecademed.org\/en\/?p=167"},"modified":"2026-09-08T12:45:20","modified_gmt":"2026-09-08T12:45:20","slug":"what-is-ocean-acidification","status":"publish","type":"post","link":"https:\/\/oceandecademed.org\/en\/what-is-ocean-acidification\/","title":{"rendered":"What Is Ocean Acidification and Why Does It Matter?"},"content":{"rendered":"

Ocean acidification is the long-term decrease in seawater pH caused mainly by the ocean absorbing carbon dioxide released to the atmosphere by human activities.<\/strong> The ocean remains alkaline, not literally acidic, but its chemistry is shifting toward the acidic end of the pH scale.<\/p>\n

This change is separate from ocean warming, although both share the same major cause\u2014rising greenhouse-gas concentrations\u2014and can affect organisms at the same time.<\/p>\n

The chemistry in simple steps<\/h2>\n
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  1. Carbon dioxide moves from the atmosphere into surface seawater.<\/li>\n
  2. It reacts with water to form carbonic acid.<\/li>\n
  3. The acid releases hydrogen ions, lowering pH.<\/li>\n
  4. Hydrogen ions combine with carbonate ions, reducing carbonate available in the water.<\/li>\n<\/ol>\n

    Corals, oysters, mussels, pteropods and some plankton use calcium and carbonate to build shells or skeletons of calcium carbonate. Lower carbonate availability can make construction more difficult and can increase dissolution under some conditions.<\/p>\n

    Does every species respond in the same way?<\/h2>\n

    No. Sensitivity varies by species, life stage, food supply, habitat and the speed of change. Some organisms can regulate their internal chemistry or benefit indirectly, while others show reduced growth, survival, reproduction or sensory performance. Food-web effects can occur when a vulnerable organism is important prey or habitat.<\/p>\n

    Coastal water can change faster than the open ocean because rivers, upwelling, nutrient pollution, photosynthesis and respiration affect local pH. That makes sustained local observations important.<\/p>\n

    Why coral reefs are vulnerable<\/h2>\n

    Reef-building corals need suitable carbonate chemistry to create and maintain their structures. Acidification can reduce calcification and weaken the balance between reef growth and erosion. At the same time, warming increases bleaching risk, creating multiple stresses.<\/p>\n

    How scientists measure acidification<\/h2>\n

    Researchers measure pH, dissolved inorganic carbon, total alkalinity and carbon dioxide with ships, moorings, autonomous instruments and laboratory experiments. Sediment records and long observation series help place current changes in context.<\/p>\n

    A classroom activity can demonstrate the principle but cannot reproduce an entire ecosystem. See the restored ocean acidification experiment<\/a> and use the linked scientific sources for interpretation.<\/p>\n

    What can reduce the risk?<\/h2>\n

    Cutting carbon dioxide emissions addresses the global driver. Coastal actions\u2014reducing nutrient pollution, protecting seagrass and wetlands, and managing fisheries and habitats\u2014can reduce added stress and improve resilience. Local restoration cannot substitute for emissions reduction, but it can help ecosystems cope.<\/p>\n

    Frequently asked questions<\/h2>\n

    Will the ocean become acid?<\/h3>\n

    The global ocean is expected to remain above neutral pH, but \u201cacidification\u201d correctly describes a decline in pH and major chemical change.<\/p>\n

    Can ocean acidification affect people?<\/h3>\n

    It can affect fisheries, aquaculture, reef protection, tourism and communities that depend on shell-forming species and coral ecosystems.<\/p>\n

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    Sources and further reading<\/h2>\n