When discussing the threats of climate change, we often hear about "global warming" and "coral bleaching," but there is an equally severe, yet more hidden, crisis: ocean acidification. Scientists call it the "evil twin" of global warming because it also stems from the massive amount of carbon dioxide emitted by human activity. Since the Industrial Revolution, our burning of coal and oil has released vast quantities of CO2. A portion of this atmospheric CO2 has been absorbed by the ocean, which slows down global warming but simultaneously triggers a series of chemical changes.
When carbon dioxide dissolves in seawater, it forms carbonic acid and releases hydrogen ions, causing the water's acidity to rise (and its pH level to drop). Over the past 40 years, the ocean's acidity has increased by approximately 17.5%, a rate of change that is up to ten times faster than any time in the last 300 million years of Earth's history.
The problem is that many marine organisms need carbonate ions to build their shells or skeletons. This includes crucial species like corals, oysters, mussels, and even the tiny plankton known as pteropods (or "sea butterflies"). As acidification makes carbonate ions scarcer, these organisms are like artisans lacking building materials; they struggle to construct their structures, and even their existing shells or skeletons can begin to dissolve.
For coral reefs, this means a reduction in skeletal density, which severely weakens their ability to withstand storms and erosion. It's estimated that by the end of this century, the skeletal density of global corals could drop by 20%, a process likened to the ocean suffering from "osteoporosis."
The impact of acidification isn't limited to single species; it sets off a chain reaction throughout the food web. When plankton or shellfish cannot survive, the fish and other creatures that depend on them for food are also affected, thereby destabilizing the entire marine ecosystem.
Faced with this chronic crisis, scientists aren't standing idly by. They are actively searching for locations with "climate resilience," known as "super reefs." These areas have demonstrated resistance to warming and acidification and are seen as vital refuges for future marine ecology.
Encouragingly, Taiwan's Dongsha Atoll is one of only four such super coral reefs currently identified worldwide. Dongsha Atoll is buffered from the impacts of warming and acidification to some extent by the deep, cool water brought in by internal waves and the photosynthesis carried out by its surrounding seagrass beds.
However, even the most resilient coral reef cannot withstand an endless stream of CO2 emissions alone. To truly protect the ocean, the key remains global carbon reduction and various marine conservation efforts, including reducing the use of fossil fuels, protecting habitats, decreasing pollution, and making energy-efficient, low-carbon choices in our daily lives.
Ocean acidification reminds us that our human way of life is intimately connected to the distant ocean. By safeguarding this unseen chemical balance, we are also protecting coral reefs, diverse marine life, and our own future.
