Oceanic waters are becoming increasingly acidic due to the absorption of carbon dioxide (CO2) from human activities, such as the burning of fossil fuels. This CO2 reacts with seawater to form carbonic acid, which lowers the water's pH and makes the oceans more acidic.
Since the industrial revolution, our activities such as the burning of oil, coal, or deforestation have massively released carbon dioxide (CO₂) into the atmosphere. A significant portion of this CO₂ does not remain solely in the air: about a quarter ends up being absorbed by the oceans. At first, this seemed super convenient because it limited the greenhouse effect. But today, the ocean absorbs so much that it is starting to saturate; the more it absorbs, the more its ordinary chemical functioning is disrupted and the water becomes more acidic. This phenomenon, known as ocean acidification, has been increasing over the years, directly following the rise in CO₂ concentration in the air.
When carbon dioxide (CO₂) is absorbed by the oceans, it chemically reacts with water (H₂O). This reaction produces carbonic acid (H₂CO₃), an unstable molecule that quickly dissociates, releasing hydrogen ions (H⁺) and bicarbonate ions (HCO₃⁻). The more hydrogen ions there are, the lower the pH becomes. As a result, the water becomes more acidic, gradually reducing the amount of carbonate ions (CO₃²⁻) essential for marine life. And that is why, little by little, the oceans are becoming more acidic.
When seawater becomes more acidic, some organisms struggle to build their shells or calcium skeletons. This is the case for corals, oysters, sea urchins, and tiny creatures called calcifying plankton. As acidity increases, these living beings have more difficulty absorbing calcium. The result: their shells or skeletons eventually weaken or even dissolve. This fragility makes these species much more sensitive to diseases and predators. Acidity also disrupts the behavior and growth of certain fish. Their ability to detect predators or find their way is affected. As a result, an entire marine food web becomes destabilized.
The balance of marine ecosystems is directly disturbed by acidification. This particularly poses a problem for organisms with shells or calcareous skeletons (corals, mollusks, some plankton) that struggle to build their shells in more acidic water. However, these organisms often form the base of the marine food chain. When they become scarce, the entire food web is disrupted: fish, birds, and marine mammals can be affected in turn. Furthermore, the decline in coral populations leads to the degradation of coral reefs, true refuges for thousands of species. This trend weakens marine biodiversity, making oceanic ecosystems less resilient to future environmental changes.
To curb ocean acidification, the top priority remains to reduce our CO₂ emissions. This primarily involves a reduced use of fossil fuels, such as oil, coal, or natural gas, and a significant boost to renewable energies like solar and wind. Restoring and protecting certain coastal environments—particularly mangroves, seagrasses, and coral reefs—also helps immensely, as they naturally capture atmospheric carbon. Promoting sustainable practices in fishing, agriculture, and industry can prevent numerous pollutants and nutrients from entering the water and further exacerbating acidity. Ultimately, acting individually (flying less, saving energy at home, prioritizing local and sustainable products) is also a simple and effective gesture to reduce our overall impact on the ocean.
Since the beginning of the Industrial Revolution, the oceans have absorbed nearly 30% of the carbon dioxide produced by human activities, thereby slowing down global warming but also leading to their acidification.
When the ocean water becomes more acidic, it can prevent corals, mollusks, and crustaceans from properly forming their shells or skeletons, significantly weakening them.
A decrease in pH of only 0.1 units since the industrial era may seem minimal, but it corresponds to an increase of nearly 30% in ocean acidity.
Some marine organisms, such as jellyfish or certain species of algae, are capable of thriving in more acidic waters, which could profoundly disrupt the balances of marine ecosystems if acidification continues.
Reducing the carbon footprint in daily life helps limit acidification: reducing energy consumption, prioritizing renewable energy, using clean transportation, and supporting responsible environmental policies—all of this contributes to slowing down carbon dioxide emissions.
Sure! Here’s the translation: "Yes, ocean acidification and climate change primarily stem from the same issue: the increasing emissions of carbon dioxide (CO₂). However, they are two different phenomena with specific impacts, although they are closely connected."
Since the beginning of the industrial era in 1750, ocean acidity has increased by about 30%. This phenomenon has been accelerating significantly over the past few decades due to the exponential growth of CO₂ emissions in the atmosphere.
Yes, polar regions and coral reefs are particularly sensitive to acidification because cold water absorbs more CO₂, and corals are directly affected in their calcium growth.
It is difficult to quickly reverse this phenomenon on a global scale, but a significant and lasting reduction in CO₂ emissions can strongly slow down or stabilize ocean acidity and enable the marine ecosystem to adapt better.
Although acidification does not pose an immediate direct danger to human health, it does have consequences for the marine food chain, thereby indirectly affecting our food supply and our economy related to fishing.
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