Ocean acidification is the process in which ocean water becomes more acidic due to increased emissions of carbon dioxide (CO 2 ).
The concentration of CO 2 emissions has been increasing rapidly since the Industrial Revolution. At that time, fossil fuel combustions became a constant in the means of production, releasing more CO 2 into the atmosphere than is naturally produced.
Oceans can absorb more than 30% of the carbon dioxide present in the atmosphere, helping to control the impacts of the increase of this gas to the planet. However, once in the water, CO 2 undergoes several chemical reactions that increase the concentration of hydrogen ions in its composition. Thus, it results in a decrease of pH in the water, making it more acidic.
pH scale and chemical reactions in seawater
The pH measurement is a scale that measures the amount of hydrogen ions present in aqueous solutions. It ranges from 0 to 14, where 7 is considered a neutral pH. A pH greater than 7 is considered basic, while a pH less than 7 is acidic. The more hydrogen there is in the solution, the lower the pH and the more acidic it becomes.
The pH of the oceans is basic, around 8.1. From the Industrial Revolution to the present, the pH of the oceans has decreased by 0.1 units. This may not seem like much, but the pH scale is logarithmic, so you could say that the oceans have become 30% more acidic. According to the latest report on climate change, the pH could decrease by 0.4 units by the end of the century if carbon emissions continueat the same rate.
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As it enters the oceans, CO 2 dissolves in water. It mixes with water (H 2 O) and forms carbonic acid (H 2 CO 3 This compound is a weak acid and breaks down naturally in chemical reactions, releasing more hydrogen ions (H+) and bicarbonates (HCO 3 -Thus, by releasing more hydrogen into the oceans, the oceans become more acidic.
And by forming more bicarbonates, this process removes the carbonates (CO 3 -This compound (CO 3 -) is very important for the shell calcification process of marine organisms such as oysters, mussels, corals and some plankton.
Consequences of a more acidic ocean
The more CO 2 in the atmosphere, the more the oceans will absorb it. The consequence of this can already be observed in the animals living in the oceans.
Until the 1990s, it was not known exactly how changes in ocean pH would affect marine organisms. Since the 1990s, greater sensitivity has been observed in animals that have shells.
Corals, for example, besides being threatened by the increase in ocean temperatures, also suffer from ocean acidification because they cannot form their skeletons. By reducing the carbonates in the environment, other animals are also prevented from calcifying their shells, such as oysters and mussels.
Besides the decrease in the formation of shells, there are studies proving that shells and calcareous skeletons can dissolve if the pH of the water is too low. This happens mainly in microscopic organisms, such as plankton.
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Most of these animals are the base of the food chain, which poses a major threat to larger groups of marine animals and the ecological balance of the oceans. In addition, humans who use the oceans for subsistence can also be directly affected. Corals also serve as protection from rough waters, leaving calmer waters for coastal communities.
Some animals that don't have shells are also being affected by ocean acidification. Clown fish, for example, are losing their ability to detect predators or find shelter in more acidic waters.
The oceans are becoming increasingly acidic at an accelerating rate. This rate is the fastest of any in 300 million years.
Regardless of the region or marine animal, ocean acidification has a global impact. Thus, it is urgent to reduce carbon dioxide emissions and slow Earth's climate change to avoid further consequences.
With information from NOAA and Live Science