Saturday, May 31, 2014

Ocean Acidification: Another consequence of climate change


Our increasing fossil fuel consumption is hurting the ocean and the life it contains in more ways than increasing temperature. Reports confirming negative impacts that climate change are inevitably going to cause in our lifetime have been spreading through the media in recent weeks. Higher temperatures, rising seas, melting ice, drought, and many other consequences are the focus. However, you may not have heard about how marine life and our agriculture will be affected by our lifestyle. For many years marine scientists have been warning us that the oceans are becoming more acidic as a result of our increasing carbon dioxide (CO2) emissions. Last month scientists found that acidic oceans are beginning to dissolve the shells of sea snails, and at least half of this damage is due to human activity. This is a threat to marine life and the economies that rely on it.

How do carbon dioxide emissions make the ocean more acidic?


Gases like CO­2 and oxygen dissolve in water the same way that salt does. Oceans absorb about 1/3 of the CO­2 emitted by humans, rather than it being released into the atmosphere. While this does slow global warming, it has a negative effect on the ocean and the life it contains. When carbon dioxide is dissolved into oceans, rivers, and lakes, it reacts with water and forms carbonic acid.

Acid separates into hydrogen and the acid component (carbonate in this case) when mixed with water. Acidity is quantified by pH, which is a measurement of the concentration of hydrogen atoms. The higher the concentration of hydrogen, the lower the pH, and the more acidic the water is.  The process of CO­2 conversion to hydrogen ions is shown in the diagram below. It is estimated that since the industrial revolution the acidity of the ocean has risen 30%, to a pH of 8.1 (pure water has a pH of 7). 

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How do we know that humans are responsible?


As the acidity of the ocean increases, this triggers other chemical reactions which negatively affect marine life. Coral and plankton can’t form strong shells and they become vulnerable to dissolution. Acidic oceans are corrosive and can also harm eggs, larvae, and dissolve shells. A new study was done on pteropods, a type a marine snail more commonly referred to as sea butterflies, to explore the severity of ocean acidification. These snails are found along the pacific coast from Baja, California, to British Columbia. The study collected data from 100 meters of ocean at 17 different sites.

The scientists found that 38% of the snail shells showed signs of damage, resembling cauliflower. By studying the trends, the scientists were able to develop a model that could estimate past and future shell damage due to ocean acidification. Oceanographers were surprised by the extent of the damage to the snail shells. They had hypothesized that the snails would show some resistance to the corrosive waters, but that was not the case.  The study also concluded that human CO­2 output has doubled the impact of ocean acidification since the industrial revolution and it will continue to get worse. The picture is likely to worsen as emissions continue, and it bodes ill for the marine food webs that depend on pteropods,” the authors of the studies said.

The progressive damage to a pteropod shell is shown. In the bottom right picture, acidic oceans have caused this shell extensive damage. Source.


What does this mean for us?


More acidic oceans make it harder for animals to fight infection, maintain metabolic activity, defend themselves, and control their buoyancy. The effects span a large chunk of the food chain including corals, crustaceans, and other shell fish.

Commercial fisheries are impacted by ocean acidification because it harms the organisms that are the base of the food webs in the arctic ocean, which includes pteropods. These food chains contain few steps from small to large organisms, so a small disruption greatly impacts the species we depends on like fish and whales. The estimated value of fish that were caught from U.S. fisheries in 2007 alone was $3.8 billion, and 73% was derived from shellfish and their predators. Ocean acidification will harm economies that rely on recreational fishing, the seafood industry, and tourism. This is happening all over the world, not just in the United States.

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The only way to mitigate the destruction of marine life due to carbon dioxide emissions is to reduce them. Policymakers around the world are trying to find solutions to reduce or contain emissions through climate engineering, regulations, and investing in newer technology.

However, changing our lifestyle is the only way to slow the problem. We need to reduce our fossil fuel consumption, invest in new technology, and regulate emissions. It will have to be a joint effort across the entire world. We all need to work together to save each other from the devastating effects of climate change. Here's to working together for the greater good!

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Thanks for reading, and cheers to your brain!


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References: 

'Sea Butterflies' Are a Canary for Ocean Acidification
  • Eli Kintisch
Science 9 May 2014344 (6184), 569. [DOI:10.1126/science.344.6184.569]





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