Ocean acidification: The silent struggle in the sea


Many people are aware of Global Climate change, but most people are unaware of the secondary consequences of this process. One of these consequences is ocean acidification. Ocean acidification can be loosely explained as the gradual decrease in ocean pH, caused by the uptake of carbon dioxide from the earth’s atmosphere. Meaning, as more and more carbon dioxide is released into the atmosphere, the ocean’s pH decreases.

Since the beginning of the industrial revolution, the release of carbon dioxide (CO2) from humankind’s industrial and agricultural activities has increased the amount of CO2 in the atmosphere. As a result, fundamental changes in seawater chemistry are occurring throughout the world’s oceans.

This process is slow. Acidification of the ocean due to rising amounts of CO2 in the atmosphere that subsequently gets absorbed by the ocean. Half of the world’s oxygen is produced by small photosynthetic organisms in the ocean. Just like land plants, they use carbon dioxide and convert it into oxygen. According to Scripps Institute of Oceanography, the ocean is responsible for absorbing 26% of all carbon emissions; this translates to 2.5 billion tons of carbon dioxide. This process is vital to all respiring organisms on the planet.

Because of this large rise in carbon dioxide in the atmosphere, the ocean has been absorbing more than it can use for photosynthesis. Because the ocean cannot use this carbon dioxide, but it is still contained within the water, it creates a more acidic environment-reducing the ocean’spH. This is a harmful process for many reasons: animals that use calcium carbonate (all shelled organisms) are now being exposed to acidic conditions. As many people know due to the egg-in-vinegar experiment, the acid dissolves calcium, which means it dissolves shell. This not only puts our favorite shellfish at risk — it harms the microorganisms that are vital to our survival. These small organisms are known as plankton. There are animal plankton (zooplankton) and plant plankton (phytoplankton). The latter are the ones that create half of our oxygen.

The predicted increase in ocean acidity is about 0.5 pH units in the next 100 years. This might not seem like much, but it’s important to remember that the pH scale is logarithmic; therefore, something that is pH 7 is actually 10x more acidic than something that is pH 8. Doing the math, a decrease of 0.5 pH units means that in 100 years, the ocean is predicted to be more than 3x more acidic than it is today.

Sea life is also sensitive to changes in ocean chemistry, and there are many ways the marine ecosystem can be thrown off balance. For example, calcifying invertebrates (things with calcium carbonate shells, like snails, andlimpets) can’t grow as well in acidic conditions. These invertebrates normally feed on algae (e.g. Seaweeds or phytoplankton), which conversely grows just fine — sometimes even better — in acidic conditions. This is not only because the algae is not being eaten as much, but also because for them, the dissolved carbon is actually a beneficial resource. Thinking back to basic plant biology, this makes sense: terrestrial plants (i.e. Plants that grow on the land) take up CO2 for photosynthesis and release oxygen, and algae have to do something similar. Since they live mostly submerged in the ocean, they don’t have ready access to CO2 gas in the air like terrestrial plants do, so instead they take up the dissolved carbon.

If algae is taking up the carbon, why do we have an ocean acidification problem at all? The answer is for two reasons: one is that there is so much extra carbon that the algae can’t possibly use it all, and the other is that carbon is not the only limiting resource for the algae to grow (they also need other key nutrients, like nitrogen and phosphorous). But this still leads to an intriguing idea — can we grow more algae to help balance the pH in the ocean? Some researchers think we can do this by creating controlled blooms of phytoplankton, which are microscopic algae like diatoms and Radiolarians. These are good candidates; diatoms alone already take up huge amounts of carbon (they are responsible for 20% of the impact of all algae combined), and would just need a local influx of fertilization to feed a massive bloom.

Ocean acidification is not just about the coral area it’s about us, the entire human race. Many of usstill cannot feel the threat but this process is actually happening. How will it feel to live in a world without fish? And breathing in an atmosphere full of carbon dioxide?  Maybe a solution for our generation is to think that we won’t have to encounter these things. But our great grandchild will surely face, oceans full of acidic water and dead species floating on them. Maybe they will roam around with an oxygen cylinder on their back.

Whether we pay attention or not ocean acidification is worsening day by day. And the primary felons arewe people. So, if we want to save life in the oceansand save ourselves, since we depend on that life, the time is to start slashing carbon dioxide emissions is now. A reduction of consuming fossil fuel is also necessary.

People cannot change the circumstances, the seasons, or the wind, but they can change themselves. That is something it takes to change a whole community, a nation, a human race.

Zarin Tasneem is a student of University of Dhaka. She can be reached at z.tasnim00@gmail.com


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