Ocean Acidification

“Ocean Acidification is just the evil twin of global warming…” As if global warming isn’t evil enough… Disappointed-Meme-Face-08

Being from a country where glass bottom boats, snorkeling and coral reef exploration are parts of tourism, Ocean Acidification is one of the global warming effects we need to discuss. Before we dive into that, let’s first understand pH, acids, bases & indicators, and the importance of pH balance.

What is pH?

pH is the measure of the hydrogen ion concentration of a compound. It is a logarithmic scale which ranges from 0-14 where 7 is neutral, >7 is basic (alkaline) and <7 is acidic.

pH= -log[H+]

pH scale (1)
pH Scale

Acids & Bases

From corrosive and sour to soapy and bitter, acids and bases make up the world as we know it. They are many different types of acids but for the simplicity’s sake, it can be defined as a chemical substance that neutralises bases, dissolves some metals, and turns litmus red or a molecule or entity that can donate a proton or accept an electron pair in reactions.

For a more in depth explanation of the pH Scale, click here!

Bases (a.k.a Alkalis) can be defined as a chemical compound that neutralises or effervesces (bubbles) with acids & turns litmus blue. Also, by being the opposite of acids, it is subsequently a compound that accepts protons or donates electron pairs in reactions.

Indicators

These are compounds which change colour and structure when exposed to certain environments. Litmus, mentioned above, is an example of an indicator; it is the first indicator you will ever learn about in science. There are many other indicators which are used in chemical tests such as methyl red, phenolphthalein (common), methyl orange and many more.

pH Importance

For every biological system, pH plays a very important role in keeping the balance. The slightest change in pH can have adverse effects. For this post, I will use aquatic environments as an example. The pH of most aquatic environments ranges between 6-8 and in these conditions organisms, both at the top and the bottom of the food chain, thrive. pH can determine how well some organisms carry out their regular day-to-day processes with said water and unsustainable changes result in decreased numbers and in extreme cases, death. For other organisms, they grow to levels which may continue to inhibit the ones already struggling. This is why keeping the balance is paramount.

What’s there to know about the Ocean?

Ocean pH, seawater composition and the general equilibrium of the ideal ocean would help to show how different things can become or are becoming via Ocean Acidification. As Caribbean natives, we tend to just go to the beach and never think about what we’re stepping into. I think it’s high time we changed that.

Ocean pH

Unaffected by anthropogenic (man-made) emissions, the pH of sea water was a basic 8.2. After the rise in carbon dioxide concentrations in the atmosphere, it has decreased to 8.1 thus, increasing in acidity. A 0.1 change in pH may seem so minuscule but the pH scale and the Richter Scale are alike in that a change of 1.o is actually 10 times that of the original value. So, this change represents a considerable decrease in the comfort of marine life.

“What is seawater even made of?”, you ask?

Seawater Composition

Ions found in seawater originate either from inside the earth (seismic/volcanic activity), the atmosphere (gases floating around in the atmosphere) or from the many organisms (coral reef, excrement or decomposing) which call the ocean their home. It is because of these above salts that the ocean tastes ‘salty’.

“How does the ocean maintain a basic pH?”

Ideal Ocean Equilibrium

You were probably thinking that a body of water should be neutral but by now I’m sure that has changed and wondering how it is basic and how does it stay basic. The answer, a Carbonate Buffer (a solution that resists pH changes when volumes of acid or alkali are added to it). A buffer usually consists of a weak acid and its salt; the carbonate buffer consists of carbonic acid (H2CO3) – formed when carbon dioxide dissolves in seawater – and the bicarbonate ion. Since carbonic acid is unstable, it breaks down into the bicarbonate and carbonate ions which are now responsible for the buffering/pH regulation of the ocean. The percentage presence of the bicarbonate ion (HCO3– ) and carbonate ion ( CO32-)make up part of the “other” percentage. Even though their percentages are scanty, they play the most important role in the ocean. All aquatic life is sensitive to the pH of the ocean therefore the buffer must be supreme.

 

buffer
The entire process of the Carbonate Buffer. In more basic conditions, the Carbonate Ion is formed. Ideally, equilibrium should be between the bicarbonate & carbonate ions.

“So! What is Ocean Acidification?” 

Ocean Acidification (OA)

Now that you have enough knowledge on the Carbonate Buffer, we can now take a look at the acidification process. Buffers are usually resistant to additions of acids and bases but given enough of one, the equilibrium will definitely shift. Since the amount of carbon dioxide in the atmosphere has increased over the years due to industrialisation, more and more carbon dioxide has been dissolving into the ocean. Therefore, the abundance of carbonic acid in the ocean is increasing, causing the buffer to become unbalanced thus, lowering the pH.

Before, the absorption of carbon dioxide by the world’s oceans was seen as natural mitigation to our climate change issue. But now it is proving to be yet another head of the hydra.

Consequences

Calcium Carbonate Breakdown

Remember that carbonate ion which is formed in more basic conditions? Well when it reacts with the calcium ions in the ocean it forms a salt called calcium carbonate. This compound is one of the building blocks used by organisms to build shells and coral reefs amongst other things. When it reacts with the carbonic acid, it dissociates causing a weakening of the shells of snails, clams and any other like organisms, as well as the destruction of coral reef. The coral reef cannot use the calcium carbonate to keep their skeletons strong, therefore they dissolve. In Barbados, damage to our coral reefs will impact on our eco-tourism package. Imagine the larger world renowned reefs. How will they survive?

Ecosystem Imbalance

With calcium carbonate out of the picture, there is the problem of organism survival. Some juveniles of aquatic organisms have hard shells to protect them making them extremely vulnerable to OA. When the mortality rate of juveniles increase, the rate of survival decreases thus, an overall decrease in populations. This causes a domino effect in the food web. Where there is a shortage of food, a shortage of feeders arises.

Socio-Economic Impact

As I mentioned before, coral reefs are a part of many tropical destinations’ eco-tourism. With them being destroyed by OA, economic problems come to the light. Not only are the coral reefs gone, but the fish that frequented them are gone too. The big fishing companies that catch the mussels and shellfish for restaurants and supermarkets can go out of business if OA goes on long enough. Jobs, livelihoods and maybe even communities could be lost taking a toll on the economy causing it to tumble, yet again.

My Two Cents

“In the last 150 years or so, the pH of the oceans has dropped substantially, from 8.2 to 8.1–equivalent to a 25 percent increase in acidity. By the end of the century, ocean pH is projected to fall another 0.3 pH units, to 7.8.” (ScienceDaily, June 2014 )

We have discussed what pH, acids & bases and indicators are, everything you need to know about the ocean (for the purpose of this blog), and what is OA as well as its consequences. You have read for yourself, the situation is a serious one. I cannot stress enough how dangerous climate change (& its family) is to the planet and how much we have taken for granted. A step in the right direction would be to become more aware of what’s going on around you. There is no such thing as too much information when it comes to something as serious as this. Once you know, you can always do better.

– the Awkward Chemist

“It is a curious situation that the sea, from which life first arose, should now be threatened by the activities of one form of that life. But the sea, though changed in a sinister way, will continue to exist: the threat is rather to life itself.” –Rachel Carson

 

Sites Used for this Post:

ScienceDaily

Teach Ocean Science

National Science Foundation

CarboSchools

 

 

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