Breaking down the chemistry of ocean acidification and why it’s important

You may have heard of this thing called climate change. But have you heard of its evil twin, ocean acidification?

Many people may know the general gist of this other phenomenon, which essentially works similarly and in tandem to climate change in that it is driven by increasing amounts of greenhouse gases in Earth’s atmosphere. But have you ever stopped to wonder what is really going on, in the largest ecosystem on Earth — our oceans?

source: climate change news

The science behind this climate issue is definitely worth knowing. And for those of you who have never been required to take a chemistry course in college, first off, lucky you, and secondly, I hope this makes the topic seem slightly more understandable.

Basically, there are two storylines that encompass the cause and impacts of ocean acidification: one that involves carbon dioxide (CO2)  and the other which follows calcium carbonate (CaCO3). Each narrative focuses on a separate molecule that is key in the ocean acidification phenomenon.

The first molecule, carbon dioxide (CO2), is the main driver of ocean acidification. The amount of carbon dioxide in the atmosphere has increased since the mid-1800s and continues to go up, mainly due to the burning of fossil fuels for energy. Where does all the carbon dioxide go? While a good deal of carbon dioxide stays in the atmosphere, about 25% dissolves into the oceans, a large percentage considering how much we produce in emissions. Oceans are carbon sinks, which means they naturally absorb and store carbon long-term.

The carbon dioxide in the atmosphere dissolves into the oceans and reacts with water (H2O) to form a molecule called carbonic acid (H2CO3). This molecule then dissociates, or breaks down, to form a bicarbonate ion (HCO3(-)) and a hydrogen ion (H+). Bicarbonate can dissociate again to form carbonate ions (CO3(2-)) and another hydrogen ion, which is an important reaction later on.

Okay, so let’s hold up. You may be thinking that that’s a lot of chemical names and not a lot of explanation. To fully understand how each of these molecules interact together with oceans, one must know the significance of the pH scale. You may remember pH from high school chemistry lessons or even from reading about ocean acidification.

To put it simply, pH measures the concentration of hydrogen ions (H+) in a substance. The scale goes from 0 to 14, with 0 to 7 levels considered acidic (a higher concentration of hydrogen ions) and 7 to 14 basic (a lower concentration of hydrogen ions). Pure water has a pH of 7.0 while salt water naturally has a more alkaline, or basic, pH of 8.2. Because the pH scale is logarithmic, a small increase or decrease in pH represents a large change in H+ ions.

source: wikipedia

What ocean acidification is doing is actually making our oceans less alkaline. The increase of hydrogen ions is dropping the pH of the oceans.This can be extremely detrimental to species that are adapted to a certain pH, and cannot withstand more acidic oceans. Also, even though oceans are important carbon sinks, their role in balancing atmospheric concentrations of carbon dioxide only goes so far. If the oceans become too saturated with carbon dioxide, the oceans’ level of intake will decrease. This leads to more carbon dioxide staying in the atmosphere and adding to additional global warming and climate related issues. This has more impacts than just changing the acidity of the oceans and climate change, which leads us to the story of our second molecule, calcium carbonate (CaCO3).

Calcium carbonate is an important ingredient in the creation of shells and structural “skeletons” for organisms such as mollusks, corals, crustaceans, and certain algae. Calcium ions (Ca+) react with carbonate ions (CO3(2-)) to form calcium carbonate. But, there is a naturally occurring reaction to help maintain the slightly basic pH of oceans, using carbonate ions. The carbonate ions react with available hydrogen ions to form more bicarbonate (as mentioned above). But with the increase of hydrogen ions, more carbonate ions are being used to balance pH instead of combining with calcium for the use of calcifying organisms. This leads to a decrease in available carbonate for organisms to use. Overtime if organisms cannot get the correct amount of calcium carbonate, their shells/skeletons begin to degrade and dissolve as they are unable to create more.e

source: acs.org

This is a major issue, not only for calcifying organisms, but the fact that coral is a major habitat for many species of marine animals. If coral no longer can produce their skeletons of calcium carbonate, it can produce a domino-like effect on other organisms which depend on coral reefs as a basis for their ecosystem.

Greenhouse gases have more of an impact on every aspect of the climate: from increasing temperatures to ocean conditions. The effects will influence life across populations, ecosystems, continents and will not take into account country borders or political policies. Even from the smallest amount of greenhouse gas emissions, each molecule can alter the planet in different ways.

Consider this a brief jumpstart to your education in ocean acidification! Overall, it is very important knowledge to have and especially spread if we plan on doing something about it. This knowledge may “sound” scientific, but ocean acidification, unless it’s stunted, will have a major impact on humans, especially those that depend on the reefs and the conjoined ecosystem for their food. Science should never just “stay” science; we need to act on it.

If you would like to learn more, feel free to read through these links or explore the multitude of articles available online. Berkeley also has a great selection of seminars and DeCals that focus on this important topic! I hope you feel inspired to learn more by this small science lesson and pursue your curiosity on the subject. Happy reading!

Links for further reading:

https://ocean.si.edu/ocean-life/invertebrates/ocean-acidification

https://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F

https://www.acs.org/content/acs/en/climatescience/oceansicerocks/oceanchemistry.html

Kate Kennedy

Kate Kennedy is a first year student majoring in Molecular Environmental Biology in the College of Natural Resources. She is a current participant of the Global Environment Theme House program and wants to learn more about connecting sustainability with lifestyle choices. Kate is passionate about marine ecosystems and later in life hopes to aid aquatic life impacted by climate change. In her free time, Kate enjoys drinking coffee, reading science fiction books, laughing at memes, participating with the Cal Triathlon team, and watching nature documentaries. Kate Kennedy covers ecology.

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