• Lisette

The Oceans as our O2 and CO2 Manager

A lot has been said and written when it comes to our oceans from plastic and microfiber pollution to overfishing, garbage patches, Dead Zones, temperature and sea level rise and much more.

With this article, I would like to focus on how our oceans play a big role in managing the CO2 and oxygen levels in our atmosphere and what this means for us, climate change and our atmosphere.

Facts and figure

The oceans are extremely important for our wellbeing here on earth. Let me tell you why that is:

oceans, global warming, acidification
Our Blue Planet, the oceans cover 71% of our earth.

1. We live on a blue planet: 29% land mass, 71% water.

2. The oceans hold 97% of the world’s water.

3. The currents play a big role in regulating our climate by transporting warm water from the equator to the poles, and cold water from the poles to the tropics. Without these currents, the weather would be extreme in some regions, and fewer places would be habitable. The ocean regulates rain and droughts.

4. It is an important source of food.

5. Millions of people depend on the oceans for their livelihood.

6. The ocean absorbs energy, heat and CO2 helping to regulate the temperature of our planet.

phytoplankton, oceans, acidification, global warming

7. The oceans are our main producer of oxygen: it is phytoplankton (microscopic organisms that live in the oceans) that absorbs energy from the sun and nutrients from the water to produce their own food. In the process of photosynthesis, phytoplankton releases oxygen into the water. It is estimated that between 50% and 85% of the world's oxygen is produced in the oceans. The rest is produced from the trees and plants on land.

Global Warming

Let’s explore number 6, how it works and what it means.

Our oceans are actually an incredible carbon sink — previous research has shown they absorb about 25% of the carbon dioxide humans produce every year. However, new research from the Intergovernmental Panel on Climate Change (IPCC) shows that it is actually underestimated by 60%.

At first sight, you would think this is a good thing since it reduces the greenhouse gasses in our atmosphere and reduces climate change and average temperature increase. However, this is not entirely accurate.

Because the oceans absorb a lot more CO2 and heat than previously thought, it means they are warming up quicker than estimated and warmer ocean water has several rather negative effects:

1. Warmer water contains less oxygen which has a huge impact on marine life and us as well since as you read earlier, the oceans are responsible for 50-85% of our oxygen.

algae, oceans, global warming
Algae bloom South England

2. If the ocean gets too warm, plants and animals that live in it must adapt—or die. Algae and plankton are at the bottom of the food chain. Plankton includes many different kinds of tiny animals, plants, or bacteria that just float and drift in the ocean. Other tiny animals such as krill (sort of like little shrimp) eat the plankton. Fish and even whales and seals feed on the krill. In some parts of the ocean, krill populations have dropped by over 80%. Why? Krill like to breed in really cold water near sea ice. What would happen if there were no sea ice? What would happen if there were very little plankton or krill? The whole food web could come unravelled.

3. Warmer oceans impact our climate and weather! Wherever you are in the world, you surely have experienced more extreme weather in the last few years: more forest fires, periods of extreme drought, high temperatures, more intense hurricanes and typhoons and flooding due to extreme rainfall.

4. Because the oceans absorb more heat than previously expected it means that the target of 1,5-2 degrees Celsius temperature increase will be a lot harder to maintain, mainly due to the fact that the ocean doesn’t hold on to this heat forever, it will release it back into the atmosphere over time.


There is another effect of increased CO2 absorption by the oceans and it is called ACIDIFICATION which is often called global warming’s evil twin.

The absorption of CO2 changes sea surface chemistry dramatically: when carbon dioxide is absorbed by the ocean, it dissolves to form carbonic acid.

The result, not surprisingly, is that the ocean becomes more acidic, upsetting the delicate pH balance that millions and millions of organisms rely on.

oceans, acidification, global warming
Normally, ocean water is less acidic than fresh water. Unfortunately, as the ocean absorbs more and more carbon dioxide from the atmosphere, it becomes more acidic. Lemon juice is an example of an acidic liquid. Toothpaste is alkaline. The ocean is slightly alkaline.

Since the Industrial Revolution, our seas have become about 30% more acidic, a rate not observed in 300 million years. This has a wide range of consequences for marine ecosystems, as well as for the billions of people who depend on the ocean for food and survival.

This process will continue to happen as long we keep burning fossil fuels and other ways of releasing greenhouse gasses into the atmosphere.

oceans, acidification, global warming
Evolution of ocean acidity.

As oceans become more acidic, some sea creatures have a more difficult time forming shells such as mussels or coral polyps. These are the “tiny builders” of coral reefs — when a polyp attaches to a rock on the seafloor, it divides into many clones and eventually creates a reef. Ocean acidification can slow the growth of coral skeletons, and make reefs more brittle and less resistant to stressors like warming water temperatures.

coral reef, global warming, oceans, acidification
Beautifully colourful coral reef.

Keeping coral reefs healthy and growing is vital. Reefs protect our coastlines from erosion and flooding, support local economies through tourism and fisheries, and host vastly productive ecosystems. The US National Oceanic and Atmospheric Administration, for example, estimates that about half a billion people live within 100 kilometres of a coral reef and benefit from the protection and natural resources it offers. Globally, coral reefs may provide goods and services worth $375 billion each year, which means threats to reefs have profound ripple effects.

bleached coral reef, oceans, acidification, global warming
Bleached coral in Australia's Great Barrier Reef near Port Douglas on Feb. 20, 2017.Brett Monroe Garner / Greenpeace via Reuters

You’ve probably heard about coral bleaching events in places like the Great Barrier Reef and others. I have witnessed it with my own eyes and let me tell you, it is heartbreaking. Coral bleaching occurs when the living organisms that make up coral reefs expel the colourful, photosynthetic algae that normally live inside their bodies, and provide them with food. Those algae give coral reefs their colour and disappear when the reefs are exposed to stressful climatic conditions, such as temperatures even a few degrees higher than normal.

Coral reefs are considered to be the most biodiverse ecosystem on the planet. When coral is hit hard by both ocean acidification and climate change, so too are the many species that humans rely on for food. According to the United Nations Environmental Programme, “fish, including shellfish, contribute 15% of animal protein for 3 billion people worldwide. A further 1 billion people rely on fisheries for their primary source of protein.”

What can you do?

OK, this concludes the bad news, no let’s explore what you can do to help turn this around.

The key is to reduce our CO2 and other greenhouse gas emissions into the atmosphere.

Here are a few ways how you can do exactly that:

  • Give your car a break and walk, cycle or use public transport once in a while

  • Shift to renewable energy systems for your home

  • Eat less fish to prevent overfishing the oceans

  • Eat less meat and dairy products; the livestock industry is a huge contributor to greenhouse gas emissions

  • Buy local products that haven’t travelled long distances

  • Buy seasonal products

  • Refuse, Reduce, Reuse, Recycle: refuse excess packaging, reduce your waste, reuse items as much as possible and recycle where possible

  • Put on a sweater or use a blanket before turning up the heating

  • Switch off the lights and appliances

  • Take a shower together instead of separately, it takes a lot of energy to heat water uses

  • Spread the message and educate others

Please, dear friends, the time to act is NOW!

Tags: #climatechange #globalwarming #oceanacidification #coralreefs #oceanwarming

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