The ocean is one of our planet’s most powerful warriors against climate change. It absorbs carbon dioxide from the atmosphere, regulates temperatures and weather patterns, and makes life on earth possible for us all. But if we continue to pump CO2 into the air at today’s rates, scientists predict oceans will continue absorbing CO2 and raising their acidity levels even more—and that could lead to an extinction-level event in the seas.
Did you know the ocean is one of the biggest warriors against extra carbon dioxide in the atmosphere?
Ocean water absorbs 30% of the carbon dioxide produced by humans, which helps to keep it from building up in our air. The result is that oceans have absorbed over 90% of all CO2 emitted since 1850. This is part of a natural process called “carbon sequestration” or “carbon storage,” which means that when we put more carbon dioxide into our atmosphere than nature can handle, some sinks are able to catch and store some extra CO2 for us.
This is a natural process that has been going on for thousands of years. As more CO2 gets added to the atmosphere, it makes its way into seawater and dissolves there, where it reacts with water molecules to form carbonic acid. The water then becomes more acidic and can dissolve calcium carbonate (CaCO3), which is found in coral reefs and shells.
The ocean is full of carbon dioxide. And that's a good thing. But it's not just a good thing for the climate—it's also a good thing for the economy, because it keeps our planet from overheating.
Carbon dioxide is an essential part of life on Earth: plants take in CO2 from the atmosphere and turn it into sugar during photosynthesis. Humans are animals too! We breathe in oxygen and breathe out CO2 in order to take energy from food (which plants turn into sugar). This process has allowed our population to grow much larger than any other animal species on Earth.
And yet we have thrown off the balance again...
The ocean sequesters carbon and helps regulate the atmosphere, but we have put too much out there.
When you hear the term "sequestration," it's probably associated with coal plants and carbon sequestration. In this case, sequestration refers to how carbon dioxide from fossil fuels is removed from the atmosphere and stored underground in an attempt to curb global warming.
But there are other types of sequestration that don't involve burying CO2 underground (like turning it into fuel). For example, photosynthesizing plants and algae can absorb CO2 during photosynthesis and store it in their tissues as carbohydrate molecules. The ocean also absorbs large amounts of CO2, at a rate ten times faster than land-based ecosystems like forests or grasslands do.
Yet, we have asked too much of the ocean. It is absorbing more CO2 than it can handle. This process is known as ocean acidification—a condition that may threaten coral reefs if left unchecked.
All that carbon dioxide makes the ocean more acidic.
As you might know already, pH is a measure of the acidity or alkalinity of a substance. In water, it's measured on a scale from 0 to 14: 7 is neutral and lower numbers indicate increasing acidity (from 0 to 6). The pH level in oceans has changed by 0.1 since pre-industrial times—a change that's caused by both absorption of CO2 and rapid dissolution of calcium carbonate (which means more acidic oceans could be releasing less CO2 than they absorb).
Acidification slows the process of photosynthesis, making it harder for phytoplankton to grow and reproduce, which could disrupt the entire marine food chain.
Ocean acidification is particularly harmful to phytoplankton at the bottom of the ocean food chain. These tiny plants live in all bodies of water and produce half of the oxygen on Earth. Acidification slows down their growth, reproduction, and photosynthesis process. This can disrupt entire marine ecosystems by depleting them of basic nutrients such as iron and nitrogen necessary for phytoplankton growth.
That acid eats away at coral reefs, killing off marine ecosystems and threatening food security for millions of people.
Coral reefs are a crucial part of the ocean ecosystem, providing food, shelter, and protection for many species. They also serve as nurseries for young fish, which means that they play an important role in helping maintain healthy fisheries around the world.
In addition to being known as one of the Earth's most beautiful natural wonders—coral reefs are home to thousands of species that can only be found there. They're also key economic drivers; tourism income from coral reef areas has been estimated at $1 million per square kilometer per year on average, with some areas earning up to $4 million per square kilometer annually.
But coral reefs are under threat from climate change itself: rising temperatures cause corals to bleach or die back when bleaching occurs because heat-stressed corals expel their zooxanthellae (the tiny photosynthetic algae that live inside them) and turn white before eventually dying off altogether.
If we keep pumping carbon into the air, scientists predict oceans will continue to absorb CO2, raising their acidity levels even more and causing an extinction-level event in the seas.
If you've ever swum in a pool that was too chlorinated or had your eyes burn from a too-salty ocean swim, then you know that water can become very acidic at high concentrations. That's what's happening as oceans absorb more CO2 from human emissions: they're becoming more acidic. Scientists estimate that large portions of them could reach pH levels not seen since the Triassic period 200 million years ago—a time when half of all species on Earth went extinct and some sea turtles had shells so weak they couldn't leave land!
When phytoplankton are growing rapidly enough to reproduce, they build up calcium carbonate shells around themselves in order to protect themselves from predators while they reproduce (also known as calcification). But suppose these organisms' shells begin to dissolve due to increased acidity levels caused by human activity (and other factors). In that case, it could disrupt their ability to survive long enough for them to reproduce--and without reproduction, there would be no new generations of phytoplankton!
The ocean plays a crucial role in mitigating climate change and we must all do what we can to protect it, or risk losing it forever.
The ocean plays a crucial role in mitigating climate change and we must all do what we can to protect it.
As scientists work to better understand this phenomenon and its potential effects on biodiversity within affected areas, we need your help raising awareness about how important it is to protect the ocean! It is one of the most powerful weapons we have against climate change. If we lose it, there will be no turning back.
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