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Ocean acidification is a major threat to coastal marine life

Scientists believed marine ecosystems could adapt to warming waters. However, rapid ocean acidification is posing an additional threat to this process.

Here at Thred, we’ve showcased several projects which have been designed to deal with one of the ocean’s biggest man-made problems – plastic pollution.

Lately though, scientists have grown increasingly concerned about one of the ocean’s natural processes, particularly its ability to absorb carbon dioxide and other greenhouse gases.

The vast blue regions of our planet naturally absorb one-third of all carbon emissions that come from burning fossil fuels.

In the early days, researchers viewed this as a positive finding. Surely less carbon in the atmosphere would help slow the warming of our planet – and wouldn’t that be a good thing?

Unfortunately, this isn’t the case. We now know that continuously emitting such large quantities of carbon is causing the ocean to become not just warmer, but more acidic. And if you’ve ever had a lemonade that was too sour – you know too much acidity is not exactly desirable.


For a short time, our oceans were coping. Rivers would carry minerals and chemicals from rocks nearby and eventually wash them out to the sea, where they’d help to keep the water’s pH levels stable.

But as we inch nearer to global temperature limits, rivers are drying up, and carbon emissions aren’t decelerating. This ripple effect on ecosystems has resulted in the ocean struggling to stay balanced. The window for recovery has narrowed completely.

Despite these looming factors, scientists remained initially optimistic about the reality of warmer oceans.

They predicted that warming waters might cause animals living in temperate areas to die. However, the possibility that tropical species could naturally migrate to populate empty coastal regions seemed feasible.

But nature is unpredictable (shouldn’t we have learned this by now?!), and this forecast wasn’t correct – especially given the rate of acidification. What scientists have found instead, is that rapidly warming waters combined with acidification is causing entire ecosystems to collapse.

A reef burned by ocean acidification

Since the start of the Industrial Revolution, acidity levels have increased by 30 percent. This altering of environmental chemistry has happened faster than any other biological change in over 50 million years.

Some of the hardest hit areas are coastal regions. They are quite literally being ‘burned’ by warmer sea temperatures, in a process called ‘tropicalisation’.

Habitats such as seaweeds and anemones can’t adapt fast enough, so when they die, the fish which rely on them for safety and breeding also begin disappearing altogether.

Shells of molluscs such as oysters, mussels, snails, and crabs are unable to form, as the acids eat away at them in their softer, developing stages.

Providing homes to lobsters, fish, and dolphins are delicate kelp forests. Dotted around the world, many are turning to slimy graveyards at the ocean floor, harmed by abnormally warm waters and acidic environments.


Scientists prior hope for a positive wave of ‘tropicalisation’ – where coral reefs would replace cool water kelp forests – is dwindling. The growth of reef-forming corals depends on stable water pH levels. If this environment isn’t available, we risk losing marine life in almost all areas.

It’s not all doom and gloom though. Instead of expecting nature to keep up with human destruction, we’re going to have to lend her a hand.

There are a handful of unique areas where coral species have adapted to warm climates, and others where ocean temperatures remain cool enough year-round to support the growth of new and existing coral reefs.

For example, in the Gulf of Aquaba near Israel, scientists have discovered heat-resistant corals thriving in abundance. Here, coral reefs continue to prosper – or blossom further – when temperatures rise up to 6 degrees above what is considered normal for the undersea organisms.

In the North Atlantic Ocean, coral reefs that surround Bermuda remain largely unscathed by ocean acidification thanks to the region’s temperate climate. The lush ecosystems here enjoy warm summers and weather easily through temperature drops of up to 4 degrees.

Marine biologists focused on coral reef restoration believe that these species could be our answer to ensuring that these undersea ecosystems don’t die out altogether. For example, heat resistant corals can be ‘replanted’ where fragile reefs have ceased to survive.

A site where corals are being replanted

But awareness of the direct causes and effects of ocean acidification should be all the motivation humans need to jumpstart mitigation.

We can no longer deny that CO2 emissions are responsible for the destruction of basically every natural ecosystem on our planet, even in the oceanic areas that most people don’t give much thought to in day to day.

The only way to save these environments is to reach net zero carbon goals, which would stabilise ocean temperatures and provide time for levels of acidification to balance out.

With COP27 and The UN Ocean Conference coming up, the pressure is on. Carbon companies and major world leaders, we’re looking at you! It’s time to make some changes.


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