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Oceans' food chain could collapse
01:26 - Source: CNN

Editor’s Note: On Fridays, CNN answers one of our audience’s climate change questions as part of the Two Degrees series. Ask your question by filling out this online form. And sign up for the Two Degrees newsletter to learn more.

CNN  — 

Two of my passions are fishing and ocean conservation. So I was happy to be asked to explain the impact of climate change on the oceans’ food chain by William Breyer, a reader of CNN’s Two Degrees series from Indian Harbour Beach, Florida.

Breyer wrote:

  • “I understand that not only are the oceans increasingly retaining more and more carbon dioxide, but the warming of their waters are reaching to ever increasing depths. This, in my opinion, is of particular concern as this may negatively affect the entire ocean-based food chain – not to mention the dangerous effect on our atmosphere.”

This is an excellent point, and one with many layers.

There are several factors that are contributing to our warming oceans, and carbon dioxide is definitely one of those. We know that carbon dioxide is increasing globally and the oceans absorb huge amounts of CO2 each year.

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Coral gardens could save ocean life
02:46 - Source: CNN

When this happens, the pH levels of the ocean are reduced. That’s because CO2 is an acid gas and when it dissolves in water, including seawater, it forms carbonic acid.

As CO2 dissolves into the oceans, it fundamentally alters ocean chemistry, making it more acidic. This acid addition is where the name “ocean acidification” comes from and is why ocean pH is declining worldwide.

According to NOAA, since the beginning of the Industrial Revolution in the late 1700s and early 1800s, the acidity of surface ocean waters has increased by 30%. NOAA goes on to say that “by the end of the century, the surface waters of the ocean could be nearly 150% more acidic, resulting in a pH that the oceans haven’t experience for more than 20 million years.”

This will have a huge impact on the world’s ocean species. A study led by Adelaide University in Australia states that there will be an “entire species collapse from the top of the food chain down.”

According to Ivan Nagelkerken, a marine ecologist with the university’s Environment Institute, the warmer waters are creating higher metabolic rates that, in turn, are creating a bigger demand for food.

“There is a mismatch with less food available for carnivores – the bigger fish that fisheries industries are based around,” Nagelkerken explains.

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Photos show coral dying in global event
02:20 - Source: CNN

Globally, 2014 was the warmest year on record. We saw a massive decline in the health of our coral reefs because of this. Coral reefs bleached in record numbers, and scientist scramble to find a ways to revive them. Coral reefs nourish about 25% of the world’s marine species.

Nurseries bring coral reefs back to life

Ocean acidification will impact ocean species on different levels. According to NOAA, “Photosynthetic algae and seagrasses may benefit from higher CO2 conditions in the ocean, as they require CO2 to live just like plants on land.”

However the same isn’t true for species such as oysters, clams, sea urchins, shallow water corals, deep sea corals and plankton.

According to NOAA, “When shelled organisms are at risk, the entire food web may also be at risk.”

This will have a major impact not only on jobs and the economy, but on nearly every country since more than 20% of the world’s population depends on ocean species as their primary source of protein.

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Reef rescuers race against time
09:51 - Source: CNN