Shellfish are dissolving due to acidifying oceans

Environment | Oceans

By Rebecca Hurford, Freelance Writer

Published March 25th, 2023

Rising levels of atmospheric carbon dioxide are being absorbed by the ocean, which is destroying the many species that inhabit one of nature’s most important ecosystems. Is it possible to reverse the clock and replenish its health?

Anthropogenic climate change is having a multitude of effects on our vast range of ecosystems. Our ocean acts as a carbon sink, absorbing around 30% of the carbon dioxide from the atmosphere. With the increasing amount of carbon dioxide in the air, it means that the ocean is absorbing more and more carbon dioxide.

Ocean acidification slows the rate at which coral reefs generate calcium carbonate, subsequently impacting their growth rates. | David P. Robinson / Ocean Image Bank

When absorbed, reactions between the seawater and the carbon dioxide transpire, causing the ocean to become more acidic. Initially, the carbon dioxide is dissolved in the ocean’s salt water, which then turns into carbonic acid. The carbonic acid is then broken down, releasing hydrogen ions and decreasing ocean pH levels.

Having a lower pH level means that a liquid is more acidic. In the last 100 years, the pH level of the ocean has gone from 8.2 to 8.1, and although this may not appear to be a huge difference, it has serious implications for species in the ocean. As a comparison, the average pH blood level for humans is around 7.4. However, a 0.2 decrease in this pH level can cause serious illnesses in humans, such as comas or in fatal conditions, even death.

For this reason, maintaining a stable and unchangeable pH level is extremely important. However, under a business-as-usual scenario where we continue to increase our fossil fuel usage, ocean PH levels will keep decreasing, harming ocean species and the livelihoods that depend on it.

The effects of ocean acidification have largely impacted molluscs and crustacean species. Molluscs are invertebrates that have hard shells, such as oysters and scallops. Crustaceans are another type of invertebrate that has a hard exterior, such as crabs and lobster.

These species are dependent on calcium to create their outer bodies, such as their shells and skeletons. However, with ocean acidification, their calcium carbonate exteriors are broken down by the disproportional presence of hydrogen ions. The increased acidity of the ocean also halts the coral from building skeletons, as the process dissolves the calcium in the sea.

The consequences of ocean acidification on shellfish create a few issues that also impact humans, one being food scarcity. If shellfish species decline, it will also have a knock-on effect on its entire food chain, depleting numbers of other marine species that rely on them.

Shellfish species are declining due to ocean acidification. | Fred Moon / Unsplash

Kenric Osgood, Chief of the Marine Ecosystems Division, stated that the process of ocean acidification will harm the $1 billion dollar shellfish industry, leaving thousands of people jobless. He also explains that ‘understanding how ocean acidification will affect marine life and the jobs and communities that depend on it is critical to a healthy ocean and blue economy.’

A coastal community that has been affected by the continuing decline of shellfish is Cordova, in Southern Alaska. The Chugach-Eyak natives, who live in Cordova, have relied on fishing for thousands of years for survival. Now, ocean acidification is taking a toll on their economy, culture and their way of life.

The southern Alaskan community, among other places, rely heavily on the salmon trade. Salmon trade accounts for around a third of Alaska’s seafood industry, which is worth over five billion dollars.

With ocean acidification playing its part, the size and numbers of salmon are decreasing in parts of Alaska, such as Cordova. This has been traced to the corrosion of the local marine food chain. The food resources that salmon rely on, such as pteropods (small planktonic snails), have been subject to their shell eroding.

Although many would not believe that these tiny snails would have an impact on an entire food chain, the reality is concerning. Approximately 40% of the world’s population relies on seafood as a source of protein, causing additional stress on a faltering supply chain.

One of the only feasible ways to protect our ocean is to decrease the carbon dioxide emissions in the atmosphere. However, this is easier said than done, as the economy highly benefits from industrial action that continues to burn copious amounts of fossil fuels.

A Coho Salmon jumps through the air. | Bureau of Land Management Oregon and Washington / Flickr

Consequently, the National Oceanic and Atmospheric Administration (NOAA) has created a 10-year plan to challenge ocean acidification. The first intention set out by the plan is that more technologies that monitor the trends and analyse the whole ocean acidification process are needed. Secondly, the roadmap will try to gain a perspective of how specific species and ecosystems are being impacted over time. Finally, it will try to gain traction with stakeholders that can invest in combatting ocean acidification.

We must diverge away from our reliance on fossil fuels and diversify our energy supply. Only then, will acidification pose less of a threat to our ocean.

Featured Image: Jean Wimmerlin | Unsplash

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