How will acidification affect ocean wildlife?

Coccolithophore (Jeremy Young)

Many animals in shallow and deep water ecosystems build shells and skeletons made of calcium carbonate; these include clams, oysters and corals. In addition, tiny organisms, such as coccolithophores, a type of single-celled algae (phytoplankton) also build their shells out of calcium carbonate. A decrease in phytoplankton due to acidification would be catastrophic to the oceans. Phytoplankton, as the primary producers of the ocean, form the base of the vast majority of marine food chains and are therefore vitally important. Sea snails (pteropods), like phytoplankton, are a critical part of the marine food chain, ultimately feeding whales and other top predators in the oceans. Sea snail shells are also made from calcium carbonate. All of these organisms, many of which are vital to marine food chains, are likely to suffer in the near future, if ocean acidification continues unabated.

Even marine animals that do not create calcium carbonate shells or skeletons will be threatened by the increasing acidity of the oceans. Squid require high levels of oxygen for their high-energy swimming. Increasingly acidic oceans interfere with the acidity of a squid's blood and consequently the amount of oxygen that it can carry. Squid are a key prey for many marine mammals, including beaked and sperm whales.

Fish too may be vulnerable to acidification. While adult fish may be relatively insensitive to ocean acidification, their eggs and larvae may not be able to develop properly due to changes in ocean chemistry. This would affect fish populations all over the globe.

After being exposed to acidic conditions similar to those likely to occur in the ocean, nothing remained of this coral's skeleton (Oculina patagonica). All that was left was the soft body of the coral (the polyps). (A. Brietstien)

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Marine Predators Eating "Junk Food"

It's not just humans that need a varied, nutritious diet. A new analysis on the diet diversity of marine predators emphasizes that food quality is just as important as food quantity.  As overfishing and climate change continue to disrupt marine food webs, marine predators are eating less nutrient-rich fish and consuming more nutrient-poor species, a diet that some scientists are calling a "junk-food" diet.  Since the 1970s, the endangered Alaskan Stellar sea lion has declined by 80% and scientists believe that climate change and a "junk food" diet are to blame.  Alterations in atmospheric and oceanic circulations caused by climate change have given Pollock, a lean fish that lacks fatty acids, an advantage over other [fatter and nutrient-rich] prey fish of the sea lion.  Even though the sea lions are consuming great quantities of the Pollock, they are losing weight due to its low quality and the sea lion population continues to decline.  Scientists working on the analysis propose that food quality is often overlooked in scientific research, as it is less measurable than food quantity.

To learn more about how climate change is contributing to the marine "junk food" diet, read the article in NewScientist.

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