Pteropods and climate change

pteropods

Southern ocean pteropods

Academy scientists work diligently on research that seeks to improve our understanding of biodiversity, evolution, water quality and climate change. We chatted with Rosie Oakes about her research on tiny pteropods and why learning about them helps us learn more about the impacts of climate change.

What is your research?

“I study pteropods, which are a group of planktonic snails that live in the ocean.”

Rosie Oakes, PhD, is the John J. & Anna H. Gallagher Fellow working with Jocelyn Sessa, PhD, in the Invertebrate Paleontology group at the Academy of Natural Sciences of Drexel University. Oakes and Sessa study these tiny marine snails, about the size of a grain of sugar, by using CT scans to create 3D models of their shells.

These images enable them to compare shell thickness of pteropods from different areas of the oceans around the world.

Pteropod shells are important to climate change research because they provide a way to understand the early effects of one major climate change consequence — ocean acidification.

Pteropods are most abundant in the coldest regions of the oceans, and coincidentally, the impacts of ocean acidification are first expressed in these polar regions. Depending on the time of year, the ocean water can be chemically unstable for pteropod shells, which are made of aragonite. Some shells are made of aragonite while some are made of calcite. Both are a type of calcium carbonite, but aragonite is 1.5 times more soluble than calcite.

The aragonite pteropod shells are the first to be susceptible to changes in the chemistry of the ocean water, a “canary in the coal mine,” Oakes explains, for ocean acidification and the potential impacts it could have on other marine life.

Hit me with the science!

Ocean acidification is one of several effects of the increasing concentration of carbon dioxide (CO2) in the atmosphere.

Oceans absorb atmospheric CO2 through natural processes. As CO2 in the atmosphere increases, more CO2 is being dissolved in the oceans. In fact, oceans have absorbed 30% of the CO2 that has been emitted since the start of the Industrial Revolution.

All that CO2 in the ocean causes an increase in concentration of hydrogen ions, which raises the acidity of ocean water, hence the term “ocean acidification.”

(It is important to note that, while oceans are becoming more acidic, leading to negative impacts on marine life, ocean water overall is still alkaline — it won’t burn your skin if you go swimming at the shore! The overall change represents a change of only 0.1 pH units — a 30% increase in acidity. For more information on ocean acidification and pH, visit this website.)

This change in ocean chemistry directly affects pteropods’ ability to form their shells. Here’s how:

The extra hydrogen ions react with carbonate ions in sea water to form bicarbonate. The problem is, carbonate ions are the building blocks of shells, and pteropods need them to remain available in the water in order to build their shells most efficiently.

In short, as CO2 in the atmosphere increases, so does dissolved CO2 in the oceans, meaning there are fewer carbonate ions available for shell building. And that means what, exactly?

“It’s a bad time to be a pteropod,” Oakes says.

Why should we care about how climate change is affecting pteropods?

Oakes answers the question with a question: “Do you like seafood?”

Pteropods are an important part of the base of the marine food chain. “We don’t yet understand the cascading effect that it would have on the rest of the marine food chain” if we lost pteropods, Oakes explains. They are a food source for zooplankton, which are eaten by larger marine organisms like whales and seabirds, as well as commercially important organisms like cod and shrimp.

In addition, there are some members of the marine food chain that eat only pteropods. Pteropods’ snackability and high fat content — as well as their delicate, “crunchy” shells — has led to them being referred to as “the potato chips of the sea.”

What are your personal thoughts about climate change?

“It’s real and it’s scary,” Oakes confesses.

In addition to personal lifestyle choices intended to reduce her carbon footprint, including cycling to work and eating less meat, Oakes stresses the value of staying informed and simply talking about climate change.

“I try to talk about climate change as much as I can,” she said. Addressing climate change can feel overwhelming at times, and Oakes is respectful of the fact that not everyone is able to make big lifestyle changes, like giving up meat or cars.

She finds that small actions, such as buying a new type of leggings she discovered that are made from recycled plastic bottles, can make a difference, whether you’re trying to reduce your carbon footprint or simply wanting to change your outlook about the climate crisis altogether.

“We have the technology to reach a climate solution,” Oakes said. “I try to help facilitate conversations about what individuals can do to make this solution a reality.”

Kathryn Christopher, The Academy of Natural Sciences of Drexel University, 11 May 2020. Article.

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Ocean acidification in the IPCC AR5 WG II

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