Rising carbon dioxide levels alter species’ interactions

Sophie McCoy
Sophie McCoy, assistant professor of biological science at Florida State.

Global climate change may actually be setting the stage for greater species diversity in the Pacific Northwest.

And that could be both positive and negative, depending on the species.

As the climate changes, scientists have been closely monitoring what happens as more carbon dioxide enters our waterways. In recognition of that issue, Florida State University Assistant Professor of Biological Science Sophie McCoy delved into old experiments that explained species diversity and how different species were competitive with one another.

Noticing physical changes in the algae’s skeletal structures, she wanted to see if ongoing ocean acidification — the increase in carbon dioxide in the water — affected species interaction.

The answer was yes.

“Ocean acidification is promoting competition and no one is dominating,” McCoy said.

The research is published today in the journal Proceedings of the Royal Society B.

McCoy, a marine ecologist by training, specifically examined types of coralline algae, a hard skeletal algae that is crucial to marine systems and a food source for several sea creatures including sea urchins and mollusks. They proved an ideal species to study because there was plenty of historical data that allowed McCoy and her colleagues to look at changes over time.

McCoy spent three years on the Makah Reservation on Tatoosh Island in Washington studying the different types of coralline algae. In the past, studies have shown that one type of algae is usually the dominant player and forces other types out. But now, as the carbon dioxide levels have grown, there is more competition among the species, and in turn, more diversity.

Pseudolithophyllum muricatum overgrows other coralline algae and barnacles at Tatoosh Island, WA. Coralline algae compete for space via overgrowth interactions on shorelines worldwide.

Researchers also found through historical data that these increased competitive interactions developed over time. There was not a sudden change.

For the bigger picture, McCoy said that means ecologists and conservationists can start looking for early signs that interactions may be about to change. If the change has negative ramifications, they can start investigating potential corrective measures.

“If you’re looking for these early warning signs, you might see these changes in interactions and catch it before a big change happens,” she said. “I think it’s important to understand that there are changes in how ecological communities are being put together or how they function, to be aware that how we think of communities working or responding to stress is changing. This could lead to reduced ability of a community to buffer change.”

McCoy, a recent addition to the FSU faculty, completed most of the research while finishing her doctoral studies at University of Chicago. Other authors on the paper are Stefano Allesina and Catherine Pfister, both professors at University of Chicago.

The research was funded by the National Science Foundation, the National Defense Science and Engineering Graduate Fellowship and the Marie Curie International Incoming Fellowship.