Good News for Abalone: Study Finds Calcifying Algae May Be Resilient During Ocean Acidification

A version of this story originally appeared on CalPoly News by Rachel Henry.

New research from Cal Poly and California Sea Grant sounds a hopeful note for the resilience of calcifying algae and California abalone in the face of climate change. The study, conducted by California Sea Grant Extension Specialist Jennifer O’Leary, evaluated the potential impacts of ocean acidification on crustose coralline algae, which provides a surface upon which larval abalone (a large, edible sea snail) settle.

Pink crustose coralline algae grow on rocks near shore and, like coral, produce a skeleton made of calcium carbonate. The algae give off a chemical signal that abalone larvae use to identify habitat to settle on so that they can metamorphosize into their adult form. In this experiment, researchers showed that when the algae are present, greater than 50 percent of abalone larvae settled from the water column and metamorphosized into their adult forms.  When algae were absent, less than 10 percent of abalone larvae settled and metamorphosized. Even under expected future changes in the California current system (ocean acidification conditions), the algae maintained their ability to induce abalone larval settlement and development.

“This research is novel in that it shows that some critical interactions between species can be maintained, even for sensitive species like this calcifying algae,” O’Leary said. “This is good news for California abalone, as loss of the algae would mean catastrophic declines in abalone replenishment.” 

Previous studies have shown that coralline algae are sensitive to ocean acidification, which is a chemical reaction that occurs when carbon dioxide is absorbed by seawater and causes low pH and acidic conditions. Since the beginning of the Industrial Revolution, ocean waters have experienced a 30 percent increase in acidity, according to the National Oceanic and Atmospheric Administration.

“Ocean acidification is one of the biggest issues facing marine communities,” O’Leary said. “It’s critical to understand the impacts of this threat and evaluate where and when organisms and communities are able to withstand acidification.” 

Though ocean acidification reduced algal growth, it did not disrupt the chemical signal the algae provide to abalone. The researchers concluded that some species interactions may continue despite acidification, which will increase the species’ resilience.  

One possible explanation for these results is that some organisms in California may be better able to withstand ocean acidification because they live in highly variable physical conditions naturally. This explanation needs to be tested before it can be confirmed, O’Leary said.