Coralline Algae Weakened by Ocean Acidification

The pH levels in the world's oceans are lowering--becoming more acidic--as a result of the high concentrations of carbon dioxide pumped into the atmosphere from burning fossil fuels. This side effect of global warming is known to cause corals to bleach and become sick, but new evidence shows that it is weakening the skeletal structure of coralline algae, a type of red algae that depends on hard rock in order to grow.

Coralline algae are an essential component of marine biodiversity because they form things called maerl beds -- a hardened form of the algae -- which serve as habitats in shallow waters. That is, the beds operate as a home and nursery for a large and varied collective of species.

High-magnesium calcite, a highly soluble type of calcium carbonate, is the main component of coralline algae's skeletal structure. That skeleton is susceptible to greater amounts of carbon dioxide being absorbed into the oceans. Typically, the skeletal structure of coralline algae is able to endure during stressful situations, however.

Scientists from the University of Bristol in the United Kingdom have been studying how climate change affects coralline algae and have formerly determined that ocean acidification causes a reduction in the breadth of the algae's cellular walls and, hence, the strength of their skeletal structure. Yet, their previous work also indicated that the coralline algae were able to bounce back, adapt, and resume growth.

Their new study, published in Scientific Reports, examined the new growth of the algae and the U.K. researchers found that the regrown skeletal structure was more brittle as a result of a change in chemical composition. Because the skeletal structure is unable to grow as strong when facing climate change conditions, the scientists stated that coralline algae will eventually become insufficiently calcified, and thus unable to offer an appropriate habitat for other species in the future.

"Coralline algae support a huge variety of marine life, with more than 460 species associated with their beds including economically important species such as scallops," senior author of the study and Head of Global Change at the Cabot Institute Professor Daniela Schmidt said in a press statement. "While a number of studies have now shown that coralline algae can continue to grow even in challenging environmental conditions, it is fundamentally important that we combine these physiological studies with potential impacts on the structural integrity of the skeleton and its consequences to habitat formation."

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