Ocean Acidification’s Potential Effects on Keratin Protein in Cetacean Baleen and Other Integumentary Tissue

Marine uptake of atmospheric CO2 from increased anthropogenic carbon emissions is leading to ocean acidification, which poses a grave threat to marine life. The potential risk of acidified seawater to cetaceans (whales, dolphins, and porpoises) and other marine mammals has received little attention, but deserves close scrutiny due to their long lifespan. Cetaceans also lack the protective fur coat which protects typical mammals, and the feeding of mysticete whales depends on a filter made of a unique tissue: baleen. Like hair and other integumentary products, baleen is made of keratin, a fibrous structural protein. We submerged baleen and skin samples from bowhead whales (Balaena mysticetus) and North Atlantic right whales (Eubalaena glacialis) for 12 weeks in seawater of varying pH representing current and projected acidification. When tested for mechanical strength via loading in compression and tension, the acid-exposed specimens were slightly but not statistically different in weakness (as measured by deformation for a given stress or the force needed to fracture the sample). Other samples exposed to low pH were examined via nuclear magnetic resonance testing to search for the presence of amino acids expected if the keratin protein deteriorated due to acid exposure; even at extreme acidity these amino acids were not found, suggesting keratin is strongly resistant to acid-induced breakdown. Finally, whale skin samples exposed to acidified seawater and examined microscopically did not demonstrate notable changes in appearance, texture, or resistance to stretching. Ocean acidification can possibly harm keratin-based cetacean tissues, but no acid-related effects were conclusively demonstrated by these tests.

Keywords: ocean acidification, pH, keratin, whale, baleen, skin, epithelium