John R. Platt of ScientificAmerican reports in his blog about the new threat to the yellowfin tuna: ocean acidification.
For this study, researchers from the University of California at Santa Barbara, the Inter-American Tropical Tuna Commission and other organizations collected yellowfin larvae from a commercial aquaculture bloodstock which is normally exposed to pH levels between 8.27 and 7.74. That’s slightly less acidic then neutral water, which has a pH of 7, but also less acidic than many natural conditions. The larvae were taken then taken to a lab and exposed to waters with four different levels of carbon dioxide, which changed the pH. The first tank, considered the control, had a pH of 8.1. The second had a pH of 7.6, which matches global warming projections for the year 2100, while the third had a pH of 7.3, matching projections for the year 2300. A fourth pH level of 6.9 was considered the “lowest projection for the Pacific Ocean.”
All of that acid added up. The researchers found that it caused damage to the liver, kidney, pancreas, muscle tissue and eyes of the yellowfin larvae—all within a week of exposure. Their growth rates also suffered, ranging from 20 to 41 percent
What does all of that mean? Well, based on the damage to the eyes alone, the researchers concluded that the larvae would have had a mortality rate of between 50 and 100 percent. Even if they survived past those odds, the damage to their kidneys and other organs would have caused all kinds of health conditions later in life, putting them even further at risk.