Increasing acidity in the world’s oceans will cause massive organ failure in yellowfin tuna larvae, according to a disturbing new study published in the Journal of Experimental Marine Biology and Ecology. Carbon dioxide in the ocean is changing the chemical conditions under which life has evolved.
This particular tuna is shaped like a torpedo and has dark metallic blue backs, yellow sides, and a silver belly. They have very long anal and dorsal fins and finlets that are bright yellow. The lifespan of a yellowfin can be six or seven years. Highly migratory, they are found throughout the Pacific, Atlantic and Indian Oceans. This fish is prized in the raw sashimi market and overfishing has impacted the Yellowfin Tuna , but populations are considered somewhat abundant. So far the world’s fisheries have managed the population so that it does not result in the same fate as the threatened bluefin tuna. “The bluefin tuna, which has been endangered for several years and has the misfortune to be prized by Japanese sushi lovers, has suffered a catastrophic decline in stocks in the Northern Pacific Ocean, of more than 96%, according to research published.” It is estimated that 90 percent of all large predatory fish—including tuna, sharks, swordfish, cod and halibut—are gone.
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.