Yellowfin tuna populations, already depleted from overfishing around the world, face another challenge in the coming years — ocean acidification. A new study published last month in the Journal of Experimental Marine Biology and Ecology has found that increasingly acidic waters in the Pacific Ocean from climate change will cause dramatic damage to the organs of yellowfin tuna larvae. This damage lessens the tunas’ ability to develop and grow to full size, and also dramatically reduces survival rates.
For this study, Scientific American reports, researchers from the University of California at Santa Barbara, the Inter-American Tropical Tuna Commission and other organizations collected yellowfin larvae normally exposed to pH levels between 8.27 and 7.74, and exposed them to waters ranging from 8.1 pH (control) to 6.9 pH, considered the “lowest projection for the Pacific Ocean.” The second and third pHs, 7.6 and 7.3, match the global warming projections for the years 2100 and 2300, respectively.
The acidic waters damaged the liver, pancreas, kidneys, eyes, and muscle tissue of the tuna larvae, all within just a week of exposure. Growth rates were impacted 20-41%, and based on the damage to the eyes alone, researchers estimate that the larvae would have a mortality rate of 50-100%.
These impacts won’t be restricted to yellowfin tuna species, either — As the researchers explain, any environmental changes causing high mortality rates for yellowfin or other fish in their larval stages “will have carry-over effects for marine fish stocks.”