The food chain off the coast of California is starting too look shorter and less diverse thanks to environmental events like El Niño and potentially climate change, say scientists who tracked the diets of dolphins.
Top predators have a higher presence of nitrogen-15 in their tissues. Since dolphins sit near the top of the food chain, their nitrogen-15 levels reflect the number of links in the chain underneath them. In tests of 204 skin samples taken from dolphins accidentally killed in California fisheries, researchers discovered “that the food chain length varied from year to year, and took a significant hit when the environment changed — for example, after the 1997-98 El Niño season, and after 2004, when the rise of a low-oxygen zone trapped many species closer to the surface than usual,” explains the Los Angeles Times.
That shortening might indicate that certain species disappeared or were in limited supply, pushing the dolphins to eat lower on the food chain. The researchers believe they can use the same method to study how climate change affects top predators, and thereby gauge the vitality of the overall food chain.