Trophic transfer of lipid-derived energy through Adélie and gentoo penguins near Palmer Station along the west Antarctic Peninsula

Although Adélie and gentoo penguins are experiencing similar climatic conditions along the west Antarctic Peninsula (WAP), Adélie populations have decreased in the northern WAP, while gentoo populations have increased. We examined the lipid component of regurgitated prey (chick diets) from each penguin species to elucidate broader population trends. Nearly 90% of chick diet samples were composed of only krill, which we confirmed contained abundant phosphatidyl choline. Chick diets rich in fish had similar total caloric content to krill-only diets; however, these “fishy” chick diets had significantly more energy derived from triacylglycerides, an important energy-rich storage molecule, and were only found in gentoo penguins. We found that whole-krill eaten by adult penguins had 1.25–3.75 times more energy than chick diets, highlighting the role of digestion in the transfer of energy to chicks. Our results highlight dynamics between climate, predator–prey relationships, and trophic transfer of energy in the Antarctic food web.