Polar explorers provide snapshot of Antarctica’s resilience

Century-old seal pelts from a hut once used by two of Antarctica’s most famous explorers have provided scientists with a rare window into how humans have encroached on the once pristine polar environment.

The pelts have enabled Luis Huckstadt and Daniel Costa from the University of California, Santa Cruz, to determine that the diet of Antarctica’s Weddell seals has not changed substantially in the past century. In particular, the seals continue to consume the same quantity of toothfish, despite concerns about the effect of commercial fishing depleting stocks.

“People have hypothesised that the toothfish are being depleted and that, as a consequence, the Weddell seal has shifted its diet to Antarctic silverfish,” Huckstadt says. He and Costa’s conclude in their paper, published in the journal Proceedings of the Royal Society B, that the Antarctic ecosystem remains robust and largely undamaged by human activity.

The frozen seal pelts are among the artefacts, including dead penguins and sled dogs, left preserved  in a wooden hut built on Ross Island for use by the expedition of Robert Falcon Scott. The hut was subsequently occupied by Ernest Shackleton’s expedition. Now owned by the Antarctic Heritage Trust, it has been relatively untouched over the past century – apart from occasional visits from scientists strolling from nearby McMurdo Station, Antartica’s largest research base.

Huckstadt and Costa, based at McMurdo Station, were familiar with the hut, and two other nearby buildings. Looking for ways to determine how the ecosystem had changed over the past century, they realised they had just the samples they needed.

They tested the preserved furs for carbon and nitrogen isotopes, then compared the results to those from modern-day pelts.

Nitrogen isotope levels in specific amino acids delivered readings describing “trophic levels” for the seals, revealing whether their diets had changed significantly.

As it turned out, they hadn’t. Toothfish currently make up about 10% of the Weddell seal diet. The isotope analysis, conducted with colleagues back in California, revealed the same level a century ago.

The testing, however, did uncover a significant change in the make-up of the phytoplankton community. The scientists suggest the change reflects a period of climatic cooling that had lasted for 400 years came to an end around the year 1900.

Huckstadt says the relative good health of the Antarctic underlines the importance of measures to protect it and regulate human activity.

“It’s not quite pristine but it’s about as pure an ecosystem as you’re going to find on this planet,” he says. “Hopefully we can keep it that way.”