Changing Arctic Climate Could be Catastrophic for Marine Food Chain

Changing climate conditions impact all sorts of marine life along the West Antarctic Peninsula, from single-celled algae to penguins, sending ripples through the food chain, according to a recent long-term study.

Researchers of the Palmer Long-Term Ecological Research program (PAL-LTER) have been studying Antarctica's fast-changing and rapidly warming region since 1990. The West Antarctic Peninsula is one of the fastest warming regions on Earth - in the last 50 years alone winter temperatures have increased by 11 degrees Fahrenheit. This current study is one of the few that provides a detailed outlook on how such drastic climate shifts can reverberate through a polar food web.

"That's the importance of long-term ecosystem monitoring," co-author Deborah Steinberg of the Virginia Institute of Marine Science said in a statement. "It provides the data needed to separate a signal from the noise, and to determine how plants and animals interact with both their physical environment and each other. That knowledge is critical as climate warming continues to impact this polar ocean ecosystem."

Maintaining balance in the Antarctic marine food chain is dependent on a negative phase of the "Southern Annular Mode," or SAM, which is a seesaw shift in atmospheric pressure between mid-latitudes and Antarctica. During the wintertime, a negative SAM means hefty winds and heavy sea ice followed by a calm spring and stable water column in summer. Once the winds die down come summer, it delays ice retreat.

The entire food chain is dependent on this SAM pattern, like photosynthetic algae, for instance, which are tiny drifting plants that support the whole food web. And where there is an abundance of phytoplankton, there is new, young krill. Adélie penguins are the top predators that krill have to worry about, as it is their main food source. Other animals like Antarctic fur seals, macaroni and gentoo penguins, albatross and humpback whales also feed on these marine creatures.

However, with the climate rapidly changing and temperatures warming, this delicate balance may be thrown off kilter.

"When climate conditions - a negative SAM and stable water column - lead to peaks in the abundance of phytoplankton and krill, Adélie penguins don't have to go far to forage," lead author Dr. Grace Saba explained. "But when SAM is positive, warm northwesterly winds blow over the Peninsula region, bringing less sea ice and a less-stable water column - factors that discourage the large blooms of phytoplankton on which krill rely. Penguins then have to forage further, and thus end up delivering less food to their chicks. That can decrease their reproductive success."

This warming world has already started to impact Antarctic populations - Adélie penguin populations have fallen 85 percent since 1974, and scientists worry that as the Earth continues to change, impacts on marine food chains will be catastrophic.

The findings were published in the journal Nature Communications.