As the Antarctic Peninsula becomes warmer, the food chain is feeling the effects — from bottom to top– according to research described in a press release from the National Science Foundation.

Over the past 50 years, winter temperatures on the peninsula, the northernmost part of mainland Antarctica, have risen five times faster than the global average and the length of time the surrounding sea is covered by ice has decreased.

Species that depend on sea-ice coverage, such as the Adelie penguins, Antarctic silverfish, and krill, have decreased. They are being replaced by species that are not dependent on sea ice, including the Gentoo and Chinstrap penguins and lantern fish.

What scientists suspected but couldn’t prove earlier was that the bottom of the food chain was being affected by the rapid warming. Satellite data on ocean color, temperature, sea ice and winds gave researchers the information they needed.

In the north of the peninsula where sea-ice coverage has diminished and retreated, strong winds now mix surface ocean waters and force phytoplankton (the base of the food chain) down to depths where it is exposed to less sunlight and cannot reproduce. The phytoplankton population in the north has vastly diminished.

In the south of the peninsula, the year-round sea ice has retreated but the sunlight can penetrate the ocean waters and sustain large phytoplankton populations.

 The findings are possible because the Long-Term Ecological Research (LTER) network, funded by the National Science Foundation, is designed to investigate ecological processes over long temporal and broad spatial scales. There are 26 field sites representing the major ecosystems of the planet. (The April issue of Beyond Penguins and Polar Bears features the Arctic LTER site where Linda Deegan studies the ecosystems in streams and lakes of the tundra.)