Antarctic clams may take a hit from global warming

Study shows climate change may affect overall population numbers

Changes in Antarctic clam populations could have a ripple effect on other species in the region like these blue-eyed cormorants in the South Shetlands. Bob Berwyn photo.

By Summit Voice

FRISCO — Warming ocean temperatures and increased glacial outflow around Antarctica may have a big impact on clams living on the ocean floor. Younger clams try to move away when they sense warmer temperature or reduced oxygen levels, but older clams stay put.

The findings by a team of British and German scientists indicate how climate change may affect biodiversity in the region, suggesting that the overall population of Antarctic clams may dwindle, since it’s the older animals that reproduce.

“Our study shows that the physiological flexibility of young clams diminishes as they get older. However, the species has evolved in such a way that the fittest animals, that can tolerate life in an extreme environment, survive to reproduce into old age,” said Doris Abele, of the Alfred Wegener Institute in Germany. “Climatic change, affecting primarily the older clams, may interfere with this evolutionary strategy, with unpredictable consequences for ecosystems all around Antarctica.”

Antarctic clams (laternula elliptica) can live up to 36 years, and produce their offspring during their mature years. They have evolved in stable temperatures over many centuries, but in their habitat around the Antarctic Peninsula, the sea temperature has risen by 1 degree Celsius during the last fifty years. The researchers concluded the changing regional climate will probably affect clams and other marine animals that live in the sea-bed sediments.

While not as charismatic as penguins or leopard seals, the long-lived clams are nevertheless a key part of the ecosystem, said the study’s lead author, Dr. Melody Clark, of the British Antarctic Survey, describing them as one of the “engines” of the ocean.

“Antarctic clams play a vital role in the ocean ecosystem. They draw down carbon into sea-bed sediments and circulate ocean nutrients. We know that they are extremely sensitive to their environment. Our study suggests that the numbers of clams that will survive a changing climate will reduce,” Clark said.

“The polar regions are the Earth’s early warning system and Antarctica is a great natural laboratory to study to future global change. These small and rather uncharismatic animals can tell us a lot about age and survival in a changing world,” she said.

Like humans, clams’ muscle mass decreases as they get older.  This means they get more sedentary.  So when changes are introduced into their habitat, the older clams tend to just sit it out until conditions revert back to normal.

“The study shows that it is important to investigate different ages of a population to understand population wide changes and responses,” said co-author Eva Phillip, with the University of Kiel. “In respect to Antarctic clams it has been indicated in previous studies that older individuals may suffer more severely in a changing environment and the new study corroborates this assumption. Only the investigation of population-wide effects makes it possible to draw conclusions for coastal ecosystems,” she said.

To test the response of clams to changing ocean conditions, divers collected both young (about three years) and older (18 years) clams off off King George Island and BAS Rothera Research Station on the Antarctic Peninsula. The animals were then placed in aquarium tanks to simulate different environmental conditions and to test the clams’ reaction to variations in oxygen and nitrogen levels.

The findings were published this week in the journal Global Change Biology. The research was funded by the Natural Environment Research Council, the German Research Foundation and the European Science Foundation.



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