Warmer Seas May Impact Antarctic Clams' Reproduction

By Kieran Cooke, Climate News Network

LONDON — Antarctic clams (Laternula elliptica) play a vital role in the ocean ecosystem, drawing down carbon into sea-bed sediments and circulating ocean nutrients.

Now a new study has found that the reproductive capacity of this long-lived and abundant species — existing in the cold, oxygen-rich waters of the Antarctic — could be seriously affected by rising ocean temperatures.

The study, by scientists at the British Antarctic Survey (BAS)  and from the University of Kiel and the Alfred Wegener Institute in Germany and published in the journal Global Change Biology, found that young clams examined — averaging 3 years old — tended to try to move and bury themselves deeper when they sensed warmer ocean temperatures or reduced oxygen levels.

An Antarctic clam (Laternula elliptica).
Credit: National Museum of Natural History

But more mature clams — of around 18 years old — stayed put. This, say scientists, is important as it is the older clams, not the younger ones, which reproduce. If they don’t adapt, their existence could be threatened.

“The polar regions are the Earth’s early warning system and Antarctica is a great natural laboratory to study future global change”, says Dr. Melody Clark of the BAS, the lead author of the study.

“These small and rather uncharismatic animals can tell us a lot about age and survival in a changing world — they are one of the ‘engines of the ocean’.

“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.”

Antarctic clams, which can live up to 36 years, have evolved in stable temperatures over the centuries. But scientists say sea surface temperatures around the Antarctic Peninsula have risen by 1°C (1.8°F) over the last 50 years.

Age Reduces Mobility

As with humans, the muscle mass of clams decreases with age, making them more sedentary. The study, which follows on from earlier research, confirmed that it is these older, reproductively active clams which will suffer most from rising water temperatures.

The study involved divers collecting both young and older clams from the the seabed off King George Island and adjacent to a BAS research station on the Antarctic Peninsula.

The clams were then placed in aquarium tanks simulating different environmental conditions, with reactions to variations in oxygen and nitrogen levels monitored. Older clams showed little sign of movement in warmer waters with less oxygen while younger clams tended to be more active.

“We are trying to correlate long term predictions for clam populations”, Dr. Clark told the Climate News Network. “What is interesting with clams is that their shells show their age more or less exactly and we are therefore able to monitor their behavior at different stages of the life cycle, in differing conditions.”

Doris Abele of the Alfred Wegener Institute says the study shows 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. Climatic change, affecting primarily the older clams, may interfere with this evolutionary strategy, with unpredictable consequences for ecosystems all around Antarctica.”

Kieran Cooke is joint editor of Climate News Network. Climate News Network is a journalism news service led by four veteran British environmental reporters and broadcasters. It delivers news and commentary about climate change for free to media outlets worldwide.