Polar Antarctic Ecosystem at Risk: Impact of Global Warming's Sunlight

Deep beneath the polar ice, communities of fan worms and sponges thrive in Antarctic waters. These species, though, may soon face some massive shifts; researchers have discovered that slight changes in the timing of the annual loss of sea ice could have dire consequences for these populations by allowing far more sunlight than usual to reach the sea floor.

What impact could more sunlight have? Invertebrate-dominated communities on the polar sea floor include sponges, moss animals, sea squirts and worms. These creatures form the bottom of the food chain and perform important functions, like filtering water and recycling nutrients. They also provide an important food source for fish and other marine animals. If sunlight were to start impacting these creatures, the entire ecosystem could also be affected.

In order to assess the influence of melting ice, the researchers deployed light meters on the sea floor at seven sites in Antarctica at depths of up to 10 meters. The scientists then used cameras to photograph the coast at midday every day for two and a half years. This allowed them to determine sea-ice cover while seeing the effect on marine organisms.

The researchers found that, in fact, sunlight could disrupt these polar communities. Earlier melt dates could increase the amount of sunlight reaching the ocean floor. This, in turn, could disrupt the ecosystems. 

"Even a slight shift in the date of the annual sea-ice departure could cause a tipping point, leading to widespread ecosystem shifts," said Graeme Clark, one of the researchers, in a news release. "On the Antarctic coast, this may cause unique, invertebrate-dominated communities that are adapted to the dark conditions to be replaced by algal beds, which thrive on light, significantly reducing biodiversity."

A similar phenomenon is actually occurring on coral reefs. Algae is taking over areas where coral cover has declined, creating algal reefs that severely reduce biodiversity and create zones where you can find little but the algae itself. This particular phenomenon in the Caribbean can be broadly attributed to environmental changes--not quite the same as in polar regions, but similar in that it disrupted the natural ecosystem.

"This is a prime example of the large-scale ecological impacts that humans can impose through global warming--even in places as remote as Antarctica," said Emma Johnston, one of the researchers, in a news release.

The findings are published in the journal Global Change Biology.