Climate change impacts krill migration patterns

The British Antarctic Survey have revealed that krill populations in the Southern Ocean are shifting towards the Antarctic pole due to climate change.

Krill are a fundamental prey species that form a staple part of many marine animals’ diets’ including whales, penguins, seals and fish.

These small crustaceans are likely the most abundant species on the planet with an estimated 100-500 million tonnes of krill living in the Southern Ocean. That’s similar to the weight of the world’s human population.

Antarctic krill represents the largest population globally and, aside from their importance in the food web, have been suggested to play a critical role in the transport of atmospheric carbon to the deep ocean.

Sir David Attenborough has described them as “the most important Antarctic creatures of all”.

Previously it has been thought that climate change may impact krill habitats.

Now, however, an international team of scientists from the British Antarctica Survey and Plymouth Marine Laboratory have shown that over the last four decades the Antarctic krill population has shifted 440km (four degrees latitude) south, towards the Antarctic pole.

“Our results suggest that over the past 40 years, the amount of krill has, on average, gone down, and also the location of the krill has contracted to much less of the habitat.

“That suggests all these other animals that eat krill will face much more intense competition with each other for this important food resource,” Simeon Hill from the British Antarctic Survey, speaking to BBC News.

Covering the Scotia Sea and the Antarctic Peninsula, scientists have collected data on krill populations since the 1920’s, initially to study the environmental impacts of commercial whaling.

Reviewing decades of data revealed that this habitat shift emerged from the late 1980s.

The researchers have suggested that, “these northern waters have warmed and conditions throughout the Scotia Sea have become more hostile, with stronger winds, warmer weather and less ice. This is bad news for young krill.”

In order to stand a chance at survival, young krill need the sea ice during their early stages of development to avoid predation.

Previously, in years of low sea ice conditions, the krill have fallen victim to salps (barrel-shaped filterfeeders).

Now, scientists suggest that the overall loss of sea ice due to the warming oceans is responsible for this southward, evolutionary migration.

However, alongside this habitat shift, it is also evident that, overall, the Antarctic krill population has declined and become older.

The study suggests that the increasingly unfavourable conditions in the Scotia Sea has led to fewer young krill replenishing the numbers, giving rise to the underwater equivalent of an aging population.

As the icy waters warm, the impacts of this southern migration could have a devastating impact on the Antarctic ecosystem, with evidence already suggesting that species of penguins and seals may be struggling to get enough krill to support their survival.

As the spotlight has been cast on yet another impact of our warming planet, lead British Antarctic Survey scientist Dr Simeon Hill reminds us that there is “no substitute for global action on climate change.”

 

Image credit: NOAA Photo Library via Flickr

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