As the Antarctic warms an invasive species is on the march

By Anders Lorenzen

Research by the University of Birmingham in collaboration with the British Antarctic Survey has found that a tiny flightless midge, which has colonised Antarctica’s Signy Island, is driving fundamental changes to the island’s soil ecosystem. 

The study reveals that the non-native midge species is significantly increasing rates of plant decomposition. This has in three to five-fold increases in soil nitrate levels, compared to sites where only native invertebrates occur.  

In the accompanying paper the research, led by Dr Jesamine Bartlett in Dr Scott Hayward’s lab within the School of Biosciences at Birmingham, outlines how the midge, called Eretmoptera murphyi, is altering soil ecosystems on the island. 

Combined with climate change accelerating ecosystem changes 

Commenting on the research Dr Bartlett explained: “Antarctic soils are very nutrient-limited systems because decomposition rates are so slow. The nutrients are there, but it has taken this invasive midge to unlock them on Signy Island. It is an ‘ecosystem engineer’ in a similar way to earthworms in temperate soil systems.“ 

Dr Hayward added:  “Up until now, low nutrient availability has been as much of a barrier to the establishment of certain terrestrial species in Antarctica as low temperatures or low moisture availability”. So the activity of Eretmoptera on Signy, in combination with climate change, potentially ‘opens the door’ for other species to become established which can further accelerate ecosystem change. 

The midge is a native of South Georgia – an island in the sub-Antarctic region. It was introduced to Signy Island by accident during a botany experiment in the 1960s, although its proliferation only became apparent during the 1980s. Prior to this, the only terrestrial sites on Signy with high nutrient levels were those associated with marine species coming ashore, for example, penguin colonies and seal wallows. 

The robust and durable nature of Eretmoptera murphyi is evident by the fact it can even survive in seawater for periods of time, leading to conjecture that it could eventually reach other islands. 

Professor Peter Convey, of the British Antarctic Survey, explained why this discovery was important and stressed the critical need for continuing monitoring: “A particular feature of the Antarctic is that it has had very few invading species so far and protecting this ecosystem is a very high priority. While at some level, there’s plenty of awareness of the implications of invading species, this research really highlights how the tiniest of animals can still have a hugely significant impact.”

This scientific work points to how climate change combined with other factors show that many parts of the world are being significantly altered, helped by warmer climates and melting ice that has been frozen for thousands of years.