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Invasive insect is transforming Antarctic soils, paving the way for new species

According to a new study led by the University of Birmingham and the British Antarctic Survey (BAS), a tiny flightless midge (Eretmoptera murphyi) that has recently colonized Antarctica’s Signy Island is currently driving major changes to the island’s soil ecosystem. This invasive insect significantly increasing the rates of plant decomposition, resulting in three to five-fold rises in soil nitrate levels compared to sites housing only native invertebrates.

“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,” said lead author Jesamine Bartlett, a field ecologist at Birmingham.

“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,” added senior author Scott Hayward, a senior lecturer in Biosciences at the same university.

E. murphyi is a native of South Georgia (an island in the sub-Antarctic region), and was first introduced to Signy Island accidentally during a botany experiment in the 1960s.

After the insect had massively proliferated in the 1980s, the levels of nitrates measured in soil colonized by this midge was comparable to that found close to seal wallows – an amazing phenomenon most likely due to the fact that population densities of midge larvae can reach in excess of 20,000 individuals per min some locations.

Since it can ride on the soles of boots of researchers and tourists, and can survive in sea water for extended periods of time, the insect is expected to soon reach and colonize other islands.

“Physiologically, Eretmoptera has the capacity to survive in many other locations in Antarctica, so monitoring its spread on Signy, and associated ecosystem impacts is important and remains part of our ongoing research,” Hayward said.

“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,” concluded co-author Peter Convey, an expert in Polar Ecology at BAS.

The study is published in the journal Soil Biology and Biochemistry.

More about Antarctic soils

Antarctic soils are quite different from the soils found in most other regions of the world due to the unique climate and ecological conditions of the Antarctic region.

Antarctica is the coldest, driest, and windiest continent on Earth. Most of Antarctica is covered by ice. The ice-free regions are mainly found in the coastal areas and in the Dry Valleys region of East Antarctica.

Due to the extreme cold, dry, and windy conditions, soil formation processes in Antarctica are very slow compared to those in other parts of the world. These soils also receive very little organic input because there are few organisms (primarily limited to bacteria, lichens, and mosses) capable of surviving in the harsh Antarctic conditions.

The most common types of soil in Antarctica are called “Cryosols”. Cryosols are permanently frozen soils (permafrost) that are characterized by ice formations and by the processes, signs and impacts of freezing and thawing. Because of the extreme conditions, Cryosols in Antarctica are often further classified as “Hyperskeletic” (more than 90% coarse material), “Skeletic” (40-90% coarse material), or “Leptic” (thin soils with a maximum thickness of 10 cm over bedrock).

Antarctic soils are also characterized by low nutrient content, high salinity in some areas, and the presence of unique features such as patterned ground and polygonal soil structures caused by freeze-thaw cycles.

These soils are important for studying past climate conditions and for understanding the limits of life on Earth. Because they are so unique and fragile, they are also protected by international treaty (the Antarctic Treaty System) from damage or contamination.

Despite the inhospitable conditions, Antarctic soils harbor diverse microbial communities. These microbes have adapted to survive and thrive in the extreme cold, dryness, and high UV radiation. They play a crucial role in nutrient cycling and organic matter decomposition in these soils, and their study provides insights into the possibilities of life in extreme environments, including other planets.

By Andrei Ionescu, Staff Writer

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