Non-Native Midge Invades Antarctica and Alters Soil Nutrient Cycles

Antarctica is known for its harsh and pristine environment, where only a few native species can survive. However, a recent study has revealed that an invasive insect is transforming the soil ecosystem of one of its islands.

The midge that unlocks nutrients

(Photo : Michael M. Santiago/Getty Images)

The insect is a flightless midge, Eretmoptera murphyi, that was accidentally introduced to Signy Island by a botany experiment in the 1960s, as per Phys.org.

The midge is originally a native of South Georgia, an island in the sub-Antarctic region. It has since spread across Signy Island by hitching a ride on the boots of researchers and tourists.

The midge is a decomposer, feeding on dead organic matter across the island. This process releases large amounts of nutrients into the soil, especially nitrates.

The study, conducted by experts from the British Antarctic Survey (BAS) and the University of Birmingham, found that soil nitrate levels were three to five times higher in sites where the midge occurred compared to sites where only native invertebrates were present.

The study, published in the journal Soil Biology and Biochemistry, was part of a PhD project by Dr. Jesamine Bartlett.

She says, "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."

The midge has several adaptations that allow it to thrive in the Antarctic conditions. It can produce antifreeze proteins that prevent ice formation in its cells.

It can also undergo rapid cold hardening, which means it can increase its cold tolerance within hours of exposure to low temperatures. It can also survive desiccation and salinity stress.

The midge prefers to live in peat and dead organic material, where it can find more food and shelter. It can reach densities of up to 20,000 individuals per square meter in some sites, making it one of the most abundant terrestrial animals in Antarctica.

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The potential threat to other islands

The high nutrient levels caused by the midge are comparable to those found near penguin colonies and seal wallows, which are natural sources of fertilization in Antarctica.

However, unlike these marine animals, the midge can survive in seawater for periods of time, raising the possibility that it could colonize other islands in the future, as per ScienceDirect.

Professor Peter Convey, a terrestrial ecologist at BAS, says, "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."

The study also suggests that the midge may have indirect effects on other aspects of the island's ecology, such as plant growth and diversity, microbial communities, and carbon cycling.

The researchers found that increased soil nitrate levels were associated with increased plant biomass and diversity, as well as changes in microbial composition and activity.

However, these changes may not be beneficial for all native species. Some plants may be outcompeted by others that can take advantage of the increased nutrients.

Some microbes may be suppressed by others that can tolerate higher nitrate levels. Some carbon may be lost from the soil due to increased decomposition rates.

The researchers call for more monitoring and management of invasive species in Antarctica to prevent further damage to its unique and fragile environment.

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