The impact of ‘alien’ species in Antarctica
Of the known non-native or ‘alien’ species found in Antarctica, a non-biting species of midge currently presents one of the highest risks to terrestrial ecosystems, researchers have found. The preliminary results are presented today (19 December) at the British Ecological Society’s annual meeting in Birmingham.
The flightless midge (Eretmoptera murphyi) is thought to have been inadvertently transferred over 500 miles from the sub-Antarctic island of South Georgia, where it is endemic, to Signy Island during a plant transplant experiment in the 1960s. It has since been able to establish itself with great success on Signy Island. The estimated biomass, or total weight of the midges, is 2 to 5 times greater than all native invertebrates combined at sites where it occurs.
Researchers from the University of Birmingham and British Antarctic Survey are studying how the midge is able to survive in extreme polar conditions and the impact it may have on the region.
The team collected information on the abundance of the midge and other invertebrates and microbes, alongside environmental variables such as water content, organic carbon and soil nitrogen content. This was compared with locations on the island where there were no midges.
They discovered that this single species, which has no competitors or predators on the island, is breaking down dead moss and turning it into soil faster than native invertebrate species. With the rapid spread in distribution, changes in this unique terrestrial environment will impact upon all levels of biodiversity.
Ecologist Jesamine Bartlett, University of Birmingham and British Antarctic Survey, says:
“The midge is basically doing the job of an earthworm, but in an ecosystem that has never had earthworms.
These preliminary results are concerning as Signy Island hosts some of the best examples of moss banks in the Antarctic region. It is also home to Antarctica’s only two flowering plant species, the hair grass and pearlwort.”
The threat of introducing invasive species into the Antarctic’s long-isolated ecosystems is growing, not least due to rapid regional warming and increased levels of human activity.
Professor Peter Convey, British Antarctic Survey, says:
“Visitors to Antarctica are subject to increasingly strict biosecurity measures but accidental introductions continue to occur.
Midge larvae, for instance, are tiny and cannot be seen easily with the naked eye. Tourists and researchers may be bringing them in from their stopovers in the sub-Antarctic and move them around the continent in the mud on their boots.”
As part of this study, the ecologists are highlighting the risk of transferring soil and invertebrates throughout the Antarctic Treaty area and are looking at existing biosecurity protocols in order to minimise the spread of invasive species.
Dr Scott Hayward, University of Birmingham, concluded:
“We already know that E. murphyi is physiologically capable of surviving conditions much further south, for example on the Antarctic Peninsula, so controlling the risk of spread is critically important.”