In parts of Signy Island in the Southern Ocean there are 150,000 flightless midges in every square metre. The insects have thrived since being accidentally introduced in the 1960s, and now the worry is that they could reach the Antarctic Peninsula 600 kilometres away.
“We need to start stepping up biosecurity measures,” says Jesamine Bartlett of the University of Birmingham in the UK.
The non-biting midges, Eretmoptera murphyi, act like earthworms, feeding on detritus and essentially defecating out fertiliser. They increase nitrogen levels by around 400 per cent, Barlett’s studies show – that’s as much as in areas where there are seals.
Land in Antarctica is usually very nutrient poor, except where there are colonies of seals and sea birds. So by making far more nutrients available, the midges could might have a big effect. “We don’t really know if it’s going to be a positive or a negative effect,” says Bartlett.
However, the midges could potentially pave the way for invasive plants that could not cope with low-nutrient conditions. “It’s almost like terraforming, ready for other plants,” Barlett says.
Her work also shows that the midge could survive conditions in the Antarctic Peninsula even without the recent warming due to global heating. The species thrives at a temperature of around 4°C, and the adults can survive being frozen in a block of ice.
Indeed, the midge did naturally occur there before the last ice age. So Bartlett, who will present her findings at a meeting of the British Ecological Society this week, thinks more needs to be done to ensure the midge is not introduced there, for instance by being carried in the mud on the boots of tourists.
The midges can reproduce parthenogenetically – without mating – like aphids, so their numbers can increase very rapidly. On Signy Island, the midge is the largest permanent animal resident and now far outnumbers the native invertebrates.
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