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Wednesday, 18 December 2019

Biodiversity on Ice

Whilst 97% of water on earth is salty and 1% is freshwater, 2% is locked up in snow and ice – but never gets a mention in the national curriculum! However, as the planet warms due to climate change, the ice is melting, and this could have an unprecedented impact on habitats and biodiversity.

Interestingly, as more water becomes available and the climate becomes more temperate, what is observed is a loss of biodiversity. Specialist organisms designed for living in harsh, cold, wintry environments die or are out-competed by more common species already found in neighbouring environments. The conclusion is that the unforgiving glaciers provide pockets for more unusual lifeforms to flourish. These lifeforms are known as extremophiles.

One example of an extremophile is the glacial worm, a black, nocturnal, algae-eating cousin of the common earthworm. The glacial worm’s metabolism only functions when they are kept below freezing point, and if allowed to reach 5oC, they stop growing, reproducing and literally fall apart, melting into a slurry. The worms actually need to be kept below freezing point for their metabolisms to function, and at 5 ÂșC. During the day, they burrow into the ice to retreat from the sun; scientists looking at how have suggested they might populate fissures or secrete a biological antifreeze!
Glacial worm or ice worm on snow. By Southwick3 via Wikipedia Commons.

Many non-extremophile species will also suffer with ice melt. Not only does ice melt increase sea levels, decreasing habitable and fertile land, but it also changes the temperature of the water. This has provoked the migrations of vast numbers of marine animals as they move to more comfortable environments. Even poorly-temperature-sensitive animals like sharks (which are mostly poikilothermic) are affected as their prey migrates, leading to increased sightings near land.

The Australian and common black-tip shark species have even demonstrated a surprising and rapid evolutionary survival tactic: cross-breeding to produce offspring that can survive in cooler water than the Australian species. The impacts of the introduction of new species on biodiversity is yet to be ascertained.

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