Algae is turning coastal Antarctica red and green – and it could have big implications.

Scientists studying the light-rich but low-nutrient ecosystems now believe they could be a model for how life could survive on other planets.

Monday, July 27, 2020,
By Jonathan Manning
Green snow at Rothera Point, Antarctica, in 2018. In coastal areas of the Antarctica Peninsula where ...

Green snow at Rothera Point, Antarctica, in 2018. In coastal areas of the Antarctica Peninsula where ice has warmed to snow slush, algae is proliferating. Scientists believe that as the climate warms further, inland areas will experience similar melt conditions, and allow the algae to flourish in areas where it has not previously observed. 

Photograph by Matt Davey

The pristine white of Antarctica’s coast and low lying areas are turning red and green in its summer months as algae bloom across the ice and snow. The microscopic plants are forming carpets about 20mm deep in the ‘warmer’ waters of the frozen continent where snow and ice turn to slush in temperatures just above 0oC. And scientists believe the algae’s survival in the most inhospitable climate on Earth could provide valuable insights into plants that might grow in space.

A study published in Nature Communications, found 1,679 green algal blooms on the frozen desert of the Antarctic Peninsula. The algae are feeding on the nutritious nitrates found in seabird and seal excrement. More than 60% of algal blooms recorded by the researchers were within 5km of penguin colonies, say researchers from the University of Cambridge and the British Antarctic Survey.

To estimate the distribution, size and biomass of snow algae blooms across the entire Antarctic Peninsula the scientists painstakingly mapped blooms of algae on the ground at two coastal Antarctic locations – Ryder Bay, Adelaide Island, and the Fildes Peninsula, King George Island – and then cross-referenced this with three years’ of data from the European Space Agency’s Sentinel 2 multispectral imaging satellites.

Matt Davey sampling snow algae at Lagoon Island.

Photograph by Sarah Vincent

“We are looking at a terrestrial ecosystem that is potentially bigger than everything we currently consider to be a terrestrial ecosystem.”

Prof. Pete Convey

“I was surprised how much algae was there compared to mosses and lichens,” said Dr Matt Davey from the University of Cambridge’s Department of Plant Sciences. “It’s a beautiful sight when you see all of these oranges, reds and greens. Some of the valleys on the island almost look like fields with the mosses and lichens and the green blooms of algae in the snow, but everywhere else it’s still white and blue and quite stunning.”

Satellite remote sensing has traditionally been used to record vegetation on exposed snow-free ground, but the researchers succeeded in refining spectral reflectance techniques to identify green algae in snow. By measuring how much light that hits a surface is reflected without being absorbed– the albedo effect – the scientists could calculate the surface area of the algae.

“Fresh white snow reflects almost 99% of light that hits it, while some of our initial results show that red algal blooms knocks this down to about 60% and for green snow it’s approximtely 45%,” said Dr Andrew Gray, report author and researcher at the University of Cambridge and NERC Field Spectroscopy Facility, University of Edinburgh.“We could pick up chlorophyll signals through 5cm of wet snow, but as the snow gets slushier and slushier it gets easier to pick up that signal.”

Multi-coloured algae is seen blooming in green and red on Anchorage Island, Antarctica.

Photograph by Matt Davey

Climate change is likely to see wet summer snow disappear from the low lying coastal snowfields of the world’s most southerly continent, causing the loss of small algal blooms. But the same changes in temperature are set to increase the seasonal melt on higher ground, creating slush where algae may flourish.

“As Antarctica warms, we predict the overall mass of snow algae will increase, as the spread to higher ground will significantly outweigh the loss of small island patches of algae,” said Dr Gray. 

His study found blooms of green algae – as vibrant as “lawn green or lime green” – covered an area of 1.9kmon the Antarctic Peninsula, where terrestrial vegetation covers just 8.5kmof the land mass. 

The Instituto Antartico Chileno (INACH) Refugio Collins on King George Island – field base for some of the latest research into Antarctic algal blooms.

Photograph by Andrew Gray

Inside the research hut on King George Island and (right) conducting field spectroscopy on the Collins Glacier. 

Photograph by Monika Mendelova

This would suggest that the algae account for a similar area to the moss, lichen and grass in Antarctica, particularly when red and orange algae are included. The spectral imaging was not able to separate these algae as it could the green algae, but, “as a ballpark figure there is as much red as there is green,” said Professor Pete Convey, a co-author of the study and researcher at British Antarctic Survey.

“Snow algae is becoming more apparent and it’s also more apparent that there is more wet snow,” he added. “Surface melt is beginning earlier in the season, so blooms of algae are appearing earlier. The impression is that you are seeing more of them and that they are getting bigger. We are looking at an [Antarctic] terrestrial ecosystem that is potentially bigger than everything we currently consider to be a terrestrial ecosystem.”

Dr Convey first visited Antarctica in 1989 and has seen profound changes as the ice has retreated and flora and fauna have colonised the newly exposed forefield.

“If you went to certain very small areas you would actually see a spectacularly colourful, quite developed ecosystem,” he said. 

This terrestrial ecology predates climate change – in some instances the mosses and lichens have survived for millions of years through glacial cycles, and they are now joined by tiny invertebrates, such as mites and springtails that are found naturally in Antarctica. 

“If an island becomes ice free, within a few years you’ll have mosses on it, algae on it, and even little arthropods,” said Dr Convey. “When I first visited Signy Island in the South Orkney Islands, one of the valleys was half filled with a receding piece of ice. Fifteen years ago that ice had already disappeared, so you can see very drastic changes.”

While algae are found in both the Arctic and alpine regions, the scientists are now keen to analyse whether the Antarctic algae are genetically unique – and to use this study as a baseline to monitor ice melts in Antarctica by tracking the spread of snow algae. This will help the team establish the ecosystem's effectiveness as a carbon sink.

There are also fascinating opportunities to explore how these single-cell organisms can grow in such an extremely cold environment with limited resources yet an abundance of light: conditions not dissimilar to outer space.

“There is an astro-biological application,”  said Dr Davey, “so we’re proposing projects with the European Space Agency to see how we can utilise some of these pigments and algal growth systems on board some of their missions.” 

Gallery: Antarctica through the eyes of NatGeo photographers

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