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Green Snow Algae Blooms in Antarctica

A study published in the journal Nature Communications showed that the phenomenon can be seen from space. It described that green snow is distributing along the Antarctic Peninsula and it is influenced by marine nutrient inputs. A study conducted that the small low-lying islands may lose a majority of blooms as they do not have high ground for range expansion, but the increase may happen on larger landmasses and it is predicted that it will outweigh biomass lost from small islands. It then explained about that blooms of snow algae as a photosynthetic primary producer- they host range of algal species, influence nutrient provision and carbon cycling. It is said that blooms were studied since expeditions in 1950-60s and that blooms shown on photographs were approximately 50m × 100m. The study says:

“Warming in the Antarctic Peninsula has already exceeded 1.5 °C over pre-industrial temperatures, and current Intergovernmental Panel on Climate Change projections indicate further global increases. Set against a background of natural decadal temperature variability, climatic changes on the Peninsula are already influencing its vegetation. With the available area for plant colonisation on the Peninsula likely to increase by up to threefold due to this warming, understanding how snow algae fit into Antarctica’s biosphere and their probable response to warming is critical to understanding the overall impact of climate change on Antarctica’s vegetation.”

The study explains that satellite remote sensing can help with monitoring the vegetation biomass and distribution. This method to map Antarctica’s terrestrial biosphere will contribute to investigating snow algae and ‘implicating algal blooms as significant drivers for darkening and enhancing melt of the Greenland ice sheet’. Although there are some challenges which are described saying: “Current spectral and spatial resolution of freely available multispectral satellite imagery limits the study of most snow and ice algae to presence detection through classification models or assessing relatively small, ground validated areas.” It also says that cloud cover and summer snowfall may interfere with satellite images. The efforts to overcome those challenges will be about analysing data from previous years to map the estimate of the size or distribution of the algal blooms as well as confirming those findings with factors relating to gas exchange or nutrient status. It says:

“We show that the Antarctic Peninsula supports at least 1.3 × 103 tonnes (dry mass) of green snow algae, covering approximately 1.9 km2. We also present data on the likely factors controlling snow algal distribution and discuss how this may be influenced by climatic warming.”

In the results and discussion section, the melt season was described from December/January and by February the green algae was seen more vividly as the seasonal snow cover melted. The scientists looked at the blooms as also containing red and orange cells, but chlorophyll pigments of green are dominant. The Antarctica Peninsula scale map used in the report to show green snow algae distribution and cell density visualises 1679 individual blooms of green snow algae being identified. Red triangles on the map were used to show the location of ground validation sites and it’s mostly focused in one area close to Adelaide Island.

The study confirmed how essential is to understand the distribution of snow algae for predicting how blooms will respond to the future warming of that region. Rising of global temperatures will be slowly changing Antarctic environment and will contribute to distribution of green snow algae in the region. The study says:

“With the IPCC’s projected 1.5 °C global temperature increase, it is predicted that the 0 °C isotherm will increase in elevation and that positive degree days will become more commonplace and occur further to the south. This will likely open up new snow for colonisation by green snow algae, should an appropriate dispersal mechanism allow transfer to new areas.”

By Julita Waleskiewicz

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