We present the first estimate of green snow algae community biomass and distribution along the Antarctic Peninsula. Sentinel 2 imagery supported by two field campaigns revealed 1679 snow algae blooms, seasonally covering 1.95 × 106 m2 and equating to 1.3 × 103 tonnes total dry biomass. Ecosystem range is limited to areas with average positive summer temperatures, and distribution strongly influenced by marine nutrient inputs, with 60% of blooms less than 5 km from a penguin colony. A warming Antarctica may lose a majority of the 62% of blooms occupying small, low-lying islands with no high ground for range expansion. However, bloom area and elevation were observed to increase at lower latitudes, suggesting that parallel expansion of bloom area on larger landmasses, close to bird or seal colonies, is likely. This increase is predicted to outweigh biomass lost from small islands, resulting in a net increase in snow algae extent and biomass as the Peninsula warms.
Explanation:
In the limited terrestrial ecosystems of Antarctica, all photosynthetic organisms will make a significant contribution to the ecology of their habitat. Ice-free ground makes up only around 0.18% of Antarctica’s continental area, and even in the Antarctic Peninsula, the most vegetated region of Antarctica, only 1.34% of this exposed ground is vegetated1,2. Photosynthetic life is not restricted to bare ground however, with algal blooms often appearing in coastal snowfields as green (Fig. 1) and red patches below and on the snow surface3,4,5. Blooms of snow algae in Antarctica were first described by expeditions in the 1950s and 1960s6,7 and have since been studied at a few locations in Antarctica, where they have been shown to host a diverse range of algal species3,4,8,9,10 and to play key roles in nutrient and carbon cycling11,12,13. Considering that a single snow algal bloom can cover hundreds of square metres4, snow algae are potentially one of the region’s most significant photosynthetic primary producers, as well as influencing nutrient provision to downstream terrestrial and marine ecosystems14.
Warming in the Antarctic Peninsula has already exceeded 1.5 °C over pre-industrial temperatures15, and current Intergovernmental Panel on Climate Change (IPCC) projections indicate further global increases16,17. Set against a background of natural decadal temperature variability18,19, climatic changes on the Peninsula are already influencing its vegetation20,21. With the available area for plant colonisation on the Peninsula likely to increase by up to threefold due to this warming22, 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.
