Habitable snow area changes across the Antarctic Peninsula. 50 km hexagonal grids showing the sum of area of habitable snow for green snow algae (GSA – (B, C)) and red snow algae (RSA – (F, G)) under 2021 (B, F) and predicted 2100 (C, G) climate conditions. Habitable area is cumulative from 1st November to 21st January (2021 or 2100). Maps (A) and (E) show the length of the 95% credible interval for areas that meet the models’ threshold criteria. Maps (D) and (H) show whether habitable area increased or decreased between 2021 and 2100 within each 50 km grid cell. The triangle marker line is the boundary of greater melt in 2021 than in 2100, where melt was greater to the east of the line and less to the west. Map insets are of the South Orkney Islands and are a different scale (also depicting a 50 km hexagonal grid). The map overview in h shows the extent of the main map views of the Antarctic Peninsula and of the South Orkney Islands inset in yellow. — Frontiers
Snow algae form extensive blooms within Antarctica’s coastal snowpacks and are a crucial contributor to its scarce terrestrial ecosystems.
There is limited knowledge about the factors that contribute to snow algal bloom occurrence, distribution, ecological niche thresholds, or the prevalence of suitable conditions for bloom formation.
To address these knowledge gaps and gain a clearer understanding of the current and potential future distribution of blooms, a habitat suitability model, using a Bayesian additive regression tree approach, was established. The model incorporated remotely sensed observations of blooms, physical environmental predictor variables, and snow melt modelling based on different climate scenarios.
This was used to describe the ecological niche of snow algae and predict its occurrence at a landscape scale across the Antarctic Peninsula. The findings revealed that most habitable snow was predicted north of latitude 66° S, with patch density, area, and habitable elevation decreasing poleward. Factors that strongly influenced bloom presence were days of snow melt and aspect, with blooms of red-colored algae being associated with longer seasons and north-facing slopes.
The model outputs also suggested heterogeneous preferences for environmental conditions amongst red and green snow algae blooms, suggesting a diversity of ecological niches for bloom-forming algae. Long-term climate-change impacts were difficult to discern as extreme summer temperatures and melt during the timeframe of this study in 2021 exceeded the projected 2100 temperatures for parts of the Antarctic Peninsula.
However, warmer conditions produced a greater area of potentially habitable snow at higher elevation and latitude. Conversely, small and low-lying islands were predicted to lose habitable snow under a warming scenario. Model and training imagery both indicated that algal blooms are forming on snow-covered icecaps in the South Shetland Islands, suggesting greater potential for glacier-based algal blooms in the future, should recent trends for extreme summer temperatures persist.
Modelling snow algal habitat suitability and ecology under extreme weather events on the Antarctic Peninsula, Frontiers (open access)
Astrobiology,
