Effects of sea-ice cover on marine benthic communities: a natural experiment in Commonwealth Bay, East Antarctica

• Published in: Polar Biology
• Main Authors: Clark, GF, Marzinelli, EM, Fogwill, CJ, Turney, CSM, Johnston, EL
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Springer Verlag 2015
• Subjects: 13 Climate Action; 14 Life Below Water; anzsrc-for: 06 Biological Sciences; Antarctic; East Antarctica; Commonwealth Bay; Antarc*; Antarctica; Iceberg*; Polar Biology; Sea ice
• Online Access: http://hdl.handle.net/1959.4/unsworks_35445; https://doi.org/10.1007/s00300-015-1688-x

Sea-ice is a key physical driver of Antarctic marine ecosystems. Understanding ecological effects of sea-ice is particularly important given current and future climate change, but a major obstacle is the impracticality of manipulating sea-ice at a relevant scale. However, large-scale anomalous events, such as those occurring in Commonwealth Bay, East Antarctica, provide opportunities for natural experiments. Historically, katabatic winds have kept Commonwealth Bay ice-free for most of each year, but since 2010, a massive grounded iceberg has resulted in year-round sea-ice cover. We surveyed benthic communities in Commonwealth Bay approximately 3 years after continuous sea-ice cover began and found algal bed communities in severe decline. The majority (~75 %) of large macroalgae were decomposing, and the remainder were discoloured or bleached, while approximately 40 % of encrusting coralline algae were bleached. Accompanying this, the presence of invertebrates such as ophiuroids and polychaetes suggests that communities are in the early stages of transitioning to an invertebrate-dominated state. With a known start date, monitoring benthic communities in Commonwealth Bay will allow quantification of rates of benthic regime shifts in response to sea-ice cover, and improve understanding of the vulnerability of polar ecosystems to climate change.