Light-driven range expansions and the underwater greening of the poles

Dr Graeme Clark1, Dr Jonathan Stark2, Dr Ben Raymond3, Professor Emma Johnston1

1University Of New South Wales, Randwick, Australia, 2Australian Antarctic Division, Hobart, Australia, 3Institute for Marine and Antarctic Studies (IMAS), Hobart, Australia

Community state on shallow polar seabed is tightly linked to sea-ice cover. Areas with prolonged sea-ice cover support unique endemic invertebrate-dominated communities, while those with less sea-ice support dense macroalgae forests. Here we present a series of studies showing the light-driven tipping-point mechanism underlying the sensitivity of polar benthos to sea-ice duration, and their acute vulnerability to climate change. Warming and early sea-ice break-out will dramatically increase the amount of light reaching shallow seabed, likely causing widespread range shifts in which invertebrate-dominated communities are replaced by macroalgae. This trend has been observed in the Arctic and parts of Antarctica where ice is retreating, leading to an underwater greening of the poles and profound changes to polar marine biodiversity and ecosystem function. Modelling shows that recent changes in ice and snow cover have already transformed annual light budgets in large areas of the Arctic and Antarctic, and both aquatic and terrestrial ecosystems are likely to experience further significant change in light. Increased light also increases the likelihood of invasion by temperate macroalgae into polar coasts, particularly on the West Antarctic Peninsula.


Dr Graeme Clark is a senior research scientist at the University of New South Wales. He specialises in coastal and marine ecology, working in diverse environments from the tropics to Antarctica. Dr Clark’s research focuses on temperate and Antarctic marine biology, invasive species, and impacts of human activities on coastal ecosystems.

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