Study reveals how sub-tropical corals cope with the cold

Corals growing in high-latitude reefs in Western Australia can regulate their internal chemistry to promote growth under cooler temperatures, according to new research at the ARC Centre of Excellence for Coral Reef Studies at The University of Western Australia.

The study, published today in Proceedings of the Royal Society B, suggests that ocean warming may not necessarily promote faster rates of calcification of corals on sub-tropical reefs where temperatures are currently cool (lower than 18C).

Lead author Claire Ross said the study was carried out over two years in Western Australia’s Bremer Bay, 515km south-east of Perth in the Great Southern region. Bremer Bay is a renowned diving, snorkelling and tourism hot spot due to its stunning crystal clear waters, white sand and high marine biodiversity.

“For two years we used cutting-edge geochemical techniques to link the internal chemistry of the coral with how fast the corals were growing in a high-latitude reef,” Ms Ross said.

“These high-latitude reefs (above 28 degrees north and below 28 degrees south) have less light and lower temperatures compared to the tropics, and essentially they provide natural laboratories for investigating the limits for coral growth.”

Ms Ross said the researchers expected the corals to grow slower during winter because the water was colder and light levels lower but they were surprised to find the opposite pattern.

“We were able to link the remarkable capacity for cold-water corals to maintain high growth during winter to the regulation of their internal chemistry,” she said.

“We also found that there was more food in the water for corals during winter compared to summer, indicating that (in addition to internal chemical regulation) corals may feed more to sustain growth.”

Coral reefs are one of world’s most valuable natural resources, providing a habitat for many ocean species, shoreline protection from waves and storms, as well as being economically important for tourism and fisheries.

However, the capacity for corals to build their skeletons is under threat due to CO₂-driven climate change. The effects of climate change on coral reefs are likely to vary geographically, but relatively little is known about the growth rates of reefs outside of the tropics.

“Our study is unique because it is among the first to fully decipher the corals’ internal chemistry,” Ms Ross said. “The findings of this study help better understand and predict the future of high-latitude coral reefs under CO₂-driven climate change.”

Images and video available here

Citation: Claire L. Ross, Verena Schoepf, Thomas M. DeCarlo, Malcolm T. McCulloch (2018). Mechanisms and seasonal drivers of calcification in the temperate coral Turbinaria reniformis at its latitudinal limits. Proceedings of the Royal Society B. Volume 285 (1879). DOI: 10.1098/rspb.2018.0215

MEDIA REFERENCE

Claire Ross
ARC Centre of Excellence for Coral Reef Studies, UWA School of Earth Sciences
(+61 4) 32 272 636

David Stacey
UWA Media and Public Relations Manager
(+61 8) 6488 3229 / (+61 4) 32 637 716

Catherine Naum
Communications Mgr, ARC Centre of Excellence for Coral Reef Studies
(+61 7) 4781 6067/ (+61 4) 28785 895