Bleached corals have reduced capacity to clear sediment

An investigation into the ability of bleached corals to cope with dredging related stressors has found that several species of thermally bleached corals cannot clear sediment that has smothered them.

The study was undertaken as part of the Western Australian Marine Science Institution’s Dredging Science Node at the AIMS National Sea Simulator in specially developed tank systems.

Corals were subjected to elevated temperatures to cause bleaching and then exposed to various rates of sediment deposition, or smothering. Bleached corals were found to be able to remove about three times less sediment than those that were not bleached.

Lead researcher Pia Bessell-Browne from The University of Western Australia Oceans Institute, Centre for Microscopy, Characterisation and Analysis and Australian Institute of Marine Science said that as coral bleaching events become more common we need to increase our understanding of how these large scale pressures interact with more local pressures, such as dredging activities.

“This has important implications for management, as it demonstrates that precautions should be put in place to reduce the impact of dredging related pressures, and in particular sediment deposition, during periods of elevated ocean temperatures that could result in coral bleaching,” Ms Bessell-Browne said.

The full results have been published in  Scientific Reports.

Bessell-Browne P, Negri A.P., Fisher R, Clode P.L., Jones R, (2017) Cumulative impacts: thermally bleached corals have reduced capacity to clear deposited sediment Scientific Reports doi:10.1038/s41598-017-02810-0

The WAMSI Dredging Science Node is made possible through $9.5 million invested by Woodside Energy, Chevron Australia and BHP Billiton as environmental offsets. A further $9.5 million has been co-invested by the WAMSI Joint Venture partners, adding significantly more value to this initial industry investment. The node is also supported through critical data provided by Chevron Australia, Woodside Energy and Rio Tinto Iron Ore. The commercial entities had no role in data analysis, decision to publish, or preparation of the manuscript.


Dredging Science