Why did some parts of the Great Barrier Reef resist the mass bleaching events in 2016 and 2017? This is one of the most important questions to be addressed at the Great Barrier Reef Restoration Symposium.

Craig Steinberg and his team at AIMS have been working on a NESP TWQ Hub Project to gather and study a vast amount of data from across the Great Barrier Reef with the aim of determining the oceanographic and atmospheric drivers behind the variability of bleaching on the Reef.

Using data from all available oceanographic observations – such as the IMOS network, AIMS temperature loggers, tide gauges and more, including citizen science groups – the team has been working to identify which reefs experienced less bleaching effects than their immediate neighbours.
They have found a direct link between the presence of natural destratification – the mixing of cooler water from deeper below the surface – and bleaching resistance.

Craig and his team will be presenting these findings at the Symposium during a special session on hydrodynamics and mixing, designed to help engineers find “ways-in” to potential small-scale interventions that could help reduce bleaching severity in future. This special session will conclude with a moderated panel discussion led by Dr Ian Poiner.

“We have a number of regions on the Great Barrier Reef like the fringing reefs at the Torres Strait, the Swain and Pompey Reefs that have persistently cooler water,” Craig said.

“When we have seen cyclones occurring outside the reef area – for example in the Coral Sea – the winds from those cyclones contribute to the cooling and essentially saved the southern Great Barrier Reef from bleaching during the last event.

“Obviously we can’t rely on cyclones to occur at the right time and place but another key mechanism is strong tidal currents de-stratifying the water column.

“We’ve identified a number of scales that this occurs at, ranging from whole reefs to individual areas on the scale of a few hundred square metres.

“What we are planning to do is provide a hazard map of where there isn’t enough current action – this will be important because those areas may be more likely to bleach. It’s not random.”

The project is also building and expanding on previous work undertaken by the Tropical Water Quality Hub, specifically on linkages between water quality and the thermal tolerance of corals.

Craig will speak on Tuesday 17th July at 13.45pm in the Urchins Ballroom.




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