As coral-bleaching events become more frequent and severe, a global decline in coral cover is occurring. Coral restoration can help, but the techniques remain largely experimental, logistically challenging and expensive.
So say researchers in Australia who have just announced their development of an advanced remote-sensing model designed to ease the challenges of managing and restoring damaged coral reefs.
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The team from the Australian Institute of Marine Science (AIMS) and the University of Western Australia (UWA) say that their brainchild enables more accurate mapping of seabed habitats. It automatically identifies those locations where young corals have the best chance of gaining a foothold and thriving.
For their project the researchers used data publicly available from the Sentinel-2 satellite, validated with lo-tech digital photos taken using drop-cameras, to collect details of the height and form of reef features on Scott Reef off Western Australia’s north-western coast.
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“The model incorporates many of the key habitat attributes that coral need for recruitment and survival,” says lead author of the study Dr Ben Radford.
“We can then use the model to help decide which reef areas to protect or actively manage to ensure that coral life-cycles continue, and hence help reefs rebuild following events such as coral-bleaching.
“We want to maximise the survivorship of corals, because it’s so expensive to undertake restoration efforts in the first place.”
Perfect combination
A combination of factors go to make the ideal reef-restoration site, say the scientists. For the best chance of success, a hard substrate lying in a relatively narrow range of depths is needed. It should not experience too much wave energy, too much – or too little – heat or light, or be exposed during low tides.
The type of substrate is critical, a key factor being the presence of crustose coralline algae (CCA). By forming a calcium carbonate skeleton that contributes to reef cementation and stabilisation, CCA improves the chances of coral larvae settling but does not compete with it, as turf algae would. Areas with destabilised coral rubble or sand should be avoided.
Unlike previous models, the one developed by the scientists is said to accurately predict areas of CCA, turf algae, coral rubble and sand at scales of tens to hundreds of metres..
“You can’t manage corals unless you know where they’re distributed on the reef and the environments that are, or are not, suitable for long-term survival and reproduction,” says study co-author Dr James Gilmour.
“Habitat models will ultimately help to infer how reefs are going to change in the future with climate change and other disturbances. We can then explore how certain interventions or management activities, like reef-restoration, may or may not help their trajectory in the future.”
The study is published in the journal Remote Sensing Of The Environment.
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