Coral reefs are highly productive ecosystems that have been threatened in recent decades due to climate change. This has fueled an increase in research into basic coral biology with a view to restoring reefs damaged by ocean warming and acidification. Reef restoration depends on the successful recruitment of juvenile corals and this is difficult to quantify using current 3D modeling techniques because juveniles are very small and cryptic.
This problem led marine biologist Dr Kate Quigley to develop a new method of monitoring coral size and growth that relies on the use of dental scanning equipment. Digital 3D scanning is commonly used in dentistry and implant manufacturing because measurements need to be precise down to the μm scale in order to produce highly accurate molds. Intraoral dental scanners can also be used safely on living tissue, whereas previous 3D modeling methods often involved destroying corals in order to measure them.
Dr Quigley, a senior researcher at the Minderoo Foundation, published details of the new method in the journal Methods in ecology and evolution. She was inspired to develop the new scanning method by a visit to her dentist.
During his visit, Dr Quigley pointed out the similarities between coral and human teeth – both being calcium-based and requiring measuring tools that can withstand wet surfaces. “One day I was at the dentist, and they rolled out this new scanner. I knew immediately that this was something that could be applied to scanning very small corals since corals and teeth actually share many similar properties. The rest is history!
Although older technologies involved in 3D modeling of coral reefs have seen substantial improvement and development in the recent past, they are really only applicable to objects ranging in size from meters to centimeters. They lack capacity in the millimeter and micrometer (μm) size range, which is necessary to measure the early life stages of corals. Understanding the critical life stage of juvenile corals allows scientists to predict ecosystem changes, the impacts of disturbances and the potential for reef recovery.
“Right now, it’s difficult to accurately measure very small 3D objects, especially if you want to measure small living animals, like coral, without hurting them. During my PhD, it took half a day to produce a scan, and I was interested in scanning hundreds of corals at once,” said Dr Quigley.
To assess the effectiveness of these dental scanners, namely the ITero Element 5D Flex, Dr. Quigley measured juvenile corals of different species and size classes. The corals were originally collected from the Great Barrier Reef Marine Park and included species with complex branching morphology, as well as those with simple branching and those with a flatter, encrusting life form. The test was conducted at the Australian Institute of Marine Science’s National Sea Simulator, where corals were temporarily removed from their indoor aquarium to have their surfaces and volumes scanned.
On average, it took less than three minutes to scan and build a model of each individual coral, compared to more than four hours with previous methods, a 99% decrease in the time needed to make such measurements. Dr. Quigley recorded equally fast and accurate performance when measuring and comparing models of dead skeletons and living coral tissue, eliminating the need to sacrifice living animals to take measurements.
“For the first time, this new method will allow scientists to measure thousands of tiny corals quickly, accurately and without any negative impact on coral health. This has the potential to expand large-scale monitoring of ocean health and scale up coral reef restoration.
Although this is a huge improvement in terms of reducing the time needed to monitor these small marine animals, the technology can only be used to make measurements out of the water. The scanning instrument is not waterproof and relies on the use of lasers. Additionally, 3D scans still have to be processed manually, which is a slow process. Dr. Quigley hopes to create an automatic scanning-to-measurement analysis pipeline in the future, potentially using AI.
“Potentially, the scanner could be made completely waterproof. However, it is unclear how fully the laser technology would work underwater. We’ve already taken this technology on the boat and bred wild, lab-bred corals to measure, so we’re getting there!”
“The combination of rapid data acquisition and processing in this way has the potential to greatly improve our understanding of coral biology for pressing conservation questions in this important biological system.”
By Alison Bosman, Terre.com Personal editor