Confirmed to work through observations made by scientific divers in the same areas of ocean, researchers from the Okinawa Institute of Science and Technology (OIST) have developed a method to measure coral biodiversity through extracting the environmental DNA (or eDNA) from a litre of surface seawater collected from above a reef. The method looks set to pave the way for large-scale comprehensive surveys of reef-building coral to take place and removes the reliance of direct observations made through scientific scuba diving or snorkelling.
To conserve coral reefs, it’s critical to know which coral exists on the reef and how the make-up of a reef is changing over time. Previously, the only way to effectively survey a reef was through divers and snorkellers directly observing the coral and recording the species and the changes over time. This was time consuming, expensive, and labour intensive. Now, the researchers have tested their new method by conducting a large-scale survey of the ocean surrounding Okinawa using both the eDNA method and scientific divers.
“We found that the eDNA analysis matched that of the direct scientific observations with more than 91% accuracy,” said OIST Research Scientist, Dr. Koki Nishitsuji, first author of the paper. “In fact, 41 out of the 62 sites were identical. The eDNA method indicated the presence of five dominant coral genera at all 62 sites surveyed. What’s more the results of the environmental DNA method suggest the presence of corals never before recorded along the coast of Okinawa.”
The eDNA method requires complex sequencing information, and due to this, only 45 of the estimated 236 genera can currently be detected. However, with more information, the effectiveness of the eDNA method will increase and the method may be even be able to indicate the presence of corals that are difficult to detect by direct observation.
Image: On a reef in Okinawa, a snorkeler notes the different coral genera present. In this research, the scientists compared the two different methods for monitoring a reef—direct observations made by scientific snorkelers and the new method that utilizes eDNA. Credit: OIST/Noriyuki
More information: Koki Nishitsuji et al, An environmental DNA metabarcoding survey reveals generic-level occurrence of scleractinian corals at reef slopes of Okinawa Island, Proceedings of the Royal Society B: Biological Sciences (2023). DOI: 10.1098/rspb.2023.0026
Journal information: Proceedings of the Royal Society B