Researchers with the University of Hawai`i at Mānoa Department of Biology have developed a method for measuring the amount of living coral on a coral reef by analyzing coral DNA in surrounding seawater.

Graduate students Patrick Nichols and Associate Professor Peter Marko of the university’s Department of Biology published their techniques, which were honed on the coral reefs of the Hawaiian Islands, in the journal Environmental DNA.

Patrick Nichols takes eDNA samples of reef seawater collected in Hawaii. Photo by Patrick K. Nichols/University of Hawaii

The traditional approach to measuring living coral on reefs is visually, via SCUBA diving, which can often be time consuming, the researchers say. Environmental DNA analysis can complement the visual approach, because reef organisms are constantly expelling DNA. This genetic resides can then be found and analyzed with molecular biology tools.

“It still amazes me that in a tiny tube of water, there is enough information to track the relative abundance of entire communities,” Nichols said in a statement released by the university. “Increasing the breadth and scope of surveys is exactly what makes the future of eDNA so exciting!”

The researchers say that their technique has the capability to measure the amount of coral cover of a given reef. The coral cover is an important measuring device to determine how well a coral reef is doing. Nichols and Marko measured eDNA on Hawaiian coral reefs via a technique called metabarcoding. This techniques measures all of the DNA present in a water sample, and is analyzed with DNA sequencing. The coral DNA sequences are then ID’d and counted, which helps to determine the abundance of specific species of corals on a given reef. Those reefs that have been compromised or are degraded have fewer coral eDNA to count, whereas healthy reefs have more eDNA to count, the researchers said.

The complete paper, “Rapid assessment of coral cover from environmental DNA in Hawai’i” can be accessed in the open access journal Environmental DNA.