Report　vol.１Inspection of Minami Daito Island:
Start of “environmental DNA analysis” of deep water!

The coast of Minami Daito Island

There are many limestone caves on Minami Daito Island.

As the first activity of the D-ARK project, we conducted an inspection of Minami Daito Island.
This island was formed near the equator 50 million years ago and continues to move northward. Minami Daito Island exists at its current position without ever being connected to any other terrestrial regions.
As the island moves northward, the Philippine Sea Plate is subducting, and reef building corals grow on top.
As a result of thousands of years of reef building coral growth, the upper 2000 meters of the island consists of limestone layers. When these limestone layers are eroded, splendid limestone caves are formed on land.

“Hoshino Cave” Minami Daito Island's largest limestone cave

Analyzing seawater to estimate organisms that live there

Deep ocean water collected from Minami Daito Island

During this inspection, a certain company gave us some deep ocean water at a depth of around 200 meters off the coast of Minami Daito Island.

Fragments of tissue such as skin, scales, and feces shed from various creatures are drifting in seawater.
By analyzing the minute traces of DNA contained in tissue fragments, it is possible to find out what kinds of organisms live in the ocean area.
This is called "environmental DNA (eDNA) analysis."

In a past research, unexpected discoveries were made through environmental DNA analysis.
When we sampled water from several seamounts in the south of Japan and conducted eDNA analysis, we found Yokozuna Slickhead DNA from three seamounts in the Nishi Shichito Ridge. Then, we conducted baited camera surveys at the ridge and recorded a valuable footage of the slickhead.

We hope that the water collected from Minami Daito Island will also be useful for future investigations.