Studying deep-sea biodiversity used to mean casting nets using long cables from seafaring vessels or sending out remotely operated and manned submersibles. But these expensive methods don’t tell the whole story. Now, to study organisms living at inaccessible depths, researchers are increasingly looking at what’s called “environmental DNA” (or eDNA), scraps of genetic material floating in open water, Scientific American reports.
Living organisms, on land and at sea, are continuously leaving behind bits of themselves in their metabolic waste, the cells they slough off, and the scales or hair they shed. That cellular detritus gives researchers access to their DNA, without actually having to collect the animals themselves. Just filter a sample of water or sediment, and then extract and amplify the DNA. By matching these bits of eDNA to entries in existing databases like GenBank, researchers are able to identify what’s present where.
In a 2012 study, a team led by Philip Francis Thomsen from the Natural History Museum of Denmark compared fish inventories created using conventional methods (traps, nets, and trawls) and using eDNA. The latter, which identified 15 species, was as good as, and maybe even better than, the traditional methods when it came to fish diversity. Furthermore, the team also found that identifiable eDNA disappears in seawater within a week, so samples wouldn’t mistakenly count a species that’s no longer around.
Battelle Memorial Institute’s John Bickham and colleagues have also applied eDNA methods in the Beaufort Sea, north of the Arctic Circle. And at the Society of Environmental Toxicology and Chemistry’s annual meeting in Vancouver last fall, the team said that this approach will inevitably replace “laborious and costly” conventional methods in deepwater biodiversity surveys, according to Scientific American.
But it’s not quite ready yet. While Bickham’s team got millions of hits, they could only identify up to three percent. The rest may come from species unknown to available databases, or species unknown to science. “In the deep sea,” Bickham adds, “we’re back in the 1700s. We have no idea what’s out there.” He believes, however, that eDNA methods will help us catch up.
[Via Scientific American]
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