Seawater Contains DNA Of Marine Fish And Mammals
August 31, 2012

Researchers Can Trace DNA of Fish And Marine Mammals By Sampling Seawater

April Flowers for - Your Universe Online

A half liter of seawater can contain evidence of local fish and whale faunas and combat traditional fishing methods, says a new study from the University of Copenhagen. Researchers there have created a new way for monitoring marine biodiversity and resources by using DNA traces in seawater samples.

The results of this study are now published in the journal PLoS ONE.

"The new DNA-method means that we can keep better track of life beneath the surface of the oceans around the world, and better monitor and protect ocean biodiversity and resources," says PhD student Philip Francis Thomsen from the Centre for GeoGenetics.

Globally, marine ecosystems are threatened by human over-exploitation. This affects global biodiversity, economy and human health. Surveying fish populations today, though, is done through selective and invasive methods mostly limited to commercial species and restricted to areas with favorable conditions.

The research team at Centre for GeoGenetics is now leading the way for future monitoring by showing that seawater contains DNA from animals such as fish and whales. The species leave behind a trace of DNA that reveals their presence in the ocean based on water samples of just half a liter.

Philip Francis Thomsen and Jos Kilgast from the Centre for GeoGenetics developed this novel approach to DNA monitoring. Last year, they showed that small freshwater samples contain DNA from several different threatened animals. Then they switched their focus to seawater, again proving it was possible to obtain DNA directly from the water, which originated from local species in the area.

"We analyzed seawater samples specifically for fish DNA and we were very surprised when the results started to show up on the screen. We ended up with DNA from 15 different fish species in water samples of just a half liter. We found DNA from both small and large fish, as well as both common species and rare guests. Cod, herring, eel, plaice, pilchard and many more have all left a DNA trace in the seawater," says Thomsen.

The researchers showed that it is also possible to obtain DNA from harbor porpoise in small water samples taken in the sea, so the approach is not only limited to fish, but can also track large marine mammals.

The researchers compared the new DNA monitoring method against more traditional methods such as trawl and pots. The DNA method proved as good or better than such existing methods. Moreover, the DNA method has a large advantage in that it can be performed virtually anywhere without impacting local habitat. It only requires a sample of water. Associate Professor and fish expert Peter Rask Møller from the National History Museum of Denmark, who also participated in the study, is optimistic.

"The new DNA method has very interesting perspectives for monitoring marine fish. We always keep our eyes open for new methods to describe marine fish biodiversity in an efficient and standardized way. Here, I look very much forward to follow the DNA method in the future, and I think it could be very useful to employ in oceans around the world," says Møller.

The researchers also see great perspectives in the method for estimating fish stocks in the future.