Author: Torbjørn Ekrem

This is one of the questions we want to answer in our EBAI sub-project in Bymarka near Trondheim. Sampling was done before and after rotenone treatment in 2016 and we now follow up with three sampling events in the 2017-season. The first was done early June and the second just finished in late July. We sampled the exact same stations as last year: three different substrates in each six lakes. Three of the lakes had been treated with rotenone, the other three are untreated reference lakes.

With our sampling scheme, we also want to compare eDNA communities with the communities recorded by traditional means (kick-sampling), and see if DNA from species found on one particular substrate leaks to nearby sites in the lake where the species are not recorded.

Reporter Guro Tarjem from The Norwegian Broadcasting Corporation (NRK) just recently visited us in Trondheim and made this radio-report from our study (Norwegian only): Hvem overlevde rotenondrapet?

The European beaver (Castor fiber) is definitely present at Haukvatnet. No surprise if we detect its DNA in our water samples! Photo: Torbjørn Ekrem CC-BY.

Results and prospects of the EBAI-project were discussed as members of the consortium met at the NTNU University Museum on November 10, 2016. Presentations were held by Mehrdad Hajibabaei, Kathrin Langen, Ola Diserud, Markus Majaneva and Torbjørn Ekrem and additional participants were Anders Hobæk, Terje Bongard, Elisabeth Stur, Karstein Hårsaker, Gaute Kjærstad and Erik Boström.

It was a very fruitful meeting where the direction of the project was corrected and the way forward fine tuned according to developments in the field of environmental barcoding of freshwater ecosystems.

The day was rounded off with an excellent meal at EmiliesEld:

Ready for desserts at EmiliesEld. Photo Torbjørn Ekrem CC-BY.

The next day, some of the participants toured the vicinities of Trondheim to take a closer look at the sample localities. Here we are at the small lake Holstdammen in Bymarka near Trondheim:

Kathrin Langen, Markus Majaneva, Anders Hobæk and Torbjørn Ekrem touring sites in the EBAI project. Here at reference lake Holstdammen close to Trondheim. Photo: Torbjørn Ekrem CC-BY.

Lauglovatnet, one of the reference lakes with early morning fog. Photo Torbjørn Ekrem CC-BY.

What will happen with the eDNA of lake fauna when much of the animal life is eradicated? We suspect that it will increase as the dead animals dissolve and then decrease to a level below that before rotenone treatment, but we don't know for sure. Previous studies also show that macroinvertebrates in lakes are less susceptible to the rotenone poison than fauna in running water. Thus, we do expect a many species and perhaps species groups to do survive the treatment.

What will happen to these populations when the benthic community is altered and all fish is gone? We will follow up with eDNA sampling through EBAI and compare results with those of traditional benthic kick-sampling at the exact same sites.

This week, a journalist and photographer from NRK - the national public broadcaster - joined us in the field. Their report can be viewed here: "Ny metode for vannovervåkning".

Gaute Kjærstad not quite believing that this is sufficient to tell who lives in Lauglovatnet. Photo Torbjørn Ekrem CC-BY.

Aina Mærk Aspaas sampling water from Theisendammen. Photo Torbjørn Ekrem CC-BY.

Markus Majaneva filtering water samples in the lab at NTNU University Museum, Department of Natural History. Photo Torbjørn Ekrem CC-BY.

Several lakes in the Trondheim city forest will soon be treated with rotenone to remove the common roach (Rutilus rutilus), an invasive alien species in our area. Together with freshwater ecologists at the NTNU University Museum, we are interested to see how the macroinvertebrates react to the treatment and if we can use eDNA to monitor changes and shifts in the species compositions.

Yesteday, we sampled three of the lakes that will undergo treatment as well as three reference lakes. We have three sampling stations at each lake and filter 2 x 1 liter of water from each station. This video shows how samples are taken.

Weather was great and fieldwork successful.

 Gaute Kjærstad sampling water at the lake Lauglovatnet. Photo Torbjørn Ekrem CC-BY.

Two water samples from the lake Theisendammen. Photo Torbjørn Ekrem CC-BY.