We are now on board of the Madrid-Oviedo train, the final step of our trip back home from Chernobyl. After driving from Slavutych to Kiev in the morning, we arrived to Madrid yesterday at midnight, all luggage with us, no problem with the samples. So, I thing this is a perfect time for writing a summary of our field research campaign in and around Chernobyl. Let’s go.

To be honest, before arriving to Ukraine, we had doubts about the length of our research campaign. We felt that we should have add a few more days, at least one more inside Chernobyl and one more in Slavutych. Just to play safe if the weather turned wrong, or we were unable to find amphibians at some point. This is the kind of unsettling feeling before the star of any field work, I guess… At the end, we worked for four days and nights inside Chernobyl Exclusion Zone, and another four outside, on clean areas around Slavutych. And that was enough. We managed to collect all the samples we needed for the different projects. A total of six different studies!! Let’s summarize them one by one.

First, our study on Pelophylax frogs, looking at mutation accumulation and genomic changes through time. We wanted to collected new samples of this group of frogs to compare with the samples collected in the Zone in 1987-1990, and that we have already in our lab. The main idea was to collect frogs in one of the original locations where the frogs were collected 30 years ago. We did that on the second night in Chernobyl, with a total of 23 individuals captured on a pond outside Chernobyl town. We also wanted to compare these frogs from nearby Chernobyl city, currently living under very low radioactive contamination, with frogs from a highly contaminated locality. And that’s why we went to the Azbuchyn lake (pretty close to the power plant) on our first night in Chernobyl. There, we captured 12 frogs. As a final touch, we aimed at collecting frogs from a un-contaminated locality outside the Exclusion Zone. We did that too, on our first night in Slavutych, when we captured 20 and 7 frogs on two different localities, one completely new for us. So, in total 62 frogs collected in areas with high radiation, low radiation and no-radiation. A really great group of samples!!

Our second goal was to repeat this sampling with the fire-bellied toad (Bombina bombina), another species for which we have samples going back 30 years. This is a species we didn’t had much experience with. Is clearly abundant in the Zone, as the males calls can be heard in many places on a warm night. But once in the ponds, is not always easy to locate where this small, brown frogs are actually calling. We were a bit unsure about how easy it would be to find them. At the end, we collected 5 individuals in high radiation area (Azbuchyn lake), 5 in a low radiation locality (close to Chernobyl), and another 5 near Slavutych, in an un-contaminated place. it wasn’t o difficult . We even caught some of them in daylight!! So, a total of 15 individuals to compare with the old samples, and check for genomic changes associated with radiation. Second goal accomplished.

A third goal was to perform a small experiment looking at how plastic is treefrog coloration over a short period of time. This study is linked to the one on treefrog coloration we have performed since 2017, after detecting a high number of dark frogs inside Chernobyl Exclusion Zone. Otherwise, these frogs are normally green, brilliant green. On our first night in Chernobyl we captured 14 Eastern treefrogs (Hyla orientalis). We photographed all of them, and put half individually in containers simulating a light background, and half in containers simulating dark background. After two days under these conditions we took another photograph of the frogs to evaluate color change. All went well. Let’s see now what these photos tell us.

We also managed to complete our study on treefrog coloration by adding individuals from two more localities outside the Exclusion Zone. Until now, we had good results, but only had frogs collected in two localities outside Chernobyl Exclusion Zone. We wanted to expand the number of localities and individuals for this study, in order to be more confident about the results. We finally caught 8 and 8 individuals in two localities around Slavutych in our second and third night there. That was particularly good, since the species is not very abundant, and not always easy to find, especially outside Chernobyl, where Sergey has less field experience. Another big goal achieved, and a big relief for us and this study in particular.

These treefrogs from new localities will be added to the study on genetic variation and connectivity that we are also performing with our colleague Jean-Marc Bonzom (IRSN-France). So, more individuals, and two really important localities to improve the power of this study too. Superb!!

Finally, something totally new this year was the sampling of environmental microbiome in water bodies of the area, both inside and outside Chernobyl Exclusion Zone. The idea is to use this info in two different ways. One is to add these samples to our studies of treefrog skin and gut microbiome, with all the samples collected in previous years (around 200 individuals, from 11 localities). We wanted to know how radiation (and other factors) affects the diversity and composition of the amphibian microbiome, and also how the frog microbiome is related to the microbes available in the environment. As a second stage, and by adding more localities, we wanted to expand the study to investigate how radiation, but also water variables, like water ph, conductivity, disolved matter, and landscape variables like the type of soil or vegetation, affect the diversity and composition of microbes living in aquatic environments here. We did two days of intense work in Chernobyl, sampling 16 localities there, from really high radioactive places like Azbuchyn and Hluboke lake, to clean areas of the south. Then, we added another 5 localities around Slavutych. A total of 21 localities with water, soil and sediment samples, an a full set of environmental variables to work with. This was, especially in Chernobyl, a very exhausting work, but also a great opportunity to move around the Zone by daylight, seeing the different habitats of the Zone, something that we didn’t had much chances to do in previous years when going for frogs during the night.

In summary, a total of eleven days out of home, three flights, one train trip, more than 1000 km driven (many of them either directly off-road, or in pretty damaged and bumpy roads), and many hours with our wadding boots in the middle of ponds. Now, we have ahead an equally important task, to enter all this data in our files, and analyse all this samples. We will finish some of the studies pretty quick (coloration, for example). Some others will take a little longer (environmental microbiome). For others, we will need to convince our colleagues and evaluators, to support our next application for a national research project later this year. Let’s see how it goes!!

At the end, as in all previous years, not only research was good. The great time and friendship with Sergey and Pablo, was one of the best things of these days. We had a lot of fun, we enjoyed the time capturing frogs and sampling microbiome, but also our picnics in the field, our time talking about life and the old Soviet times with Sergey, even the bumps and bumps in the roads!! Working, learning, and improving with other colleagues is one of the great things of these campaigns, no doubt. Thanks for being so great!!

I am going to finish this blog here for now. I will add more entries next time we will work in the field, or at the time we will publish a paper on this work. From now on, you can keep track of our research on Twitter, where I am pretty active at @GOrizaola.

Thanks everyone for following us during our #ChernobylFrogs19 campaign. I hope you have like it. Until next time!!