Danube water science

Two ships - the Argos and the Istros - pull away from the dock at Vienna and swing out into the broad, fast-flowing Danube - Europe's second longest river. The ships are loaded with scientists and scientific gear.

There are small craft and huge freight barges to avoid and thus plenty of tension on the vessels' bridges. The passengers, out on deck to watch the city's skyscrapers glide past, wear a mix of white lab coats and wetsuits, confirming that this is no pleasure cruise. In fact, it's the world's biggest river research expedition and by the time it reaches the Black Sea it will have travelled two thousand kilometers and passed through ten countries.

"We analyze species, species diversity and also we count or estimate some biomass and based on this we calculate some indices which characterize the water quality," says Jarmila Makovinska from Slovakia's Water Research Institute as she leans over a microscope below decks.

One of the main aims of the expedition is to measure the Danube's water quality.

Makovinska says her assessment of the water between the German city of Regensburg and the Austrian capital Vienna is that it's "somewhere in the middle, so it's good or moderate water quality."

Fishing for dangerous substance

Two dozen scientists make up the core team on the two ships. Their leader is Bela Csanyi - a bagpipe playing hydrologist from the Hungarian Academy of Scientists.

As the ship pulls out of port he stands at the prow - launching each new leg of the journey with a tune on his shepherd's goatskin instrument. But when the music stops the science starts.

"The target of this mission is covering the most dangerous substances, emissions, discovering them in the water, in the sediment and in the body of the fish," says Csanyi.

Even the livers of the fish are analyzed for pollutants.

To ensure the fish are caught and returned to the river unharmed scientists from the Hungarian Academy of Sciences developed a new fishing technique known as electro fishing.

"Electro fishing means that [electric] current immobilizes the fish and actually it is not possible for it to escape," says Csanyi. He is keen to point out that after measurements are taken and the tests are conducted, the fish are returned to the water.

Messing about on the river

"We are looking for compounds - for example there are pharmaceuticals, there are plasticizers, there are fire retardants, all compounds which are dissolved in water," says Tobias Schultzer, a scientist from Leipzig in Germany, as he demonstrates a shiny stainless steel high capacity water sampler on board the Argus.

His colleague Peter Tarabek, an Austrian expert in hydro morphology explains how pharmaceutical compounds find their way into the river.

"When you take a drug for your health it just goes through the municipal waste water treatment and these facilities, they are not able to remove them completely or degrade them, and so they end up in the river," Tarabek says.

After the journey is over and the testing is complete the scientists will have an accurate picture of the Danube's water quality along its entire length. The expedition is also looking at the health of the entire river and its ecosystems.

"There is probably no other river in the world which is so intensively studied as the river Danube and since this is a very international river there are a lot of different nationalities involved," says Austrian scientist Martin Dokulil, who joined the Joint Danube Survey, as it's known, in Regensburg.

Let the river run

This is the third major scientific survey of the Danube. They take place every six years and are organized by the International Commission for the Protection of the Danube.

Chief scientist Bela Csanyi was on those earlier expeditions but has also spent most of his life on the Danube - as a child, playing on its shores and as an adult, probing its scientific secrets.

He hopes that some of the human impact on the river, such as the channeling for ships and the flood controls can one day be reversed.

"When the last disastrous flood happened lots of flat territory was inundated. I could see the result of the successful spawning of many species," says Csanyi, explaining that as the flood waters dried up the newly spawned fish died because they were cut off from the main stream.

"This is a very simple thing, just to connect these water bodies together and to the main river, as it happened in the past," says Csanyi.

Down the river to the delta

Each evening the scientists gather at the captain's table to compare notes and celebrate.

They all agree that life on board a scientific survey vessel brings more than just samples to be tested.

"Some of us… we've known each other for decades, we grew up together on the Danube, it's very important for us," says chief scientist Csanyi.

The journey will take six weeks and will end at the Danube delta where water from Germany's Black Forest, the Austrian Alps and countless tiny tributaries will finally flow into the Black Sea. But the science will go on for years after the voyage is over as laboratories across Europe analyze the results of this unique scientific journey.