Elemo brings a bounty of results
© 2014 EPFL – Alain Herzog
Two Russian submersibles, Europe’s largest alpine lake, and a trove-full of insights. A special issue of the journal Aquatic Sciences highlights a selection of results from elemo, an extraordinary experimental campaign that was carried out in 2011.
It was an unforgettable sight, when in summer of 2011 the two Russian submersibles MIR 1 and MIR 2 embarked on their first dive into the depths of Lake Geneva. The submersibles were part of elemo, an international effort to study the dynamics and the health of Europe’s largest alpine lake, which is under constant pressure from over one million residents living nearby. Ever since the three-month field campaign came to an end, scientists have been working in the lab to analyze the collected data and samples, generating a bounty of results. A selection of eight research articles reporting the results from the campaign has now been compiled into a special issue of the journal Aquatic Sciences, published June 2014. This extraordinary research campaign was made possible thanks to the support from Ferring Pharmaceuticals, and the Honorary Consulate of the Russian Federation through the FEEL Foundation.
The eight articles cover two main themes: gaining a better understanding of the lake’s geology, and evaluating the impact of pollutants on water quality. Among other topics, dives carried out close to the mouth of the Rhône River near Villeneuve focused on the formation and evolution of the spectacular underwater canyons formed by the river. And near the outlet of the wastewater treatment plant of the City of Lausanne, researchers used the submersibles to gain insight into the presence and persistence of micro-pollutants and their spreading within the lake.
Canyons and contamination
The submersibles gave some of the research teams a unique opportunity to probe Lake Geneva’s underwater canyons, providing new insight into how they built up and are destabilized through the deposition and erosion of sediments from the Rhône River. Working on a sediment core extracted from the river delta, another group of researchers developed a novel approach to assess the impact of agricultural pollutants on the health of the lake ecosystem, which involves studying the diversity bacterial populations trapped in the sediment.
Off the shore of Lausanne, the submersibles helped demonstrate that micro-pollutants – invisibly small compounds mainly from medical and cosmetic products that enter the lake with treated wastewater from the City of Lausanne – could be traced within an area of at least one square kilometer, reaching deep into the lake, and sometimes spreading in the direction of the drinking water intake for St. Sulpice. In a parallel study in the same area, another group of researchers established a link between certain types of bacteria and the transport and deposition of trace metals in sediments.
A once in a lifetime opportunity
The special issue of Aquatic Sciences recognizes the importance of the elemo field campaign, which has already led to a total of fourteen research papers and is likely to give rise to many more. “It was a once in a lifetime opportunity for us all to use manned submersibles to study the lake in our backyard,” says Alfred Wüest, the director of EPFL’s Margareta Kamprad Chair for Lake Science. As he wrote in the editorial of the journal: “The researchers’ ability to selectively sample both horizontal and vertical features at close visual range, enabled by the MIR submersibles, created unparalleled scientific opportunities in this extremely complex subaquatic terrain.”