On LeXPLORE, scientists investigate Lake Leman with novel instruments

The first project "In situ pursuit of a whitening event in Lake Geneva applying a micro-titrator for alkalinity" is led by Patrick Kathriner, Thomas Steinsberger and Beat Müller from Eawag Kastanienbaum. Their goal is to understand what drives calcite precipitation. Indeed, whitening events with biogenic induced calcite are well known, however, it remains unclear what initializes precipitation (e.g. picoplankton, decreasing P-concentration due to phytoplankton growth, increasing temperature, mineral particles from the catchment, etc.), and at what depth below the surface it occurs. Eawag team developed a microtitrator for alkalinity running autonomously on a winch recording vertical profiles several times per day down to 50 m depth, to understand the trigger for whitening events.

The project "Surface Turbulence and CO­₂ Lake Exchange Experiment (CO₂LEX)" aims at quantifying the air-water CO₂ exchange, and is led by Cary Troy, Johny Wuest, Bieto Fernandez and Hannah Chmiel, in collaboration with Damien Bouffard and Marie-Elodie Perga. Their objectives are:

• to quantify the exchange of CO₂ between the lake surface and the atmosphere
• develop quantitative linkages between near-surface turbulence, meteorology and the measured CO₂ exchange