AU Lake Mesocosm Warming Experiment (LMWE)

Description of the infrastructure: The Lake Mesocosm Warming Experiment (LMWE) is a unique long-term (with 16 years so far the world’s longest running) flow-through mesocosm experiment addressing climate-change effects on lakes under contrasting nutrient levels and water clarity. Twenty-four cylindrical outdoor mesocosms are used, each with a capacity of 2.8 m3. The mesocosms receive groundwater 6 times per day, resulting in a theoretical water retention time of 2.5 months. Water in the mesocosms is continuously mixed by paddles and heated by electrical elements. Three temperature regimes are run: ambient temperature and two elevated temperatures according to IPPC climate scenarios A2 and A2 + 50%, down-scaled to local 25 25 km grid cells. The modelled temperature difference for the A2 scenario is generally higher in August to January (max. 4.4 °C in September) than during the rest of the year (min. 2.5 °C in June). Individual mesocosms of each temperature regime are run at either low or high nutrient concentrations (4 replicates per treatment). The latter are obtained by weekly dosing of N and P.

Located 15 km from AU Silkeborg, the facility is equipped with a small lab building to facilitate accessory small-scale studies and analyses. A fully equipped lab is available at the AU freshwater central lab in Silkeborg. The mesocosm facility is part of the Danish AnaEE project and it is also included in the European AnaEE list of experimental facilities for ESFRI.