Silkeborg lake experimental facility


Enclosed Ecosystem Platform

Parent institution: Dep. of Bioscience, Aarhus University
Active since 2003
Active through all year

Fields of study

  • Environmental sciences, Pollution
  • Microbiology
  • Paleolimnology
  • Paleoecology
  • Limnology

Contact Information

Jeppesen, Eric


A unique long-term (with 11 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. This results in two alternative states typical of shallow lakes: a clear-water, macrophyte-dominated state with small zooplanktivorous fish populations versus a turbid, phytoplankton-dominated state with relatively large zooplanktivorous fish populations. Twenty-four cylindrical outdoor mesocosms, each 2.8 m3 in volume are used. Ground water is pumped into the mesocosms just above the sediment and drained through an outlet at the water surface. The theoretical water retention time is 2.5 months. The 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 the 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. The latter are obtained by weekly dosing of N and P. There are four replicates of each treatment. Samples of macrophytes, zooplankton, phytoplankton, and ciliates are regularly sampled, currently at monthly intervals. Occasional bacterioplankton and flagellate samples are also collected.

Whole-system gross primary production and respiration are continuously determined by measuring diel concentration changes of oxygen and pH with permanently installed probes in all mesocosms.

The Location

Country: Denmark

Latitude: 56.23333333

Longitude: 9.516667

Nearest town: Silkeborg

Distance from neaerst town: 15 km

Relevant Research Questions

Climate change effect on shallow lake ecosystems (at contrasting nutrient levels (clear water and turbid water lakes, respectively). Short and longer term effects of heatwave. Short and long term effects of sudden browning. 


The unique facilities provide opportunities to work on the world's longest-running warming experiment on shallow lakes, enabling tests of long-term warming impacts on trophic dynamics, nutrient balances, ecosystem metabolism, greenhouse gas exchange, adaptation and microevolution that are not possible at any other lake location worldwide. Visiting scientists and students are encouraged to cooperate with local scientists to learn new techniques and explore new approaches as well as being given access to facilities that may not be available at their home institutions.


No major limitations. we wish to upgrade the system so we can continuously measure 1) greenhouse gas exchange (GGE) 2) algal pigments (AP) 3) alkalinity (AL).

Experimental Capabilities

Experimental Facilities

Various lab fincubation facillities that can be run at different temperatures- studies of sediment dynamics, plant growth etc. Workshop present that can help with developing special lab experiments.

Experiments duration: Weeks, Months, Years, Decades;

Experimental Aerea

Total area: 200 m²

Available area: 1000 m²

have to be negotiated with the owner

Experimental Unit Size

unit size: 3 m²


Replicates number: 24

Temporary storage

  • Dark room
  • Drying oven
  • Freeze drier
  • Freezer
  • Liquid N
  • Refrigerator
  • Other

Available Instruments

  • Standard gears for sampling biota ,water chemistry and sediment
  • Multiprobe sampler for water
  • Microscopes (invers and wild lup)
  • HPLC
  • Isotop lab facilities, including scintillation counter for spiked samples

Electricity available on site.

Distance from Laboratory facilities


Years measured: 30


Mean Temperature: °C

February Mean Temperature: °C

July Mean Temperature: °C


Mean Annual Speed: 7.8 m/s

Max. Annual Speed: m/s

Dominant Direction: NW


Precipitation type: Rain;

Total annual precipitation: mm

Mean snow cover duration: 0 days

State Variables

Continuously Measured

  • (aquatic) Conductivity
  • (aquatic) Oxygen content
  • (aquatic) pH
  • (aquatic) Water temperature
  • Air humidity
  • Air temperature
  • Atmospheric pressure
  • Incident PAR

Spot Measured

  • (aquatic) Chlorophyl
  • (aquatic) Nutrient levels
  • Phenology
  • Population densities
  • Species richness

Environmental Pressures

Variable Ecosystem Status
Warming Lake Active
Precip Lake
Watereutroph Lake Active
Management - Nutrients (levels or nutrient type) Lake Active
Management - tilling or other physical manipulation Lake Active
Biodiversity Lake Active

On site Staff and Accomodation

Peak season staff

No on-site staff.

Off season staff

No on-site staff.

Visiting personnel

No visitors allowed.

No beds on site

No showers on site

No laundry on site