•Water quality deterioration, namely eutrophication of lakes was well defined in Northern temperate lakes. But there is not sufficient data for semi-arid regions.

Clear Water State:

Turbid Water State:

Alternative Stable States


As a consequence of the alternative stable states the lake shows hysteresis in response to changes in nutrient loading.


Restoration Techniques:

•Reduced external loading
- Biomanipulation is a useful tool for lake restoration.
- It is based on top-down control of phytoplankton by either adding piscivorous fish or removal of planktivorous fish.
- This change in fish community leads to increase in large-bodied zooplankton, causing reduction in phytoplankton. 



METU Limnology Lab Conducted First Biomanipulation Experiment in Turkey:

Basic Information About the Biomanipulation Experiment 

 Biomanipulation Experiment was conducted in Lake Eymir, ANKARA

•August 1998- December 1999

Fish Species that are Removed


– Tinca tinca


– Cyprinus carpio


•% 50 Reduction in Fish Stock


• Decrease in Chlorophyll-a and Suspended Solid Concentration


• Decrease in Nutrient Concentrations especially Phosphorus in parallel with increase in aquatic plant cover.