Disturbances in lake ecosystems

In aquatic ecosystems, the topic of environmental change is very timely, since aquatic habitats are in a rapid state of change. For instance, climate warming, brownification and eutrophication influence lake ecosystem patterns and processes. Our research covers the effects and consequences of different anthropogenic disturbances on the lake ecosystems.
Project topics


Eutrophication is the most widely spread environmental disturbance in freshwater ecosystems. Eutrophication causes multiple changes in the physical-chemical conditions of lakes (turbidity nutrient concentrations, vertical oxygen profiles) with consequences for biotic communities. Numerous of our projects have been and are connected to the effects of eutrophication. For instance the effects of increasing turbidity and decreasing hypolimnetic oxygen concentrations on predator prey interactions have been studied in numerous field sampling campaigns and experiments. The effects of catchment land use on external P loading of lakes has also been included. The studies have been funded by the Academy of Finland, Maj and Tor Nessling Foundation, Lake Vesijärvi Foundation, the City of Lahti and Maa- ja Vesitekniikan tuki ry.


Due to the increasing load of humic substances, the water colour of numerous lakes is rising. Human activities in the catchment (peat mining, forestry) can have a strong effect on this brownification process. Brownification again strongly affects temperature stratification, light and oxygen circumstances and predator prey interactions in lakes. We have carried out numerous field studies and experimental studies on this subject area. The studies have shown, for instance, that brownification has differential effects on the prey capture rate and prey choice of different fish species and even on the different genders of the same fish species. Presently a large and long-lasting (2018-2027) project (funded by R. Erik and Bror Serlachius Foundation) studies the effects of increasing loading of humic substances on lake food webs and seeks for new measures for monitoring the effects of such loading. Financial support for the brownification studies has been granted also by the University of Helsinki and the Academy of Finland.


Turbulence is an important but very poorly known factor affecting the physical-chemical water quality and food web interactions in lakes. Turbulence levels in lake ecosystems are probably increasing due to changing water levels and wind velocities. We have carried on numerous experimental studies to study the effects of turbulence on food web interactions. Additionally, the interactive effects of turbulence and water quality (turbidity, water colour) have been investigated.

The studies have shown for instance that the importance of invertebrate vs. vertebrate predators in lake food webs will probably change along increasing turbulence, with consequences for other components of the food web (e.g. zooplankton). The studies have been financed by the Academy of Finland.