For instance the food web studies on fish and invertebrate predators have been closely connected to the applicability of biomanipulation in different circumstances and have shown for instance that in clay-turbid conditions manipulation of fish stocks may not affect the water quality in a manner predicted by the trophic cascade hypothesis. Studies on littoral communities are closely connected to the management of macrophyte stands. Nutrient cycling studies are connected for restoration activities aiming to diminish the internal nutrient loading of lakes. A recent large project suggested for instance, that due to the weak effects of anoxia on water quality the use of artificial aeration in the restoration of many eutrophicated lakes should be critically re-evaluated. A model describing the lake characteristics justifying aeration was developed. The side effetcs of aeration (e.g, increasing turbulence) have also been under investigation. Many studies have been and are conducted in actual restoration projects, including biomanipulation, artificial aeration and hypolimnetic withdrawal and purification. Our study results have affected the management strategy of numerous lakes, including Lake Vesijärvi, Lake Hiidenvesi and Lake Kymijärvi. To increase the impact of the study results, the projects have also included societal ascpects. We are also looking for new solutions in lake restoration. In a new project, we are studying a novel application of hypolimntetic withdrawal and nutrient recycling in Lake Kymijärvi; nutrient-rich water from the anoxic lake deep is pumped to a calcium filter located in the catchment, and led through a wetland back to the lake.
In 2018, we launched a research and piloting project at Lake Kymijärvi, Lahti (southern Finland) to study a novel lake restoration technique called hypolimnetic withdrawal and treatment. In this project, we study the possibility to remove and capture phosphorus and other nutrients from stratifying lakes by pumping nutrient-rich hypolimnetic water through a treatment unit and wetland, and back into the same lake. This is a closed-circuit application of hypolimnetic withdrawal, in which the withdrawn water is conventionally discharged downstream of the treated lake. The advantages of a closed-circuit system are that 1) nutrients and other substances are not passed to the next ecosystem, and 2) the water withdrawal rate is not limited by the outflow of the lake.
Our goal is to investigate the potential and optimization of this technique in lake restoration as well as nutrient recovery.
The project is funded by the and Ministry of Environment, the City of Lahti, Lake Vesijärvi Foundation, Maa- ja vesitekniikan tuki ry, and Häme Centre for Economic Development, Transport and the Environment.
Aeration and oxygenation are very commonly used methods to manage and restore eutrophicated lakes, but scientific evidence successful water quality improvement with these methods is sparse. Therefore, numerous of our studies have focused on the effectivity of artificial aeration and on the role of oxygen as a water quality regulator. The side effects of aeration (e.g, increasing turbulence) have also been under investigation.
The studies have been conducted for instance in Lake Vesijärvi and Lake Tuusulanjärvi. The results have demonstrated that although the effects of aeration on hypolimnetic water quality may be pronounced, the impact on surface water quality is often questionable. The low coverage of anoxic deeps often limits the effectivity of aeration. A large project with data from 56 lakes suggested that due to the weak effects of anoxia on water quality the use of artificial aeration in the restoration of many eutrophicated lakes should be critically re-evaluated.
The studies have been funded by the Academy of Finland, the City of Lahti, Lake Vesijärvi Foundation, Maj and Tor Nesslin Foundation and Maa- ja vesitekniikan tuki ry.
Food web management (biomanipulation) is an important study topic of the research group. Studies have been conducted for instance in Lake Vesijärvi and Lake Hiidenvesi, where food web management has been applied. For instance, many of our studies on fish and invertebrate predators are connected to the applicability of biomanipulation in different circumstances. Together with field sampling, the studies have also included many experimental studies on the mechanisms affecting the success of food web management. Possibilities to reduce the nutrient loading in the Archipelago of the Baltic Sea through removal of benthivorous fish have also been included. The results have shown for instance that in clay-turbid conditions manipulation of fish stocks may not affect the water quality in a manner predicted by the trophic cascade hypothesis.
The studies have been funded by the Academy of Finland, Lake Vesijärvi Foundation, and Ministry of Agriculture and Forestry.