Finnish Environment Institute (SYKE)

Vegetation changes in water bodies may be rapid and dramatic


Source: Finnish Environment Institute (SYKE)

The aquatic vegetation in water bodies around the world may change rapidly and dramatically due to climate change and other human influences. New invasive species may form massive stands and smother everything else, but even native species may spread quickly in the changed conditions, e.g. due to eutrophication or water level regulation.

'In Finland, one of the problems is that we have not decided who is responsible for the alien species. However, the Ministry of Agriculture and Forestry is currently preparing a strategy for alien species', says Seppo Hellsten, aquatic macrophyte specialist at the Finnish Environment Institute.

The Finnish Environment Institute, the University of Jyväskylä, the European Weed Research Society and the International Society of Limnology (SIL) are the organizers of the European Weed Research Society Symposium on Aquatic Weeds in Jyväskylä, 24-28 August 2009. Some 120 scientists and experts from 30 countries will meet and discuss the impact on invasive species on the environment.

Vegetation belongs to the aquatic ecosystem

Vegetation in lakes and rivers is an essential part of the aquatic ecosystem. Aquatic macrophytes form a living habitat for other species, plants protect the shores from erosion. Visible vegetation is in many places an essential feature of the landscape. However, vegetation at the interface of two different kinds of habitats - terrestrial and aquatic - is vulnerable to various kinds of disturbances and changes.

The eutrophication of large water bodies is first seen as changes in the vegetation of the shore zone, e.g. as increased growth of reed stands. Water level regulation can harm the vegetation of shores, even if no changes can be observed in other part of the lake or river.

Aquatic plants as indicators of the condition of water bodies

Aquatic plants are excellent indicators of the status of water bodies. Due to their long life cycle, aquatic plants can give information on long-term changes. In Finland, water bodies are relatively clean, and the increase of aquatic vegetation is in general regarded as a problem. In some other regions of Europe, water bodies are heavily polluted, and the objective is to restore the aquatic vegetation.

In tropical regions the worst problem is that invasive species from South America, notably the water hyacinth, take over many water bodies. These species, originally used as ornamental plants, have no natural predators in their new habitats, and they form massive stands that smother everything else. Due to the warming climate, the water hyacinth has spread northwards. In Southern Europe, millions of euros must already be used for attempts to control this aquatic weed. In Portugal, water hyacinths have in four years taken over 150 km of the river Guadina. In northern Finland, the North American species Elodea canadensis, also known as the pondweed, has spread quickly and taken over parts of the lake Kitka in Kuusamo, despite the excellent water quality. But even some domestic species have spread quickly, e.g. the rigid hornwort (Ceratophyllum demersum) which has formed massive stands in Joutsa and some other places in Finland.

Distinguished aquatic weed experts meet in Finland

The European Weed Research Society Symposium on Aquatic Weeds is for the first time organized in Finland. The symposium is a forum for the best aquatic plant experts in the world. It takes place in Agora, at the University of Jyväskylä. There will be almost one hundred presentations on the indicator value of aquatic plants, on the structure of vegetation and on the most important theme of the symposium, the control of noxious invasive and alien species. The day excursion takes place on 27 August. The participants will acquaint themselves with the vegetation-rich lakes of the Jyväskylä region and the problems caused by the growth of reed stands in the lake Päijänne.

The symposium is supported by the Federation of Finnish Learned Societies and the Waterpraxis project of the Baltic Sea Programme of the European Union.

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