Human activity threatens the water quality of Finnish lakes and rivers.

The use of agricultural fertilizers causes nutrients such as phosporous and nitrogen to accumulate in the Finnish lakes, causing eutrophication. If and when these fertilizers end up in the lakes, they cause plants to grow and reproduce rapidly. Finally, this leads to a rise in the number of decomposers in the lakes ecosystem. This will cause lakes to lose their oxygen supplies, making them unsuitable for supporting life.

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Eutrophication changes the organism community of a lake.