Effectiveness of reducing external nutrient load entering a eutrophicated shallow lake ecosystem in the Naardermeer nature reserve, The Netherlands.

摘要

Successes and complications in eutrophication abatement in the title nature reserve are described. Restoration of the lake was started in 1985. The main measurement of success was the reduction of external nutrient load by the supply of phosphate-free water. Water quality and aquatic vegetation were monitored and the usefulness of a modelling approach in designation of management programmes was investigated. The monitoring showed that for the first 4 years, recovery was retarded, possibly as a result of phosphorus release from the lake-bed sediments. After 10 years, turbidity was reduced and characteristic vegetation with Najas marina and Characeae species were re-established in large parts of the lake. Due to spatial heterogeneity the lake-bed sediments were dredged locally. The model predicted most changes in aquatic vegetation correctly. However, it was concluded that to predict restoration perspectives for rare species, expert judgement was still necessary. Suggestions are presented for the selection of successful management measures depending on the conditions of lake ecosystems.