Nutrient pollution Biodiversity of small waterbodies

The 2024 status report shows that most of the small water bodies surveyed between 2018 and 2021 were classified as being in moderate to very poor condition with regard to their nutrient load. A status update will be provided in 2028.

Due to limited data, the pollution indicator "nutrient pollution" could previously only be applied to the pond type 'Ponds of the North German Plain' without a temporal comparison or differentiation by agricultural region. A total phosphorus concentration below 20 µg/l indicates very good status, between 20 and 30 µg/l good status and above 30 µg/l moderate to very poor status for water bodies of lake type 14 (LAWAAO, 2021). According to the indicator, 20 small water bodies are in a mesotrophic state, 30 in a eutrophic state, 19 in a polytrophic state, and 12 in a hypertrophic state. 68% of the water bodies showed a phosphate concentration above 30 µg/l and 27% a phosphate concentration below 20 µg/l.

The data basis consists of phosphate (P) concentrations in µg/l per small water body. These values serve directly for classification into trophic levels. The indicator values, calculated using representative samples within the small water body area (> 0.15 ha to < 1.0 ha), are reported at the national level. Where the spatial coverage of the samples allows, the national reporting level can be supplemented with agricultural-specific information. With the start of the monitoring implementation, initial results will be available from 2023 onwards. The indicator is to be reported completelyEx after a new data collection every five years. Due to their size and the resulting marginal effects, small water bodies are subject to different conditions than small lakes, which is why a higher natural trophic level and a correspondingly better assessment of higher trophic levels can be assumed than for the small lakes used as a reference here.