A new tool uses small crustaceans to indicate levels of nutrients in freshwater. Valuable for monitoring impacts from agriculture, forestry, urbanisation, and development activities.
Sampling zooplankton with nets close to shore. Photo: Thomas C. Jensen, NINA.
Zooplankton are excellent indicators of water quality, as they are sensitive to various changes in the environment, and we know what it takes for them to thrive.
A water sample can indicate acidity and amount of nutrients in the water at the exact time of sampling. Zooplankton, however, can give us knowledge of water conditions over a much larger time span, explains Thomas Jensen, researcher at the Norwegian Institute for Nature Research (NINA).
Together with colleagues, Jensen has now developed a new addition to the toolbox for assessing water quality in freshwater ecosystems based on small crustaceans. The index is based on a composition of species sensitive and tolerant to phosphorus, which is considered the most important nutrient in freshwater.
A valuable cost-efficient and easy-to-use tool
Zooplankton have long been used to assess degree of acidification of lakes, and in some countries also nutrient levels. In Norway, phytoplankton have mainly been used to indicate nutrient levels in freshwater lakes, although limited to open water bodies. Zooplankton, of which the majority are found along the shore, are therefore an excellent supplement to indicate water quality closer to shore, says Jensen.
In addition to being sensitive to environmental impact, the small crayfish are also widely distributed and can be easily collected with simple equipment at low cost, representing a suitable tool for assessing water quality.
The tool can be used by anyone involved in monitoring waterways to examine how lakes and small ponds are affected by nutrient runoff from agriculture, forestry, densely built-up areas, construction activities, roads and more, Jensen concludes.
Find out more (Norwegian only): Jensen, T.C., Pilotto, F., Schartau, A.K & Walseng, B. 2024. Eutrofieringsindeks for småkreps: Crustacean Index of Trophic State (CIT). En trofi-indeks for klassifisering av økolgisk tilstand i innsjøer og dammer. NINA Rapport 2436.
Contact: Thomas Jensen