ReviewDissolved reactive manganese as a new index determining the trophic status of limnic waters

Dissolved reactive manganese seems to be one of the parameters which determines the trophic status of limnic waters, as suggested by its strong correlations with total phosphorus, chlorophyll a, and water pH. The determination of the trophic status involved the application of reactive manganese due to its bioavailability, providing information on the actual, not just the potential (as in the case of total phosphorus or total organic carbon), threat of water eutrophication.The calculation of trophic states index (TSI) based on the reactive manganese concentration, as determined by TSIDRMn = 20.61 ln (DRMn) − 35.03, permits the rational assessment of the trophic status of lakes. Oligotrophic lakes are distinguished by concentrations of DRMn < 25 μg/L, mesotrophic by 25-60 μg/L, eutrophic by 60-150 μg/L, and hypertrophic by >150 μg/L.The trophic status of 25 lakes located in central Europe in north-eastern Poland was determined based on the proposed “manganese index” and verified by commonly applied indices proposed by Carlson, Kratzer and Brezonik, and Dunalska.