A new tool for the assessment of severe anthropogenic eutrophication in small shallow water bodies

•Unlike deep stratified lakes, the assessment of eutrophication in shallow systems should be based on the interaction between water and sediment.•The bioavailability of P is naturally higher in shallow systems because the sediment plays an active part in nutrient recycling.•We have provided a diagnostic tool that distinguish anthropogenic eutrophication from a background of natural eutrophy.•When the sediment P-binding capacity becomes saturated, the ratio of total-P/particulate-P >2.0 during the growing season.