A recent study by the Helmholtz Centre for Environmental Research and Aarhus University has challenged a longstanding theory in limnology, which posits that shallow lakes can exist in two alternative stable states. The research, published in Nature Communications, analyzed data from 902 shallow lakes (average depth of three meters) in Denmark and the USA, and found no evidence supporting the existence of these two states, which had characterized one state by turbid water and the other by clear water. The authors argue that current lake management practices, which often rely on this theory to improve ecological conditions (such as adding piscivorous fish), are misguided. Instead, they emphasize the necessity of reducing nutrient inputs to maintain ecological balance, as higher nutrient levels directly correlate with increased phytoplankton growth. The research results indicate a linear relationship between nutrient and phytoplankton concentrations, contradicting the notion of stable alternative states. This finding suggests that instead of biomanipulation strategies, consistent reduction of nutrient pollution is essential for the long-term maintenance of shallow lake ecosystems, reinforcing the need for revised management approaches in light of these findings.
