Lake 227 algae blooms continued decades after nitrogen was removed

For more than half a century, scientists have used a small lake in northwestern Ontario to study why freshwater ecosystems develop harmful algal blooms. Lake 227, part of the Experimental Lakes Area, began receiving carefully measured additions of nitrogen and phosphorus in 1969. The experiment later changed dramatically. Researchers reduced nitrogen inputs during the 1970s and stopped adding nitrogen entirely in 1990, while phosphorus additions continued. Yet the lake remained highly eutrophic, with algal blooms continuing year after year. The International Institute for Sustainable Development describes Lake 227 as the world’s longest-running whole-lake experiment, while a peer-reviewed study in the Proceedings of the National Academy of Sciences found that nitrogen-fixing cyanobacteria compensated for the missing nitrogen.