Nutrient pollution has contributed to degraded water quality across many lakes in Canada, and billions of dollars have been invested in helping address this problem. In this critical review, we examined the recycling of phosphorus from sediment to water, known as internal phosphorus loading – a within-lake process that can delay ecosystem recovery from nutrient pollution. We found that internal phosphorus loading is common in Canadian fresh waters, but its importance is variable across the country, with the highest rates occurring in small prairie lakes and the lowest in Precambrian shield lakes. Low oxygen, pH, geology, and trophic status are key drivers of this process – often creating positive feedbacks that substantively slow lake recovery.
Read the review, titled "Internal phosphorous loading in Canadian fresh waters: a critical review and data analysis", for more details.