Water Security in the Canadian Prairies: Science needs and management challenges
THURSDAY, MAY 10, 2012 - 3:30 PM TO 4:30 PM IN EIT 3142 AT THE UNIVERSITY OF WATERLOO
Abstract:
Eutrophication of freshwaters is generally attributed to excessive nutrient inputs, but sulfur pollution may be exacerbating this global problem by stimulating internal phosphorus loading in lakes. Because sulfur forms insoluble complexes with iron, sulfur may render lakes deficient in the element that sequesters phosphorus in sediments. However, the role of iron in controlling the trophic state of freshwaters is poorly elucidated due to its antagonistic effects on primary productivity. Iron is an essential micronutrient that stimulates algal growth, if other nutrients are in adequate supply. In contrast, iron increases the phosphorus-binding capacity of sediments which may inhibit algal growth, if phosphorus is in short supply. We tested these competing hypotheses by adding different amounts of iron to fifteen mesocosms in an iron-deficient hypereutrophic Canadian lake. Iron reduced phosphorus levels, decreased algal biomass, and suppressed cyanobacterial dominance. This research suggests that iron may act as a master variable controlling lake trophic state, and that the consequences of sulfur pollution on iron availability – and hence water quality – in freshwaters need to be considered.