by Steve Carpenter
Summer is the season for unsightly and toxic blooms in lakes, and 2016 has been a banner year, with major blooms in Florida, Wisconsin’s Lake Petenwell, and other Wisconsin lakes, including those in Madison. The blooms of cyanobacteria produce toxins that threaten human health, like the bloom in Lake Erie that shut down Toledo’s water supply in 2014.
What’s more, many cyanobacteria float and form scums that accumulate, rot on beaches, and cause fish kills.
These severe blooms amplify the urgency behind a statement issued today by Canadian and American scientists, myself included, for governments around the world to focus on a proven solution — that is, we must control phosphorus to decrease the intensity and frequency of harmful algal blooms.
Readers of this blog know that phosphorus inputs to lakes and reservoirs, which come from agricultural and urban runoff, are the main driver of blooms, and that phosphorus reduction is the key to improving water quality. Some government agencies, however, have lost sight of this basic fact of lake management.
Recently, some scientists and managers have argued for the control of nitrogen and phosphorus at sewage treatment plants. In response, the European Union has required the removal of both nitrogen and phosphorus from sewage effluents, and in 2011 the US EPA announced that it would be “partnering” with states to control both phosphorus and nitrogen. New Zealand imposed a nitrogen-loading cap on the watershed of its largest lake, Lake Taupo, but failed to define a limit for phosphorus loading. Continue reading