On August 2nd, Mayor of Toledo Michael Collins, issued a ban on drinking water. Microcystis, a bacteria*, reached toxic levels in the City’s drinking water supply in western Lake Erie. The ban lasted two days and left nearly half a million people without water including residents of Monroe County, Michigan. During that time there was much media coverage discussing cause, response, extent of the impacts and who was to blame.
What you may not have read is that this event is not unique. Increasingly, and across the globe, our lakes and oceans are experiencing booms of algae and bacteria populations that are reaching levels toxic to both wildlife and people. The question I want to explore here is how may climate change be contributing to this issue that is plaguing Lake Erie and many other coastal waterways?
Lake Erie has seen an increase in the frequency and size of blooms since the 1990’s. A harmful bloom of algae and bacteria occurs when waters are warm and nutrients are high. Lake Erie is shallow and therefore warmer than other Great Lakes. Additionally, there is extensive agricultural and urban development in the watersheds that drain to the lake. Nitrogen and phosphorus reach our rivers from farm fields, leaking septic systems and discharge pipes from industry.
Climate change can make conditions worse in two major ways. As air temperatures increase, water temperatures increase. In our area we have already experienced a 1.1° F increase in average annual temperature in the past 30 years.** Models predict an additional increase of 4-12° F (depending on what carbon emissions values are used) over the course of this century. Additionally, not all rains are created equal. More nutrients run off of land and through pipes during large rain events. These nutrients are carried from the source, to a river, which eventually delivers the “food” to Lake Erie where it is used to fuel a bloom. In Southeast Michigan we are already experiencing an average of 2.9 inches more precipitation (much falling as rain) each year than we were 30 years ago. Models predict further increases to our average annual rainfall, and more importantly to this story, that rain is expected to fall in larger events. An analysis of Toledo rainfall records revealed that they have experienced a 40% increase in the number of strongest storms in the last 30 years when compared to the previous 30 years. This is typical for the entire Midwest region of the US.
So, while harmful algal blooms have occurred in Lake Erie for decades, there is reason to believe that climate change is an additional, and increasingly important, factor leading to the uptick in frequency and severity of these events.
You can read more about microcystis and the Huron River watershed in our upcoming newsletter scheduled for release in December. If you do not receive our newsletter, you can subscribe here.
________*Point of clarification — Microcystis is a bacteria, not an algae, though the two tend to bloom simultaneously under the right conditions. ** All climate data was provided by the Great Lakes Integrated Science and Assessments Center www.glisa.umich.edu