Mapping harmful algal blooms in the Laurentian Great Lakes: an analysis of HAB occurrences since 2002

Harmful Algal Blooms (HABs) occurrence in the Great Lakes is becoming increasingly problematic as they occur more frequently, in larger areas, and with rising severity. Remote sensing that utilizes both satellite and airborne imagery has been effectively used to map and monitor HAB events in the Great Lakes in order to help decision makers understand the extent of the problem. The mapping algorithm uses MODIS satellite imagery to identify areas of high chlorophyll concentration as well as areas of floating scum. The mapping algorithm was used to process cloud free imagery covering Green Bay, WI, Saginaw Bay, MI and the Western Basin of Lake Erie, MI/OH from 2002 through the fall of 2013. The resultant time series for each AOC was analyzed to show trends in HAB onset/offset dates, trends in average total HAB area for each year as well as average floating extent and average high chlorophyll area extent. The time series study was also able to highlight locations within each study area that are consistently plagued by long-term HAB inundation. Together, these spatial and temporal measures were used to show how harmful algal blooms have changed over time