THE EFFECTS OF NONPOINT SOURCE POLLUTION ON CYANOBACTERIAL BLOOMS IN LAKE ERIE FROM AGRICULTURALLY APPLIED FERTILIZERS IN NORTHWESTERN OHIO, USA, FOR THE YEARS (1999-2003)

Since the mid 1990’s, Lake Erie has experienced seasonal eutrophication. This investigation was designed to look at potential causes for eutrophication in Lake Erie. It was also designed to see if any correlations exist between agriculturally applied fertilizers (including sewage sludge) and cyanobacterial blooms in the Western Basin of Lake Erie that occurred during the months of July, August, and September for the years 1999-2003. An algorithm was used on available LANDSAT Thematic Mapper (TM) frames to monitor phycocyanin growth caused by cyanobacteria. These images were analyzed in conjunction with Maumee River water quality data, planted winter wheat, local weather data, and records of agriculturally applied sewage sludge nutrient data from the local wastewater treatment plant.

The year 2003 provided the largest algal bloom in this study, which extended beyond the upper threshold of the phycocyanin algorithm of 15mg/L. The largest total acreage of high phycocyanin content occurred on September 20, 2003, which had 285, 451 phycocyanin-rich acres present in the Western Basin of Lake Erie. The average acreage of high phycocyanin content for the month of September in the Western Basin of Lake Erie displayed strong correlations with Maumee River flow rate, Maumee River nutrients (including nitrogen, phosphorus, and suspended solids), and planted winter wheat acreage for Northwestern, Ohio. Agriculturally applied sewage sludge provides circumstantial evidence that it contributes to cyanobacterial blooms in the Western Basin of Lake Erie, but there is not enough evidence to implicate or exonerate sewage sludge as the main driving force promoting cyanobacterial blooms.