What is causing the harmful algal blooms in Lake Erie?

Abstract

I n the early to mid-1990s, Lake Erie was regarded as one of the great water quality success stories stemming from the Clean Water Act. Annual total phosphorus (TP) loading to the lake decreased from nearly 30,000 t (33,069 tn) in the late-1960s to less than 11,000 t (12,125 tn) by 1990 (Richards and Baker 1993). These reductions in TP loading were achieved through permitting of point sources and through conservation efforts to decrease sediment loss from agricultural fields. While TP loads to Lake Erie have remained relatively stable since the mid-1990s, soluble phosphorus (SP) loads have been steadily increasing. The harmful and nuisance algal blooms (HNABs) that paralyzed regional tourism and fishing industries decades ago have reappeared and have been linked with the amount of SP transported to the lake (Davis et al. 2009). In August of 2014, HNABs in Lake Erie became a national headline when microcystin toxin produced by cyanobacteria was discovered and approximately 400,000 residents in Ohio were left without drinking water. There has been much debate among researchers, conservationists, and industry representatives on the specific causes of the increased HNABs in Lake Erie. Our objective here is to document many of the recently suggested theories that…