The city of Toledo, Ohio has warned residents not to use its tap water because of the toxin Microcystin in the water system. A state of emergency was declared by the state governor on Saturday. Microcystin is produced by algae living in Lake Erie and is a liver toxin. Boiling the water will not destroy it and residents were advised to avoid contact with lake water since mycrocystin can cause skin rashes. Pets are particularly vulnerable to the toxin. A severe algae bloom is affecting the Lake Erie this summer; The New York Timesdeclared Lake Erie "sick" from eutrophication. Scientists think algae blooms are caused by agricultural runoff that is high in phosphorus content. Indeed, algae blooms occur each summer after spring rains wash heavily fertilized fields into the Erie's waters. The heavier the rains, the worse the bloom will be. 2011 was a particularly bad year [NOAA photos show beginning and largest extent, 2011]. Lake Erie suffered from runoff and industrial pollution in the 60's earning it the nickname, "the Dead Sea", but once dumping was cleaned-up and reduced, Erie recovered. Thanks to a multi-million dollar effort by the US and Canada, the lake became an environmental success story. Anglers enjoyed a rejuvenated sport fishery, catching five million walleye a year. However, the algae blooms have returned, bigger than ever. The fish catch is one-fifth its previous size. Algae thrive on phosphorous and eventhough the chemical was reduced by limiting sewage and industrial dumping in the 70s and 80s, the levels of phosphorous are rising again. When algae die and sink to the lake bed, they are consumed by bacteria which in turn consumes most of the oxygen in the water column leaving a dead zone. Lake Erie's dead zone now covers a third of the lake bottom in bad years.
To mitigate algae blooms, 70,000 farmers along the lake shore have to alter their use of fertilizers containing phosphorus. Most of the algae affecting the lake originates near Toledo where the Maumee River empties into the shallow western basin. The Maumee drains Ohio's intensive agricultural land where mostly corn and soybeans are raised. Fertilzer pellets, about 48 lbs per acre used to be plowed under, but now stay on top of soil in no-till fields (no- till practices are intended to reduce erosion and loss of topsoil). Increased rains and snows caused by global climate change are washing 1lb of the fertilizer into the Maumee which is then delivered to Lake Erie. High summer temperatures also contribute to accelerated toxic algae growth. Agricultural experts think fertilizer application can be improved, and leaving fallow land besides stream will reduce fertilzer run-off.