A newly released study says cutting phosphorus levels is important for Lake Erie but isn't a cure-all for one of its biggest environmental hazards: "dead zones" where fish can't survive.

The report by researchers with the Carnegie Institution for Science says the lake's biggest dead zone on record formed in the summer of 2012. Phosphorus runoff from farms was partly responsible. But drought and low flows from tributary rivers were even bigger factors.

Lead researcher Anna Michalak says the findings suggest that policymakers working on plans for preventing dead zones and harmful algae blooms should consider weather trends as well as agricultural practices — especially as climate change brings about more extreme conditions.

Lake Erie is the smallest of the five Great Lakes but produces more fish than the others.