TOLEDO, Ohio (AP) — Ohio’s latest response to the toxic algae in Lake Erie that last year contaminated one of the state’s largest drinking water systems will put a stop to practices environmentalists have complained about for years.

Now the big question is will it make a big difference – but the answer won’t come for at least several years. That’s because what’s causing the algae blooms is a complicated mix of problems that have been blamed on farmers, changing weather patterns, aging wastewater systems, leaking septic tanks and invasive species in the lake.

Backers of legislation approved last month in the Ohio Statehouse said it’s impossible to predict what the end result will be from banning farmers in northwestern Ohio from spreading manure on frozen and rain-soaked fields and bringing an end to the dumping of dredged sediment in the lake within five years.

The changes – the first made by the legislature since a toxin contaminated the drinking water for more than 400,000 people in northwestern Ohio and southeastern Michigan last August – also include more testing of farm field runoff and at wastewater plants along with a new state coordinator to oversee monitoring, treating and testing of algae.

While a great deal of the phosphorus that feeds the algae comes from Ohio, the pollutants also enter the western end of the lake from the Detroit River and they come from farm fields in neighboring Indiana and southern Canada.

“In the end, it’s a multifaceted problem,” said Ohio Senate President Keith Faber. “And until we can get our friends in Indiana and Michigan and Canada to also address this in some of the same ways, we’re going to continue to have issues. But certainly we’re trying to do our part.”

Environmental groups, who long have been calling for tighter regulations on manure and the dumping of sediment in the lake, say Ohio’s new rules are a step in the right direction but more needs to be done. Adam Rissien, the Ohio Environmental Council’s director of agricultural and water policy, said the state addressed when manure and chemical fertilizers should be applied to farm fields, but it didn’t specify how much could be added.