The P.E.I. government is trying to figure out how much nitrates from agricultural fertilizer Island rivers can withstand.

'Smelly anoxic estuaries are not really a big draw for tourists.' — Mike van den Heuval, Canadian Rivers Institute

Every year, some of P.E.I.'s rivers and streams end up starved of the oxygen marine animals need. Huge blooms of sea lettuce grow and then rot, sucking the oxygen out of the water, causing fish and other creatures to die in what's called anoxic conditions.

Mike van den Heuvel of the Canadian Rivers Institute at UPEI has been looking at the example of the Wilmot River near Summerside, where the equivalent of several pickup trucks full of fertilizer is going into the water every day. Van den Heuvel, who is being consulted by the government, is one of the scientists trying to find that safe level of nitrates for Island rivers.

While that level has not been established, he told CBC News Thursday too much is making its way into some rivers, and if changes aren't made, the consequences could be dire.

"Ultimately it could have effects on economically important industries. For example, the mussel farming industry depends on the estuaries," said van den Heuvel.

"Also tourism is also a very important industry for P.E.I., and smelly anoxic estuaries are not really a big draw for tourists."

Bruce Raymond, manager of watershed management with the provincial Environment Department, said there are a number of approaches possible to reduce nitrates in rivers.

"You could actually change what you do in the agricultural sector, that might be different crops, could be different fertilizer regimes. There's a variety of things that could be done to reduce the load," said Raymond.

The province has already increased the size of buffer zones required between waterways and farm fields. It is not ready to commit to any further laws or regulations regarding nitrates, in the water or on the land.