Anoxic rivers turn green or white, and give off an unpleasant odour.

A P.E.I. researcher has shown a marine plant that has been suffocating Island estuaries makes good compost, but getting it out of the rivers is still an issue.

Sea lettuce grows in large blooms caused by excess nutrients in the water, mostly from farm field run off. When the sea lettuce dies it sucks the oxygen out of the water, creating anoxic conditions deadly to marine life.

For the last two summers Roger Henry, a research technician with Agriculture Canada, has teamed up with the PEI Adapt Council and an O'Leary potato farmer to test out sea lettuce as fertilizer. He found that sea lettuce works almost as well as cow manure.

But Henry said harvesting sea lettuce is too expensive for farmers to do on their own.

"If he can get that product landed, you know, at very low cost  or for no cost then there's some real benefit there. It's going to take a lot of parties working together to solve the issue," he said.

"This shows that, you know, the material is of value, so if it is landed there's not going to be a waste or disposal cost."

Henry is presenting his findings Tuesday at the Access PEI centre in O'Leary.