Excess nutrients choke rivers with algae. (CBC)

A lack of oxygen in Prince Edward Island waterways, a problem that kills sections of rivers, is the focus for a team of researchers this summer and fall.

Excessive nutrients in rivers start a chain reaction. Algae grow in huge masses, then die. As algae rot, oxygen is consumed in the water, a condition known as anoxia. The river turns green and stinks.

"When oxygen levels drop too low it makes it hard for things to survive, especially anoxic events, when the oxygen levels drop so much, that things can't survive," provincial Environment Department researcher Shawn Schofield told CBC News Tuesday.

These anoxic events can go on for days or weeks. Fifteen waterways in P.E.I. have gone anoxic this year.

Schofield and student researcher James MacPhee are working through this summer and fall to determine the extent of the problem, identify the sources and propose some solutions. Sources of extra nutrients in the water can be farming, septic systems and clear-cut logging.

The province's researchers have been monitoring Island rivers for several decades, and the problem is getting worse. Anoxic events are happening earlier in the year, lasting longer and some rivers are having two or three in one season.

Student researcher James MacPhee says buffer zones are important to protect rivers from run-off. (CBC)

MacPhee said the algae ova are not a pretty sight in an anoxic event.

"Entire bottoms of rivers, covered in green ova," he said.

"You're driving through it and you see mats all over and the shores are just covered in this dried, decomposed ova."

The province hopes to work with landowners and land users once they identify problem areas. Anoxic events can be prevented by removing algae, but that's a labour-intensive, expensive solution. Schofield and MacPhee would like to see more buffer zones around rivers.

"It makes it seem more important to maintain those buffers because they're actually like a natural filter," said MacPhee.

The two will continue to monitor Island rivers until December.