The issue of anoxia in PEI rivers and estuaries is getting worse with 15 waterways on PEI experiences areas of anoxia this year.

From 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.

...

Anoxic rivers a growing problem for P.E.I.
http://www.cbc.ca/canada/prince-edward-island/story/2010/07/21/pei-anoxi...