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July 19, 2010
For immediate release

Anoxic Conditions Evident in Island Estuaries

Environment, Energy & Forestry

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The provincial government is taking steps to address the growing number of anoxic events occurring in Prince Edward Island’s estuaries, says Environment, Energy and Forestry Minister Richard Brown.

“Anoxia indicates how human activity is harming the health of our rivers and bays,” said the minister. “It is a sign that we have upset the balance of nature in our waterways.”

Anoxia is the absence of oxygen in water caused by a build up of nutrients which causes plants to grow. When the plants die and decay, oxygen is stripped from the water. The water turns milky white or cloudy green and gives off a strong rotten egg odour. The lack of oxygen is often deadly for fish and shellfish.

Because nutrients enter estuaries from a number of sources including agricultural activity, wastewater management, clear cutting forests and runoff, there are no quick, easy solutions to the problem, said Mr. Brown.

“Reducing the amount of nutrients entering our rivers and bays is the most effective way to address to this growing problem,” he said. “It requires long-term solutions and the support of many stakeholders.”

The Government of Prince Edward Island is taking significant steps to protect and enhance the quality of water on Prince Edward Island.

Mr. Brown has written to Fisheries and Oceans Minister Gail Shea proposing that the two departments partner, along with the University of Prince Edward Island, on a detailed analysis of the problem and recommendations to prevent anoxia.

“We have increased support to watershed groups, introduced environmental incentives through the Alternative Land Use Services program, increased buffer zones, improved erosion control, banned the spreading of septic waste on land, as well as other measures to protect the environment,” said the minister.

Anoxia occurs during warm weather and often follows the smallest tides in the tide cycle.

It is more common on the North Shore than the South Shore where there is greater tidal activity. Anoxia can last for a couple of days or a couple of weeks depending upon the amount of decaying material, the wind and the tides.

Anoxic conditions have been reported in a number of areas already this summer including portions of Brackley Bay, Covehead Bay, Barbara Weit River, Indian River, Bentic Cove, Southwest River, Hunter-Clyde River, Wheatley River, Chapel Creek, Hills (Mill) River, Cardigan River, Trout/Stanley River (including Founds River and Granville Creek), Hope River, Anderson’s Creek and Montrose River.

Government is working with farmers, landowners, industry, communities and the public to improve the quality of water on Prince Edward Island, said Mr. Brown.

“All Islanders share a collective responsibility for protecting and enhancing the quality of water on Prince Edward Island,” said Mr. Brown.

People can report anoxic conditions in estuaries by contacting the Department of Environment, Energy and Forestry at 368-5000.


Anoxia means the absence of oxygen. In an aquatic system, it is caused by a build-up of nutrients in the water.

An excess of nutrients causes too much plant growth. When this plant material dies, it decays and this process causes oxygen depletion.

During an anoxic event, the oxygen is depleted and the water turns milky white or cloudy green and gives off a strong rotten egg odour.

These events occur in Island estuaries (salt water rivers) and bays.

Anoxic events are most likely to occur during warm weather months with long hours of daylight. The events can begin as early as mid-June and may continue into the fall. They can occur during or just following the smallest tides in the tide cycle. Periods of cloudy, cold or rainy weather can also trigger the events.

Anoxic events can be identified by the presence of decaying algae or sea lettuce which produces milky white or cloudy green discoloration of the water and a rotten egg odor. These symptoms are most often observed in the shallow upper reaches of estuaries.

Eutrophication is another term commonly associated with anoxic events. It means a high level of productivity or plant growth.

What Causes Eutrophication?

Most estuaries are naturally productive areas, which makes them ideal for activities like fisheries and aquaculture. However, when the productivity is too high, poor water quality conditions may result.

Eutrophication is caused by a build up of nutrients in affected estuaries. In essence, the body of water receives more nutrients than the organisms within it need for normal life, growth and reproduction.

These excess nutrients are the result of human activities in the land surrounding the estuary that drains water into it (watershed). Nutrients can result from all kinds of activities including agricultural activities, wastewater management (septic systems, sewage treatment systems, industrial or commercial effluents), clear cutting forests and runoff.

What Can be Done to Stop Anoxic Events Once They Start?

Unfortunately, there is very little that can be done, in the short term, to make anoxia go away. Anoxic conditions may persist for a few days or a few weeks depending on the amount of decaying plant material, as well as wind and tide conditions.

Harvest or collection of the sea lettuce is being discussed by some groups as a way of preventing events from occurring in certain areas. Removal of sea lettuce requires a great deal of effort and would be very costly due to the large amounts present in our estuaries.

Removing it is not an effective option, as it would simply grow back.

Reduction of nutrient inputs to the system is ultimately the best way to deal with it.

What is the Province Doing to Address Anoxia?

The Report of the Commission on Nitrates in Groundwater identified concern about nitrate levels in our water. Since the release of this report in 2008, a great deal of progress has been made in determining the level of nutrients that our estuaries can tolerate before anoxia starts to happen.

The changes in land use required to reduce nutrient levels are achievable but only with support of Islanders.

Expansion of the Watershed Management Initiative has led to the strengthening of community watershed groups across the province who are actively engaged in the process of watershed planning.

Furthermore, the government is directly supporting the efforts of the agricultural sector to achieve environmental improvements with the Alternative Land Use Services (ALUS) Program. This program rewards producers and landowners for things they do above and beyond legislative requirements to conserve and protect the environment on PEI.

What Can I Do to Help?

Get involved! Your watershed group needs members, support and your input into their planning process. Eighty percent of PEI now has an active community watershed group. Contact the Department of Environment, Energy and Forestry at 368-5000 for information about the group in your area.

Own agricultural land? Contact the Department of Agriculture at 368-4145 to find out your options for nutrient management and soil conservation.

See an anoxic event? Islanders can also help the Department of Environment, Energy and Forestry by contacting the Department at 368-5000 when they observe anoxic conditions in PEI estuaries. This will help us document where they are occurring, when and how often they occur, and the severity.

Media Contact: Kim Devine
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