Canadian Study Finds Algae, Parasites In U.S. Water

A new study by the Manitoba government found that water from North Dakota's Devils Lake, does not contain any invasive species of fish or plant life. However, the study did reveal "biota of potential concern" that have not been previously found in a Canadian lake.

In August, the U.S. and Canadian governments reached a compromise after Manitoba tried to block a project under which North Dakota started draining water from Devils Lake into the Sheyenne River, which empties into the Red River and Lake Winnipeg.

The compromise provided for the construction of a temporary gravel filter to treat the lake's water until a permanent filtration system could be built.

The study, released on Nov. 15 by Manitoba Water Stewardship, found algae and fish parasites in Devils Lake water that officials said have not been previously found in Lake Winnipeg.

The findings from the study are now available to assist in designing the advanced filtration system at Devils Lake to replace the temporary gravel filter that was installed prior to operation of the outlet. This is consistent with the agreement reached between Canada and the United States in August, which will also assist Manitoba in reducing the levels of phosphorus and nitrogen entering the Red River and Lake Winnipeg, officials said.

"It is very good news that none of the 12 known invasive species, such as zebra mussels, were found in Devils Lake. However, not surprisingly, some differences were discovered between the biota in Devils Lake and Lake Winnipeg," said Water Stewardship Minister Steve Ashton.

"These findings underscore the importance of the Aug. 5 agreement between Canada and the United States, which provides for mitigation should potentially risky biota be discovered. The test results also point to the need to move quickly on the agreement to build a more advanced, permanent barrier at the outlet."

Manitoba Water Stewardship participated in the first-ever multi-agency effort to study the biota in Devils Lake starting in late July. The study was focused on determining whether or not 12 known invasive species were present in Devils Lake. A 13th known invasive species, the striped bass, was once present in Devils Lake but is no longer thought to be there, according to separate studies.

The multi-agency study also included additional work on fish pathogens and parasites, as well as a study of the phytoplankton, zooplankton and the bottom-dwelling invertebrate community in Devils and Stump lakes.

The study's key findings include the following:

  • None of 12 known invasive species were found in Devils Lake.
  • Four types of blue-green algae were identified in Devils Lake that have not been found in Lake Winnipeg. These algae are potential species of concern to Manitoba as they are capable of producing toxins.
  • Three fish parasites were found that are potential species of concern for Manitoba as they are not known to be present in Lake Winnipeg or the Hudson Bay basin and all have the capability to impact fish. Two of the parasites had been found previously in Devils Lake while a third was discovered during this study.

Because Devils Lake has largely been isolated from the rest of the Hudson Bay basin for about 1,000 years, there were concerns that there may be species such as fish pathogens or parasites that could cause ecological or economic harm if transferred downstream to Lake Winnipeg through operation of North Dakota's outlet.

In total, the survey tested more than 300 fish for fish pathogens and parasites following U.S. Fish and Wildlife protocols. Evidence of one fish disease (bacterial kidney disease) also was found in most of the fish using a screening test, but could not be confirmed to be present using a more specific test. This disease has been found in Manitoba fish hatcheries in the past.

As well, five species of plankton (four algae and one zooplankton) were found in Devils and Stump lakes that have not been found in Lake Winnipeg. However, these five species prefer highly saline habitats, so then likely would not survive if introduced to Lake Winnipeg. As a result, these are not likely to be considered species of concern to Manitoba.

Manitoba Water Stewardship: http://www.gov.mb.ca/waterstewardship

This article originally appeared in the 11/01/2005 issue of Environmental Protection.

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