Run-off receptacle.

6 There used to be a vast lake that covered much of Manitoba as well as parts of Ontario, Saskatchewan, Minnesota, and North Dakota. Called Lake Agassiz, after a Swiss geologist, it was formed about 12,000 years ago from glacial melt water. At its biggest, the lake covered 540,000 [km.sup.2], big enough to submerge 83 percent of Manitoba.

As the ice receded, the water of Lake Agassiz was able to drain northwards into Hudson Bay. That was about 8,000 years ago. High ground started to appear and the huge Lake Agassiz broke up into smaller bodies of water. The largest of these is Lake Winnipeg (23,750 [km.sup.2]); others are Lakes Manitoba and Winnipegosis, and Lake of the Woods.

During the summer of 2003, scientists were pottering about Lake Winnipeg in their boat when they ran into something unpleasant. It was described as a "toxic stew as thick as paint." What they ploughed into was all algal bloom covering 4,000 [km.sup.2]; about one-sixth of the lake's surface.

The explosive growth of algae on Lake Winnipeg happens every summer, when a thick, green slime forms on the surface.

The algae rob the water of dissolved oxygen and this causes fish to die. This process of oxygen loss is called eutrophication and its cause can be traced back to the presence of nitrogen and phosphorus. These two chemicals are meat and potatoes for blue-green algae and their concentrations in Lake Winnipeg are rising.

The big culprit is agriculture. Nitrogen fertilizer is spread on fields to increase crop yields. According to Stuart Laidlaw, a Toronto Star reporter, only a third of the fertilizer applied is actually used by the crops. The rest migrates to streams and rivers that feed lakes. Some of that fertilizer is artificial (see side bar on page 32) and some is hog manure: and, Manitoba has a lot of the latter. Hog production in the province has gone from 870,000 head in 1975 to 6.4 million in 2001.

Dr. David Schindler is an ecologist at the University of Alberta who's been keeping an eye on Lake Winnipeg for 35 years. He calls it Canada's sickest lake, although he's quick to point out it's not beyond rescue. For that to happen, farmers will have to go back to the old ways of raising crops before the use of artificial fertilizers and the spraying of huge quantities of pig manure. Or, wastes will have to be treated to remove phosphorus and nitrogen.

Will it happen? Dr. Schindler isn't overly optimistic; "We'll probably need major episodes of waterborne disease to smarten up politicians and bureaucrats before there's any action," he told writer Robert Ferguson in 2004.

In 2003, the Manitoba government announced a "Lake Winnipeg Action Plan." However, it looks like a lot of plan and very little action. Meanwhile, a government website makes the lake sound like paradise:

"With its beautiful beaches and wide open waters, Lake Winnipeg is one of Manitoba's greatest freshwater resources. The world's 10th largest freshwater lake plays a critical role in tourism, recreation, commercial and sport fisheries, and hydroelectric generation in Manitoba. The lake is home to abundant aquatic life including fish, invertebrates, and plants. Over 23,000 permanent residents live in 30 communities along the shores of Lake Winnipeg. Lake Winnipeg's world-class beaches attract many visitors to the province and opportunities for swimming, paddling, sailing, and windsurfing can be found on the east and west shores. Each year, approximately 800 commercial fishers operate on Lake Winnipeg, catching a variety of species including world-class pickerel, goldeye, sauger, whitefish, plus others."

No mention of the world-class algal blooms or pig poo.

PROGRESS TRAP

We can blame all that algal bloom on Fritz Haber. During the first decade of the 20th century, he and colleague Carl Bosch cracked a puzzle that had stumped chemists for a long time; they found a way of making artificial, nitrogen fertilizer. Until Mr. Haber's breakthrough, the world's farmers had to rely on a dwindling supply of bird droppings (known by its Spanish name--guano) as a crop-yield booster.

The abundant supply of low-cost, artificial fertilizer changed agriculture; industrial scale farming became possible, driving down the cost of food and reducing the risks of famine. However, farmers and their fields have become addicted to nitrogen fertilizers, and the run-off of residue is causing the problems seen in Lake Winnipeg and in many other places around the world.

Incidentally, Fritz Haber has another dubious claim to fame. As director of the Kaiser Wilhelm Institute for Physical Chemistry in Berlin, Germany he served his country with great energy during World War I. He developed chlorine gas as a weapon and directed its first use against enemy troops. This happened on the pleasant spring evening of 22 April 1915 near the town of Ypres in Belgium, when hundreds of French soldiers choked to death in agony. Fritz Haber is often referred to as the father of modern chemical warfare, but this did not stop the Nobel committee from awarding him the 1918 prize for chemistry.

FACT FILE

Lake Winnipeg is not alone; algal blooms have occurred in the English Channel, the Gulf of Mexico, the Baltic Sea, the Black Sea; and a host of other places.

Website

Lake Winnipeg Research Consortium--http:// www.lakewinnipegresea rch.org/