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State of the Lake

Winnipeg Free Press
Sunday April 18, 2004

Sherri-Lynn Kowalchuk, wearing a white hardhat with a label that says “Mud Monkey”, leans over the ship’s rail and lowers a spring-loaded brass box into the waters of a troubled Lake Winnipeg. When the box hits the lake bottom, she sends a brass weight down the rope.

The weight hits a trigger, the box snaps shut around the soft mud on the bottom of Lake Winnipeg and Kowalchuk hauls up a football-sized hunk of muck. She will rinse and sieve this bite of the lake bed and pick through it for insect larvae, worms, shrimp-like animals and other tiny bottom dwellers.

Kowalchuk, a master’s student at the University of Manitoba, was aboard Canada Coast Guard Ship Namao on Lake Winnipeg Oct. 2. While Kowalchuk gathered up mud, other researchers collected water and plankton samples and measured water temperatures and wind speeds. U of M master’s student Kristie Lester sorted through a shimmering tub of tiny cisco, goldeye, silver bass, emerald shiners and one large walleye caught in a 30-minute surface trawl.

Department of Fisheries and Oceans (DFO) chemist Steve Page emptied another trawl net, this one with tiny 253-micron holes (about one quarter the size of a pinhead). The payload looked like a cup of green Pablum.

These researchers are part of the Lake Winnipeg Research Consortium (LWRC). Founded in 1998 to study water quality and the human-caused super-fertilization — or eutrophication — of Lake Winnipeg, the LWRC is a collaboration of scientists, communities, government and private agencies. The consortium’s research activities, so far, have been carried out by scientists from the universities of Manitoba, Winnipeg and Toronto, as well as Manitoba Water Stewardship and DFO.

“We want to bring as many people, from as many different disciplines together as we can,” says LWRC co-ordinator Al Kristofferson. The LWRC ship, the CGS Namao (which means “sturgeon” in Cree) is a retired Coast Guard Class 900 buoy-tender, 32 metres long, with berths for a ship’s crew of nine plus six scientists. The Namao was scheduled for disposal until the LWRC, over a period of two years, managed to find $326,000 to make her lake-worthy.

The annual operating budget of $380,000 is cobbled together from parties who care about the lake and care to know how they affect the lake: Manitoba Hydro (“They know that dirty water generates as much energy as clean water,” says Kristofferson, “but they also know that they have a responsibility to the people who use the lake”), the Manitoba Pork Council, Fish Futures, the Rural Municipalities of Gimli and Alexander, and even individual fishers.

In spring, summer and fall of 2002 and 2003, the LWRC sampled 65 stations across the entire lake, the first all-season full lake surveys since 1969. The surveys confirmed how little we know about the biggest lake in Manitoba and the 10th largest freshwater lake in the world. It’s a lake that in 2003, when more than one half of the surface of the north basin was covered with a slick of potentially toxic algae, still managed to support a record-breaking $21-million walleye fishery.

Fish trawling on Lake Winnipeg
Preparing for a fish sampling trawl on the Namao research vessel, Lake Winnipeg

One water sample from each of the Namao stations and some of the green Pablum from the stern trawl goes to Hedy Kling. Kling is a retired DFO research scientist and an expert at identifying the thousands of algae species that commonly grow in fresh water. Despite her retirement, she still identifies algae for other scientists, university colleagues and government water quality departments in Canada, the U.S., Africa and Europe, and she still publishes scientific research papers.

Kling analyzed the algae samples from the 1969 lake survey. In 1969, when she peered through the microscope at the phytoplankton suspended in Lake Winnipeg water samples, she identified an assortment of one-celled plants — diatoms (transparent silica-shelled organisms), brown algae, bluegreen algae and green algae.

The Namao samples are different. The total amount of algae in the lake has increased. An algae-rich litre of lake water in 1969 had 10,000 micrograms of algae (about one fifth the weight of a drop of water). In 2003, the same volume of water had as many as 80,000 micrograms of algae, of which 96 per cent were bluegreens. Conditions had changed. Although no one has a collection of water samples to fill in the 30-year gap, Kling had access to another type of sample.

In a small lake survey in 1994, scientists with the Geological Survey of Canada pushed a hollow tube-like instrument into the lake bed in the south basin. They extracted a 30-centimetre-long cylinder of mud –100 years of fallen soil particles and remnants of lake organisms. In this historic record, Kling looked for algae.

Clearly visible in the mud were the cool-temperature algae, pollen and plant fragments blown into the lake in the cold, dry and windy mid-1920s. The fires of the hot, dry 1970s left a layer of charcoal as well as the remains of heat-loving bluegreen algae. From the 1960s to the top 1994 layer, algae were increasing.

“Basically, the core is saying that since the 1960s, all the algae have increased, but particularly the bluegreens have increased,” says Kling.

When Kling looked at an eight-metre, 10,000-year core from the north basin, she found that the last time the lake had high numbers of bluegreen algae was during a hot period about 3,000 to 4,000 years ago, when much of Lake Winnipeg dried up.

Bluegreens are problem algae. They are poor food for hungry fish or zooplankton. They produce chemicals that make water taste muddy. Dying bluegreens congregate at the water surface, forming yellow-green or blue-green scums that can blow into beach waters. Some dying blooms produce liver and nerve toxins that can kill. 
Dogs and livestock have died from drinking water in a toxic bloom. People swimming in toxic blooms have suffered rashes, stomach upset, and breathing problems, some leading to pneumonia. In 2002, a 17-year-old Wisconsin boy died after swimming in an Anabaena flos-aquae bloom (a common bluegreen in Lake Winnipeg).

Lake Winnipeg blooms produce toxins. Kling has also found bluegreen toxins in the liver of burbot and long-nosed sucker and in the breast and liver of a blue-winged teal duck and the lungs of a pintail duck.

No one knows to what extent toxins build up in animals that use the lake, or how it affects them over time. And no one knows to what extent toxins build up in people who eat contaminated fish and waterfowl, or how it affects them. But studies suggest that people or animals who regularly eat or drink algal toxins may, over time, be more susceptible to liver and colon cancers.

Even with treatment, drinking water from contaminated lakes or reservoirs can contain low levels of some toxins. On Lake Winnipeg, fish processing plants use lake water. So does the community of Victoria Beach.

Not all bluegreen blooms produce toxins. A species that makes toxin on one occasion may be innocuous another time. Sometimes blooms are a mix of several species of bluegreens that produce a super-lethal toxin cocktail — or they may produce none at all. If there’s a pattern to bluegreen blooms and toxin production, researchers haven’t found it.

“We haven’t measured enough samples,” Kling says. “We don’t know anything about what a lot of Lake Winnipeg species produce for toxins or what causes them to produce toxins. We just don’t know.”

Researchers sort fish caught in the trawl net.

“We’ve travelled all day long in the Namao, continuously through bluegreen blooms,” says Greg McCullough, a PhD student at the University of Manitoba.

McCullough has satellite pictures from last July that show an enormous bloom stretching from the narrows, engulfing Berens and Reindeer Islands, and extending north, basin-wide, to Long Point. Beyond Long Point, the bloom followed the east shore and sent massive curls into the centre of the north basin. Hundreds and hundreds of kilometres of algal bloom.

McCullough uses satellite images of the colours reflected from the lake to measure algal blooms. In the satellite pictures, algal blooms are yellow-green. Sediments carried by the muddy Red River are tan. The clear, tea-like dissolved organics that enter the north basin from the Canadian Shield rivers — the Berens, the Bloodvein, the Pigeon — appear reddish-brown.

From the colours, McCullough can tell an innocuous diatom bloom from a potentially toxic Aphanizomenon bluegreen bloom. From the satellite picture, he can estimate the amount of chlorophyll on the lake (which is an indicator of the amount of algae), give or take 30 per cent. He knows he’s within 30 per cent because instruments on board the Namao continuously sample the lake and record chlorophyll in the surface water. He’s checked his satellite estimates. Every two days, when the satellite passes over the lake, if the view is cloud-free, McCullough has a very good idea how much chlorophyll covers Lake Winnipeg.

What’s worrying about the chlorophyll numbers that come off Lake Winnipeg, from both satellite images and the Namao, is that they are three to four times higher, on average, than those from Lake Erie in the 1970s. At that time, human-caused eutrophication of Lake Erie led to bluegreen algal blooms and created a “dead zone” of chronic low oxygen levels covering almost 7,000 square kilometres of the lake bed.

In the Lake Erie dead zone, bottom-dwelling mayfly and other low-oxygen sensitive insect larvae declined or disappeared. Coldwater whitefish, cisco and lake trout also declined. Thirty years and billions of dollars later, Lake Erie is in recovery. Total algae has dropped in half, bluegreens have declined by 90 per cent and fish are rebounding. Even so, nutrient levels in the lake are higher than the target, perhaps due to increasing nutrient waste from growing urban centres, and for some reason, oxygen depletion has plateaued. Even after 30 years, the renewal of Lake Erie depends on more science.

“To my mind, we have a worse situation in northern Lake Winnipeg than Lake Erie had,” says McCullough. “The extent and amount and intensity of the algal blooms I see… they’re huge.”

Aboard the Namao, Sherri-Lynn Kowalchuk holds a box containing mud from the lake bottom.

The blooms feed on water-borne nutrients. Lake Winnipeg collects water from almost a million square kilometres of Saskatchewan, Manitoba, Ontario, North Dakota and Minnesota. In that area, soil, manure and fertilizer run-off from all the farmlands washes into ditches, then streams, then rivers and then into Lake Winnipeg. All town sewage effluents and all industrial river discharges end up in Lake Winnipeg. Lake Winnipeg is the wastewater receptacle for a region the size of British Columbia.

Most of the nutrients come from cropland runoff, and most enter Lake Winnipeg from the Red River. The Red is a muddy river, and it spews not only its nutrients, but also flecks of eroded prairie soils into the south basin. This Red River silt mixes with the often equally muddy, shallow south basin. A plate-sized black and white disc lowered into the water by a cord, like a giant spinning top, is invisible after only 20 or 30 centimetres. The same disc in the north basin is visible for two, three, up to six metres.

The murkiness of the south basin partially protects it from algal blooms. The water has enough nutrients for algae to grow. What’s missing is light. Only during windless periods, when the silt settles, can light penetrate far enough for algae to grow and rapidly multiply into blooms.
As the waters of the south basin flow north, much of the silt drops to the lake bottom but many of the dissolved nutrients remain unused by algae. What merges with the clear waters of the north basin are relatively transparent, high-nutrient waters. Liquid fertilizer.

Even in death, bluegreen algae haunt the lake.

In the north basin in 2003, Namao scientists found a low-oxygen layer that smothered somewhere between 7,000 and 10,000 square kilometres of lake bottom. That’s an area equal to Lakes Manitoba and Winnipegosis combined. Oxygen readings were as low as two parts per million. At that level, organisms living on the lake bottom “choke” for lack of oxygen, and some may die. It’s not enough oxygen for most fish. It’s the kind of oxygen depletion that creates a dead zone.

“That was a major surprise,” say McCullough. “When I came back from the Namao trip I talked to limnologists all over the country. Hardly anybody expected this to happen on Lake Winnipeg.”

The north basin has an average depth of 16 metres. When the lake warms up in the spring and summer, scientists thought that because the lake was shallow, the wind would mix the waters completely, all the way to the bottom. Last August, the mixing only went down to about 14 metres. Above 14 metres the water was 21º C. Below, the water was 15º. The bottom waters had been isolated since June.

In the last 80 years, there have only been 12 whole-lake surveys of Lake Winnipeg and most didn’t span the entire season. None has ever found a separated layer of bottom water. McCullough says: “It would be perfectly fair for someone to look at that and say ‘Well, we hadn’t looked very hard.'”

The primary source of lake oxygen is air. Oxygen dissolves in the top layer of water and the wind mixes it into the rest of the lake. Last year in Lake Winnipeg, no oxygen reached the lake bottom for about two months. During this time, organisms such as Kowalchuk’s insects and worms, and fish drawn to the cool bottom water, survived on the oxygen that was already there. Unfortunately, so did the community of bacteria on the lake bottom that gorged on the bountiful remains of bluegreen algal blooms. Although decomposition of plant and animal remains is an important source of recycled nutrients in a lake, in 2003, excessive bacterial demand for oxygen almost suffocated a third of the bottom of Lake Winnipeg.

The lab on board the Namao.

In the 1970s, during the Lake Erie crisis, DFO research scientist Len Hendzel participated in a nutrient addition study that demonstrated that phosphorus was the nutrient that caused algal blooms in lakes. Hourglass-shaped Experimental Lake 226 in northern Ontario was divided in half at the narrows. The half that researchers supplemented with extra nitrogen and carbon didn’t change. The half that received extra nitrogen, carbon and phosphorus turned “pea soup green.”

Hendzel has studied algae and nutrients in lakes in Manitoba and Ontario for 30 years.
“You get to understand the long-term character of lakes,” Hendzel says.

In Lake Winnipeg, Hendzel measures how algae use nitrogen (the first number on a bag of fertilizer) and phosphorus (the second number on a bag of fertilizer) through the season.

In early spring, as the ice melts and the water warms, diatoms and green algae gorge on lake nutrients. Rarely they form blooms. Hendzel has found that for these species, the feast doesn’t last.
For every gram of phosphorus, algae need about 15 grams of nitrogen. In spring, lake water supplies algae with plenty of both. By early summer, diatoms and green algae are struggling. Although they have enough phosphorus, they don’t have enough nitrogen. Most years, Lake Winnipeg algae run out of nitrogen by mid-summer.

As the green algae and diatoms decline, the bluegreens increase. Unlike green algae and diatoms, most species of bluegreens don’t depend on nitrogen from water nutrients. They can get it from the air. For several months, peaking in July and August, bluegreen algae dominate the lake. Their reign ends when the phosphorus runs out.

“These bluegreen algae grow so luxuriantly on nitrogen fixed from the air that they force themselves into phosphorus limitation,” Hendzel says.

Lack of phosphorus, combined with shorter days and cooler water temperatures in early fall, conclude the Lake Winnipeg bluegreen bloom season — a season reborn every year by waters enriched with too much phosphorus and proportionately too little nitrogen.

Eutrophication profits some species. The spring flush of diatoms and green algae provide food for zooplankton, insects and fish. In Lake Erie, although whitefish suffered with eutrophication, fish species that live above the bottom waters — such as yellow perch, fresh-water drum, white bass, carp, catfish and walleye — increased.

“We’re dealing with cultural eutrophication, a human-caused increase in productivity,” Kristofferson says. “You get more phytoplankton (algae), which really drives the system. You get more zooplankton, more forage fish, more larger fish — at least initially.”

It’s what happens after “initially” that researchers want to know. Researchers are still studying if the low oxygen bottom waters affected the tiny creatures on the lake bed. Although whitefish are currently considered “not in decline,” they are coldwater bottom feeders and would be among the first fish species to suffer from a Lake Winnipeg “dead zone.” Water control structures on the Nelson River outflow make Lake Winnipeg one of the largest hydroelectric reservoirs in the world, so researchers are studying how altered lake flows affect algae and nutrients.

“It’s going to require a lot of research,” Kristofferson says. “But the more research we do, the more we’re finding out about how the lake is reacting to eutrophication.”
By the last week of the Namao’s 2003 Lake Winnipeg surveys, right before Thanksgiving, DFO Namao field science co-ordinator Claire Herbert had overseen 10 weeks of scientific collections. Her green hardhat was festooned with pink flagging tape, a red label reading “fish trawler extraordinaire” and, in red, yellow and blue the letters LWB, for Lake Winnipeg Babe.

Time on the Namao is so costly that after collecting samples all day, Herbert and the science crew processed them long into the evening. After supper, Herbert climbed down a ladder into the ship’s hold, through a plywood door with a window the shape of Lake Winnipeg and into a tiny laboratory. At 8 p.m., Herbert was still analyzing algae and water samples, a daily ritual that would take her another two hours.

Lake Winnipeg is changing. The LWRC has only 10 precious weeks a year on the Namao to figure it out.

“Nobody’s deliberately trying to ruin the lake,” says Kristofferson. “People are loathe to jump on the bandwagon if someone says, ‘Well, I think I saw a change.’ You have to have the data. And that’s what we’re doing.”

This was the most complex story I did for the Winnipeg Free Press. The DFO researchers were generous with their time and knowledge, and I thank them for that. My Winnipeg Free Press editor, Boris Hrybinski, wrangled this into a piece for a Sunday special section, complete with a large colour photo of a Lake Winnipeg algal bloom and images of various algae found throughout the lake.

In the original publication I included a line about the lack of dedicated funding from the federal government. Obviously the government of Canada was paying researchers, students and providing other resources for the project as pointed out to me post-publication by a DFO researcher. I’ve corrected that inaccuracy in this online version, with apologies.

Frances Russell used excerpts from this article in her beautiful book, Mistehay Sakahegan, The Great Lake: The Beauty and the Treachery of Lake Winnipeg.