by Kelly-Anne Richmond and Gordon Goldsborough
Winnipeg, Manitoba
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In July 1882, John Rigby wrote from his home in the new prairie town of Killarney. About the lake that lay beside the town, he enthused:
[Killarney] Lake is a beautiful sheet of water, clear as crystal and abounding with fish and fowl. I think we would travel the world over before we would hit another spot to equal Manitoba and this locality in particular. [1]
Today, Killarney residents perceive that their lake is no longer the way that Rigby described. They believe that lake water quality has deteriorated markedly. For at least fifty years, they have worked vigorously to improve the situation, by adding chemicals to kill the massive growth of algae (called “blooms”) that appear in its waters most summers. Besides the obvious impacts of algae blooms on lake aesthetics and the willingness of people to swim at the public beach, the blooms make it harder to treat lake water as a potable source for the town, they can produce toxins that jeopardize the health of humans and animals consuming lake water, and the inevitable collapse of the blooms consumes oxygen, causing fish to die. It is claimed that algae blooms are the cause of declining numbers of fish caught by sport fishers at Killarney Lake.
Bathers enjoy a refreshing day at the public beach on Killarney Lake, circa 1956.
Source: Archives of Manitoba, Killarney Lake 4.
Many people think that algae blooms are recent phenomena resulting from human pollution of the environment. In fact, the mere presence of blooms is not evidence of lake deterioration, as they have occurred for millennia and may have played a role in human affairs numerous times through history. It is speculated, for instance, that blooms of red-colored algae were responsible for biblical stories of seas turning to blood. Algae blooms have been reported in Canadian waters for well over a century. Captain George Huyshe travelled with the Wolseley Expedition to the Red River Settlement during the summer of 1870. While canoeing through Lake of the Woods, he observed that:
The most noticeable feature ... is the peculiar green colour of the water, arising from a profuse vegetable growth ... they abound all over the lake, in some place so thickly that the water has the consistence and colour of pea soup. Some of the deep bays receding from the lake, such as Clearwater Bay, are free from this growth, but it extends even a few miles down the Winnipeg River below Rat Portage [now Kenora]. It was impossible to drink the water, or use it for making tea or cooking, until it had been carefully strained. [2]
Huyshe also saw algae blooms in Lake Winnipeg, long before the lake began to receive agricultural fertilizers and domestic sewage from its large prairie watershed.
Unfortunately, it is difficult to evaluate whether Killarney Lake has truly changed as much as locals claim, because no one analyzed lake water back in 1879, when intensive agricultural land use began in its vicinity. Even if someone had thought to collect water samples, improvements in analytical methods in the past century (and especially in the past couple of decades) would make comparison with modern measurements nearly impossible. So we must turn to information on historical water quality that exists elsewhere to determine the nature and extent of changes which have occurred in the lake.
Bottom sediments preserve a detailed record of biological changes in a lake basin and its surrounding area. Algae, plants, fish and other animals living in the lake sink to the bottom after death, along with soil, plants and other materials that flow in from the surrounding landscape. Depending on their chemical composition and the environmental conditions at the sediment surface, these materials can survive intact for hundreds to thousands of years, preserving a long-term record of conditions in and around the lake at the time of deposition. A vertical column of intact lake sediment can be collected readily, and analysis of discrete core layers for constituent chemical, physical and biological parameters is a well-established and powerful technique for studying changes in lake conditions due to changes in regional and local climate, hydrology, nutrient loading, and other environmental factors.
James Ritchie, a botanist at the University of Manitoba in the 1960s, studied pre-historical plant communities in southern Manitoba using fossilized pollen contained in lake sediment cores. He worked in the Riding Mountain area, [3] at Sewell Lake southeast of Brandon, [4] and in the Tiger Hills. [5] Ritchie concluded that a boreal forest covered this entire area about 10,000 years ago. The forest gave way to grassland, probably due to warmer, drier conditions. The modern mixed wood forest was established about 2,500 years ago as climate became cooler and wetter. Unfortunately, Ritchie did not study sites from the mixed grass, aspen parkland of southwestern Manitoba where Killarney Lake is located.
We collected sediments from Killarney Lake and analyzed them for their content of organic matter, phosphorus, and pigments. [6] These parameters correlate closely with plant growth in modern lakes – growth is high when their levels are high—so measurements of sediment layers can be used to infer past plant growth in Killarney Lake. We also examined sediments for the remains of single-celled algae called diatoms, whose uniquely patterned silicon-based shells preserve well in sediments. Diatoms occur across a wide range of environmental conditions and the conditions favored by particular diatom species living today are known. This enabled us to use the abundance of those same species preserved in sediment layers for environmental reconstruction. For example, if a particular diatom species is found today only in shallow lakes, the presence of its shells at a particular layer in a sediment core indicates the lake was most likely shallow at that time.
Location of the sediment coring site in Killarney Lake, Manitoba. A core was collected at the site indicated a circular symbol, with lake water depths (in meters) indicated by lines.
Our sediment core was 270 centimeters (8.8 feet) long, representing about 4,700 years of lake history, starting in a warm and dry period in the middle of the Holocene Epoch. However, it does not represent the entire history of Killarney Lake since the last glaciation about 12,000 years ago. A coarse layer of sand and gravel occurred at a sediment depth of about 2.8 meters (9.2 feet). We speculate this layer was deposited during a period of watershed instability and low lake level, as coarse materials were eroded into the lake from the surrounding landscape. Prairies lakes commonly contain dry and cement-like layers corresponding to periods of lake drawdown and soil formation during dry or extremely low water conditions between 9,500 and 4,500 years ago. For example, geologists have found discrete layers of terrestrial soil in sediment cores recovered several kilometers offshore in Lake Manitoba that formed when the lake was nearly dry. [7]
Changes in the algae and plant growth of Killarney Lake have been conservative. The lake’s diatoms, for instance, have not changed substantially, being generally typical of alkaline, high-nutrient water during the 4,700 period of our core. However, there were changes through time which permitted us to divide the history of water quality in Killarney Lake into five phases.
Analysis of a sediment core from Killarney Lake. Organic matter, total phosphorus, and total chlorophyll are graphed against the depth in the sediment core, where zero represents the modern sediment surface. The horizontal bands represent core layers that were radiocarbon dated, with their ages indicated on the right side. In general, peaks and valleys in the respective lines match one another. High levels of organic matter, phosphorus, and chlorophyll indicate high algae and plant growth at the time of the sediment layer.
Killarney Lake was shallow and relatively unproductive during this period, possibly recovering from a period of being dry. This is indicated by the sand and gravel at the base of the core and the abundance of diatom species typical of shallow conditions. Over a period of about 1,000 years, the water level increased gradually, perhaps due to increased precipitation, causing algae and plant growth to decrease. Production increased as the near-shore shallow zones of the lake were colonized by algae and plants.
Water levels and plant growth began to rise, probably in response to a cooler and wetter climate about 3,000 years ago. The trend that commenced in the late stages of Phase 1 continued to 1,800 years ago. Increasing abundance of diatoms typical of deep water suggests that Killarney Lake was getting deeper and more productive with abundant aquatic plants and algae in its expansive, highly productive near-shore areas. Blooms of cyanobacteria (also known as blue-green algae) probably occurred frequently. [8] Cyanobacteria are often responsible for massive blooms in prairie lakes today, with consequent taste and odor problems, as well as wild and domestic animal deaths from ingestion of toxins produced by some algal strains. The lake reached its deepest point by 2,100 years ago, when plant growth was low as compared to a peak about 2,500 years ago.
Lake production was low during a wet period to 1,500 years ago. Water levels were at or near their maximum value for the entire 4,700 year period. Cyanobacterial blooms were infrequent in a lake that probably was, at most, only moderately productive.
After the deep water period around 2,100 years ago, Killarney Lake became progressively shallower and more productive. Conditions similar to those in Phase 2 prevailed and the lake was probably very nutrient rich, with abundant cyanobacterial blooms. Maximum plant growth occurred about 500 to 700 years ago. The lake began to deepen again around 500 years ago but it probably did not attain the level achieved during Phase 3. Conditions similar to in the present lake were established about 300 years ago.
Killarney Lake has become deeper over the past 300 years, and some diatoms have appeared in its flora which were previously absent. This suggests that the lake has changed in recent times, perhaps as a result of human settlement and agricultural development around it. The ensuing nutrient inputs have caused the lake to become more nutrient rich although cyanobacteria, while frequent in the modern Killarney Lake, are probably less abundant than in the past, especially about 500 years ago.
Killarney Bay, the easternmost arm of Killarney Lake, had open grassland and few homes around it when this postcard photo was taken around 1908 by the Winnipeg Photo Company.
Source: Gordon Goldsborough
Our inferred trends in the water level and plant growth of Killarney Lake agree with those from other lakes on the northern prairies, suggesting that regional climate has played a role in lake changes. Several scientific studies indicate that the prairie climate was distinctly warmer and drier during the middle portion of the Holocene Epoch. In Lake Manitoba, fluctuating periods of wet and dry conditions occurred between 9,200 and 4,500 years ago. [9] About 4,000 years ago, Waldsea Lake in south-central Saskatchewan was shallow and extremely saline with extensive exposed mudflats around it. [10] Chappice Lake in southeastern Alberta oscillated between high and low water from 7,300 to 6,000 years ago. [11] At Moon Lake in south-central North Dakota, a period of high salinity from 7,300 to 4,700 years ago indicated that evaporation exceeded precipitation, probably due to dry conditions. [12] Collectively, these findings support a conclusion of widespread drought and dryness throughout the Great Plains of North America between 8,000 and 4,000 years ago.
Like Killarney Lake, many sites on the prairies indicate a climatic change from this arid period to one of increasing moisture about 4,000 years ago, which continued until about 2,000 years ago. Levels in Waldsea Lake, for example, increased about 4,000 years ago, culminating in deep-lake conditions by about 3,000 years ago. [13] Between 4,400 and 2,600 years ago, lake level was more stable but gradually rising. Plant growth was high at Chappice Lake while a large, relatively freshwater lake existed from 2,600 to 1,000 years ago. [14]
Our data for Killarney Lake correspond remarkably well to those made for Kenosee Lake in eastern Saskatchewan. [15] There, an early shallow lake phase from 4,000 to 3,000 years ago gave way to deeper water between 3,000 and 2,000 years ago. A deep-water period characterized the most recent 600 years. The similarity of the respective records between the two lakes, over 200 kilometers apart, and especially the period of wetter conditions from 3,000 to 2,000 years ago, supports the theory of regional climate as a driving force for water level change. One notable way in which the Kenosee and Killarney records differ, however, is that Killarney Lake diatoms showed no indication of lower salinity during increased water level, unlike profound changes in Kenosee Lake due to high salinity during infilling. Low lake level in Killarney Lake about 1,000 years ago was evident at several other prairie sites, including Chappice Lake (about 1,000 to 600 years ago) [16] and Waldsea Lake (about 1,000 to 700 years ago). [17] These low lake period roughly correspond to the Medieval Warm Period, about 950 to 750 years ago. [18] Evidence of high lake levels at Chappice Lake from about 600 to 100 years ago [19] suggests wetter conditions may have existed during this time. Unlike many other prairie lakes, Killarney Lake appears to have remained fresh and moderately deep during the late Holocene. The abundance of diatom species typical of deep water is a clear indication that Killarney Lake was consistently deeper than lakes such as Harris in southwestern Saskatchewan where diatoms indicated shallow conditions throughout a 9,200-year record. [20]
Our study of Killarney Lake sediments provides a basis to evaluate recent concerns of residents in the vicinity of the lake regarding the frequent occurrence of algae blooms and their undesirable effects on water quality, fisheries, and recreation. Some people believe that deterioration of Killarney Lake has been accelerated in the century since the town was established, a conclusion that is supported by the appearance in surface sediments of diatoms indicative of human-caused nutrient enrichment. However, as other scientists have found for nutrient-rich lakes elsewhere on the prairies, [21] the abundance of algae fossils and pigments deep in the core indicates that algae blooms are not a recent development. In fact, they have probably occurred throughout the 4,700 year period represented by our core. Recent (last 100 years) plant growth in the lake appears to be low in comparison with two peaks that occurred between 3,000 to 1,800 years ago, and between 1,500 to 300 years ago.
As compared to pre-historic levels of algae and plant growth in Killarney Lake inferred here, we suspect that human influences on the currently deep lake are minor. A noteworthy exception is the dramatic accumulation of copper in surface sediments of Killarney Lake. This copper is a result of lake-wide applications of “bluestone” (copper sulphate) since at least the 1950s for control of algae blooms, to the point where its concentration is many times higher than any other lake and farm pond sediments collected in Manitoba. [22] These bluestone additions are occasionally—but rarely—successful at treating the result of nutrient inputs to the lake from fertilizers applied to surrounding agricultural land and a golf course, manure from cattle feed lots, and domestic sewage and runoff from the Town of Killarney.
In conclusion, we believe that John Rigby was wrong in his assertion that Killarney Lake was “clear as crystal.” It is possible that he saw the lake in an usually clear period. Or perhaps he was overcome with pioneering zeal for his new home so he used less-than-accurate language in an attempt to entice others to follow his lead to the Canadian prairies. Our research shows that Killarney Lake has been naturally nutrient rich and abundant with algae, and at times extremely so, for over 4,000 years. In other words, the change in Killarney Lake’s water quality during the past century or so has been smaller than changes occurring during the past four millennia. But this does not mean that humans are not causing lake water quality to deteriorate. There is increasing evidence that most prairie lakes are changing as a result of agricultural, residential, and industrial discharges into them. Lake Winnipeg, for instance, is undergoing marked ecological change as a result of fertilizers, manures, sewage, and other chemicals put into it for over 100 years by people in several US states and Canadian provinces in its enormous watershed. Unlike the algae blooms seen by George Huyshe in 1870, modern blooms in Lake Winnipeg are probably larger, more widespread, and more frequent.
A pair of boaters enjoy a day on Killarney Lake in this postcard scene, circa 1908.
Source: Archives of Manitoba, Killarney Lake 15.
We thank all those who helped with sediment core collection and analyses, including Mike Forster, Scott Gadsby, Tom Henderson, Debbie Hysop, Hugh Kiffen, Don Lemmen, Rhonda McDougal, Ryan McGregor, Pauline Morton, Iain Pimlott, Bob Vance, and Maria Zbigniewicz. Financial support was provided by the Manitoba Sustainable Development Innovations Fund, the Town of Killarney, the Rural Municipality of Turtle Mountain, the Geological Survey of Canada Palliser Triangle Global Change Program, the Brandon University Research Committee, and the Natural Sciences and Engineering Research Council of Canada.
1. Garland, A. Trails and Crossroads to Killarney. The Killarney and District Historical Committee, p. 5, 1967.
2. Huyshe, G. L. 1871. The Red River Expedition. Macmillan and Co., New York, p. 162.
3. Ritchie, J. C. “Absolute pollen frequencies and carbon-14 age of a section of Holocene lake sediment from the Riding Mountain area of Manitoba.” Canadian Journal of Botany 47:1345-1349, 1969.
4. Ritchie, J. C. “The late-Quaternary vegetational history of the Western Interior of Canada.” Canadian Journal of Botany 54:1793-1818, 1976.
5. Ritchie, J. C. and Lichti-Federovich, S. “Holocene pollen assemblages from the Tiger Hills, Manitoba.” Canadian Journal of Earth Sciences 5:873-880, 1968.
6. A sediment core was collected using a percussion-type corer deployed through winter ice at a site in the deepest part of the lake basin. A plastic pipe was pounded as deeply in the lake bottom as possible, then pulled out with a block-and-tackle pulley system. On return to the laboratory, the pipe was cut lengthwise with a circular saw, then sediment samples were collected at five-centimeter intervals along its length. Sediment organic matter was determined by successively drying and burning the sample at high temperature and measuring the loss of mass. Total phosphorus was determined by burning sediment samples to mineralize organic matter, then boiling the residue in acid, after which chemicals were added which reacted with phosphorus to produce a blue color. Its intensity was measured and converted to an equivalent phosphorus concentration by comparison with standards. Plant pigments in wet sediment samples were extracted in alcohol and, like the method for phosphorus, the green color intensity was used to calculated the chlorophyll concentration in the sample. Diatoms in core samples were separated from the sediment matrix using a series of water washings, then examined and counted with a microscope. Bulk sediment samples were collected at three positions in the core for radiocarbon dating. Analyses were performed at the Alberta Environmental Centre at Vegreville. These dates were used to interpolate sediment ages for other sediment layers.
7. Teller, J. T., and Last, W. M. “Pedogenic zones in postglacial sediment of Lake Manitoba, Canada.” Earth Surface Processes and Landforms 7:367-379, 1982.
8. This conclusion is based on our finding – not reported here – that levels of two pigments found in cyanobacteria but not other algae – myxoxanthophyll and oscillaxanthin – were also higher during this period. For further details, see Richmond, K-A. “The paleolimnology of Killarney Lake, Manitoba.” Master of Science thesis, University of Manitoba, 1997.
10. Last, W. M., and Schweyen, T. H. “Late Holocene history of Waldsea Lake, Saskatchewan, Canada.” Quaternary Research 24:219-234, 1985.
11. Vance, R. E., Clague, J. J., and Mathewes, R. W. “Holocene paleohydrology of a hypersaline lake in southeastern Alberta.” Journal of Paleolimnology 8:103-120, 1993.
12. Laird, K. R., Fritz, C. S., Grimm, E. C., and Mueller, P. G. “Century-scale paleoclimatic reconstruction from Moon Lake, a closed-basin lake in the northern Great Plains.” Limnology and Oceanography 41:890-902, 1996.
14. Vance, Clague, and Mathewes, 1993.
15. Vance, R. E., Last, W. M., and Smith, A. J. “Hydrologic and climatic implications of a multidisciplinary study of late Holocene sediment from Kenosee Lake, southeastern Saskatchewan, Canada.” Journal of Paleolimnology 18:365-393, 1997.
16. Vance, Clague, and Mathewes, 1993.
17. Last, W. M., and Slezak, L. A. “Paleohydrology, sedimentology, and geochemistry of two meromictic saline lakes in southern Saskatchewan.” Geographische Physique et Quaternaire 60:5-15, 1986.
18. Laird, Fritz, Grimm, and Mueller, 1996.
19. Vance, Clague, and Mathewes, 1993.
20. Wilson, S. E., Smol, J. P., and Sauchyn, D. J. “A Holocene paleosalinity diatom record from southwestern Saskatchewan, Canada: Harris Lake revisited.” Journal of Paleolimnology 17:23-31, 1997.
21. Hickman, M., and Schweger, C. E. “Oscillaxanthin and myxoxanthophyll in two cores from Lake Wabamun, Alberta, Canada.” Journal of Paleolimnology 5:127-137, 1991.
22. To illustrate the extent of copper contamination of Killarney Lake, between 1974 and 1993, municipal officials added 76,840 kilograms (85 tons) of copper to the lake, most of which did nothing to suppress algae blooms because, being added mostly in granular form, it quickly sank to the bottom. Our unpublished measurements of copper in surface sediments from Killarney Lake are over 900 μg/g compared to less than 20 μg/g in nearby Pelican Lake.
Page revised: 29 April 2017
