Ellie
E, Prepas Ellie
E, Prepas Professor
Mailing address: Department of Biological Sciences, University
of Alberta,
Edmonton, Alberta, Canada, T6G 2E9
Office Number: Z806 Bio Sciences or G213 Bio Sciences
Email address: e.prepas@biology.ualberta.ca or eprepas@gpu.srv.ualberta.ca
Fax address: (780) 492-9234
Phone Number: (780) 492-3463/3625
Major paper entitled: An historical view of the Canadian petroleum industry
Thesis entitled: An approach to predicting short-term changes in the phosphorus concentration in lake water
Academic Appointments:
Courses Taught:
University of Alberta:
McGill University:
Awards:
Membership in Scientific Societies:
My research objective is to understand factors which control productivity in eutrophic lakes and rivers such as those found in western Canada. As these factors are identified, it may be possible to manipulate them to enhance the recreational and/or fisheries potential of lakes and rivers.
Over the past fourteen years, I have collected data on nitrogen, phosphorus, and chlorophyll concentrations in over 150 lakes in central Alberta. I have shown that phytoplankton productivity in freshwater lakes (TDS < 1000 mg/L) on the prairies is controlled by the nutrient phosphorus. In contrast, high salinity (TDS > 1000 mg/L) has a strong inhibitory influence on lake phytoplankton, particularly when nutrient concentrations are considered. The effect of molybdate to sulfate ratios on phytoplankton biomass in prairie saline lakes is being investigated in conjunction with Dr. B. Howarth (Cornell Univ.) Moreover, when I began here, there was little basis with which to assemble an external nutrient budget (i.e., including terrestrial inputs through channelized and nonchannelized runoff and aeolian loading, and losses through the outflow). At the same time, there was no basis to quantify internal nutrient exchanges, in particular with groundwater flux and transport by various processes back from the bottom sediments. Over the past decade we (including four graduate students) have assembled detailed total phosphorus budgets on over 15 Alberta lakes which include internal inputs. We have shown that internal phosphorus inputs are usually far more significant on an annual basis, than external inputs. These large internal phosphorus inputs, in association with low dissolved oxygen conditions over the bottom sediments, are likely responsible for the unusually high concentrations of potentially noxious cyanobacteria in Alberta lakes. In addition, the ratio of external versus internal inputs in these lakes has a strong influence on the depth to which rooted plants grow. These studies emphasize the need to develop new and affordable technology to control internal phosphorus loading in eutrophic hardwater lakes such as those found on the Canadian prairies.
From 1985-1993, and in conjunction with Drs. T.P. Murphy and P.G. Manning at the National Water Research Institute (Burlington), Drs. P.A. Chambers, J. Culp and R. Robarts at the National Hydrology Research Institute (Saskatoon), and Dr. B. Pinel-Alloul at the Université de Montréal, we have investigated the feasibility of using lime (CaCO3 and Ca[OH]2) as an alternative to CuSO4 for phytoplankton control in eutrophic dugouts and lakes. This programme has involved: up to eight years of study on two hyper-eutrophic lakes (Figure Eight and Halfmoon lakes) near Peace River and Edmonton, respectively, and on over 20 farm dugouts located between Edmonton and Peace River, Alberta, three years of study on five hyper-eutrophic lakes in and about the county of Athabasca, Alberta, and three graduate students based in my laboratory. From 1988-1993, Drs. Murphy, Tonn (University of Alberta), Lawrence (University of British Columbia) and I also began a programme to use pure oxygen to enhance dissolved oxygen concentrations in the hypolimnion of a deep eutrophic prairie lake (north basin, Amisk Lake) and evaluate its impact on the entire ecosystem. This work is now being assembled for publication in The Canadian Journal of Fisheries and Aquatic Sciences as a block of eight papers, and includes papers by three graduate students and one postdoctoral fellow based in my laboratory.
Over the past five years I have worked with Drs. S. Hrudey and C. Holmes (University of Alberta) on the prevalence of toxins associated with cyanobacteria in prairie drinking water supplies. Our team, including three graduate students based in my laboratory, found cyanobacterial toxins in all eutrophic lakes and drinking water dugouts sampled. We documented that certain algicides (such as CuSO4, Reglone) cause release of these deadly toxins into surrounding water whereas chemicals such as lime, which coat the target phytoplankton cells intact, do not. We are now focusing on the impact of these cyanobacterial toxins on invertebrates and fish.
Beginning in 1991 I began to consider the impact of activities in the drainage basin and land management practices on riparian zones and aquatic communities in northern Alberta. At the same time, the world's largest unharvested tracks of boreal mixed-wood forest were being targeted for logging. That focus has resulted in funding for a 5-year (minimally) experimental cooperative program with 10 other research scientists. Studies are now underway to evaluate the impact of varying buffer strip width around lakes, and disturbance intensity in drainage basins, on the ecology of aquatic communities in lakes and streams, and terrestrial communities their immediate drainage basin. In addition, I am the Scientific Leader for the recently awarded Networks Centres of Excellence for Sustainable Forest Management (NCE-SFM), with 108 other scientists from across Canada. The SFM looks at the entire boreal forest and the process of logging from the forest to the finished product, from an ecological, sociological and economical viewpoint.
Dinsmore, P. and E.E. Prepas. (in press a). The impact of hypolimnetic oxygenation on profundal macroinvertebrates in a eutrophic lake in central Alberta. I. Changes in macroinvertebrate abundance and density. Can. J. Fish. Aquat. Sci. (Accepted 1 May 1995, 33 ms pp + 2 tables + 5 figures).
Dinsmore, P. and E.E. Prepas. (in press b). The impact of hypolimnetic oxygenation on profundal macroinvertebrates in a eutrophic lake in central Alberta. II. Changes in Chironomus spp. (Chironomidae) abundance and biomass. Can. J. Fish. Aquat. Sci. (Accepted 1 May 1995, 40 ms pp + 1 table + 10 figures).
Evans, J.C. and E.E. Prepas. (in press). Potential effects of climate change on ion chemistry and phytoplankton communities in prairie saline lakes. Limnol. Oceanogr., Special Climate Change Issue (Accepted 15 May 1995, 27 ms pp + 1 table + 9 figures).
Field, K. and E.E. Prepas. (in press). Increased depth distribution and abundance of pelagic zooplankton during hypolimnetic oxygenation of a eutrophic Alberta lake. Can. J. Fish. Aquat. Sci. (Accepted 15 August 1994, 33 ms pp + 3 tables + 8 figures).
Lam, A.K-Y. and E.E. Prepas. (in press). In-situ evaluation of options for chemical treatment of hepatotoxic cyanobacterial blooms. Can. J. Fish. Aquat. Sci. (Accepted 18 November 1994, 27 ms pp + 3 tables + 7 figures).
Nalewajko, C. and E.E. Prepas. (in press). Responses of phytoplankton photosynthesis and phosphorus kinetics to resuspended sediments in CuSO4-treated ponds. J. Envir. Qual. (Accepted 17 July 1995, 18 ms pp + 6 tables + 4 figures).
Peters, R.H., G. Ball, R. Carignan, P.D.N. Hebert and E.E. Prepas. (in press). An assessment of research in evolution and ecology supported by the Natural Sciences and Engineering Research Council of Canada. Can. J. Fish. Aquat. Sci. (Accepted 14 June 1995, 30 ms pp + 7 tables + 3 figures).
Prepas, E.E., J.M. Burke and T.P. Murphy. (in press a). The effect of five years of hypolimnetic oxygenation on the water quality in Amisk Lake, a hardwater eutrophic lake where annual total phosphorus loading is primarily internal. Can. J. Fish. Aquat. Sci. (Accepted October 1994, 32 ms pp + 1 table + 9 figures).
Prepas, E.E., K.M. Field, T.P. Murphy, W. Johnson and W.M. Tonn. (in press b). Introduction to the Amisk Lake project: oxygenation of a naturally eutrophic lake. Can. J. Fish. Aquat. Sci. (Accepted 15 April 1995, 17 ms pp + 1 table + 1 figure).
Prepas, E.E., A. K-Y. Lam, and A.M. Trimbee. (in press c). Influence of trophic status and water depth on the size structure of the plankton community and total phosphorus pool in hardwater lakes. Can. J. Fish. Aquat. Sci. (Accepted April 1995, 12 ms pp + 3 tables + 6 figures).