EQAL Manager and Analytical Scientist Department of Biology University of Regina Regina, SK. Canada S4S 0A2 office: (306) 585-4890 fax: (306) 337 2410 email: bjoern.wissel@uregina.ca Cirriculum Vitae

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My current research focuses on food web structure and energy flow in saline Prairie lakes. Using stable isotope technology combined with traditional sampling and experimental techniques, I am concentrating on the following four research goals:
1. quantify landscape patterns of food web variability in response to climate and water chemistry,
2. identify unique effects of salinity relative to other environmental parameters, e.g. nutrients, DOC, morphometry,
3. determine importance of predation regime changes along salinity gradient, and
4. test the potential of prairie lakes as early-warning system for impacts of climate change and hydrologic variability.

Research Projects

Environmental controls of food web structure and energy flow in prairie lakes

Due to an arid climate and endorheic (interior) drainage basins, prairie lakes in the northern plains exhibit a tremendous variability in hydrology and concentration of solvents, e.g., lake waters can vary from fresh to hypersaline (salinity >> ocean water). Despite the paucity of comprehensive saline lake studies in the literature, saline lakes are found on all continents and account for almost half of the total volume of inland surface standing water on Earth. As the onset of osmotic stress varies among trophic levels, the complexity of food webs in saline lakes should be highly variable and more diverse than in freshwater lakes. The suppression of fishes at moderate salinities should successively shift the crucial role of the top-planktivore to a series of less affected invertebrate predators, and depending on their feeding mode, the effects on the plankton community may vary tremendously. Recent work has confirmed that community composition in saline lakes strongly varies with salinity, but suggests that other physical, chemical, and morphometric characteristics exert important influences as well. Consequently, I started a lake survey to quantify landscape patterns of food web variability in response to climate and lake chemistry. In subsequent experiments, I will more specifically evaluate the unique effects of salinity on food web dynamics relative to other key parameters, such as nutrients, dissolved organic carbon (DOC), and lake depth. Based on stable isotope measurements, I will develop mixing models to quantify elemental and nutrient sources and major pathways of energy flow within food webs (e.g. trophic cascade vs. intra-guild predation) of contrasting predation regimes, which will propel our understanding of aquatic food webs beyond what we know from studies in freshwater systems. Finally, global climate change scenarios predict that the Canadian plains (and other regions worldwide) will experience more droughts in the future, and consequently, water shortages will increase. Water-use practices will add additional strain to many already stressed aquatic environments, especially to saline lakes that are known to be sensitive to hydrologic changes. As a result, a better understanding of saline lake dynamics will allow us to forecast impacts of future changes in these systems.

Effects of acid deposition on headwater lakes in northern Saskatchewan

Excessive oil production in tar sands of northern Alberta is generating a large potential for acid deposition (as NOX and SOX) in down-wind areas located in northern Saskatchewan. While previous effects of acidification were well studied for aquatic systems in Europe and eastern Canada, this new threat due to high energy demands is unprecedented for western Canada. Because most lakes that are down-wind from the tar sand production sites have very low alkalinity they are sensitive to acid deposition. Therefore, effects of acidification of these extremely pristine systems are expected to be severe. This initial study is aimed at documenting baseline conditions for water chemistry, sediment biogeochemistry and food web compositions for a large number of control and impact-lakes (n > 150). Subsequently, risk assessment will be performed for lake regions and tested during continuing monitoring.

Food web composition of lakes recovering from acidification

Many lakes in central Ontario were heavily impacted by acidification due to atmospheric depositions originating from mining activities. While most lakes seem to have recovered in respect to physical and chemical parameters, food webs are still impoverished relative to pre-acidification conditions. The species composition and biomass of benthos, zooplankton and fishes can provide energetic bottlenecks in the development of more complex food webs. For example the absence of benthos is suggested to prevent the colonization of lakes with piscivorous fishes, while the dominance of invertebrate predators has the potential to suppress the success of higher trophic levels. To better understand the trophic interactions and potential bottlenecks that might prevent recovery, we combine traditional sampling techniques with stable isotope methodology to study a series of lakes (n = 10) with different degrees of recovery from acidification.