Project Title:  Environmental Controls of Food Web Structure and Energy 
Flow in Saline Prairie Lakes

Project Desciption:  This project will evaluate the unique effects of 
salinity on food web dynamics relative to other key parameters, such as 
nutrients, DOC, and lake depth.  As the onset of osmotic stress varies 
among trophic levels, the complexity of food webs in saline lakes is 
highly variable and more diverse than in freshwater lakes.  The 
suppression of fish 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.  To evaluate the effects 
of salinity on food web composition, water chemistry, algae, zooplankton, 
invertebrate predators, and fish from 21 prairie lakes across a large 
salinity gradient will be collected.  After identification and enumeration 
of the most abundant biota to characterize food web compositions, stable-
isotope-based mixing models will be developed to quantify elemental and 
nutrient sources as well as major pathways of energy flow within food webs 
of contrasting predation regimes.  This project will propel our 
understanding of predator-prey interactions beyond what we know from well-
studied freshwater systems.  Furthermore, 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 forecasting of the 
impacts of future changes in these systems.

Students with an interest in aquatic ecology and stable isotope technology 
are encouraged to apply.  The student is expected to participate in field 
collections and laboratory analyses, including microscopy and stable 
isotope analysis.  Financial support will be provided though a combination 
of research and teaching assistantships.  Starting date of the position is 
negotiable, but will be no later than fall 2006. 


For further information, please contact Björn Wissel at the address below:

Dr. Björn Wissel
EQAL Manager, Faculty of Science; Adjunct Professor, Dept. Biology,
University of Regina;  265.2 Lab Building;  Regina, SK S4S 0A2, Canada
phone: 306 585-4890;  fax: 306 337-2410;  e-mail: [log in to unmask]