Graham, M. D.. University of Regina, grahamma@meena.cc.uregina.ca
Vinebrooke, R. D.. University of Regina, vinebrro@meena.cc.uregina.ca
Leavitt, P. R.. University of Regina, Peter.Leavitt@uregina.ca

 
INFLUENCE OF HERBIVORY AND UV RADIATION ON INTERACTIONS BETWEEN PHYTOPLANKTON AND PERIPHYTON IN A PRAIRIE WETLAND
 
A factorial experiment was used to compare effects of UV radiation (ambient, -UVR) and grazing zooplankton (ambient, 10x) on interactions between attached algae and phytoplankton in wetland enclosures of Last Mountain Lake, Saskatchewan. High performance liquid chromatography and species enumerations were used to quantify changes in algal abundance and community composition. Added zooplankton, but not UVR, reduced phytoplankton biomass three-fold (RM-ANOVA P < 0.0001) and altered community composition (RM-MANOVA P < 0.05) relative to populations in unamended treatments. Phytoplankton were predominately composed of siliceous algae which were substantially reduced by grazers (RM-ANOVA P < 0.00X). In contrast, cryptophytes were inhibited by UVR alone (P < 0.06), whereas chlorophytes and cyanobacteria were unaffected by any treatment. Final periphyton abundance, as pigments or biovolume, increased by >200% (ANOVA P < 0.005) following loss of phytoplankton, and was greatest in +grazer, -UVR treatments. In contrast, species richness of periphyton was greatest in +UVR -grazer trials. Analysis of unamended zooplankton communities demonstrated that UVR suppressed rotifers, but not other zooplankton, by 50%. These analyses suggest that UVR impacts were greatest for small suspended algae and invertebrates, but that grazing by large herbivores may expose benthic flora to high UVR.
 
Day: Monday, Feb. 1
Time: 02:30 - 02:45pm
Location: Sweeney Center
 
Code: SS45MO0230S