Fire affects on lake ecosystems: Water Chemistry and Zooplankton Community Structure Stephen J. Nikolai 1, Randall Kolka 2, Trent Wickman 2 and Todd Wellnitz 1,3 1. University of Wisconsin –Eau Claire 2. U.S. Forest Service 3. Faculty Advisor Introduction Lakes are dependent on their catchments for nutrients. Catchment forest fires can increase lake nutrient concentrations and algal biomass. We predicted that these alterations to lake water chemistry and algae would alter the zooplankton community. Hypothesis: Increases in nutrients after a fire will cause a shift in zooplankton community composition. Methods The Ham Lake Fire of 2007 burned Lake Everett’s 900 acre catchment. From nutrients and zooplankton were collected from the lake. Nutrients were sampled 1 m below the surface and analyzed for Total Phosphorus, Total Nitrogen and Total Organic Carbon. Zooplankton were sampled 1 m above the lake bottom and identified to species Pictures of the burned lake (Everett) one year before (2006) and one year after (2008) the Ham Lake Fire of Map of the 2007 Ham Lake fire (Burnt Orange) and the 2006 Cavity Lake fire (Gold). Dashed Line Denotes the Gunflint Trail. Red dots are the beginning locations of the respective fires Microcylops spp mm mm 36%-50% of counts in 2006 Group (Adult.Cyclopoids) Bosmina longirostris ~ 0.5 mm Group (Bosminids) Daphnia mendotae 1.3 mm mm Group (Daphnia) Mesocyclops edax 1.0 mm – 1.7 mm Group (Adult.Cyclopoids) Daphnia mendotae 1.3 mm mm Group (Daphnia) Diaptomous oregonensis 1.2 mm – 1.4 mm Group (Adult.Calanoids) Bosmina longirostris ~ 0.5 mm Group (Bosminids) Microcylops spp mm mm Group (Adult.Cyclopoids ) Dominant Species Pre-Fire Post-Fire Figure 1. NMDS of zooplankton species (in red) and sample date (black) (Stress=10.43). Ellipses (green) represent the 95% confidence interval of the average community for a given year. Arrows (blue) are labeled with significant explanatory environmental variables (p<0.05) and the direction of arrow denotes increasing value of the variable. Variables: Total Organic Carbon (TOC), Carbon/Phosphorus ratio (C.P), Nitrogen/Phosphorus ration (N.P), Water Level (WL.above), Year (Year), Month (Month). Figure 2. NMDS of zooplankton groups (in red) and sample date (black) (Stress=10.38). Ellipses (red) represent the 95% confidence interval of the average community for a given year. Arrows (blue) are labeled with significant explanatory environmental variables (p<0.05) and the direction of the arrow denotes increasing value of the variable. Variables: Total Phosphorus (TP), Total Organic Carbon (TOC), Carbon/Phosphorus ratio (C.P), Nitrogen/Phosphorus ratio (N.P), Water Level (WL. above), Year (Year). Conclusions Before the forest fire, species composition was dominated by small species (Microcylops spp. and Bosmina longirostris). After the fire, the community shifted to larger species (Daphnia mendotae and Skistodiaptomus oregonensis) Past research has shown that Daphnia, Cladoceran, and Bosmina species tend to be phosphorus-limited and Cyclopoid species tend to flourish in high nitrogen conditions. The change in the environmental stoichiometry may be the driver of the observed shift. In the case of Everett Lake, our data suggest that increased nutrients after a forest fire will alter zooplankton community, species rank, and size distribution. To fully test this hypothesis, a large scale replicated experiment must be conducted. Importance Since the 1970’s, the area of boreal forest burned annually by wildfires has doubled. With longer and warmer summers predicted as a consequence of global climate change, this trend will likely continue. As consumers of algae and food for fish, shifts in zooplankton community composition have the potential to profoundly affect lake ecosystems and the organisms they contain. Excellence. Our Measure. Our Motto. Our Goal (Left to Right) Stephen Nikolai conducting a plankton tow, taking a water sample, ands portaging a canoe. Acknowledgements I would first like to thank ORSP and differential tuition for the funding. My four years of undergraduate research would not have been possible if these programs were not available. Second, I would like to thank the U.S. Forest Service for their support, field experience and access to data. Finally, I would also like to thank Dr. Todd Wellnitz. For the past three years Todd has been my mentor and coach for this project. Without his time and guidance, I would not have developed into the young scientist I am today.