Nutrient limitation and zooplankton grazing in Subarctic ponds

Climate change is expected to have large impacts in northern regions over then next few decades. This may be especially true in subarctic regions where thawing permafrost is expected to result in changes in landscape hydrology and the cycling of nutrients and organic matter.

In an initial effort to understand how aquatic ecosystems in subarctic regions will respond to future climate change, we assessed the bottom-up and top-down control of phytoplankton biomass using nutrient enrichment bioassays and a zooplankton community grazing experiment. Although 38% of lakes’ phytoplankton communities did not respond to N or P additions, the remaining 62% were limited by nitrogen, phosphorus or co-limited by both nutrients. Zooplankton grazing can control phytoplankton biomass; however, the results from the grazing experiment suggest that zooplankton community grazing rates are low (mean of 5.2% grazed per day) compared to average community grazing rates in temperate regions. Overall, the bottom-up and low top-down control on phytoplankton biomass suggests climate change will likely have a large impact on lake productivity in this region.

Project timeline: These projects were completed between 2009-2011 as an undergraduate honours thesis student and summer NSERC student in Shelley Arnott's lab at Queen's University.

Papers: 

Symons, C.C., Arnott, S.E. and Sweetman, J.N.  2012. Nutrient limitation of phytoplankton communities in Subarctic lakes and ponds in Wapusk National Park, Canada. Polar Biology 35: 481-489. PDF

Symons, C.C., Arnott, S.E. and Sweetman, J.N. 2012. Grazing rates of crustacean zooplankton communities on intact phytoplankton communities in Canadian Subarctic lakes. Hydrobiologia 694: 131-141. PDF