Changes in Algal Trends and Nutrient Budgets in Arctic Tundra Ponds Over the Past 40 Years in Barrow, Alaska

In the 1970’s, Barrow, Alaska was host to a detailed ecological study, the International Biological Program (IBP), which examined physical, chemical and biological characteristics of Arctic tundra ponds. Forty years later, this area has experienced warming and potential release of nutrients from permafrost; however, there have been no follow up studies since the 1970’s and biological changes in these ponds remain unknown.  The 1970’s IBP research suggested that algae had warmer temperature optima than ambient temperatures and that phosphorus was the limiting nutrient.  The goal of this study was to understand algal growth trends during the 2010 growing season, the role of limiting nutrients, and how both these have changed through time in light of shifting climate regimes. Algae was collected and quantified weekly from periphyton (algae attached to sediment) and phytoplankton (free floating algae) from several IBP ponds over the summer of 2010. Nutrient addition and release experiments with known quantities of nitrogen (N) and phosphorus (P) were utilized to determine algal nutrient limitation. Algal biomass was significantly greater in 2010 than in the 1970s.  Nutrient addition experiment showed a shift from phosphorus limitation in the 1970s to nitrogen limitation of periphyton in 2010, while phytoplankton was co-limited by nitrogen and phosphorus in 2010. These preliminary results indicate substantial changes have occurred over the past 40 years. Further studies are being completed in summer 2010 to understand inter-annual variability in these trends and to reveal their implications in algal production and nutrient budgets in the Arctic.