An experiment to examine the effects of nutrient enrichment and warming on Arctic tundra pond communities

Background/Question/Methods

With warming in the Arctic, more nutrients are being released from thawing permafrost into Arctic aquatic ecosystems. The impact of these changes on aquatic food webs is largely unknown.  Zooplankton are abundant in Arctic tundra ponds, and recent studies have indicated that these communities are changing as ponds warm and become more nutrient rich. This study was done to examine the effects of nutrient enrichment and warming on algal community structure and consequently on the Daphnia reproduction. Daphnia pulex, an organism commonly found in the Arctic, and generally used to determine the quality of water for living organisms, was grown in arctic algae cultures enriched with either phosphorus (P), nitrogen (N) or NP.  We measured the reproduction, mortality, and growth rates of Daphnia, as well as the gross taxonomic algal composition. A similar experiment would be completed under different warming scenarios. We hypothesized that nutrient enrichment and warming would produce a cascading effect on aquatic organisms.

Results/Conclusions

Preliminary results indicate an increase algal productivity and changes in algal composition in P and NP treatments beginning within the first week of the trial and that continued to escalate throughout the experiment. These outcomes suggested that phosphorus is a limiting factor for algal growth. D. pulex also showed increased growth and reproduction in these same treatments. These results support field observations where increased nutrient levels and algal biomass in Arctic tundra ponds lead to changes at higher trophic levels.