Algal Phosphorus Storage During Storm Runoff Events in Streams

Rapid phosphorus (P) fluctuations in streams coupled with the potential for microorganisms to store P as polyphosphate suggests that P pulses during storm runoff are important drivers of stream nutrient dynamics. We used a recently-developed 4’,6-diamidino-2-phenylindole (DAPI)-based approach for quantifying polyphosphates in microbial assemblages to compare the response of stream algae to natural runoff events in a small headwater tributary to Fishing Creek, a larger fifth order section of Fishing Creek near Bloomsburg, PA and in twelve 15 L recirculating stream mesocosms. Increases in polyphosphate storage following P pulses appear to be a function of pulse concentrations and duration with algae in the mid order section displaying substantial increases in polyphosphate concentrations following storm events, while the headwater reach did not display detectable increases. These results were confirmed by two laboratory mesocosm experiments and suggest that under certain conditions P- pulses may significantly affect lotic ecosystem functional processes, such as primary productivity, nutrient spiraling and organic matter processing, which could persist long after the pulse has subsided