A survey of algal productivity and nutrient concentrations across a land-use gradient using pulse-amplitude modulated (PAM) fluorometry as a rapid assessment and measure of ecosystem function on a spatial and temporal scale

Elaine Langone, Gallery Theater

Using pulse amplitude modulated (PAM) fluorometry to measure algal biomass and productivity is becoming more common and has the potential to become a valuable tool in our arsenal for rapidly monitoring the response of potentially bloom-producing algae to nutrient pollution. However, more studies are needed to demonstrate the efficacy of using PAM fluorometry to monitor the response of algae to nutrient pollution in the context environmental variability, especially in stream periphyton. The purpose of this study was to use PAM fluorometry to monitor stream periphyton over a wide range spatial and temporal scales to allow for a large variety of nutrient concentrations and other environmental factors to be included in the sample. We also compared PAM to other methods of assessing nutrient impacts to periphyton and overall ecosystem function. We sampled a site in Fishing Creek, Pennsylvania, over the course of three years, and nineteen other streams over a nutrient gradient in Pennsylvania during the summer of 2017. We used pulseamplitude modulated (PAM) fluorometry and saturating pulses to measure algal photosynthetic capacity and efficiency. We compared these data to water column and mat nutrient concentrations, as well as visual assessment of growth and enzymatic activity. We also compared the relative rate of electron transport (ETR) with ecosystem metabolism to assess how PAM might be used as a measure of ecosystem function. By using both a spatial and temporal scale to compare PAM data with nutrient measurements, we will be able to get a more complete picture of the ability of PAM fluorometry to act as a rapid nutrient and growth assessment and ascertain its role in the overall measure of ecosystem function.