1. The Ecological Engineering Group Biological and Agricultural Engineering University of Arkansas Algal Growth with Nutrient Limitation Compared to Light-Limiting Conditions in Ozark Streams Andrea Ludwig Marty Matlock, PhD, PE, CSE Brian Haggard, PhD Bob Morgan, PE

2. EPA use attainability study

3. Research Goals Identify a nutrient, periphytic chlorophyll-a relationship in Ozark streams Investigate circumstances of light- limitation to native algae Predict response of algal growth to differentiating canopy covers in the presence of variable nutrients

4. Methodology Matlock periphytometers deployed at all sites Chlorophyll-a used as indicator of abundance of algae Chlorophyll-a analysis done using trichromatic methods Grab samples collected at each site and analyzed for nutrient concentrations Light meters attached to Matlock periphytometers at selected sites Site Selection Coupled sites according to locations of WWTPs

5. Site Selection

6. The Matlock Periphytometer Assembly NutrientSolution Lid w/ hole Glass fiber filter 0.45  m Nylon Membrane 1 liter bottle Nutrient Solution Nutrients passively diffuse through nylon membrane and GFF Flow

7. The Matlock Periphytometer In the field

8. Target PO 4 -P Level 0 25 50 75 Annual - average PO 4 -P (ppb) Annual - average chl a (ug/L) 0 100 200 300400 500

9. Methodology 2-day and 14-day deployments of light meters Sites chosen with comparison of light availability as single variable Canopy cover used as indicator

10. Methodology Hardware HOBO Micro Station Sensed temperature and photosynthetic active radiation (PAR) Reading every 5 sec Logged every 10 min Software BoxcarPro

11. Results Phosphorous concentrations only account for 7% of variability of chlorophyll-a across sites

12. Results Site Avg Temp C Avg PAR uE Chlr a ug/cm2 OSG030 16.2294.00.43 SPG931UP 16.4133.10.06 SPG931UP 16.649.80.16 SPG931DN 21.230.31.88 OSG930UP 15.996.20.11 OSG930DN 17.5468.20.11 OSG045UP 17.8343.11.47 OSG045DN 17.468.90.31 Two-day deployments of light meters provided inaccurate representation of average light availability to periphytometer

13. Results 2-day deployments failed to give good representation of light conditions at sites 14-day deployments logged definite diurnal cycles and more data points

14. Due to time restrictions, only one round of 14-day deployments were completed Results

15. Summary Nutrient concentrations do affect algal growth However, when nutrients are high and light is low, algal growth becomes light limited at very low production levels Riparian zone management is critical for protecting nutrient enriched streams

16. Future Work / Improvements Additional study of nutrient-limited situations in Ozark streams Removing any variability of nutrients in sites Deployment of light meters and Matlock periphytometers at same site with different canopy covers Defining a relationship of chlorophyll-a and nutrient concentrations with a second variable of light Multiple light meter couples at sites with multiple nutrient and canopy characteristics

17. Acknowledgements Eric Cummings Brian Schaffer Matt Bruton Debrata Sahoo Sujit Ekka Kyle Kruger