Restoring Stream Base Flow in an Urban Stream

1
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
The Ecological Engineering Group Biological and
Agricultural Engineering University of Arkansas
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

7
The Matlock Periphytometer

• In the field

8
Target PO4-P Level
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

• 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
Results

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

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