Investigating Algal Growth in Eutrophic Rivers

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Investigating Algal Growth in Eutrophic Rivers
Streams

• William T. StringfellowSharon E. BorglinJeremy
  S. Hanlon University of the PacificEnvironmenta
  l Engineering Research ProgramStockton, CA

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Outline

• San Joaquin River
• Research Objectives Hypothesis
• San Luis Drain Studies
• Summary Conclusions
• San Joaquin River Studies
• Summary

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San Joaquin River
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Highly Engineered Ecosystem
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Nutrient Rich Ecosystem

• Examples of potential NPS nutrient sources

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Algal Accumulation in SJR

• Algal load contributes to DO impairment
• Low DO barrier to fish migration

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Research Objectives

• Understand describe algal biokinetics (growth
  yield) in eutrophic rivers and streams
• Understand how NPS discharges influence algal
  growth water quality
• Develop scientifically based management
  strategies (best management practices)

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Unlimited Hypothesis

• Algae growth is essentially unlimited
• Nutrients are too high to control
• Algae grow at constant rate down river
• Control algal inoculum

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Limited Hypothesis

• Algae growth is limited
• Algae reach a maximum carrying capacity
• Reducing inoculum ineffective, algae grow back in
  river
• Control limiting factor (nutrients)

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Management Implications

• Which is more important to control?
• Sources of inoculum?
• Sources of nutrients?

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San Luis Drain Study
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San Luis Drain

• Twenty-eight mile channel
• Hydraulically simple
• One input one output
• Conveys agricultural return flow
• Nutrients needed for algal growth
• Warm temperatures sunlight
• Ideal system for algal growth study
• Model as plug-flow reactor

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San Luis Drain Study Area
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San Luis Drain Sampling
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Growth Follows Limited Model
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Biokinetic Variables for Algae in SLDLogistic
Model Results

• Growth yield is limited and growth rate varies
• What is limiting growth?

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Temperature Effects Growth Rate
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Solids Decrease as Algae Increase
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Light Penetration Increases in SLD
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Mineral Nutrient Availability
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Mechanistic Model

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Biokinetic Parameters for Mechanistic Model
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Mechanistic Model
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Direct Measurement of Grazing Population
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SLD Study Results

• Rapid algal growth reaching limits of
  environmental carrying capacity was observed
• Logistic, not exponential
• Algal growth in nutrient rich drainage water is
  not limited by light
• Correlation of limiting factors complicates
  analysis
• Used mechanistic model for data analysis

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SLD Model Results

• Nutrients and grazing are most important
  non-seasonal factors
• Carbonate can be limiting
• Suspended minerals are a source of limiting
  nutrients for algal, independent of phosphates
• Results suggest removal of sediments would limit
  suspended algae growth
• Management based on unlimited model not
  recommended

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San Joaquin River Studies
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Measurements - Grab Sample

• Chlorophyll
• BOD10
• CBOD
• NBOD
• TOC/DOC
• Ammonia nitrogen
• Nitrate nitrogen
• Total nitrogen
• o-Phosphate
• Total phosphate
• Total iron

• Total suspended solids
• Volatile suspended solids
• Alkalinity
• pH
• Turbidity (NTU)
• Incident light
• Dissolved oxygen
• Specific conductivity
• Temperature
• Algae cell counts
• Stable isotopes
• Lipids

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Flow Water Quality Monitoring
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Application of SLD Model to SJR Data
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Apply SLD Lessons to SJR Studies

• Reexamine role of sediments in algal growth
• New emphasis on zooplankton grazing impacts
• Improved measurement of inorganic carbon
• Incorporation of pilot model parameters into
  larger river water quality model
• Conduct algal growth studies between monitoring
  points

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