Assessing phytoplankton growth along Tisza River Hungary

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Assessing phytoplankton growth along Tisza River
(Hungary)
Mark Honti, Vera Istvanovics, Zsolt Kozma
Department of Sanitary and Environmental
Engineering Budapest University of Technology and
Economics
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Study Location River Tisza
Measurement cruise on the Hungarian section
Start / End 703 rkm
Kisköre Dam 403 rkm
Return 167 rkm
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Aim Detection of Growth Zones

• Locations where the net growth rate of
  phytoplankton is systematically positive
• Hypothesized dead or retention zones should
  serve as recruitment sources for phytoplankton
• Must separate in-flow processes from impacts
  bound to a specific location
• Available methods
• Water Parcel Study
• (Simultaneous high frequency monitoring at
  various locations)
• We used a downstream-upstream cruise with high
  freq. monitoring

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High Frequency Phytoplankton Data

• Recorded with a Delayed Fluorescence spectroscope
  (for methodology see Istvanovics Honti)
• Measuring interval 5 min 900 m along river

Upstream cruise
BM mg Chl-a m-3
Downstream cruise
Location rkm
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Assuming Permanent Hydraulics and Concentrations
Upstream
Net growth rate d-1
Position river km
Downstream
Paradox and impossible growth rates unsteady
conditions rule
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Mass Transport in River

• 1D hydraulic model (Kozma Koncsos) velocity
  field (v)
• Transport equation (1D advection-dispersion)
• Exclusion of the longitudinal dispersion (Dx),
  since that assumes the knowledge of a complete
  initial state.

Hydraulic modeling is always required to specify
travel times (even with multiple measurement
sites or a water parcel study).
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Space-Time Diagram
Kisköre dam 403 rkm
Time date
Space river km
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Ship Route
Upstream route
Time date
Downstream route
Space river km
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Useful Water Parcels
Measured 3x
Time date
Measured 2x crosses dam
Space river km
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Estimation of Growth Rate
Biomass change in useful water parcels
BM1 _at_ x1 BM2 _at_ x2
Estimation of Gnet for the covered track
Reduction of errors
E from BM measurement E from hydrodynamic model
Resolution of overlapping estimates
Weighted average
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Reduction of Errors
Dispersion would lower the peaks and rise the
valleys in the concentration curve as water
travels downstream. (Not solved)
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Estimated Growth Rates
Around Kisköre dam
Maros plume
Below Szamos
Gnet d-1
river km
Kisköre dam represents great hydraulic
uncertainty.
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Estimated Growth Rates
Excluding tracks crossing the dam
Maros plume
Below Kisköre dam
Below Szamos
Gnet d-1
river km
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Notes on Growth Rates

• A significant amount of data does not belong to
  useful water parcels (coverage may be weak
  somewhere).
• The resolving algorithm seeks for growth bound to
  specific locations (transient in-flow growth may
  be suppressed).
• The estimations are valid for the covered periods
  only.
• Dispersion was omitted, which may decrease growth
  rates.
• There were only 3 detected growth zones.

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Min/Max Growth Rates
Excluding tracks crossing the dam
Gnet d-1
river km
Temporary in-flow growth almost everywhere
possible.
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Growth Rates and River Morphology
RS -
Sand banks
River sinuosity
Average Gnet d-1, sand banks rkm-1
Avg. Gnet
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Conclusions

• Phytoplankton decayed along the River Tisza in
  July, 2006.
• Dead or retention zones could not
  significantly increase the concentration of
  phytoplankton.
• The few growth zones were located at high
  turbulence sections with complex morphology.
• River cruise coupled with hydraulic modeling is
  useful to estimate the net growth rate of
  phytoplankton.
• But the calculation method is very sensitive to
  the velocity field, the measurement frequency and
  the cruise schedule.