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Simulating multiple functional groups ofphytoplankton in Cannonsville Reservoir
Hampus Markensten1, Don Pierson2, Emmet M. Owens1, Susan M.O'Donnell1 and Steven W. Effler1.
Email: hm@upstatefreshwater.org
1) Upstate Freshwater Institute
Syracuse, USA
2) Department of Environmental Protection (DEP)
NYC, USA
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Cannonsville reservoir
•Second largest reservoir serving New York City withdrinking water.
•Mesotrophic with a retention time of 2.6 years and astorage capacity of 373*106 m3 of water (98.5 billiongallons).
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•In the past Cannonsville experienced high averagechlorophyll concentrations and frequentphytoplankton blooms.
•Cyanobacteria often dominate in summer and autumne.g. Aphanizomenon, Anabaena and Microcystis.
•A one dimensional (1D) lake model that simulatestemperature, hydrodynamics, nutrient dynamics andtotal phytoplankton biomass has previously beendeveloped by the Upstate Freshwater Institute (UFI)(Doerr et al, 1998) and applied to the reservoir.
Background
DOERR, S.M., E.M. OWENS, R.K. GELDA, M.T. AUER & S.W. EFFLER. 1998. Development and testing of a
nutrient-phytoplankton model for Cannonsville Reservoir. Lake and Reservoir Management 14.: 301-321.
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Overview of UFI 1D reservoir water quality model
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•A need to predict the occurrence of bloomforming phytoplankton.
•Solution: Merge the existing 1D reservoirwater quality model, which includes a gooddescription of hydrodynamic and chemistry,with a model focused on the dynamics ofphytoplankton groups.
•Compare the model performance before andafter merging the two models.
Objectives
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•PROTECH (phytoplankton response to environmentalchange) is a model developed by Colin Reynolds in UKthat focuses on the phytoplankton biology.
•Phytoplankton can respond to changes in nutrient, lightand temperature by vertical movements to reach themost favorable depth.
•Phytoplankton growth rates are calculated from size andvolume relationships that affect nutrient uptake lightharvesting and temperature dependence.
•Eight different functional groups of phytoplankton aresimulated that differ in their surface area/volume,capability to fix nitrogen, use silica and regulate theirbuoyancy
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Size and Shape Influences
•Growth
•Temperature adaptation
•Light absorption
•Grazing
•Passive movement (up or down)
•Nutrient uptake not explicitlyaffected
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What is different in PROTECH?
•Morphological relationships describe growth: r20
Reynolds (1989)
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(Reynolds in Sommer 1989)
Temperature-sensitivity of growth rate (rθ) as afunction of s/vTemperature-sensitivity of growth rate (rθ) as afunction of s/v
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(Reynolds in Sommer 1989)
Light effect on phytoplankton growth
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Overview of the hybrid 1D model including
phytoplankton functional groups
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Feature
UFI ver 4.1
UFI PROTECH hybrid
Representationof phyto-plankton
Carbon-based; constantstoichiometry; single(lumped) algae class
Carbon-based; constant stoichiometry;multiple (eight) algae classes(PROTECH)
Nutrients
N, P.
N, P, Si.
Zooplankton
Specified frommeasurements.
Modeled.
SuspendedSolids
FSS; VSS=Detritus + Algalmaterial.
VSS=Detritus + Algal material.
PhytoplanktonSettling
Always downward atspecified rate.
Some phytoplankton may move up ordown.
Resuspension
Wave-driven resuspension inlittoral areas; flux computedfrom critical stressrelationship.
Complete resuspension of depositedalgal particulates (Algal C) in mixedlayer
Deposition
At rate determined bysettling velocity.
Below mixed layer: determined bysettling velocity.
In mixed layer: no deposition.
SedimentRelease,Diagenesis
Specified release rate of SRP(via TRP) and NH3; notransformation of depositedorganic material.
Release of SRP, NH3 and Si fromphytoplankton at same rate as in thewater column (respiration).
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Phytoplankton Functional Groups
•Large Filamentous diatoms - Aulacoseira
•Small diatoms – Stephanodiscus
•Small Flagellates – Cryptomonas Rhodomonas
•Large Flagellates - Ceratium
•Large non N fixing cyanobacteria - Microcystis
•Large N fixing cyanobacteria - Anabaena Aphanizomenon
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Expectations
•To simulate realistic seasonal patterns of chlorophylland functional group biomass.
•To simulate inter annual variations in phytoplanktonbiomass
•The phytoplankton model was not tuned to localconditions – Alometric coefficients influencingphytoplankton growth are those given by Reynolds.
•Minimal tuning of the sub-models describinghydrodynamics and nutrient kinetics.
Model Calibration
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Measured
PROTECH
Results
Comparison of Measured and Modeled Data 1998
Hydrothermal Model
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UFI 1D
PROTECH-
hybrid1D
Measured
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Comparing hybrid model results with measurements
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Comparing hybrid model results with measurements
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•Both models perform well in predicting chlorophyllon an annual scale, and also realistically simulatedseasonal patterns in chlorophyll.
•The PROTECH hybrid model successfully simulatedoccurrence of major functional groups in theCannonsville Reservoir.
•The model is a valuable tool for predicting seasonalvariability in chlorophyll and phytoplanktonfunctional groups
•Evaluation of the model using other reservoirs andlonger time series of data is underway.
Conclusions
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Baseline
Delta Change based on ECAM A2 2081-2300
Cannonsville Isopleths 1966 - 1990
Chlorophyll a (mg m-3)
Water Temperature (C)
Chlorophyll a (mg m-3)
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