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Coagulation Efficiency of Phytoplankton Cells During Different Growth Stages
and Its Relationship to Exopolymer
Particle Properties
*Jenni Szlosek1,2, Anja Engel2, Cindy Lee1, Robert Armstrong1
1Marine Sciences Research Center, Stony Brook University, Stony Brook, NY USA
2Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
Approach:• Compare effect of TEP number vs. exopolymer chemical
quality on • Limit variability in due to experimental set-up• Compare results for diatoms vs. coccolithophores
increases with drop in phytoplankton growth rate
• Increase in TEP abundance leads to increased • No indication that differences in dissolved
polysaccharide composition with growth affects
• Phytoplankton aggregation is an important mechanism for the export of organic carbon
• Exopolymer particles such as TEP may play an important role in the coagulation efficiency of cells
• The value of used in aggregation calculations may not always represent the “real” value of the system.
Goal:
Understand the role exopolymer particle abundance and exopolymer chemical composition plays in enhancing phytoplankton aggregation.
Introduction
Drapeau et al., 1994
photo of Couette flow deviceschematic of Couette flow device
Coagulation Efficiency
=Qln(∑C(t))
time sampled
slope=Q
1
7.82Gm
ln Ct C0 t
What affects
…?
Known:• Gm, mean shear• Constants describing physics: 7.82, πUncertain:• , volume fraction TEP contribution• Chemical quality of exopolymers as cell coatings and transparent particles
# of particlesunit volume
Ci =
after Kiørboe et al., 1990:
Experimental Set Up
Emiliania huxleyi grown as chemostat cultures
• Grown at 15˚C in enriched media:
50 µM N 3 µM Pf/2 trace metals and vitamins
• Steady-state growth reached for turnover times of:
0.48, 0.25, 0.1, 0.05 d-1
• Cell exponential growth rates equaled turnover times
R2 =
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
00.20.40.6
Coagulation Efficiency
• No indication of coagulation at highest growth rate (0.48 d-1)
• The magnitude of the slope (Q) increases with decreasing exponential growth rate
• Alpha increases with decreasing exponential growth rate
1
7.82Gm
ln Ct C0 t
=Q
Alpha with Growth Stage
Exponential Growth Rate (d-1)
alpha
TEP Abundance
• Increase in TEP with decrease in growth stage
• Correlation between TEP abundance and yields an R2 of 0.85
0
500
1000
1500
2000
2500
3000
00.20.40.6
E. hux TEP with Growth Stage
Alpha with Growth Stage
Exponential Growth Rate (d-1)
Exponential Growth Rate (d-1)
TEP conc. (µg Xanthan Gum L-1)
alpha
direction of “bloom” progression
R2 =
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
00.20.40.6
Dissolved Aldose Composition
• Decrease in Mol% Glucose with decreasing exponential growth rate
• Sugars found in coccoliths of E. huxleyi present in nearly constant amounts throughout growth stages
• Effect of changes in dissolved sugar composition on requires further work
0%
20%
40%
60%
80%
100%
0.48 0.25 0.1 0.05
Mol %
GluA
GalA
Man + Xyl
Fuc
Ara
Rha
Gal
Gluc
Exponential Growth Rate (d-1)
Exponential Growth Rate (d-1)
0%
20%
40%
60%
80%
100%
0.48 0.25 0.1 0.05
Mol %
(exclu
din
g G
luc)
GluA
GalA
Man + Xyl
Fuc
Ara
Rha
Gal
R2 = 0.9056
R2 = 0.8524
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 500 1000 1500 2000 2500
Diatoms vs. Coccolithophores
Thalassiosira weissflogii (batch culture)
Emiliania huxleyi (chemostat culture)
TEP concentration (µg Xanthan Gum L-1)
Conclusions
• Attachment probability, , increases with decreasing exponential growth rate (progression of “bloom”)
correlates with TEP abundance as expected
• Possible importance of DOM chemical composition on attachment probability of cells is undetermined
• Chemostat culturing is a useful technique to reduce the experimental variability of
Acknowledgements
• Nicole Händel, AWI• Umesh Gangeshetti, AWI• Stephanie Koch, AWI
