Chlorophyll a in the lower Cape Fear Estuary
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Chlorophyll a in the lowerCape Fear Estuary
Leilani McMillanThe University of North Carolina at Wilmington
November 29, 2010
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Chlorophyll a• Chlorophyll
– Green pigment common to photosynthetic cells
– Absorbs all wavelengths of visible light, except green
– Three types: a, b, c• Chlorophyll a
– Photosynthetic pigment present in chloroplast
– R=CH3
– Complex arrangement of alternating single and double bonds in the porphyrin ring are optimal for absorbing light
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Chlorophyll a
• Absorbs energy around wavelengths 430nm and 662nm
• While accessory pigments, absorb what chlorophyll a does not
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Why measure chlorophyll a
• “Estimate” the spatial and temporal variability of planktonic biomass
• Only an “estimate” since abundance of chlorophyll a per cell varies
• Taxonomic distinction is based on distribution between different pigments
• Different pigments help identify types of algae present in sample
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How to measure chlorophyll a
• Fluorescence– Sensitive, cheap, not affected by turbidity– Must use standards, less precise, noisier background
• Absorbance– No standards, all chlorophyll concentrations– Turbidity interference, slower
• Chlorophyll fluoresces around 665nm, excites around 440nm
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How to measure chlorophyll a• Obtain water
samples• Samples were
then filtered• Frozen until
further analysis• Soaked in
acetone for 24 hours
• Fluorescence
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Chlorophyll a
M18 M23 M35 M42 M54 M61 HB0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Cruise 2 (2010)
SurfaceDeep
Station
Chl a
(µg/
L)
M18 M23 M35 M42 M54 M61 HB0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Cruise 1 (2010)
SurfaceDeep
Station
Chl a
(µg/
L)
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Chlorophyll a Surface
M18 M23 M35 M42 M54 M61 HB0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Surface (2010)
SeptemberNovember
Station
Chl a
(µg/
L)
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Chlorophyll a Deep
M18 M23 M35 M42 M54 M61 HB0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Deep (2010)
SeptemberNovember
Station
Chl a
(µg/
L)
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• Comparing 2010 results to class average over the past 5 years• Increase of Chl a
surface on cruise 1, but decrease on cruise 2
• Increase of Chl a deep on both cruise 1 and 2
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Other affects of chlorophyll a in the Cape Fear?
• Light attenuation (Kd)
• Salinity
• Turbidity
• DOC
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Light Attenuation• Chlorophyll
concentration higher when Kd was low
• Kd increases, chlorophyll concentration decreases
• Higher Kd value, less light, low chlorophyll concentration
• Cruise 1 exhibited higher concentrations of chlorophyll
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Light Attenuation• Chlorophyll decreases
as Kd value increases
• Less light available for photosynthesis
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Salinity• Salinity has little
significance on chlorophyll concentration• Linear correlation• Salinity increase,
chlorophyll concentration increased
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Turbidity• Turbidity has little
effect on the chlorophyll a concentration
• Increase in turbidity, there is a decrease in chlorophyll a concentration
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Turbidity• Cruise 1
• Turbidity increases, resulting in a decrease in chl a
• Cruise 2• Little effect with
presence of turbidity
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DOC• Presence in surface
water samples causes decrease in chlorophyll concentration
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DOC• The presence of DOC
on cruise one seems to be affect Chl a concentration• DOC increase led
to a decline in Chl a • Cruise two had no
significant effects from DOC
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Conclusion
• Chlorophyll concentration was much higher in September compared to November
• More light available results in production of chlorophyll
• Increase in chlorophyll due to clearer water, when there was an increase in salinity
• Presence of turbidity and DOC, tends to reduce chlorophyll concentration
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References
• Dr. Robert Kieber lecture notes• http://
www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html (accessed on November 22, 2010)