Chlorophyll a in the lower
Cape Fear Estuary
Leilani McMillan
The University of North Carolina at
Wilmington
November 29, 2010
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
Chlorophyll a
• Absorbs energy around
wavelengths 430nm
and 662nm
• While accessory
pigments, absorb what
chlorophyll a does not
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
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
How to measure
chlorophyll a
• Obtain water
samples
• Samples were
then filtered
• Frozen until
further analysis
• Soaked in
acetone for 24
hours
• Fluorescence
Chlorophyll a
Cruise 2 (2010)
7.0
7.0
6.0
6.0
5.0
5.0
4.0
Surface
3.0
Deep
Chl a (µg/L)
Chl a (µg/L)
Cruise 1 (2010)
4.0
Surface
3.0
2.0
2.0
1.0
1.0
0.0
Deep
0.0
M18 M23 M35 M42 M54 M61
Station
HB
M18 M23 M35 M42 M54 M61
Station
HB
Chlorophyll a Surface
Surface (2010)
7.0
Chl a (µg/L)
6.0
5.0
4.0
September
3.0
November
2.0
1.0
0.0
M18
M23
M35
M42 M54
Station
M61
HB
Chlorophyll a Deep
Deep (2010)
7.0
Chl a (µg/L)
6.0
5.0
4.0
September
3.0
November
2.0
1.0
0.0
M18
M23
M35
M42 M54
Station
M61
HB
• 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
Other affects of chlorophyll a in the Cape Fear?
• Light attenuation (Kd)
• Salinity
• Turbidity
• DOC
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
Light Attenuation
• Chlorophyll decreases
as Kd value increases
• Less light available for
photosynthesis
Salinity
• Salinity has little
significance on
chlorophyll
concentration
•
•
Linear correlation
Salinity increase,
chlorophyll
concentration
increased
Turbidity
• Turbidity has little
effect on the
chlorophyll a
concentration
• Increase in turbidity,
there is a decrease
in chlorophyll a
concentration
Turbidity
• Cruise 1
• Turbidity
increases,
resulting in a
decrease in chl a
• Cruise 2
• Little effect with
presence of
turbidity
DOC
• Presence in surface
water samples causes
decrease in
chlorophyll
concentration
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
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
References
• Dr. Robert Kieber lecture notes
• http://www.emc.maricopa.edu/faculty/farabe
e/BIOBK/BioBookPS.html (accessed on
November 22, 2010)