Chlorophyll a in the lowerCape Fear Estuary

Leilani McMillanThe 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

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)

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)

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)

• 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/farabee/BIOBK/BioBookPS.html (accessed on November 22, 2010)