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The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic quantum efficiency (PQE) in the western English Channel Jim Aiken 1 , James Fishwick 1 , Gerald Moore 1 and Katharine Pemberton 2 1 Plymouth Marine Laboratory, Plymouth, Devon, U.K. 2 now at UWAEG, Dept. Biology, University of Waterloo, Ontario, CANADA MAG workshop, Villefranche, Mar 2004

The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

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Page 1: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic quantum efficiency (PQE) in the western English Channel

Jim Aiken1, James Fishwick1, Gerald Moore1

and Katharine Pemberton2

1Plymouth Marine Laboratory, Plymouth, Devon, U.K.2now at UWAEG, Dept. Biology, University of Waterloo, Ontario, CANADA

MAG workshop, Villefranche, Mar 2004

Page 2: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Main objective:To monitor the variation and co-variation of pigments, carbon, phytoplankton absorption and photosynthetic quantum efficiency (PQE) over a seasonal cycle.

Prior knowledge driving the study:• Preferential Chla synthesis in healthy algae and vice versa.

• Ratio of optical absorption of phytoplankton extracts atdifferent wavelengths reflects pigment concentrations and the “health” ofcells:

- 430/665nm (Tpig/Chla) – increased at low nutrients - Margalef, 1967 - 480/665nm (red to blue, Car.:Chla) – increased as cells aged -Jeffrey &

Hallegraeff, 1980 and Heath et al., 1990.• Co-variance of a480/a665 and Cph/Chla – low in “healthy cells” –

Heath et al., 1990.

• This study: a674/a443 and a674/a490• Link to an indicator of photosynthetic quantum efficiency.

Page 3: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Overview of presentation• Introduce the study site

• Methods and materials

• Overview of seasonal variation at the site

• Relationships between:• PAR and other parameters• PQE, pigments and pigment ratios• Absorption ratios, pigments and PQEm• Phytoplankton carbon pigments and PQEm

• SummaryReference for this work: Jim Aiken, James Fishwick, Gerald Moore and Katharine Pemberton (2004) The annual cycle of phytoplankton photosynthetic quantum efficiency, pigment composition and optical properties in the western English Channel. J. Mar. Biol. Ass, U.K. 84: 1-13.

Page 4: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Case study - the siteStation ‘L4’

• Weekly sampling in 2001 (n = 44)

• 10 km off the coast of Plymouth in the Western English Channel

• 51m depth• Seasonally stratified• Succession of blooms

from Mar to Sep

L4

(50º15’N,

4º13’W)

Page 5: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Methods 1. Parameters measured:

• Photosynthetic quantum efficiency (PQE) – FRRF• CTD measurements• Optical profilers in 7 wavebands• HPLC analysis for pigments (surface)• Nutrient analysis (surface)• Phytoplankton particle absorption spectra (surface)• Phytoplankton species counts – converted to carbonusing formulae of Strathmann (1967). (surface)

Page 6: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Methods 2. Calculation of phytoplankton photosynthetic quantum efficiency (PQE)

PQE’ = Fv’ / Fm’

where Fv’ = Fm’ – F0’

- Reflects the efficiency of photosystem II in the light adapted state. - FRRF Dark chamber 0.2 to 1.0s flushing time allow relaxation ofphotochemical but not non-photochemical quenching.

Page 7: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Methods 3. Derivation of daily values of PQEma) Typical FRRF profiles during “non-stratified” part of year

PAR (µmol photons m-2 s-1)

1 10 100

1000

Dep

th (m

)

0

10

20

30

Temp (C)

10.2 10.4 10.6 10.8

PARTemp

Fm

0.6 0.8 1.0 1.2

FmLFmD

PQE

0.2 0.3 0.4 0.5

Temp (C)

10.2 10.4 10.6 10.8

PQELPQEDTemp

•PQE used was subsurface value where constant value had been obtained and L and D chamber values converged.

Page 8: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Methods 3b. Derivation of daily values of PQEmb) Typical FRRF profiles during summer stratification

PAR (µmol photons m-2s-1)

1 10 100

1000

1000

0

Dep

th (m

)

0

10

20

30

40

50

60

Temp (C)

10 12 14 16

PARTemp

Fm

0 4 8 12

FmLFmD

PQE

0.0 0.2 0.4 0.6

Temp (C)

10 12 14 16

PQELPQEDTemp

•PQE derived for both surface and thermocline layer where possible.•Not possible when quenching extended below surface layer.

Page 9: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Seasonal variation of parameters: Overview

Pigm

ent (

mg

m- 3

)

0

2

4

6

8

10

12

Chla TPig

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Dai

ly P

AR

(µm

ol p

hoto

ns m

-2)

0

10000

20000

30000

µΜ

0

1

2

3

4

5

6PAR Nitrate Phosphate

Nut

rient

s (

)

Page 10: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Pig

men

t con

cent

ratio

n (m

g m

)

Jan Feb Mar Apr May

Pig

men

t con

cent

ratio

n (m

g m

3 )

0

2

4

6

8

10

12Chla Total Pig

Jan Feb Mar Apr May

Sig

maD

0

100

200

300

400

500

600

700

PQ

Em

& C

hla/

Tota

l pig

0.3

0.4

0.5

0.6

0.7

SigmaD PQEm Chla/TPig

Jan Feb Mar Apr May

Tota

l Dai

ly P

AR

(µm

ol p

hoto

ns m

-2)

010

000

2000

030

000

Nut

rient

s (µ

mol

l-1)

0

1

2

3

4

5

6

PAR Nitrate Phosphate

Jan Jun Nov

Chl

a (m

g m

-3)

0

3

6

PAR

030

000

Seasonal variation of parameters:Mid Winter to Spring Bloom (MWSB)

Page 11: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Seasonal variation of parameters:Summer Stratification (SS)

May Jun Jul Aug

Pig

men

t con

cent

ratio

n (m

g m

3 )

0

2

4

6

8

10

12Chla Total Pig

May Jun Jul Aug 0

100

200

300

400

500

600

700

PQ

Em

& C

hla/

Tota

l pig

0.3

0.4

0.5

0.6

0.7

SigmaD PQEm Chla/TPig

May Jun Jul Aug

Tota

l Dai

ly P

AR

(µm

ol p

hoto

ns m

-2)

010

000

2000

030

000

Nut

rient

s (µ

mol

l-1)

0

1

2

3

4

5

6

PAR Nitrate Phosphate

Jan Jun Nov

Chl

a (m

g m

-3)

0

3

6

PAR

030

000

Sig

maD

Page 12: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Seasonal variation of parameters: Autumn bloom to Early Winter (ABEW)

Jan Jun Nov

Chl

a (m

g m

-3)

0

3

6

PAR

030

000

Sep Oct Nov Dec

Pig

men

t con

cent

ratio

n (m

g m

3 )

0

2

4

6

8

10

12Chla Total Pig

Sep Oct Nov Dec

Sig

maD

0

100

200

300

400

500

600

700

PQ

Em

& C

hla/

Tota

l pig

0.3

0.4

0.5

0.6

0.7

SigmaD PQEm Chla/TPig

Sep Oct Nov Dec

Tota

l Dai

ly P

AR

(µm

ol p

hoto

ns m

-2)

010

000

2000

030

000

Nut

rient

s (µ

mol

l-1)

0

1

2

3

4

5

6

PAR Nitrate Phosphate

Page 13: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Relationship with PAR – Chla/Tpig

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Chl

a/Tp

ig

0.40

0.45

0.50

0.55

0.60

0.65

0.70

Dai

ly P

AR

(µm

ol p

hoto

ns m

-2)

010

000

2000

030

000

Chla/TPig PAR

MWSB ABEW

Significant relationship between - 4 day PAR and Chla/Tpig for MWSB (R2 = 0.96)- 1 day PAR and Chla/Tpig for ABEW (R2 = 0.83)

Page 14: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Relationship with PAR – a674/a443

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

a674

/a44

3

0.0

0.2

0.4

0.6

0.8

1.0

Dai

ly P

AR

(µm

ol p

hoto

ns m

-2)

010

000

2000

030

000

a674/a443 PAR

MWSB ABEW

Significant relationship between - 4 day PAR and a674/a443 for MWSB (R2 = 0.76)- 4 day PAR and a674/a443 for ABEW (R2 = 0.80)

Page 15: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Relationship with PAR – PQEm

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

PQ

Em

0.36

0.38

0.40

0.42

0.44

0.46

0.48

0.50

0.52

0.54

Dai

ly P

AR

(µm

ol p

hoto

ns m

-2)

010

000

2000

030

000

PQEmPAR

MWSB ABEW

Significant relationship between - 1 day PAR and PQEm for MWSB (R2 = 0.90)- 1 day PAR and PQEm for ABEW (R2 = 0.71)

Page 16: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Relationship between pigments and pigment ratios

Pigments throughout 2001

Pigm

ent (

mg

m-3

)

02468

1012

Pigment ratios through 2001

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Chl

a/Tp

ig &

AC

/Tpi

g

0.3

0.4

0.5

0.6

0.7

Chl

a/A

C

0

1

2

3

Chla/Tpig Chla/AC AC/Tpig

Chla Tpig AC

Page 17: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Relationship between pigments and pigment ratiosTpig vs Chla/Tpig

0 2 4 6 8 10 120.4

0.5

0.6

0.7

Tpig vs Chla/AC

TPig (mg m-3)

0 2 4 6 8 10 120.4

0.8

1.2

1.6

2.0

Chla vs Chla/TPig

0 2 4 6 8

Chl

a / T

pig

0.4

0.5

0.6

0.7

Chla vs Chla/AC

Chla (mg m-3)

0 2 4 6 8

Chl

a / A

C

0.4

0.8

1.2

1.6

2.0

TPig (mg m-3)Chla (mg m-3)

Chl

a / T

pig

Chl

a / A

C

R2 = 0.69

R2 = 0.62R2 = 0.68

R2 = 0.62

Page 18: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Relationship between PQEm and Chla or TPig

Tpig vs PQEm

Chla (mg m-2)0 2 4 6 8 10 12

PQ

Em

0.4

0.5

Chla vs PQEm

Chla (mg m-2)0 2 4 6 8

PQEm

0.4

0.5

R2 = 0.78 R2 = 0.81

TPig

Page 19: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Relationship between PQEm and Pigment ratiosAll data

Chla/TPig0.4 0.5 0.6 0.7

PQ

Em

0.35

0.40

0.45

0.50

0.55

Mid Jan - Mid Aug exc. DCM(MWSB & SSur)

Chla/TPig

0.4 0.5 0.6 0.7

PQ

Em

0.35

0.40

0.45

0.50

0.55

Jan - Mid May (MWSB)

Chla/TPig0.4 0.5 0.6 0.7

PQ

Em

0.35

0.40

0.45

0.50

0.55

Sep - Dec (ABEW)

Chla/TPig

0.4 0.5 0.6 0.7

PQ

Em

0.35

0.40

0.45

0.50

0.55

R2 = 0.59 R2 = 0.89

R2 = 0.85 R2 = 0.76

Page 20: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Relationship between absorption ratios and other parameters

• Absorption ratios showed similar patterns to cycles of Chla/Tpig and PQEm• Fewer data and low signal to noise• Ratios low in winter, peaked in spring bloom, fluctuated through summer,peaked again in autumn and declined in winter

250.490.3790.293Lineara674/a443Chla/AC

250.65-0.5962.819Lineara674/a443PQEm

250.52-0.2231.322Lineara674/a443Chla/Tpig

250.63-0.6132.347Lineara674/a443PQEm

250.670.4190.130Loga674/a443Tpig

250.660.4990.115Loga674/a443Chla

NRInterceptSlopeType relationship

Dependent variable

Independent variable

Page 21: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Relationship between phytoplankton carbon (Cph) and other parameters

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Cph

(mg

m-3

)

0

50

100

150

200

250Small phytoplanktonLarge phytoplankton

•Similar pattern to pigments: low in winter, peak in spring, summer andautumn blooms and declining from autumn to winter

•Original phytoplankton data condensed into 2 groups:• small (picoplaknton and flagellates) and •large (coccolithophores, dinoflagellates, diatoms and other).

Page 22: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Relationship between carbon and other parameters:

Carbon (mg m-3)

0 100 200 300

TPig

(mg

m-3

)0

2

4

6

8

10

12

Carbon (mg m-3)

0 100 200 300

Chl

a (m

g m

-3)

0

1

2

3

4

5

6

7

R2 = 0.88 R2 = 0.86

Cph vs Chla Cph vs TPig

• Chla and Tpig significantly correlated to carbon • Outliers occurred when high proportion of flagellates

Page 23: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Relationship between carbon and other parameters:

Chla/TPig0.50 0.55 0.60 0.65

Chl

a/C

ph

0.00

0.01

0.02

0.03

0.04

PQEm0.44 0.46 0.48 0.50 0.52 0.54

Chl

a/C

ph0.00

0.01

0.02

0.03

0.04

0.05

0.06

R2 =0.65 R2 =0.62

Chla/Tpig vs Chla/Cph (Spring to Summer)

PQEm vs Chla/Cph (Spring to Early winter)

• Chla/C and Tpig/C significantly correlated to PQEm outside of periods with high flagellates in the population.

Page 24: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

SummaryChla and Tpig• closely correlated for whole year• correlated to CphChla/TPig • low in winter and higher during blooms• correlated to recent light fluxes, PQEm, optical absorption

ratios and for most of year to Chla/CphOptical absorption ratios• correlated with Chla/Tpig and PQEm

Final notes...•PQEm, Chla/Tpig, Chla/Cph and a674/a443 are greater whenplants are growing actively

• When nutrients sufficient, PQEm, Chla/Tpig and a674/a443are linear functions of light

Page 25: The annual cycle of phytoplankton pigment composition, optical … · 2004. 4. 21. · The annual cycle of phytoplankton pigment composition, optical properties and photosynthetic

Acknowledgements

We’d like to thank the following people for their collaboration:

Ian Joint, Roger Harris,Angel Lopez-Urrutia,Tania Smith,Carole Llewellyn, Denise Cummings, Malcolm Woodward,the crews of RV Squilla and Sepiaand special thanks to Derek Harbour

This work was part funded by the Natural Environment Research Council.