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= LHCs. Reminder from last Lecture. The structure/function of Chl a -dominated PS I and PSII reaction centers is the same in all phytoplankton groups.

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= LHCs

Reminder from last Lecture

The structure/function of Chl a-dominated PS I and PSII reaction centers is the same in all phytoplankton groups.

However, outer LHCs associated with these PS I and PS II antenna vary depending upon taxonomic group and give phytoplankto their characteristic colors. Eg. Red Tide Dinoflagellates

Alexandrium

Dinoflagellates in coastal Red Tide

2 LHCs = some Chl a-Chl c- protein complexes Lots of Peridinin-Chl a- protein complexes


Photosynthesis Light-Dependent Reactions and Bio-optical Measures of Primary Production

LHCs

For PSI

NADPH2

=

H+

Chemical electron acceptor

Chemical electron acceptor

NADPH

Light-Harvesting

Pigment-protein

Complexes (LHCs)

For PS II

e

PS I

Ejects electron

Ejects electron

PS II

680

IEC

e

IEC

Light Harvesting

Chl a-protein complexes

e

IEC

e

4e

Light Harvesting

Chl a-protein complexes

For every 8 photons absorbed, 1 O2 molecule “evolved”

4e

e

2H2O

H2O splitting complex

O2 + 4H+

Predictive Modeling is based upon Mechanistic Understanding

Stroma (fluid outside the thylakoids but inside the chloroplast)

INTERMEDIATE ELECTRON CARRIERS (IECs)

Lumen ( fluid in fully enclosed space inside the thylakoids)


Phytoplankton pigmentation evolved to absorb different types of UWL fields.

Measure of Spectral Irradiance, QPAR(l)z = PFD= how many photons available for PS

Measure Phyto absorption spectrum, aph(l) = what kinds of photons can be absorbed

(cDOM)

QPAR(l)z x aph(l) = QPHAR(l), photosynthetically absorbed radiation

= number of photons absorbed to drive photosynthesis

(particles)

QPHAR(l)

= maximum number of O2 molecules that could be evolved

8

aph(l)

QPAR(l)

QPHAR(l)

For each photon of QPHAR(l), 1/8th or 0.125 molecules of O2 will be evolved

= maximum quantum efficiency for photosynthesis (fmax)


Bio-optical estimation of rates of primary production based upon optical measures only

Rate of Primary Production

= PP (umoles O2 evolved/mg Chl/hr), used to get phyto plankton specific rates

= PP (umoles O2 evolved/m3/hr), used to get volume specific rates

= PP (umoles O2 evolved/m2/hr), used to get integrated water column rates

Upper limit of PP z,t = QPAR(l)z,t x aph(l z,t) x fmax z,t

Where max = 0.125

Caveat: in situ f at depth z and time t = operational fz,t is often much less than 0.125 and highly variable depending upon environmental and cellular conditions.

Today’s great challenge: Hunt for methods to measure/predict in situ fz,t

Underwater gliders

Satellite: MODIS-AQUA Absorption Products (APS)

Optical moorings


Photosynthesis Light-Dependent Reactions and Bio-optical Measures of Primary Production

LHCs

For PSI

NADPH

=

H+

Chemical electron acceptor

Chemical electron acceptor

NADP

Light-Harvesting

Pigment-protein

Complexes (LHCs)

For PS II

e

PS I

Ejects electron

Ejects electron

PS II

680

IEC

e

IEC

Light Harvesting

Chl a-protein complexes

e

IEC

e

4e

Light Harvesting

Chl a-protein complexes

For every 8 photons absorbed, 1 O2 molecule “evolved”

4e

e

2H2O

H2O splitting complex

O2 + 4H+

Stroma (fluid outside the thylakoids but inside the chloroplast)

INTERMEDIATE ELECTRON CARRIERS (IECs)

Lumen ( fluid in fully enclosed space inside the thylakoids)


Chemical energy Measures of Primary Production

Reducing Power

LHCs

For PSI

PO4

PO4

3

ADP

2

ATP

PO4

NADPH

PO4

PO4

=

H+

Pi =PO4

Chemical electron acceptor

NADP

H+

H+

e

PS I

Ejects electron

IEC

e

IEC

e

IEC

e

Light Harvesting

Chl a-protein complexes

H+

H+

H+

O2

H+

H+

H+

photophosphorylation


Photosynthesis (PS) Measures of Primary Production

Light reactions = Light dependent reactions

Dark reactions = Light-independent reactions

Optional review/details www.steve.gb.com/science/photosynthesis.html


Generally 1 O2 molecule is evolved for 1 CO2 molecule fixed Measures of Primary Production

Gross Photosynthesis

Respiration

Gross Photosynthesis - Respiration = Net Photosynthesis (growth potential)


Measuring Gas Exchange to estimate Photosynthetic rates and Primary Production.

When photosynthesis rates from several experiments are plotted against light intensity, the result is a photosynthesis light response curve

O2 evolution (PSII)

C02 uptake/fixation

(Calvin cycle)

P -I (photosynthesis-irradiance) curve = P-E (photosynthesis -energy) curve

Why do all P-I curves first increase in proportion to increasing irradiance and then level off to an upper limit = maximum rate of photosynthesis?


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