Reminder from last Lecture

1. = 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

2. 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)

3. 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)

4. 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

5. 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)

6. Chemical energy 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

7. Photosynthesis (PS) Light reactions = Light dependent reactions Dark reactions = Light-independent reactions Optional review/details www.steve.gb.com/science/photosynthesis.html

8. Generally 1 O2 molecule is evolved for 1 CO2 molecule fixed Gross Photosynthesis Respiration Gross Photosynthesis - Respiration = Net Photosynthesis (growth potential)

9. 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?