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Photosynthetic Capacity in Coral Reef Systems: Applications for the Underwater PAM Fluorometer

Marine Botany The University of Queensland. Photosynthetic Capacity in Coral Reef Systems: Applications for the Underwater PAM Fluorometer. Adrian Jones & William Dennison.

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Photosynthetic Capacity in Coral Reef Systems: Applications for the Underwater PAM Fluorometer

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  1. Marine Botany The University of Queensland Photosynthetic Capacity in Coral Reef Systems: Applications for the Underwater PAM Fluorometer Adrian Jones & William Dennison Thanks to the students of Coral Reef Biology & Geology (ID211) of 1996 and Terrestrial & Marine Environmental Physiology (BT230) of 1997

  2. Aims • Generate photosynthesis versus irradiance (PI) curves using Pulse Amplitude Modulated (PAM) fluorescence techniques • For a variety of marine macroalgae, determine relationships between PI curves and various environmental factors • Use ecophysiological responses to infer light availability, desiccation stress and nutrient status

  3. Submersible Housing Leaf Clip Fibre Optic Cable PAM Fluorometer • PAM generates saturating pulse of light which is used to measure photosynthetic rates

  4. PAM Fluorescence(Pulse Amplitude Modulation) Saturating Pulse from PAM Light Fluorescence Heat Photosynthetic Yield ( Fmax - Finitial ) / F max = PSI PQ PQ PSII Photochemistry Electron Transport Rate (ETR; µmol e- m-2 s-1) = Photosynthetic Yield x Absorbed Light

  5. Rapid Light Curve 1 Second Saturating Pulse } 10 20 30 40 50 80 90 0 60 70 Time (s) 10 Second Actinic Irradiance

  6. Maximum ETR Photoinhibition Rapid Light Curve 40 35 30 25 (µmol e- m-2 s-1 ) 20 Electron Transport Rate (ETR) 15 10 5 0 0 200 400 600 800 1000 1200 1400 1600 Photosynthetically Active Radiation (PAR) (µmol quanta m-2 s-1)

  7. Great Barrier Reef Australia Heron Island Brisbane Study Site Heron Island Southern Reef Flat Heron Island Wistari Channel Heron Reef

  8. Terrestrial Species Marine Species Argusia Zooxanthallae (Acropora) 100 100 ETR (µmol e- m-2 s-1 ) 50 50 0 0 500 1000 1500 0 0 500 1000 1500 Pisonia Chlorodesmis 100 100 ETR (µmol e- m-2 s-1 ) 50 50 0 0 0 500 1000 1500 0 500 1000 1500 PAR (µmol quanta m-2 s-1) PAR (µmol quanta m-2 s-1) Species Comparison

  9. Beach Reef Crest Reef Flat Gutter 15m 200m Experimental Design(Reef Transect) • Photosynthesis in Chlorodesmis was measured along a transect from 15m depth along the reef flat to the beach

  10. 80 60 ETR (µmol e- m-2 s-1) 40 20 0 0 500 1000 1500 PAR (µmol quanta m-2 s-1) 5m 10m 15m Transect of Max ETR in Chlorodesmis 80 70 Reef Crest 60 Gutter Beach Maximum ETR (µmol e- m-2 s-1) 50 40 30 20 0 20 40 60 80 100 120 140 160 180 200 220 2 5 10 15 Depth (m) Distance from Beach (m)

  11. Experimental Design(Desiccation) • Chlorodesmis collected from the reef flat and 15m was subjected to desiccation and fluorescence was monitored. Beach Reef Crest Reef Flat Gutter 15m 200m

  12. Recovery Desiccation Reef Flat 15m Desiccation and Recovery 50 40 30 Maximum ETR 20 (µmol e- m-2 s-1) 10 0 0 20 40 60 80 Time (mins)

  13. Experimental Design(Shading) • Several species of macroalgae and coral were shaded and the change in fluorescence measured over 5 days.

  14. Day 1 Day 1 Day 2 Day 2 Day 3 Day 3 Day 4 Day 4 50% PAR Shading Chlorodesmis 80 60 40 ETR (µmol e- m-2 s-1 ) 20 0 0 500 1000 1500 2000 PAR (µmol quanta m-2 s-1) 180 Chnoospora 120 ETR (µmol e- m-2 s-1 ) 60 0 0 500 1000 1500 2000 PAR (µmol quanta m-2 s-1)

  15. UV Shading Padina 100 80 60 ETR (µmol e- m-2 s-1) 40 20 0 0 200 400 600 800 1000 1200 1400 PAR (µmol quanta m-2 s-1) Control UV Screened

  16. Experimental Design(Fertilisation) • Several species of macroalgae and coral were incubated for 10 days in flow-through aquaria with added nitrogen (88g m-2) and phosphorus (22g m-2)

  17. Nutrient Sufficiency Status Fertilisations Padina Chlorodesmis 50 30 40 25 30 20 ETR (µmol e- m-2 s-1 ) 15 20 10 10 5 0 0 0 200 400 600 800 1000 1200 1400 0 500 1000 1500 2000 PAR (µmol quanta m-2 s-1) PAR (µmol quanta m-2 s-1) Unfertilised Fertilised Unfertilised Fertilised

  18. Fertilisations Colpomenia Acropora ETR (µmol e- m-2 s-1 ) PAR (µmol quanta m-2 s-1) PAR (µmol quanta m-2 s-1) Unfertilised Fertilised Unfertilised Fertilised

  19. Summary • Rapid light curves in terrestrial and marine plants can be used to assess a variety of ecophysiological responses • Ability to generate in situ PI curves rapidly, non destructively to determine relationships with various environmental factors • Ecophysiological responses to environmental gradients such as desiccation, light, and depth can be ascertained • PI responses can be used to infer a nutrient sufficiency status

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