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 Marine Botany The University of Queensland

Aims Generate photosynthesis versus irradiance (PI) curves using Pulse Amplitude Modulated (PAM) fluorescence techniquesGenerate 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 factorsFor 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 statusUse ecophysiological responses to infer light availability, desiccation stress and nutrient status

PAM Fluorometer Fibre Optic Cable Leaf Clip SubmersibleHousing PAM generates saturating pulse of light which is used to measure photosynthetic ratesPAM generates saturating pulse of light which is used to measure photosynthetic rates

PAM Fluorescence (Pulse Amplitude Modulation) Heat Fluorescence Light Photochemistry PQ PSI F max - F initial = Saturating Pulse from PAM PQ PSII PhotosyntheticYield PhotosyntheticYieldAbsorbedLight Electron Transport Rate (ETR; µmol e - m -2 s -1 ) x = / F max ( )

Rapid Light Curve Time (s) Second Saturating Pulse 10 Second Actinic Irradiance }

Rapid Light Curve Photosynthetically Active Radiation (PAR) (µmol quanta m -2 s -1 ) Electron Transport Rate (ETR) (µmol e - m -2 s -1 )Photoinhibition Maximum ETR

Study Site Australia BrisbaneGreat Barrier Barrier Reef ReefHeronIsland HeronIsland HeronReef WistariChannel Heron Island Southern Reef Flat

Species Comparison

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

Maximum ETR (µmol e - m -2 s -1 ) Transect of Max ETR in Chlorodesmis Beach ReefCrest Gutter Distance from Beach (m) Depth (m)

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

Time (mins) Maximum ETR (µmol e - m -2 s -1 ) Reef Flat15m Desiccation and Recovery Desiccation Recovery

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

50% PAR Shading Day 1Day 2Day 3Day 4 Chlorodesmis ETR (µmol e - m -2 s -1 ) PAR (µmol quanta m -2 s -1 ) Chnoospora Day 1Day 2Day 3Day 4 ETR (µmol e - m -2 s -1 ) PAR (µmol quanta m -2 s -1 )

PAR (µmol quanta m -2 s -1 ) ETR (µmol e - m -2 s -1 ) UV Screened Control UV Shading Padina

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 )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 )

FertilisationsNutrient Sufficiency Status FertilisedUnfertilised Padina ETR (µmol e - m -2 s -1 ) PAR (µmol quanta m -2 s -1 ) FertilisedUnfertilised Chlorodesmis PAR (µmol quanta m -2 s -1 )

FertilisedUnfertilised Colpomenia ETR (µmol e - m -2 s -1 ) PAR (µmol quanta m -2 s -1 ) Fertilisations FertilisedUnfertilised Acropora PAR (µmol quanta m -2 s -1 )

Summary Rapid light curves in terrestrial and marine plants can be used to assess a variety of ecophysiological responsesRapid 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 factorsAbility 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 ascertainedEcophysiological responses to environmental gradients such as desiccation, light, and depth can be ascertained PI responses can be used to infer a nutrient sufficiency statusPI responses can be used to infer a nutrient sufficiency status