Diffusive boundary layers and photosynthesis of the epilithic algal community of coral reefs

Larkum, A; Koch, EW; Kuhl, M

Diffusive boundary layers and photosynthesis of the epilithic algal community of coral reefs

Larkum, A

Koch, EW Kuhl, M

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Publisher:: Springer-Verlag
Publication Type:: Journal Article
Citation:: Marine Biology, 2003, 142 (5), pp. 1073 - 1082
Issue Date:: 2003-01

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Field	Value	Language
dc.contributor.author	Larkum, A https://orcid.org/0000-0002-0420-134X	en_US
dc.contributor.author	Koch, EW	en_US
dc.contributor.author	Kuhl, M https://orcid.org/0000-0002-1792-4790	en_US
dc.date.issued	2003-01	en_US
dc.identifier.citation	Marine Biology, 2003, 142 (5), pp. 1073 - 1082	en_US
dc.identifier.issn	0025-3162	en_US
dc.identifier.uri	http://hdl.handle.net/10453/8621
dc.description.abstract	The effects of mass transfer resistance due to the presence of a diffusive boundary layer on the photosynthesis of the epilithic algal community (EAC) of a coral reef were studied. Photosynthesis and respiration of the EAC of dead coral surfaces were investigated for samples from two locations: the Gulf of Aqaba, Eilat (Israel), and One Tree Reef on the Great Barrier Reef (Australia). Microsensors were used to measure O2 and pH at the EAC surface and above. Oxygen profiles in the light and dark indicated a diffusive boundary layer (DBL) thickness of 180590 ?m under moderate flow (~0.08 m s-1) and >2,000 ?m under quasi-stagnant conditions. Under light saturation the oxygen concentration at the EAC surface rose within a few minutes to 200550% air saturation levels under moderate flow and to 600700% under quasi-stagnant conditions. High maximal rates of net photosynthesis of 825 mmol O2 m-2 h-1 were calculated from measured O2 concentration gradients, and dark respiration was 1.33.3 mmol O2 m-2 h-1. From lightdark shifts, the maximal rates of gross photosynthesis at the EAC surface were calculated to be 16.5 nmol O2 cm-3 s-1. Irradiance at the onset of saturation of photosynthesis, Ek, was <100 µmol photons m-2 s-1, indicating that the EAC is a shade-adapted community. The pH increased from 8.2 in the bulk seawater to 8.9 at the EAC surface, suggesting that very little carbon in the form of CO2 occurs at the EAC surface. Thus the major source of dissolved inorganic carbon (DIC) must be in the form of HCO3-. Estimates of DIC fluxes across the DBL indicate that, throughout most of the daytime under in situ conditions, DIC is likely to be a major limiting factor for photosynthesis and therefore also for primary production and growth of the EAC.	en_US
dc.publisher	Springer-Verlag	en_US
dc.relation.ispartof	Marine Biology	en_US
dc.subject.classification	Marine Biology & Hydrobiology	en_US
dc.title	Diffusive boundary layers and photosynthesis of the epilithic algal community of coral reefs	en_US
dc.type	Journal Article
utslib.citation.volume	5	en_US
utslib.citation.volume	142	en_US
utslib.for	0602 Ecology	en_US
utslib.for	05 Environmental Sciences	en_US
utslib.for	06 Biological Sciences	en_US
utslib.for	07 Agricultural and Veterinary Sciences	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Strength - C3 - Climate Change Cluster
utslib.copyright.status	closed_access
pubs.consider-herdc	false	en_US
pubs.issue	5	en_US
pubs.volume	142	en_US

Abstract:

The effects of mass transfer resistance due to the presence of a diffusive boundary layer on the photosynthesis of the epilithic algal community (EAC) of a coral reef were studied. Photosynthesis and respiration of the EAC of dead coral surfaces were investigated for samples from two locations: the Gulf of Aqaba, Eilat (Israel), and One Tree Reef on the Great Barrier Reef (Australia). Microsensors were used to measure O2 and pH at the EAC surface and above. Oxygen profiles in the light and dark indicated a diffusive boundary layer (DBL) thickness of 180590 ?m under moderate flow (~0.08 m s-1) and >2,000 ?m under quasi-stagnant conditions. Under light saturation the oxygen concentration at the EAC surface rose within a few minutes to 200550% air saturation levels under moderate flow and to 600700% under quasi-stagnant conditions. High maximal rates of net photosynthesis of 825 mmol O2 m-2 h-1 were calculated from measured O2 concentration gradients, and dark respiration was 1.33.3 mmol O2 m-2 h-1. From lightdark shifts, the maximal rates of gross photosynthesis at the EAC surface were calculated to be 16.5 nmol O2 cm-3 s-1. Irradiance at the onset of saturation of photosynthesis, Ek, was <100 µmol photons m-2 s-1, indicating that the EAC is a shade-adapted community. The pH increased from 8.2 in the bulk seawater to 8.9 at the EAC surface, suggesting that very little carbon in the form of CO2 occurs at the EAC surface. Thus the major source of dissolved inorganic carbon (DIC) must be in the form of HCO3-. Estimates of DIC fluxes across the DBL indicate that, throughout most of the daytime under in situ conditions, DIC is likely to be a major limiting factor for photosynthesis and therefore also for primary production and growth of the EAC.

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http://hdl.handle.net/10453/8621