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Light respiratory processes and gross photosynthesis in two scleractinian corals.

Schrameyer V, Wangpraseurt D, Hill R, Kühl M, Larkum AW, Ralph PJ - PLoS ONE (2014)

Bottom Line: Light respiration in Pocillopora damicornis was higher than in Pavona decussata under low irradiance, indicating species-specific differences in light-dependent metabolic processes.Overall, the coral P. decussata exhibited higher CO2 uptake rates than P. damicornis over the experimental irradiance range.Differences in light respiration and CO2 availability could be due to host-specific characteristics that modulate the symbiont microenvironment, its photosynthesis, and hence the overall performance of the coral holobiont.

View Article: PubMed Central - PubMed

Affiliation: Plant Functional Biology and Climate Change Cluster, School of the Environment, University of Technology, Sydney, Ultimo, New South Wales, Australia.

ABSTRACT
The light dependency of respiratory activity of two scleractinian corals was examined using O2 microsensors and CO2 exchange measurements. Light respiration increased strongly but asymptotically with elevated irradiance in both species. Light respiration in Pocillopora damicornis was higher than in Pavona decussata under low irradiance, indicating species-specific differences in light-dependent metabolic processes. Overall, the coral P. decussata exhibited higher CO2 uptake rates than P. damicornis over the experimental irradiance range. P. decussata also harboured twice as many algal symbionts and higher total protein biomass compared to P. damicornis, possibly resulting in self-shading of the symbionts and/or changes in host tissue specific light distribution. Differences in light respiration and CO2 availability could be due to host-specific characteristics that modulate the symbiont microenvironment, its photosynthesis, and hence the overall performance of the coral holobiont.

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Conceptual model of light and carbon availability, in the two hard coral species, Pocillopora damicornis and Pavona decussata in moderate light (∼100 µmol photons m−2 s−1).The schematic diagram of a coral shows the coral tissue containing algal symbionts (green circles), which lies above the calicoblastic layer. Photosynthetic active radiation (PAR) (rainbow arrow) penetrates the coral tissue. In P. decussata a higher density of symbionts reduced light availability compared to P. damicornis. Dissolved inorganic carbon (grey arrows; quantity is relative to arrow thickness) can originate from internal sources such as the calicoblastic layer or from the external environment, where P. decussata draws stronger on the external carbon uptake. Light respiration (R) (strength indicated through size), was greater in P. damicornis than in P. decussata.
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pone-0110814-g003: Conceptual model of light and carbon availability, in the two hard coral species, Pocillopora damicornis and Pavona decussata in moderate light (∼100 µmol photons m−2 s−1).The schematic diagram of a coral shows the coral tissue containing algal symbionts (green circles), which lies above the calicoblastic layer. Photosynthetic active radiation (PAR) (rainbow arrow) penetrates the coral tissue. In P. decussata a higher density of symbionts reduced light availability compared to P. damicornis. Dissolved inorganic carbon (grey arrows; quantity is relative to arrow thickness) can originate from internal sources such as the calicoblastic layer or from the external environment, where P. decussata draws stronger on the external carbon uptake. Light respiration (R) (strength indicated through size), was greater in P. damicornis than in P. decussata.

Mentions: This is the first study reporting an integrated approach measuring coral light respiration and gross photosynthesis with O2 microsensors and CO2 gas exchange techniques across a range of irradiance. The two main finding of this study are that i) light-saturated (at 210 µmol photons m−2 s−1) respiration rates (Rlight O2 micro) were multiple times higher than steady-state dark respiration rates (Rdark O2 micro) (11 times for P. decussata and 25 times for P. damicornis, and ii) P. damicornis and P. decussata differ in their photophysiological function despite likely harbouring the same symbiont subclade C1 [42] (see Fig. 3 for a conceptual diagram of the main findings).


Light respiratory processes and gross photosynthesis in two scleractinian corals.

Schrameyer V, Wangpraseurt D, Hill R, Kühl M, Larkum AW, Ralph PJ - PLoS ONE (2014)

Conceptual model of light and carbon availability, in the two hard coral species, Pocillopora damicornis and Pavona decussata in moderate light (∼100 µmol photons m−2 s−1).The schematic diagram of a coral shows the coral tissue containing algal symbionts (green circles), which lies above the calicoblastic layer. Photosynthetic active radiation (PAR) (rainbow arrow) penetrates the coral tissue. In P. decussata a higher density of symbionts reduced light availability compared to P. damicornis. Dissolved inorganic carbon (grey arrows; quantity is relative to arrow thickness) can originate from internal sources such as the calicoblastic layer or from the external environment, where P. decussata draws stronger on the external carbon uptake. Light respiration (R) (strength indicated through size), was greater in P. damicornis than in P. decussata.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4216011&req=5

pone-0110814-g003: Conceptual model of light and carbon availability, in the two hard coral species, Pocillopora damicornis and Pavona decussata in moderate light (∼100 µmol photons m−2 s−1).The schematic diagram of a coral shows the coral tissue containing algal symbionts (green circles), which lies above the calicoblastic layer. Photosynthetic active radiation (PAR) (rainbow arrow) penetrates the coral tissue. In P. decussata a higher density of symbionts reduced light availability compared to P. damicornis. Dissolved inorganic carbon (grey arrows; quantity is relative to arrow thickness) can originate from internal sources such as the calicoblastic layer or from the external environment, where P. decussata draws stronger on the external carbon uptake. Light respiration (R) (strength indicated through size), was greater in P. damicornis than in P. decussata.
Mentions: This is the first study reporting an integrated approach measuring coral light respiration and gross photosynthesis with O2 microsensors and CO2 gas exchange techniques across a range of irradiance. The two main finding of this study are that i) light-saturated (at 210 µmol photons m−2 s−1) respiration rates (Rlight O2 micro) were multiple times higher than steady-state dark respiration rates (Rdark O2 micro) (11 times for P. decussata and 25 times for P. damicornis, and ii) P. damicornis and P. decussata differ in their photophysiological function despite likely harbouring the same symbiont subclade C1 [42] (see Fig. 3 for a conceptual diagram of the main findings).

Bottom Line: Light respiration in Pocillopora damicornis was higher than in Pavona decussata under low irradiance, indicating species-specific differences in light-dependent metabolic processes.Overall, the coral P. decussata exhibited higher CO2 uptake rates than P. damicornis over the experimental irradiance range.Differences in light respiration and CO2 availability could be due to host-specific characteristics that modulate the symbiont microenvironment, its photosynthesis, and hence the overall performance of the coral holobiont.

View Article: PubMed Central - PubMed

Affiliation: Plant Functional Biology and Climate Change Cluster, School of the Environment, University of Technology, Sydney, Ultimo, New South Wales, Australia.

ABSTRACT
The light dependency of respiratory activity of two scleractinian corals was examined using O2 microsensors and CO2 exchange measurements. Light respiration increased strongly but asymptotically with elevated irradiance in both species. Light respiration in Pocillopora damicornis was higher than in Pavona decussata under low irradiance, indicating species-specific differences in light-dependent metabolic processes. Overall, the coral P. decussata exhibited higher CO2 uptake rates than P. damicornis over the experimental irradiance range. P. decussata also harboured twice as many algal symbionts and higher total protein biomass compared to P. damicornis, possibly resulting in self-shading of the symbionts and/or changes in host tissue specific light distribution. Differences in light respiration and CO2 availability could be due to host-specific characteristics that modulate the symbiont microenvironment, its photosynthesis, and hence the overall performance of the coral holobiont.

Show MeSH