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Diurnal hysteresis in coral photosynthesis., Levy, O., Z

Diurnal hysteresis in coral photosynthesis

Coral host respiration is just one source of inorganic carbon for symbiont photosynthesis –; external inorganic carbon sources such as seawater are also utilised. However, the supply of inorganic carbon via passive diffusion from the surrounding seawater and host tissue is restricted by several factors: 1) the generally low CO2 content of seawater, 2) the presence of a diffusive boundary layer, and 3) the presence of multiple membranes of the host tissue surrounding the endodermal Symbiodinium cells, which need to be traversed. Both, coral host and symbionts employ a range of carbon concentrating mechanisms (CCMs) – to enhance the carbon supply from the external medium and thus increase CO2 availability to the Symbiodinium chloroplasts as well as for calcification purposes .

Pacala, 2005: Fish aggregation results in inversely density dependent predation on continuous coral reefs.

Diurnal Hysteresis in Coral Photosynthesis

Among the many plausible choices, dangerousinterference with the climate system may be interpreted as anthropogenic radiative forcing causingdistinct and widespread climate change impacts such as a widespread demise of coral reefs or adisintegration of the West Antarctic ice sheet.

Light Respiratory Processes and Gross Photosynthesis in Two Scleractinian Corals

The higher mean 15N/14N of NO3 observed in snow fromspring (δ18O versus air N2 = +5.9% in 2000 and -1.4% in 2001) and summer (+0.1% in2000 and -0.8% in 2001) than fall (-9.2% in 2000) and winter( -10.0% in 2000–01)is more difficult to explain with seasonal photochemistry, given current knowledge.

the circadian rhythmicity of photosynthesis in Symbiodinium, coral-


Inorganic carbon uptake for photosynthesis by the symbiotic coral ..

Theseassertions are based on projecting the coarse output from atmosphere–ocean generalcirculation models (GCMs) to the local conditions around representative coral reefs.

2004) Diurnal hysteresis in coral photosynthesis.

Recent studies have warned that global climate change could increasethe frequency of coral bleaching and threaten the long-term viability of coral reefs.

In terms of coral cover, what is the hysteresis ..

First, we develop and testalgorithms for predicting mass coral bleaching with GCM-resolution sea surface temperaturesfor thousands of coral reefs, using a global coral reef map and 1985–2002bleaching prediction data.

tmp469A | Coral | Life Sciences

Photoacclimation is a process of morphological (here in terms of coral host) and physiological adjustments of a phototrophic organism towards growth irradiances. Pigmentation (coral host pigmentation and light harvesting pigments such as accessory pigments and chlorophyll ), as well as photochemical quenching capacity (xanthophyll pool , ) can be increased and decreased in abundance and concentrations. During high light exposure these adjustments help acclimatization in the phototroph only to some extend, and as a result, high light stress results in the accumulation of reactive oxygen species , the stimulation of alternative electron transport systems , , often consuming oxygen, and of photorepair mechanisms , . The cost of all these processes results in low net photosynthesis , due to increased respiration and other oxygen uptake , . The light source in the experiments of this study excluded the naturally occurring ultraviolet radiation, which corals experience in the field and which is a major cause of photodamage , . Translating our findings to corals in the field, the increase of oxygen uptake rates on going from dark to light (or from low to high light) might therefore not be as great as found in this study; however, once photorepair processes are entrained the actual oxygen uptake rates might be just as high or even higher.

Jovem Revela a Matemática Por Trás de Seus 95% de Acertos.

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 (see for a conceptual diagram of the main findings).