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Photosynthetic response of Persian Gulf acroporid corals to summer versus winter temperature deviations.

Vajed Samiei J, Saleh A, Mehdinia A, Shirvani A, Kayal M - PeerJ (2015)

Bottom Line: Corals exposed to warming during summer showed a decrease in net photosynthesis and ultimately died, while corals exposed to cooling during winter were not affected in their photosynthetic performance and survival.Coral autotrophic capability Pn/R was lower at the warmer thermal level within eachseason, and during summer compared to winter.Our results suggest that the autotrophic performance of the Persian Gulf A. downingi is sensitive to the extreme temperatures endured in summer, and therefore its populations may be impacted by future increases in water temperature.

View Article: PubMed Central - HTML - PubMed

Affiliation: Iranian National Institute for Oceanography and Atmospheric Science , Tehran , Iran.

ABSTRACT
With on-going climate change, coral susceptibility to thermal stress constitutes a central concern in reefconservation. In the Persian Gulf, coral reefs are confronted with a high seasonal variability in water temperature, and both hot and cold extremes have been associated with episodes of coral bleaching and mortality. Using physiological performance as a measure of coral health, we investigated the thermal susceptibility of the common acroporid, Acropora downingi, near Hengam Island where the temperature oscillates seasonally in the range 20.2-34.2 °C. In a series of two short-term experiments comparing coral response in summer versus winter conditions, we exposed corals during each season (1) to the corresponding seasonal average and extreme temperature levels in a static thermal environment, and (2) to a progressive temperature deviation from the annual mean toward the corresponding extreme seasonal value and beyond in a dynamic thermal environment. We monitored four indictors of coral physiological performance: net photosynthesis (Pn), dark respiration (R), autotrophic capability (Pn/R), and survival. Corals exposed to warming during summer showed a decrease in net photosynthesis and ultimately died, while corals exposed to cooling during winter were not affected in their photosynthetic performance and survival. Coral autotrophic capability Pn/R was lower at the warmer thermal level within eachseason, and during summer compared to winter. Corals exposed to the maximum temperature of summer displayed Pn/R < 1, inferring that photosynthetic performance could not support basal metabolic needs under this environment. Our results suggest that the autotrophic performance of the Persian Gulf A. downingi is sensitive to the extreme temperatures endured in summer, and therefore its populations may be impacted by future increases in water temperature.

No MeSH data available.


Related in: MedlinePlus

Metabolic performance of corals in constant seasonal temperature levels.Net photosynthesis in light Pn (A), respiration in darkness R (B) and autotrophic capability Pn/R ratio (C) of corals exposed to a range of temperatures as observed on Hengam reefs. The mean ± SE values are indicated on graphs. Letters on top indicate statistically different groups within each season in (A) and (B), and among the four thermal environments in (C). The thermal levels correspond to the winter minimum of 20.2 °C, winter average of 23 °C, summer average of 32 °C, and summer maximum of 34.2 °C.
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fig-2: Metabolic performance of corals in constant seasonal temperature levels.Net photosynthesis in light Pn (A), respiration in darkness R (B) and autotrophic capability Pn/R ratio (C) of corals exposed to a range of temperatures as observed on Hengam reefs. The mean ± SE values are indicated on graphs. Letters on top indicate statistically different groups within each season in (A) and (B), and among the four thermal environments in (C). The thermal levels correspond to the winter minimum of 20.2 °C, winter average of 23 °C, summer average of 32 °C, and summer maximum of 34.2 °C.

Mentions: Coral net photosynthesis was relatively consistent between the seasonal extreme and mean thermal levels of winter (0.12 ± 0.03 versus 0.13 ± 0.03 SE mgO2 respectively, p = 0.946), while it was considerably lower at the seasonal extreme compared to the mean temperature in summer (0.06 ± 0.02 versus 0.12 ± 0.02 SE mgO2 respectively, p < 0.0001). Coral respiration was highest at the warmer thermal level within each season (Fig. 2B). The net photosynthesis to dark respiration ratio Pn/R showed a significant decrease with increasing temperature both within and between seasons (Fig. 2C).


Photosynthetic response of Persian Gulf acroporid corals to summer versus winter temperature deviations.

Vajed Samiei J, Saleh A, Mehdinia A, Shirvani A, Kayal M - PeerJ (2015)

Metabolic performance of corals in constant seasonal temperature levels.Net photosynthesis in light Pn (A), respiration in darkness R (B) and autotrophic capability Pn/R ratio (C) of corals exposed to a range of temperatures as observed on Hengam reefs. The mean ± SE values are indicated on graphs. Letters on top indicate statistically different groups within each season in (A) and (B), and among the four thermal environments in (C). The thermal levels correspond to the winter minimum of 20.2 °C, winter average of 23 °C, summer average of 32 °C, and summer maximum of 34.2 °C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493696&req=5

fig-2: Metabolic performance of corals in constant seasonal temperature levels.Net photosynthesis in light Pn (A), respiration in darkness R (B) and autotrophic capability Pn/R ratio (C) of corals exposed to a range of temperatures as observed on Hengam reefs. The mean ± SE values are indicated on graphs. Letters on top indicate statistically different groups within each season in (A) and (B), and among the four thermal environments in (C). The thermal levels correspond to the winter minimum of 20.2 °C, winter average of 23 °C, summer average of 32 °C, and summer maximum of 34.2 °C.
Mentions: Coral net photosynthesis was relatively consistent between the seasonal extreme and mean thermal levels of winter (0.12 ± 0.03 versus 0.13 ± 0.03 SE mgO2 respectively, p = 0.946), while it was considerably lower at the seasonal extreme compared to the mean temperature in summer (0.06 ± 0.02 versus 0.12 ± 0.02 SE mgO2 respectively, p < 0.0001). Coral respiration was highest at the warmer thermal level within each season (Fig. 2B). The net photosynthesis to dark respiration ratio Pn/R showed a significant decrease with increasing temperature both within and between seasons (Fig. 2C).

Bottom Line: Corals exposed to warming during summer showed a decrease in net photosynthesis and ultimately died, while corals exposed to cooling during winter were not affected in their photosynthetic performance and survival.Coral autotrophic capability Pn/R was lower at the warmer thermal level within eachseason, and during summer compared to winter.Our results suggest that the autotrophic performance of the Persian Gulf A. downingi is sensitive to the extreme temperatures endured in summer, and therefore its populations may be impacted by future increases in water temperature.

View Article: PubMed Central - HTML - PubMed

Affiliation: Iranian National Institute for Oceanography and Atmospheric Science , Tehran , Iran.

ABSTRACT
With on-going climate change, coral susceptibility to thermal stress constitutes a central concern in reefconservation. In the Persian Gulf, coral reefs are confronted with a high seasonal variability in water temperature, and both hot and cold extremes have been associated with episodes of coral bleaching and mortality. Using physiological performance as a measure of coral health, we investigated the thermal susceptibility of the common acroporid, Acropora downingi, near Hengam Island where the temperature oscillates seasonally in the range 20.2-34.2 °C. In a series of two short-term experiments comparing coral response in summer versus winter conditions, we exposed corals during each season (1) to the corresponding seasonal average and extreme temperature levels in a static thermal environment, and (2) to a progressive temperature deviation from the annual mean toward the corresponding extreme seasonal value and beyond in a dynamic thermal environment. We monitored four indictors of coral physiological performance: net photosynthesis (Pn), dark respiration (R), autotrophic capability (Pn/R), and survival. Corals exposed to warming during summer showed a decrease in net photosynthesis and ultimately died, while corals exposed to cooling during winter were not affected in their photosynthetic performance and survival. Coral autotrophic capability Pn/R was lower at the warmer thermal level within eachseason, and during summer compared to winter. Corals exposed to the maximum temperature of summer displayed Pn/R < 1, inferring that photosynthetic performance could not support basal metabolic needs under this environment. Our results suggest that the autotrophic performance of the Persian Gulf A. downingi is sensitive to the extreme temperatures endured in summer, and therefore its populations may be impacted by future increases in water temperature.

No MeSH data available.


Related in: MedlinePlus