Common reef-building coral in the Northern Red Sea resistant to elevated temperature and acidification

Julia Marie Jeanne Yvonne Bodin, Stéphane Laurent Escrig, Maoz Fine, Maria-Evangelia Giovani, Thomas Krüger, Anders Meibom
Royal Soc, 2017
Article

Résumé

Coral reefs are currently experiencing substantial ecological impoverishment as a result of anthropogenic stressors, and the majority of reefs are facing immediate risk. Increasing ocean surface temperatures induce frequent coral mass bleaching events—the breakdown of the nutritional photo-symbiosis with intracellular algae (genus: Symbiodinium). Here, we report that Stylophora pistillata from a highly diverse reef in the Gulf of Aqaba showed no signs of bleaching despite spending 1.5 months at 1–2°C above their long-term summer maximum (amounting to 11 degree heating weeks) and a seawater pH of 7.8. Instead, their symbiotic dinoflagellates exhibited improved photochemistry, higher pigmentation and a doubling in net oxygen production, leading to a 51% increase in primary productivity. Nanoscale secondary ion mass spectrometry imaging revealed subtle cellular-level shifts in carbon and nitrogen metabolism under elevated temperatures, but overall host and symbiont biomass proxies were not significantly affected. Now living well below their thermal threshold in the Gulf of Aqaba, these corals have been evolutionarily selected for heat tolerance during their migration through the warm Southern Red Sea after the last ice age. This may allow them to withstand future warming for a longer period of time, provided that successful environmental conservation measures are enacted across national boundaries in the region.

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https://infoscience.epfl.ch/record/228274?ln=fr

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Julia Marie Jeanne Yvonne Bodin, Stéphane Laurent Escrig, Maoz Fine, Maria-Evangelia Giovani, Thomas Krüger, Anders Meibom
Royal Soc, 2017
Article

Résumé

Official source

https://infoscience.epfl.ch/record/228274?ln=fr

À propos de ce résultat

Concepts associés (14)

thumb|upright=1.5|Le corail, dont les colonies forment les récifs. thumb|upright=1.5|Colonie d’Acropora pulchra. Un récif corallien ou barrière de corail est une structure naturelle bioconstruite à l

vignette|droite|upright=2|Le cycle de l'azote dans le sol Le cycle de l'azote est un cycle biogéochimique qui décrit la succession des modifications subies par les différentes formes de l'azote neutre

Stylophora pistillata est une espèce de coraux appartenant à la famille des Pocilloporidae. Description et caractéristiques Habitat et répartition Études scientifiques

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The exchange of metabolites between photosynthetic symbionts and their coral host in shallow-water scleractinians provides the nutritional basis for their successful evolution and the existence of massive coral reefs in oligotrophic tropical waters. Autotrophic nutrition, based on carbon- and nitrogen-rich photosynthetic metabolites, is complemented by heterotrophic uptake and assimilation of organic matter to obtain additional carbon, nitrogen and phosphorus. By combining TEM ultrastructural observations with quantitative NanoSIMS isotopic imaging of tissue sections at sub-cellular resolution, we have compared the exchange of nutrients from the autotrophic assimilation of 15N-nitrate and 13C-bicarbonate with the heterotrophic uptake from 15N- and 13C-labelled brine shrimps in Stylophora pistillata from the Red Sea. Our results confirm that heterotrophy serves as the dominant source of nitrogen for the coral holobiont. On a time scale of 6 hours, heterotrophy provided approximately nine times more nitrogen to the host gastrodermal anabolism than symbiont nitrate fixation and translocation. Heterotrophic nitrogen was also used in anabolic processes in the symbionts, but at a level about 40% lower compared with nitrogen incorporation from nitrate fixation. The role of photosynthesizing symbionts the major contributors of carbon to the coral host was evident from the observation that autotrophic carbon enrichment in the gastrodermal layer was seven times higher in comparison to the heterotrophic carbon acquisition. Our observations directly demonstrate the complementing roles of heterotrophic and autotrophic food acquisition and support the notion that recycling of nutrients in symbiotic coral holobionts is critical to their vitality. The effects of stress from environmental change, including increasing water temperature and ocean acidification, are under investigation.

2015

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Intracellular competition for nitrogen controls dinoflagellate population density in corals

Julia Marie Jeanne Yvonne Bodin, Stéphane Laurent Escrig, Maoz Fine, Maria-Evangelia Giovani, Anders Meibom

The density of dinoflagellate microalgae in the tissue of symbiotic corals is an important determinant for health and productivity of the coral animal. Yet, the specific mechanism for their regulation and the consequence for coral nutrition are insufficiently understood due to past methodological limitations to resolve the fine-scale metabolic consequences of fluctuating densities. Here, we characterized the physiological and nutritional consequences of symbiont density variations on the colony and tissue level in Stylophora pistillata from the Red Sea. Alterations in symbiont photophysiology maintained coral productivity and host nutrition across a broad range of symbiont densities. However, we demonstrate that density-dependent nutrient competition between individual symbiont cells, manifested as reduced nitrogen assimilation and cell biomass, probably creates the negative feedback mechanism for symbiont population growth that ultimately defines the steady-state density. Despite fundamental changes in symbiont nitrogen assimilation, we found no density-related metabolic optimum beyond which host nutrient assimilation or tissue biomass declined, indicating that host nutrient demand is sufficiently met across the typically observed range of symbiont densities under ambient conditions.

ROYAL SOC2020

Chargement

High summer temperatures amplify functional differences between coral‐ and algae‐dominated reef communities

Nils Rädecker

Shifts from coral to algal dominance are expected to increase in tropical coral reefs as a result of anthropogenic disturbances. The consequences for key ecosystem functions such as primary productivity, calcification, and nutrient recycling are poorly understood, particularly under changing environmental conditions. We used a novel in situ incubation approach to compare functions of coral‐ and algae‐dominated communities in the central Red Sea bi‐monthly over an entire year. In situ gross and net community primary productivity, calcification, dissolved organic carbon fluxes, dissolved inorganic nitrogen fluxes, and their respective activation energies were quantified to describe the effects of seasonal changes. Overall, coral‐dominated communities exhibited 30% lower net productivity and 10 times higher calcification than algae‐dominated communities. Estimated activation energies indicated a higher thermal sensitivity of coral‐dominated communities. In these communities, net productivity and calcification were negatively correlated with temperature (>40% and >65% reduction, respectively, with +5°C increase from winter to summer), while carbon losses via respiration and dissolved organic carbon release were more than doubled at higher temperatures. In contrast, algae‐dominated communities doubled net productivity in summer, while calcification and dissolved organic carbon fluxes were unaffected. These results suggest pronounced changes in community functioning associated with phase shifts. Algae‐dominated communities may outcompete coral‐dominated communities due to their higher productivity and carbon retention to support fast biomass accumulation while compromising the formation of important reef framework structures. Higher temperatures likely amplify these functional differences, indicating a high vulnerability of ecosystem functions of coral‐dominated communities to temperatures even below coral bleaching thresholds. Our results suggest that ocean warming may not only cause but also amplify coral‐algal phase shifts in coral reefs.

2020

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High summer temperatures amplify functional differences between coral‐ and algae‐dominated reef communities

Nils Rädecker

2020