Posts Tagged 'Red Sea'

Stylophora pistillata in the Red Sea demonstrate higher GFP fluorescence under ocean acidification conditions

Ocean acidification is thought to exert a major impact on calcifying organisms, including corals. While previous studies have reported changes in the physiological response of corals to environmental change, none have described changes in expression of the ubiquitous host pigments—fluorescent proteins (FPs)—to ocean acidification. The function of FPs in corals is controversial, with the most common consideration being that these primarily regulate the light environment in the coral tissue and protect the host from harmful UV radiation. Here, we provide for the first time experimental evidence that increased fluorescence of colonies of the coral Stylophora pistillata is independent of stress and can be regulated by a non-stressful decrease in pH. Stylophora pistillata is the most abundant and among the most resilient coral species in the northern Gulf of Eilat/Aqaba (GoE/A). Fragmented “sub-colonies” (n = 72) incubated for 33 days under three pH treatments (ambient, 7.9, and 7.6), under ambient light, and running seawater showed no stress or adverse physiological performance, but did display significantly higher fluorescence, with lower pH. Neither the average number of planulae shed from the experimental sub-colonies nor planulae green fluorescent protein (GFP) expression changed significantly among pH treatments. Sub-colonies incubated under the lower-than-ambient pH conditions showed an increase in both total protein and GFP expression. Since extensive protein synthesis requires a high level of transcription, we suggest that GFP constitutes a UV protection mechanism against potential RNA as well as against DNA damage caused by UV exposure. Manipulating the regulation of FPs in adult corals and planulae, under controlled and combined effects of pH, light, and temperature, is crucial if we are to obtain a better understanding of the role played by this group of proteins in cnidarians.

Continue reading ‘Stylophora pistillata in the Red Sea demonstrate higher GFP fluorescence under ocean acidification conditions’

Taking the metabolic pulse of the world’s coral reefs

Worldwide, coral reef ecosystems are experiencing increasing pressure from a variety of anthropogenic perturbations including ocean warming and acidification, increased sedimentation, eutrophication, and overfishing, which could shift reefs to a condition of net calcium carbonate (CaCO3) dissolution and erosion. Herein, we determine the net calcification potential and the relative balance of net organic carbon metabolism (net community production; NCP) and net inorganic carbon metabolism (net community calcification; NCC) within 23 coral reef locations across the globe. In light of these results, we consider the suitability of using these two metrics developed from total alkalinity (TA) and dissolved inorganic carbon (DIC) measurements collected on different spatiotemporal scales to monitor coral reef biogeochemistry under anthropogenic change. All reefs in this study were net calcifying for the majority of observations as inferred from alkalinity depletion relative to offshore, although occasional observations of net dissolution occurred at most locations. However, reefs with lower net calcification potential (i.e., lower TA depletion) could shift towards net dissolution sooner than reefs with a higher potential. The percent influence of organic carbon fluxes on total changes in dissolved inorganic carbon (DIC) (i.e., NCP compared to the sum of NCP and NCC) ranged from 32% to 88% and reflected inherent biogeochemical differences between reefs. Reefs with the largest relative percentage of NCP experienced the largest variability in seawater pH for a given change in DIC, which is directly related to the reefs ability to elevate or suppress local pH relative to the open ocean. This work highlights the value of measuring coral reef carbonate chemistry when evaluating their susceptibility to ongoing global environmental change and offers a baseline from which to guide future conservation efforts aimed at preserving these valuable ecosystems.

Continue reading ‘Taking the metabolic pulse of the world’s coral reefs’

Reproductive and trans-generational effect of ocean acidification and warming on the coral Stylophora pistillata in the Gulf of Aqaba

Global warming is threatening 75 % of the world’s coral reefs. The reproduction of corals is a driver for the development of the whole reef ecosystem. Then, it is essential to better understand the transgenerational mechanisms in the response of parents and offspring to elevated temperature and lowered pH. Colonies of Stylophora pistillata from the Gulf of Aqaba during their reproduction period were exposed to a 4°C increase in temperature and a pH of 7.6 for 36 days, then a 6°C increase for six days. Planulae were counted on seven consecutive nights, two times during the experiment period. Physiological characteristics of adult and planulae were assessed on four and five sampling points respectively, as well as the behaviour of the planulae through their incubation. Results show no effect of OWA on the reproduction, parents, and planulae physiology. They suggest that the natural resistance of corals in the Gulf of Aqaba is transmitted from parent to offspring. Data on planulae quantity, survival, settlement, and metabolism provides additional and useful information to understand the biology of this coral, specially in its early-life stage. This study’s outcome is adding evidences of the future development of corals reefs in this region, unlike several other tropical reefs in the world.

Continue reading ‘Reproductive and trans-generational effect of ocean acidification and warming on the coral Stylophora pistillata in the Gulf of Aqaba’

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

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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Mediterranean versus Red sea corals facing climate change, a transcriptome analysis

The anthropogenic increase in atmospheric CO2 that drives global warming and ocean acidification raises serious concerns regarding the future of corals, the main carbonate biomineralizers. Here we used transcriptome analysis to study the effect of long-term gradual temperature increase (annual rate), combined with lowered pH values, on a sub-tropical Red Sea coral, Stylophora pistillata, and on a temperate Mediterranean symbiotic coral Balanophyllia europaea. The gene expression profiles revealed a strong effect of both temperature increase and pH decrease implying for synergism response. The temperate coral, exposed to a twice as high range of seasonal temperature fluctuations than the Red Sea species, faced stress more effectively. The compensatory strategy for coping apparently involves deviating cellular resources into a massive up-regulation of genes in general, and specifically of genes involved in the generation of metabolic energy. Our results imply that sub-lethal, prolonged exposure to stress can stimulate evolutionary increase in stress resilience.

Continue reading ‘Mediterranean versus Red sea corals facing climate change, a transcriptome analysis’

Spatial competition dynamics between reef corals under ocean acidification

Climate change, including ocean acidification (OA), represents a major threat to coral-reef ecosystems. Although previous experiments have shown that OA can negatively affect the fitness of reef corals, these have not included the long-term effects of competition for space on coral growth rates. Our multispecies year-long study subjected reef-building corals from the Gulf of Aqaba (Red Sea) to competitive interactions under present-day ocean pH (pH 8.1) and predicted end-of-century ocean pH (pH 7.6). Results showed coral growth is significantly impeded by OA under intraspecific competition for five out of six study species. Reduced growth from OA, however, is negligible when growth is already suppressed in the presence of interspecific competition. Using a spatial competition model, our analysis indicates shifts in the competitive hierarchy and a decrease in overall coral cover under lowered pH. Collectively, our case study demonstrates how modified competitive performance under increasing OA will in all likelihood change the composition, structure and functionality of reef coral communities.

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Environmental controls on daytime net community calcification on a Red Sea reef flat

Coral growth and carbonate accumulation form the foundation of the coral reef ecosystem. Changes in environmental conditions due to coastal development, climate change, and ocean acidification may pose a threat to net carbonate production in the near future. Controlled laboratory studies demonstrate that calcification by corals and coralline algae is sensitive to changes in aragonite saturation state (Ωa), as well as temperature, light, and nutrition. Studies also show that the dissolution rate of carbonate substrates is impacted by changes in carbonate chemistry. The sensitivity of coral reefs to these parameters must be confirmed and quantified in the natural environment in order to predict how coral reefs will respond to local and global changes, particularly ocean acidification. We estimated the daytime hourly net community metabolic rates, both net community calcification (NCC) and net community productivity (NCP), at Sheltered Reef, an offshore platform reef in the central Red Sea. Average NCC was 8 ± 3 mmol m−2 h−1 in December 2010 and 11 ± 1 mmol m−2 h−1 in May 2011, and NCP was 21 ± 7 mmol m−2 h−1 in December 2010 and 44 ± 4 mmol m−2 h−1 in May 2011. We also monitored a suite of physical and chemical properties to help relate the rates at Sheltered Reef to published rates from other sites. While previous research shows that short-term field studies investigating the NCC–Ωa relationship have differing results due to confounding factors, it is important to continue estimating NCC in different places, seasons, and years, in order to monitor changes in NCC versus Ω in space and time, and to ultimately resolve a broader understanding of this relationship.

Continue reading ‘Environmental controls on daytime net community calcification on a Red Sea reef flat’

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Ocean acidification in the IPCC AR5 WG II

OUP book