Posts Tagged 'corals'



Fate of Mediterranean Scleractinian cold-water corals as a result of global climate change. A synthesis

This chapter addresses the question as to how Mediterranean cold-water corals might fare in the future under anthropogenically-induced global climate change. The focus on three most prominent scleractinian cold-water corals species, the two branching and habitat-forming forms Madrepora oculata, Lophelia pertusa and the solitary cup coral Desmophyllum dianthus. We provide an introduction to climate change principals, highlight the current status of the marine environment with regard to global climate change, and describe how climate change impacts such as ocean acidification are predicted to affect key calcifiers such as scleractinian cold-water corals in the Mediterranean region. A synthesis of the experimental cold-water coral studies conducted to date on climate change impacts: The present state of knowledge reviewed in this chapter takes into account the number of experiments that have been carried out in the Mediterranean as well as for comparative purposes in other parts of the world, to examine the effects of climate change on the corals. We assess the statistical robustness of these experiments and what challenges the presented experiments. A comprehensive multi-study comparison is provided in order to inform on the present state of knowledge, and knowledge gaps, in understanding the effects of global climate change on cold-water corals. Finally we describe what the fate could be for the important scleractinian coral group in the Mediterranean region.

Continue reading ‘Fate of Mediterranean Scleractinian cold-water corals as a result of global climate change. A synthesis’

Paleobiological traits that determined Scleractinian coral survival and proliferation during the late Paleocene and early Eocene hyperthermals

Coral reefs are particularly sensitive to environmental disturbances, such as rapid shifts in temperature or carbonate saturation. Work on modern reefs has suggested that some corals will fare better than others in times of stress and that their life history traits might correlate with species survival. These same traits can be applied to fossil taxa to assess whether life history traits correspond with coral survival through past intervals of stress similar to future climate predictions. This study aims to identify whether ecological selection (based on physiology, behavior, habitat, etc.) plays a role in the long‐term survival of corals during the late Paleocene and early Eocene. The late Paleocene‐early Eocene interval is associated with multiple hyperthermal events that correspond to rises in atmospheric pCO2 and sea surface temperature, ocean acidification, and increases in weathering and turbidity. Coral reefs are rare during the late Paleocene and early Eocene, but despite the lack of reef habitat, corals do not experience an extinction at the generic level and there is little extinction at the species level. In fact, generic and species richness increases throughout the late Paleocene and early Eocene. We show that corals with certain traits (coloniality, carnivorous, or suspension feeding diet, hermaphroditic brooding reproduction, living in clastic settings) are more likely to survive climate change in the early Eocene. These findings have important implications for modern coral ecology and allow us to make more nuanced predictions about which taxa will have higher extinction risk in present‐day climate change.

Continue reading ‘Paleobiological traits that determined Scleractinian coral survival and proliferation during the late Paleocene and early Eocene hyperthermals’

Characterizing the multivariate physiogenomic response to environmental change

Global change is altering the climate that species have historically adapted to – in some cases at a pace not recently experienced in their evolutionary history – with cascading effects on all taxa. A central aim in global change biology is to understand how specific populations may be “primed” for global change, either through acclimation or adaptive standing genetic variation. It is therefore an important goal to link physiological measurements to the degree of stress a population experiences (Annual Review of Marine Science, 2012, 4, 39). Although “omic” approaches such as gene expression are often used as a proxy for the amount of stress experienced, we still have a poor understanding of how gene expression affects ecologically and physiologically relevant traits in non‐model organisms. In a From the Cover paper in this issue of Molecular Ecology, Griffiths, Pan and Kelley (Molecular Ecology, 2019, 28) link gene expression to physiological traits in a temperate marine coral. They discover population-specific responses to ocean acidification for two populations that originated
from locations with different histories of exposure to acidification. By integrating physiological and gene expression data, they were able to elucidate the mechanisms that explain these population‐specific responses. Their results give insight into the physiogenomic feedbacks that may prime organisms or make them unfit for ocean global change.

Continue reading ‘Characterizing the multivariate physiogenomic response to environmental change’

Impact of ocean acidification on crystallographic vital effect of the coral skeleton

Distinguishing between environmental and species-specific physiological signals, recorded in coral skeletons, is one of the fundamental challenges in their reliable use as (paleo)climate proxies. To date, characteristic biological bias in skeleton-recorded environmental signatures (vital effect) was shown in shifts in geochemical signatures. Herein, for the first time, we have assessed crystallographic parameters of bio-aragonite to study the response of the reef-building coral Stylophora pistillata to experimental seawater acidification (pH 8.2, 7.6 and 7.3). Skeletons formed under high pCO2 conditions show systematic crystallographic changes such as better constrained crystal orientation and anisotropic distortions of bio-aragonite lattice parameters due to increased amount of intracrystalline organic matrix and water content. These variations in crystallographic features that seem to reflect physiological adjustments of biomineralizing organisms to environmental change, are herein called crystallographic vital effect (CVE). CVE may register those changes in the biomineralization process that may not yet be perceived at the macromorphological skeletal level.

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Species-specific calcification response of Caribbean corals after 2-year transplantation to a low aragonite saturation submarine spring

Coral calcification is expected to decline as atmospheric carbon dioxide concentration increases. We assessed the potential of Porites astreoides, Siderastrea siderea and Porites porites to survive and calcify under acidified conditions in a 2-year field transplant experiment around low pH, low aragonite saturation (Ωarag) submarine springs. Slow-growing S. siderea had the highest post-transplantation survival and showed increases in concentrations of Symbiodiniaceae, chlorophyll a and protein at the low Ωarag site. Nubbins of P. astreoides had 20% lower survival and higher chlorophyll a concentration at the low Ωarag site. Only 33% of P. porites nubbins survived at low Ωarag and their linear extension and calcification rates were reduced. The density of skeletons deposited after transplantation at the low Ωarag spring was 15–30% lower for all species. These results suggest that corals with slow calcification rates and high Symbiodiniaceae, chlorophyll a and protein concentrations may be less susceptible to ocean acidification, albeit with reduced skeletal density. We postulate that corals in the springs are responding to greater energy demands for overcoming larger differences in carbonate chemistry between the calcifying medium and the external environment. The differential mortality, growth rates and physiological changes may impact future coral species assemblages and the reef framework robustness.

Continue reading ‘Species-specific calcification response of Caribbean corals after 2-year transplantation to a low aragonite saturation submarine spring’

Spatiotemporal variability in seawater carbonate chemistry at two contrasting reef locations in Bocas del Toro, Panama

There is a growing concern for how coral reefs may fare in a high-CO2 world. The majority of laboratory and mesocosm experiments have revealed negative effects on the growth and calcification of reef builders exposed to elevated CO2 conditions. However, coral reefs are highly dynamic systems and the interplay between different biogeochemical and physical processes on reefs results in large variability of seawater carbonate chemistry on different functional scales. This can create localized seawater conditions that can either enhance or alleviate the effects of ocean acidification (OA). Consequently, in order to predict how coral reef ecosystems may respond to OA in the future, it is necessary to first establish a baseline of natural carbonate chemistry conditions. This includes characterizing the range and variability of carbonate chemistry and the physical and biogeochemical controls across a broad range of environments over both space and time. Here, we have characterized the spatial and temporal physiochemical variability of two contrasting coral reef locations in Bocas del Toro, Panama that differed in their benthic community composition, reef morphology, and exposure to open ocean conditions, using a combination of research approaches including stationary autonomous sensors and spatial surveys during the month of November 2015. Mean and diurnal temporal variability in both physical and chemical seawater parameters were remarkably similar between sites and sampling depths, although, the magnitude of spatial variability was quite different between the sites. Spatial gradients in physiochemical parameters at Punta Caracol reflected the cumulative modification from terrestrial runoff and benthic metabolism. Based on graphical vector analysis of salinity normalized TA-DIC data, reef metabolism was dominated by organic carbon cycling over inorganic carbon cycling at both sites, where the outer reef reflected net heterotrophy likely owing to remineralization of organic matter from terrestrial inputs. Altogether, the results of this study highlight the strong influence of terrigenous runoff on reef metabolism and seawater chemistry conditions and demonstrate the importance of considering external inputs of alkalinity in reefs when interpreting TA-DIC data in systems with large freshwater inputs. Predicting future changes to coral reef ecosystems requires an understanding of the natural complexity of these systems in which various physical, ecological and biogeochemical drivers interact creating large variability in seawater chemistry over space and time.

Continue reading ‘Spatiotemporal variability in seawater carbonate chemistry at two contrasting reef locations in Bocas del Toro, Panama’

Changes in coral reef community structure in response to year-long incubations under contrasting pCO2 regimes

Coral reefs are threatened by ocean acidification (OA), which depresses net calcification of corals, calcified algae, and coral reef communities. These effects have been quantified for many organisms, but most experiments last weeks-to-months, and do not test for effects on community structure. Here, the effects of OA on back reef communities from Mo’orea, French Polynesia (17.492 S, 149.826 W), were tested from 12 November 2015 to 16 November 2016 in outdoor flumes maintained at mean pCO2 levels of 364 µatm, 564 µatm, 761 µatm, and 1067 µatm. The communities consisted of four corals and two calcified algae, with change in mass (Gnet, a combination of gross accretion and dissolution) and percent cover recorded monthly. For massive Porites and Montipora spp., Gnet differed among treatments, and at 1067 µatm (relative to ambient) was reduced and still positive; for Porolithon onkodes, all of which died, Gnet was negative at high pCO2, revealing dissolution (sample sizes were too small for analysis of Gnet for other taxa). Growth rates (% cover month−1) were unaffected by pCO2 for Montipora spp., P. rus, Pocillopora verrucosa, and Lithophyllum kotschyanum, but were depressed for massive Porites at 564 µatm. Multivariate community structure changed among seasons, and the variation under all elevated pCO2 treatments differed from that recorded at 364 µatm, and was greatest under 564 µatm and 761 µatm pCO2. Temporal variation in multivariate community structure could not be attributed solely to the effects of OA on the chemical and physical properties of seawater. Together, these results suggest that coral reef community structure may be more resilient to OA than suggested by the negative effects of high pCO2 on Gnet of their component organisms.

Continue reading ‘Changes in coral reef community structure in response to year-long incubations under contrasting pCO2 regimes’


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Ocean acidification in the IPCC AR5 WG II

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