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LD 50 (time to 50% survival; open bars) and critical point (solid bars) values (in hours) of early life history stages of Rhytisma fulvum fulvum: (A) planulae, (B) azooxanthellate primary polyps, and (C) zooxanthellate primary polyps exposed to UVR at different ambient temperatures . Number of tested animals is indicated above bars.
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The interaction between ambient water temperature and UVR and its possible effect on the survival of coral early life-history stages was investigated in the Red Sea soft corals Heteroxenia fuscescens Eherenberg, 1834, and Rhytisma fulvum fulvum Forsskål, 1775. Planulae and azoo- and zooxanthellate polyps were obtained from colonies collected from t...
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... experiments, exhibiting a slow decline in survival and high values of critical point and Ld 50, ranging between 30-64 and 217-460 cumula- tive hrs of exposure to UVR, respectively. The UVR-treated planulae retained their normal appearance throughout all experiments. Survival of the planulae at 26 °C was significantly higher than at 25 °C ( Fig. 6; Kaplan-Meier Survival analysis, Logrank tests: P = 0.0063). The critical point for azooxanthellate primary polyps was achieved after 24 hrs of UVR exposure and their Ld 50 was 128 hrs at 26 °C and 95.5 hrs at 28 °C (Fig. 6). For the zooxanthellate primary polyps, the critical point was recorded after 30 hrs at 28 °C in both ...
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... normal appearance throughout all experiments. Survival of the planulae at 26 °C was significantly higher than at 25 °C ( Fig. 6; Kaplan-Meier Survival analysis, Logrank tests: P = 0.0063). The critical point for azooxanthellate primary polyps was achieved after 24 hrs of UVR exposure and their Ld 50 was 128 hrs at 26 °C and 95.5 hrs at 28 °C (Fig. 6). For the zooxanthellate primary polyps, the critical point was recorded after 30 hrs at 28 °C in both experiments, with Ld 50 of 170 and 135 hrs. Mortality also occurred in the control group and reached 65% of the initial number of polyps after 168 hrs of exposure. Survival of planulae at 26 °C was significantly higher than that of ...
Citations
... Given the sensitivity of early life stages of animals to changing environmental conditions, it is important to understand how UVR interacts with other stressors to influence the early survival and recruitment success of corals. This would be especially true for the egg and planktonic larval stages that are generally more buoyant and remain near the ocean surface and would be exposed to potentially high levels of UVR (Zeevi-Ben-Yosef and Benayahu, 2008). Taken together, the combined impacts of UVR and environmental change on early life history stages may identify potential bottlenecks in recruitment and survivability that may impact future populations of corals. ...
... Previous studies have identified that elevated temperature and extreme ultraviolet can act synergistically, thereby leading to impacts of multiplicative magnitude (Ban et al., 2014;Jin et al., 2019). For instance, elevated temperature and UVB irradiances were found to act synergistically on the symbiont density (Drohan et al., 2005) and the survival and photosynthetic efficiency (Ferrier-Pages et al., 2007;Zeevi Ben-Yosef and Benayahu, 2008) of tropical reef cnidarians, which bears the question if Red Sea scleractinian corals will be able to acclimate to the increased temperatures and UVB exposure in future environmental conditions. ...
Despite being exposed to extreme water temperatures and solar irradiances, Red Sea corals are relatively resistant to bleaching. While their thermal tolerance is well described, little is known about their resistance to ultraviolet-B radiation (UVB). Here, we performed a short-term (2 days) UVB-removal incubation with Stylophora pistillata, and in situ measurements with Pocillopora verrucosa complemented by a long-term (46 days) transplantation and UVB-removal experiment. Using a suite of physiological parameters (effective quantum yield (F v’/F m’), oxidative stress (lipid peroxidation, LPO), and primary production), we assessed the impacts of UVB on the physiology and acclimation capacity of Red Sea corals. Shielding S. pistillata from UVB did not change the gross primary production or F v’/F m’, and respiration and LPO in the host remained unaffected. In situ, P. verrucosa exhibited less varying and significantly higher F v’/F m’ in 8 m depth (0.61 ± 0.04) than in 4 m (0.52 ± 0.06), 2 m (0.51 ± 0.09), and 0.5 m (0.50 ± 0.11), where water temperatures ranged from 30.5–33.4, 30.6–34.0, 30.8–34.5, 30.6–37.3°C and daily UVB exposures averaged 0.9, 2.9, 11.8 and 21.4 kJ m⁻², respectively. F v’/F m’ correlated the strongest with UVB (-0.57), followed by PAR (-0.54) and temperature (-0.40), suggesting that UVB is a key determinant of photosynthetic efficiency. F v’/F m’ of upward transplanted specimens (T 1m) was initially decreased but gradually increased and reached the same values as shallow corals (1 m) after 44 days. UVB removal significantly increased the F v’/F m’ of transplanted corals in the first 20 days. Oxidative stress was initially highest in T 1m samples under full sunlight but equalized with 1 m specimens by day 46, whereas oxidative stress was significantly reduced by day 4 in T 1m corals sheltered from UVB. Overall, UVB-removal generally had little impact on the physiology of shallow-water S. pistillata and P. verrucosa but considerably accelerated the acclimation of upward transplanted corals. Our study highlights that UVB is a crucial stressor governing the photoacclimation capacity of these Red Sea coral species.
... In contrast, there is a very long history of taxonomic work on octocorals in the northern Red Sea (in Israel, Egypt, and Jordan), with early publications such as Lamarck (1816), Ehrenberg (1834), Klunzinger (1877), and Kükenthal (1913) documenting octocorals (Haverkort-Yeh et al. 2013). Furthermore, extensive ecological studies have been performed on octocorals in the Red Sea (e.g., Benayahu and Loya 1981;Benayahu et al. 1989;Benayahu 1995;Zeevi-Ben-Yosef and Benayahu 2008); therefore, it is likely that more species are known from there than from the Persian Gulf, where very few studies have been done. Benayahu (2002) stated the high diversity of the Red Sea soft corals is due in large part (families Alcyoniidae and Xeniidae) on more recent identifications and revisions (ca. ...
Octocorals (Octocorallia, Alcyonacea) are distributed worldwide and their taxonomy in the Persian Gulf has been a subject of controversy among experts due to their cryptic features. Here, we present a primary review of the Alcyonacea in the Iranian Persian Gulf with molecular documentation to provide insight into the real diversity within this order. Our molecular study was based on two mitochondrial protein-coding (COI and mtMuts) and one nuclear (28S rDNA) gene sequences, which identified seven families, 14 genera, and 21 species of Octocorallia in the Persian Gulf that were well-supported by maximum likelihood and Bayesian analyses. Our results indicate consistency between morphological and molecular characteristics at the species level. We conclude the presence of some heterogeneous groups of genera creates ambiguity in our analysis.
... Though previous studies have identified that elevated temperature and extreme ultraviolet can act synergistically, thereby leading to impacts of multiplicative magnitude (Ban et al., 2014;. For instance, elevated temperature and UVB irradiances were found to act synergistically on the symbiont density (Drohan et al., 2005) and the survival and photosynthetic efficiency Zeevi Ben-Yosef and Benayahu, 2008) of tropical reef cnidarians, which bears the question if Red Sea scleractinian corals will be able to acclimate to the increased temperatures UVB exposure in future environmental conditions. ...
... Al-Aidaroos et al.(2015) found increased mortality rates in ten different zooplankton taxa in response to natural UV-B exposure intensities comparable to those received in situ at ~ 3.5 m depth, while a study byBoelen et al. (2002) reported UV-induced DNA damage in natural communities of bacterio-and phytoplankton from the surface down to a depth of 50 m.For Red Sea corallimorpharians, UV exposure induces a reduction in the concentration of chlorophyll pigments as well as the abundance of endosymbionts living in association with Rhodactis rhodostoma, while exposure to UV causes Discosoma unguja to physically migrate away from exposed locations towards shaded habitats in order to avoid UV damage(Kuguru et al., 2010). For other anthozoans in the Red Sea, such as soft corals, a decreased survival rate in response to combined UV-B (0.8 W m -2 ) and UV-A (3.0 W m -2 ) exposure has been reported during the early developmental stages of Heteroxenia fuscescens and Rhytisma fulvum fulvum(Zeevi Ben-Yosef and Benayahu, 2008). ...
Oligotrophic (sub-)tropical oceans receive intense incident ultraviolet radiation (UV, 280–400 nm) and their water columns are highly transparent due to their nutrient-deficient state. This combination suggests a high potential for adverse effects on organisms, yet only few reports describe the UV exposures received in these waters and the associated impacts on marine biota. Here, we aimed to investigate the UV bio-optics of various open ocean locations and, using the Red Sea as a representative oligotrophic environment, we investigated the pattern of UV attenuation over a wide latitudinal range, quantified UV exposures in the water column, and determined impacts of UVB (280–320 nm) on indigenous phytoplankton and scleractinian corals. Globally, the lowest average downwelling diffuse attenuation coefficients (Kd) in the UV spectrum were recorded in the ultra-oligotrophic Indian Ocean Subtropical Gyre (Kd(313nm): 0.110 m-1) and South Pacific Gyre (Kd(313nm): 0.098 m-1), while aCDOM(λ) was ~1–2 orders of magnitude higher than ap(λ), In the Red Sea, UV attenuation mirrored the prevailing latitudinal gradient in nutrients, with the lowest and highest Kd(313) of 0.130 m-1 and 0.357 m-1 measured in the far north and in the south of the basin, respectively. Central Red Sea waters were most transparent to UV in late summer, i.e., a few weeks after incident irradiances and SSTs reach their annual maximum. Although, the projected increase of SST due to climate change means that extreme UV exposure and temperatures could coincide in the near future. This finding is of particular relevance since we found that Red Sea diatom species such as C. closterium are highly sensitive to UVB-induced photoinhibition and cell decay (LRD50: 11.4 kJ). Water temperature also governed the UVB sensitivity of Synechococcus sp., although this group exhibited a high resistance overall (LRD50: 57 kJ to non-detectable). For corals, we found that UVB-removal generally had little impact on the oxidative stress levels and photophysiology of S. pistillata and P. verrucosa from shallow waters, but considerably accelerated the acclimation of upward transplanted corals, which highlights that UVB is a crucial stressor that governs the photoacclimation capacity of Red Sea corals.
... For Red Sea corallimorpharians, UV exposure induces a reduction in the concentration of chlorophyll pigments as well as the abundance of endosymbionts living in association with Rhodactis rhodostoma, while exposure to UV causes Discosoma unguja to physically migrate away from exposed locations toward shaded habitats in order to avoid UV damage (Kuguru et al., 2010). For other anthozoans in the Red Sea, such as soft corals, a decreased survival rate in response to combined UV-B (0.8 W m −2 ) and UV-A (3.0 W m −2 ) exposure has been reported during the early developmental stages of Heteroxenia fuscescens and Rhytisma fulvum fulvum (Zeevi Ben-Yosef and Benayahu, 2008). ...
Ultraviolet radiation (UV) is a crucial abiotic stressor that can have severe impacts on biota residing in the upper euphotic zone, especially if UV stress coincides with other stressors such as extreme sea surface temperatures (SSTs). Exposure-dependent effects of UV exposure have been described for a broad range of marine taxa and ecosystems such as coral reefs, yet little is known about the magnitude and seasonality of UV exposure in natural waters. In the present study, we determined how daily exposure of UV-B and UV-A varies seasonally along the water column of a reef system in the central Red Sea, and identified periods when damaging UV levels are likely to coincide with episodes of extreme SST, both presently and in the future. Between July 2016 and September 2018, UV spectroradiometer profiles were recorded fortnightly at a pelagic site adjacent to a mid-shore reef off the Saudi Arabian Red Sea coast, while atmospheric UV-B and UV-A irradiances were measured in 10-min intervals. Additionally, we quantified the concentration of chlorophyll-a (Chl-a) and absorption by chromophoric dissolved organic matter (aCDOM) in the reef as well as the surrounding waters. Biologically effective optical depths (Z10%) ranged from 6.3–12.9 m (UV-B) and 14.4–27.3 m (UV-A), with the highest UV transparency being observed in late summer when photodegradation of dissolved organic matter (DOM) was most intense and the concentration and molecular weight of CDOM were at their lowest. Incident UV peaked a few weeks prior to this later summer maximum in UV transparency. Consequently, organisms living close to the water surface experienced their most intense UV exposure in May/June, while the timing of maximum UV exposure for biota below ∼2–4 m coincided with the annual peak in water transparency and water temperature, i.e., in July/August. However, SSTs in the Red Sea are increasing at a rapid rate due to climate change, with the consequence that extreme temperatures are occurring earlier in the year and may eventually coincide with extreme UV radiation in shallower areas of the reef. This development could have potentially detrimental effects on highly sensitive, immotile reef biota such as reef-building corals.
... Previous studies demonstrated that temperature and UV-B radiation are unlikely to operate independently ; so, synergistic or antagonistic responses are more likely than additive ones. For instance, elevated UV-B radiation and temperature act synergistically on the symbiont density in gorgonians and the survival and photosynthetic efficiency of corals Zeevi-Ben-Yosef & Benayahu, 2008), while they have an antagonistic effect on the growth of two intertidal algae species (Hoffman, Hansen, & Klinger, 2003). Meta-analyses examining the interactive effects of temperature and UVR (UV-A + UV-B) found that synergistic interactions are more common than additive or antagonistic interactions in marine biota [number of observations: 18;Crain et al. (2008)], while antagonistic effects occurred most frequently in freshwater biota [number of observations: 13; Jackson et al. (2016)]. ...
Aim: The interactive effects of increased temperature and ultraviolet‐B (UV‐B) radiation on terrestrial and aquatic biota remain poorly understood. Our goal is to increase knowledge by providing a comprehensive assessment of the combined effects of warming and increased UV‐B on organisms across these domains.
Location: Global.
Time period: 1995–2016.
Major Taxa studied: Terrestrial plants and animals, and marine and freshwater microalgae, macroalgae and animals.
Methods: We examined, using a meta‐analysis based on 1,139 published experimental assessments, the combined effects of temperature and UV‐B across terrestrial, freshwater and marine biota. We characterized the prevailing mode of combined effects (additive, synergistic or antagonistic), and assessed whether these were dose‐dependent or differed between terrestrial, freshwater and marine species, or between organisms growing in the Northern and Southern Hemispheres.
Results: Our results show that the two stressors generally acted opposingly, with a significant positive effect of increased temperature and a significant adverse effect of elevated UV‐B radiation. Regarding their interactive impact, additive interactions (84%) appeared to be much more common compared with multiplicative (16%) effects. The frequencies of interaction types differed significantly among the three habitats and different plant functional groups. The proportion of both synergistic and antagonistic effects increased with increasing magnitude of temperature and UV‐B changes, suggesting that additivity is constrained by an organism’s thermal and physiological limits.
Main conclusions: Our analysis demonstrates that due to their mostly opposing nature, elevated temperature, within the thermal limits of organisms, tends to compensate for the negative impact of UV‐B radiation when acting together, while their additive interaction is likely to assist impact prognosis. Our study, therefore, provides new insights into the predictions of the interactive effects of global change drivers across different habitats.
... In addition, the number of reactive oxygen species molecules (ROS) can increase (Courtial et al. 2017b). Furthermore, UVR can lower the settlement, development and survival rate of juvenile corals (Kuffner 2001;Zeevi Ben-Yosef and Benayahu 2008;Torres-Pérez and Armstrong 2012;Zhou et al. 2016). UVR may reduce Symbiodinium density (Gleason 1993) by increasing their expulsion rate (Zhou et al. 2017a), degrade chloroplasts (Camaya et al. 2016), or cause photoinhibition (Zhou et al. 2016) as a result of damage to the photosystems (Lesser 1996). ...
Ultraviolet radiation (UVR) can exacerbate the effects of elevated seawater temperatures concomitant with climate change. Such stressors can collapse the mutualism of scleractinian corals with their endosymbiotic unicellular algae, Symbiodinium spp. Conversely, we found that the Caribbean octocorals Pseudoplexaura crucis and Eunicea tourneforti coped with thermal and UVR stress. But, the responses differed and depended on the species’ biochemical properties. Furthermore, the effects of the stressors varied seasonally. For 7 d, during summer and winter, we exposed the octocorals to either 3 °C above ambient temperature, UVR, or both. In either season, the stressors did not affect protein or carbohydrate content nor the Symbiodinium genotype. At the elevated temperature in the summer, the lipid content in P. crucis fell alongside a 35% decline in Symbiodinium. Conversely, in E. tourneforti, algal density dropped 26% with no lipid loss. In both species, the remaining Symbiodinium retained their chlorophyll and carotenoid content. In the winter, + 3 °C and UVR led to increased algal density, mitotic index, and chlorophyll and carotenoid contents. Temperature affected more parameters than UVR, but additive, synergistic and antagonistic interactions occurred. These findings show the resilience of Caribbean gorgonian corals against stressful environmental conditions and highlight the importance of including organismal biochemical differences and seasonal responses into interpreting the effects of multiple stressors associated with global climate change.
... As temperature alters physiological rates and causes stress at the thermal limits of a species, temperature can alter or add to the response to UV-R in processes such as oxidative stress, DNA damage, and DNA repair . Several studies have examined the interaction between temperature and UV-R in tropical corals, with results indicating synergistic negative affects on the survival of planulae larvae and polyps (Yosef and Benayahu, 2008), coral bleaching (Gleason and Wellington, 1993), and reductions in zooxanthallae productivity (photosynthetic efficiency, Pages et al., 2007), responses largely attributed to oxidative stress. For four species of hermatypic corals, Pages et al. (2007) noted that exposure to UV-R (20.5 and 1.2 W m −2 UV-B) decreased photosynthetic efficiency (Fv/Fm), as did increases in temperature (up to 34 °C) for two of the species. ...
... There is a long history of octocoral collections from the Red Sea, with early publications such as Lamarck (1816), Ehrenberg (1834), Klunzinger (1877), and Kükenthal (1913). Numerous ecological studies on octocorals have also been conducted there (e.g., Benayahu and Loya 1981;Benayahu et al. 1989;Benayahu 1995;Zeevi-Ben-Yosef and Benayahu 2008). Many of these studies laid the foundation for similar studies worldwide (e.g., references in Benayahu 2002;Kahng et al. 2011). ...
A preliminary survey of Saudi Arabian Alcyonacea is presented, which combines classical taxonomy, multilocus molecular barcodes, and in situ photographs. We explored 14 locations along the west coast of the Kingdom of Saudi Arabia to assess the regional taxonomic diversity of non-gorgonian alcyonaceans. We collected samples from a total of 74 colonies, distributed among four families: 18 colonies of Alcyoniidae, 14 of Nephtheidae, 9 of Tubiporidae, and 33 of Xeniidae. We sequenced the octocorals using multiple nuclear [ribosomal Internal Transcribed Spacers (ITS) and ATP Synthetase Subunit α (ATPSα)] and mitochondrial [MutS homolog (mtMutS) and Cytochrome C Oxidase subunit one (COI)] loci, providing molecular barcodes which will: (1) allow direct comparison of biodiversity from this location to others for which molecular data are available, and (2) facilitate future identifications of these taxa. Finally, this preliminary phylogeny of sampled taxa provides insights on the resolution of mitochondrial versus nuclear loci, and highlights octocoral taxa that require further taxonomic attention.
... The description of these bleaching events was based largely on qualitative observations and contained very limited quantitative data. Of the remaining publications, four examined the effects of thermal stress or ultraviolet radiation on zooxanthellae and coral regulatory pathways (Winters et al. 2006(Winters et al. , 2009Zeevi-Ben-Yosef and Benayahu 2008;Kvitt et al. 2011), two discussed oceanographic aspects of thermal stress (Veal et al. 2010;Davis et al. 2011), and one used coral cores to quantify the deleterious effects of ocean warming on coral growth rates (Cantin et al. 2010). Other relevant papers investigated the possibility of Red Sea corals acting as refugia of biodiversity in scenarios of severe global environmental stress (Riegl and Piller 2003), included the Red Sea in a comparative review of global trajectories of the state of coral reefs (Pandolfi et al. 2003) or discussed the relationship between coral disease and bleaching (Rosenberg and Ben-Haim 2002;Danovaro et al. 2008). ...
The Red Sea has long been recognized as a region of high biodiversity and endemism. Despite this diversity and early history of scientific work, our understanding of the ecology of coral reefs in the Red Sea has lagged behind that of other large coral reef systems. We carried out a quantitative assessment of ISI-listed research published from the Red Sea in eight specific topics (apex predators, connectivity, coral bleaching, coral reproductive biology, herbivory, marine protected areas, non-coral invertebrates and reef-associated bacteria) and compared the amount of research conducted in the Red Sea to that from Australia’s Great Barrier Reef (GBR) and the Caribbean. On average, for these eight topics, the Red Sea had 1/6th the amount of research compared to the GBR and about 1/8th the amount of the Caribbean. Further, more than 50 % of the published research from the Red Sea originated from the Gulf of Aqaba, a small area (<2 % of the area of the Red Sea) in the far northern Red Sea. We summarize the general state of knowledge in these eight topics and highlight the areas of future research priorities for the Red Sea region. Notably, data that could inform science-based management approaches are badly lacking in most Red Sea countries. The Red Sea, as a geologically “young” sea located in one of the warmest regions of the world, has the potential to provide insight into pressing topics such as speciation processes as well as the capacity of reef systems and organisms to adapt to global climate change. As one of the world’s most biodiverse coral reef regions, the Red Sea may yet have a significant role to play in our understanding of coral reef ecology at a global scale.
