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Gabay Y.,Tel Aviv University | Gabay Y.,The Interuniversity Institute for Marine Science | Benayahu Y.,Tel Aviv University | Fine M.,The Interuniversity Institute for Marine Science | And 2 more authors.
Ecology and Evolution

Increasing anthropogenic pCO2 alters seawater chemistry, with potentially severe consequences for coral reef growth and health. Octocorals are the second most important faunistic component in many reefs, often occupying 50% or more of the available substrate. Three species of octocorals from two families were studied in Eilat (Gulf of Aqaba), comprising the zooxanthellate Ovabunda macrospiculata and Heteroxenia fuscescens (family Xeniidae), and Sarcophyton sp. (family Alcyoniidae). They were maintained under normal (8.2) and reduced (7.6 and 7.3) pH conditions for up to 5 months. Their biolological features, including protein concentration, polyp weight, density of zooxanthellae, and their chlorophyll concentration per cell, as well as polyp pulsation rate, were examined under conditions more acidic than normal, in order to test the hypothesis that rising pCO2 would affect octocorals. The results indicate no statistically significant difference between the octocorals exposed to reduced pH values compared to the control. It is therefore suggested that the octocorals' tissue may act as a protective barrier against adverse pH conditions, thus maintaining them unharmed at high levels of pCO2. Several biological features of selected octocorals were examined under high pCO2 conditions. The results indicate no difference between the octocorals exposed to reduced pH values compared to the control. It is therefore suggested that the octocorals' tissue may act as a protective barrier against adverse pH conditions, thus maintaining them unharmed at high levels of pCO2. © 2012 The Authors. Ecology and Evolution published by Blackwell Publishing Ltd. Source

Meron D.,Bar - Ilan University | Buia M.-C.,Stazione Zoologica Anton Dohrn | Fine M.,Bar - Ilan University | Fine M.,The Interuniversity Institute for Marine Science in Eilat | Banin E.,Bar - Ilan University
Microbial Ecology

Ocean acidification, resulting from rising atmospheric carbon dioxide concentrations, is a pervasive stressor that can affect many marine organisms and their symbionts. Studies which examine the host physiology and microbial communities have shown a variety of responses to the ocean acidification process. Recently, several studies were conducted based on field experiments, which take place in natural CO2 vents, exposing the host to natural environmental conditions of varying pH. This study examines the sea anemone Anemonia viridis which is found naturally along the pH gradient in Ischia, Italy, with an aim to characterize whether exposure to pH impacts the holobiont. The physiological parameters of A. viridis (Symbiodinium density, protein, and chlorophyll a+c concentration) and its microbial community were monitored. Although reduction in pH was seen to have had an impact on composition and diversity of associated microbial communities, no significant changes were observed in A. viridis physiology, and no microbial stress indicators (i. e., pathogens, antibacterial activity, etc.) were detected. In light of these results, it appears that elevated CO2 does not have a negative influence on A. viridis that live naturally in the site. This suggests that natural long-term exposure and dynamic diverse microbial communities may contribute to the acclimation process of the host in a changing pH environment. © 2012 Springer Science+Business Media New York. Source

Lavy A.,Tel Aviv University | Eyal G.,Tel Aviv University | Eyal G.,The Interuniversity Institute for Marine Science in Eilat | Neal B.,University of Queensland | And 3 more authors.
Methods in Ecology and Evolution

Summary: In order to understand physiological, ecological and biological processes, it is often crucial to determine an organism's volume and surface area (SA). Most of the available methods require sacrificing the organism or at least removing it from its natural habitat, in order to measure these parameters. Advances in computer vision algorithms now allow us to determine these parameters using non-destructive, three-dimensional modelling. The addition of cloud computing and the availability of freeware make this tool widely accessible. Photographs of corals and sponges were taken in natura and used to create digital 3D models using the 'structure-from-motion' technique. Modelling was done online using 123D Catch freeware (Autodesk Inc.). Volume and SA of the corals and sponges were calculated from these 3D models. Comparing in situ 3D modelling to current measuring methods (e.g. water displacement, paraffin dipping) showed that volume calculation by 3D modelling gave fast results accurate to within 8% of estimated true volume. Using cloud computing enabled the creation of a 3D model in <30 min. SA accuracy was found to differ significantly, depending on the shape of the modelled object, with an accuracy ranging widely from 2% to 18%. We found that in situ volume and SA measurements created by 3D modelling enable easy, fast and non-intrusive studies of benthic aquatic organisms, without removing the subject organisms from their habitat, thus enabling continuous study of natural growth over extended time periods. The freely available freeware, along with ease of use, makes this method accessible to many areas of research. © 2015 British Ecological Society. Source

Ben-Zvi O.,Tel Aviv University | Eyal G.,Tel Aviv University | Eyal G.,The Interuniversity Institute for Marine Science in Eilat | Loya Y.,Tel Aviv University

Light in the sea is one of the major factors influencing corals, with changes in light being rapid along the depth gradient. Those changes can be a potential stress factor for coral-reef organisms and affect different aspects of the coral’s physiology, including its fluorescence. Fluorescence is a physical phenomenon, comprising the emission of light by a substance that has absorbed light with a different wavelength. Major hypotheses concerning the role of coral fluorescence include that of photoprotection and the facilitation of photosynthesis. We sought to further investigate some ecophysiological aspects of coral fluorescence. We focused on the effect of different light conditions on fluorescence of the coral Galaxea fascicularis and used photography, confocal microscopy, and spectral measurements to assess changes in its fluorescence. We show that fluorescence is significantly influenced by light and, therefore, by depth. Coral fluorescence increased with the increase in light intensity and when the spectrum of light was broader. Hence, we support the “sunscreen” hypothesis and conclude that fluorescence plays a role in the coral’s defense mechanism against harmful radiation. However, multiple fluorescent proteins, as found in different locations of the coral tissue, might suggest more than one functional role of fluorescence in the coral’s physiology. © 2014, Springer International Publishing Switzerland. Source

Kuguru B.,Bar - Ilan University | Kuguru B.,The Interuniversity Institute for Marine Science in Eilat | Achituv Y.,Bar - Ilan University | Gruber D.F.,City University of New York | And 3 more authors.
Journal of Experimental Marine Biology and Ecology

Rhodactis rhodostoma and Discosoma unguja are the most common corallimorpharians on coral reefs in the northern Red Sea, where individuals of R. rhodostoma form large aggregations on intertidal reef flats and those of D. unguja occupy holes and crevices on the reef slope. Aside from these contrasting patterns of microhabitat, little is known concerning their mechanisms of photoacclimation to environmental conditions. We demonstrate here that different mechanisms of photoacclimation operate in both species and that these differences explain, in part, the contrasting patterns of distribution and abundance of these common corallimorpharians. Experimental exposure of the species' respective polyps to the synergistic effects of ultraviolet and photosynthetically active radiation revealed that endosymbiotic zooxanthellae protected the host R. rhodostoma from photooxidation damage. Zooxanthellae do so by reducing their chlorophyll pigment and cellular abundance, as well as by adjusting their efficiency of light absorption and utilization according to the level of irradiance. The host photoprotects its endosymbionts from harmful ultraviolet radiation (UVR) by synthesizing enzymatic antioxidants against oxygen radicals. In contrast, individuals of D. unguja utilize a behavioral mechanism of photoacclimation in which they physically migrate away from exposed areas and towards shaded habitats and thus avoid the damaging biological effects of UVR. We conclude that a combination of physiological and behavioral mechanisms appear to control microhabitat segregation between these corallimorpharian species on tropical reefs. These various mechanisms of local adaptation to environmental conditions may be largely responsible for the wide distributional ranges of some corallimorpharians, and may enable these common reef organisms to tolerate environments that are highly variable, both spatially and temporally. © 2010 Elsevier B.V. Source

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