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Allison N.,University of St. Andrews | Cohen I.,The Interuniversity Institute of Eilat | Finch A.A.,University of St. Andrews | Erez J.,Hebrew University of Jerusalem
Geochimica et Cosmochimica Acta | Year: 2011

The Sr/Ca of aragonitic coral skeletons is a commonly used palaeothermometer. However skeletal Sr/Ca is typically dominated by weekly-monthly oscillations which do not reflect temperature or seawater composition and the origins of which are currently unknown. To test the impact of transcellular Ca 2+ transport processes on skeletal Sr/Ca, colonies of the branching coral, Pocillopora damicornis, were cultured in the presence of inhibitors of Ca-ATPase (ruthenium red) and Ca channels (verapamil hydrochloride). The photosynthesis, respiration and calcification rates of the colonies were monitored throughout the experiment. The skeleton deposited in the presence of the inhibitors was identified (by 42Ca spike) and analysed for Sr/Ca and Mg/Ca by secondary ion mass spectrometry. The Sr/Ca of the aragonite deposited in the presence of either of the inhibitors was not significantly different from that of the solvent (dimethyl sulfoxide) control, although the coral calcification rate was reduced by up to 66% and 73% in the ruthenium red and verapamil treatments, respectively. The typical precision (95% confidence limits) of mean Sr/Ca determinations within any treatment was <±1% and differences in skeletal Sr/Ca between treatments were correspondingly small. Either Ca-ATPase and Ca channels transport Sr 2+ and Ca 2+ in virtually the same ratio in which they are present in seawater or transcellular processes contribute little Ca 2+ to the skeleton and most Ca is derived from seawater transported directly to the calcification site. Variations in the activities of Ca-ATPase and Ca-channels are not responsible for the weekly-monthly Sr/Ca oscillations observed in skeletal chronologies, assuming that the specificities of Ca transcellular transport processes are similar between coral genera. © 2011 Elsevier Ltd. Source

Kvitt H.,Haifa University | Kvitt H.,The Interuniversity Institute of Eilat | Kvitt H.,Israel Oceanographic And Limnological Research | Rosenfeld H.,Israel Oceanographic And Limnological Research | And 3 more authors.
PLoS ONE | Year: 2011

Elevated seawater temperatures are associated with coral bleaching events and related mortality. Nevertheless, some coral species are able to survive bleaching and recover. The apoptotic responses associated to this ability were studied over 3 years in the coral Stylophora pistillata from the Gulf of Eilat subjected to long term thermal stress. These include caspase activity and the expression profiles of the S. pistillata caspase and Bcl-2 genes (StyCasp and StyBcl-2-like) cloned in this study. In corals exposed to thermal stress (32 or 34°C), caspase activity and the expression levels of the StyBcl-2-like gene increased over time (6-48 h) and declined to basal levels within 72 h of thermal stress. Distinct transcript levels were obtained for the StyCasp gene, with stimulated expression from 6 to 48 h of 34°C thermal stress, coinciding with the onset of bleaching. Increased cell death was detected in situ only between 6 to 48 h of stress and was limited to the gastroderm. The bleached corals survived up to one month at 32°C, and recovered back symbionts when placed at 24°C. These results point to a two-stage response in corals that withstand thermal stress: (i) the onset of apoptosis, accompanied by rapid activation of anti-oxidant/anti-apoptotic mediators that block the progression of apoptosis to other cells and (ii) acclimatization of the coral to the chronic thermal stress alongside the completion of symbiosis breakdown. Accordingly, the coral's ability to rapidly curb apoptosis appears to be the most important trait affecting the coral's thermotolerance and survival. © 2011 Kvitt et al. Source

Oron S.,Ben - Gurion University of the Negev | Oron S.,The Interuniversity Institute of Eilat | Angel D.,Haifa University | Goodman-Tchernov B.,The Interuniversity Institute of Eilat | And 5 more authors.
Marine Micropaleontology | Year: 2014

For about 20. years, finfish were reared in floating cages at the northern end of the Gulf of Aqaba-Eilat, Red Sea. The benthic ecosystem at the fish cages area was severely impacted by organic enrichment, resulting in an environment with no living foraminifera. A government decision led to the fish cages' removal in June 2008, creating a unique opportunity to monitor and assess post-removal changes in the benthos. Three years of benthic foraminiferal assemblage monitoring, beginning in July 2008 and ending in July 2011, are summarized here. Monitoring was carried out monthly by collecting sediment samples from stations of varying distances from the fish farm location, and, after its appearance in the summer of 2009, sampling the native seagrass Halophila stipulacea.Living foraminifera first appeared in the sediment in January 2009, progressively increasing in abundance thereafter. A clear difference in the rate of the rehabilitation process was observed on a spatial scale, related to distance from the point source of the organic enrichment. Recovery began with the first appearances of a few living individuals of Ammonia spp., Amphistegina lessonii and Nonion spp. By July 2009, a significant increase in overall abundance was recorded in the stations furthest from the fish cages, with Operculina ammonoides strongly dominating the assemblages. Populations of O. ammonoides revealed polymorphism in the coiling mode of their shells. Inflated involute and semi-involute forms dominate the living assemblages, whereas flattened evolute tests are more common in the dead assemblages, representing the period that preceded the fish farms. Unlike previous interpretations in the literature, in which such morphological variation was attributed to hydrodynamic energy or depth habitats, here it is hypothesized that the inflated involute and semi-involute forms are a morphological trait characteristic of the pioneer assemblages colonizing the area after its recovery from fish cages eutrophication. The reestablishment of the native H. stipulacea seagrass community was an important factor enabling epiphytic foraminifera to colonize the previously impacted sediments. All living foraminiferal species found on the seagrasses were also found in the former assemblages, suggesting that seagrass meadows existed before eutrophication and were the main habitats of the dead assemblages. © 2014 Elsevier B.V. Source

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