207 research outputs found
High-resolution ground verification, cluster analysis and opticalmodel of reef substrate coverage on Landsat TM imagery (Red Sea, Egypt)
No full textA combination of high-resolution ground verification, cluster analysis using Landsat Thematic Mapper (TM) data, and optical modelling, was applied to Red Sea reef substrate. Ground verification, in an area of 3 by 20 pixels (90 by 600 m) with one metre scale resolution, identified the presence of 30 different bottom types that were later reduced to twelve dominant bottom types. A combination of bispectral plots and principal component analysis using spectral bands 1, 2 and 3 confirmed the presence of nine bottom types. The identified clusters were separated and used as a training set to classify substrate. Optical modelling, using literature radiance values and coverage of the original twelve dominant bottom types and a simple model for atmospheric and water column absorption, revealed a difference of up to 60 W m-2 between predicted substrate radiance and the satellite sensor values in the reef top area. Considering the simple atmospheric correction model, the lack of in situ radiance measurements and the uncertainties with respect to possible changes in bottom type distribution since the acquisition of the 14 year old image, the results show the potential use of satellite imagery for reef research in both biological and geological analysis through very precise and semi-quantitative ground verification, including in situ reflectance measurements
Controlled photocatalytic hydrocarbon oxidation by uranyl complexes
No full textControlled, photocatalytic C−H bond activations are key reactions in the toolkits of the modern synthetic chemist. While it is known that the uranyl(VI) ion, [UVIO2]2+, the environmentally dominant form of uranium, is photoactive, most literature examines its luminescent properties, neglecting its potential synthetic utility for photocatalytic C−H bond cleavage. Here, we synthesise and fully characterise an air‐stable and hydrocarbon‐soluble uranyl phenanthroline complex, [UVIO2(NO3)2(Ph2phen)], UPh2phen, and demonstrate that it can catalytically abstract hydrogen atoms from a variety of organic substrates under visible light irradiation. We show that the commercially available parent complex, uranyl nitrate ([UVIO2(NO3)2(OH2)2]⋅4H2O; UNO3), is also competent, but from electronic spectroscopy we attribute the higher rates and selectivity of UPh2phen to ligand‐mediated electronic effects. Ketones are selectively formed over other oxygenated products (alcohols, etc.), and the catalytic oxidation of substrates containing a benzylic C−H position is particularly improved for UPh2phen. We also show uranyl‐mediated photocatalytic C−C bond cleavage in a model lignin compound for the first time
Morphometric parameters of the Coral Belt Mounds (CBM), Namibian coral mound province
No full textQuantitative morphometric analyses were carried out for each mound following the workflows presented by Purkis et al. (2007) The coral mound base was defined following the methodological approach of Correa et al. (2012) using the dip angle map, generated from the digital elevation model (DEM), to extract closed polygons that follow the 3°-contour line. This 3°-cutoff has been qualitatively validated with a comparison between the DEM and the dip angle. Small-scaled polygons within mound perimeters and resulting from bathymetry artefacts were filtered out. Manual editing was applied to split simple merged mound structures (e.g. twin-peak mounds) based on higher cut-off slope values (4-5°). Furthermore, polygons describing the mound footprint have been corrected to remove unrealistic shapes especially common for the CBM. The DEM was subsequently re-gridded to generate hypothetical bathymetric maps without mounds, for which the vertical relief beneath each removed mound was interpolated from the mound perimeters. The newly interpolated surfaces were then subtracted from the original DEMs to evaluate the volume and heights of the coral mounds. Only features with a footprint area greater than 900 suared meters (corresponding to a two-dimensional array of 3 × 3 DEM grid cells) and with a height of >2 m above the surrounding seafloor (4 × 0.5 m of vertical precision) were considered as coral mounds and quantitatively analyzed
Morphometric parameters of the Squid Mounds (SQM), Namibian coral mound province
No full textQuantitative morphometric analyses were carried out for each mound following the workflows presented by Purkis et al. (2007) The coral mound base was defined following the methodological approach of Correa et al. (2012) using the dip angle map, generated from the digital elevation model (DEM), to extract closed polygons that follow the 3°-contour line. This 3°-cutoff has been qualitatively validated with a comparison between the DEM and the dip angle (Fig. 2). Small-scaled polygons within mound perimeters and resulting from bathymetric artifacts were filtered out. Manual editing was applied to split simple merged mound structures (e.g. twin-peak mounds) based on higher cut-off slope values (4-5°). Furthermore, polygons describing the mound footprint have been corrected to remove unrealistic shapes especially common for the CBM. The DEM was subsequently re-gridded to generate hypothetical bathymetric maps without mounds, for which the vertical relief beneath each removed mound was interpolated from the mound perimeters. The newly interpolated surfaces were then subtracted from the original DEMs to evaluate the volume and heights of the coral mounds. Only features with a footprint area greater than 900 squared meters (corresponding to a two-dimensional array of 3 × 3 DEM grid cells) and with a height of >2 m above the surrounding seafloor (4 × 0.5 m of vertical precision) were considered as coral mounds and quantitatively analyzed
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Defining the geochemical composition of the newly discovered NEOM brine pool and underlying sedimentary pore waters, Gulf of Aqaba, Red Sea
No full textBrine pools are dense bodies of highly saline water that accumulate in depositional lows in the seafloor, and they often host rich extremophile microbial communities with metabolisms analogous to those that arose on early Earth. Since the early 1960’s, several deep-sea brine pools have been discovered in the Red Sea, and many researchers have worked to classify these pools into conceptual models. The first integrates the brine pool temperature and general depositional setting (Duarte et al., 2020). In this model, brine pools like Discovery and Atlantis II are considered ‘hot, axial’ brine pools, while brine pools like Afifi and Thuwal Seeps, which are located much closer to the coastlines with lower temperatures, are considered ‘cool, coastal brines’ (Anschutz et al., 1999; Antunes et al., 2011; Backer & Schoell, 1972; Batang et al., 2012; Cochran et al., 1986; Duarte et al., 2020; Gurvich, 2006). The second conceptual framework classifies the brine pools based on the origin of the brines (Schmidt el al., 2015). In this model, two types of brines were delineated: Type 1 and Type 2 (Schmidt el al., 2015). The brine chemistry of Type I pools is predominantly controlled by evaporite dissolution and sediment alteration, while Type II brine pools are primarily influenced by hydrothermal activity (Schmidt et al., 2015). In 2020, a first of its kind brine pool was discovered in the Gulf of Aqaba during the NEOM-facilitated OceanX ‘Deep Blue’ research cruise. The NEOM brine pool is a cold-water, anoxic brine pool that is situated at abyssal depths (1,770m) in close proximity to the coastline, and was the first brine pool discovered outside the Red Sea proper (Purkis et al., in review). During the OceanX cruise, a transect of 5 short sediment cores (50-150cm) were collected across the western edge of the brine pool, radiocarbon dating indicates that the sediments recovered from these cores span the past 1,200 years (Purkis et al., in review). Thus, motivated to better understand the geochemical conditions that characterize the NEOM brine pool, we compare elemental measurements of the brine pool chemistry to interstitial pore waters extracted using Rhizon samplers in each of the 5 sediment cores. The pore water samples collected from Core 5 were analyzed for elemental composition, alkalinity, and pH. Our preliminary results suggest that sediments directly underlying the center of the brine pool (0-10 cm below the sediment-brine pool interface) contain interstitial pore waters that are less saline than the overlying brine. CTD measurements of in situ temperature indicate that the NEOM brine pool (21oC, Purkis et al., in review) is not a hot brine pool, suggesting that it is most similar to the Thuwal Seeps and Afifi Brine Pools (Batang et al., 2012; Duarte et al., 2020). As proposed by Schmidt et al. (2015), cross plots of Mg/Ca ratios and boron concentrations indicate that the NEOM brine pool is chemically most similar to Type 1 pools like Oceanographer and Kebrit, suggesting that a combination of hydrothermal alteration and sediment-water interaction have produced the brines observed in the NEOM pool. This new elemental dataset allows for a characterization of the range of chemical environments existing within the NEOM brine pool and permits comparison to the other brine pools of the Red Sea. When coupled with metagenomic analysis of the resident microbial communities, characterization of these extreme environments can provide better understanding of the limits of life (Kargel, 1991; Gaidos and Nimmo, 2000; van der Wielen et al., 2005), providing insight calibrated by modern analogues into the geological past, when life may have evolved in high salinity, anoxic seawater, and may inform the search for extraterrestrial life in that brine pools are a high priority target for exploration
Distribution, ecology, and status of the white shark, Carcharodon carcharias, in the Mediterranean Sea
No full textThe occurrence of the white shark, Carcharodon carcharias, in the Mediterranean Sea has been reported since the Middle Ages (476–1453). Several studies have documented its presence in various areas of the basin, but no comprehensive review of the distribution and status of this species is available for the area. We compiled a total of 628 white shark records from 476 to 2015. Data suggests that the white shark is more common in the western Mediterranean Sea, especially in the Adriatic Sea and in the Sicilian Channel and is more frequently observed during summer months. However, analysis using night-time satellite imagery showed the existence of an anthropogenic bias in the distribution of white sharks. All size classes have been recorded in the region. However, the highest occurrence of young of the year has been recorded in the Sicilian Channel, in the Adriatic Sea and in the Aegean Sea, in summer, suggesting these areas might serve as nursery grounds. In the Mediterranean Sea, the white shark exhibits a broad diet. The most common prey found include small cetaceans (Tursiops truncatus, Stenella coeruleoalba), tuna (Thunnus spp.), swordfish (Xiphias gladius) and loggerhead sea turtle (Caretta caretta). A total of 53 white shark records refer to interactions between sharks and humans that resulted in a detrimental impact on humans, which include 42 bites and 11 reports of the presence of human remains in the stomach of captured animals. Analysis of the temporal variation in mean total lengths of white sharks found a decreasing trend from 1913 to 2012. The decreasing length of white sharks suggests this species might be declining in the Mediterranean Sea
A new species of Bathypathes (Cnidaria, Anthozoa, Antipatharia, Schizopathidae) from the Red Sea and its phylogenetic position
No full textA black coral, Bathypathes thermophila Chimienti, sp. nov. is described from the Saudi Arabian coasts of the Gulf of Aqaba and north Red Sea (Neom area) using an integrated taxonomic approach. The morphological distinctiveness of the new species is confirmed by molecular analyses. The species thrives in warm and high salinity waters typical of the Red Sea at bathyal depths. It can form colony aggregations on muddy bottoms with scattered, small hard substrates. Colonies are monopodial, feather-like, and attached to a hard substrate through a thorny basal plate. Pinnules are simple, arranged biserially and alternately, and all the same length (up to approximately 20 cm) except for few, proximal ones. Spines are triangular, laterally compressed, subequal, smooth, and simple or rarely bifurcated. Polyps are elongated transversely, 1.5–2.0 mm in transverse diameter. Large colonies can have one or few branches, whose origin is discussed. The phylogenetic position of B. thermophila sp. nov. within the order Antipatharia, recovered using three mitochondrial markers, shows that it is nested within the family Schizopathidae. It is close to species in the genera Parantipathes, Lillipathes, Alternatipathes, and Umbellapathes rather than to the other available representatives of the genus Bathypathes, as currently defined based on morphology. In agreement with previous findings, our results question the evolutionary significance of morphological characters traditionally used to discriminate Antipatharia at higher taxonomic level
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The Role of Topography in Promoting Fractal Patchiness in a Carbonate Shelf Landscape
No full textSatellite remote sensing has shown numerous aspects of coral reef seascapes to be fractal. That is, they display characteristics of scale-invariance and complexity. To date, an understanding of why reefscapes adopt this curious scaling has been lacking. This property was investigated using high-resolution terrain models built using bathymetric LiDAR soundings of the shallow Puerto Rico insular shelf. A computer-simulation model constructed using simple random processes was adequate to describe many of the intricacies of actual coral reef terrain. This model, based on fractional Brownian motion (fBm), produced surfaces that were visually and statistically indistinguishable from natural seabeds, at spatial scales of 0.001–25 km2. The conformity between model and nature allowed us to ascertain the importance of topography as a driver for the fractal patchiness that has been shown to occur in plan-view maps of reefscapes (e.g. Purkis et al. J Sediment Res 75:861–876, 2005, J Geol 115:493–508, 2007. For the considered Puerto Rican shelf, the necessary Brownian-like seabed topography likely arose through karst erosion overprinted by several episodes of reef development
Making Digital Heritage about People's Life Stories
No full textActively creating new digital heritage content about people’s life historiesis part of the democratisation of heritage engagement with the public. Theapproach of documenting unofficial histories is supported by a growingliterature. Unofficial stories contribute new perspectives on the heritageidentity of a region. The case study of the ‘Local People’ exhibition, curatedby the author in 2013 in the North West of Ireland, is used to discuss themethodology of a digital curatorial process, www.localpeopleireland.com.This article argues that gathering and presenting unofficial histories ofindividuals’ life experiences, can disrupt official narratives of The Troublesand challenge a regional identity based on conflict and division. The makingof digital history is analysed as a curatorial process, rather than the easeof use of technology. The methods used included: filmed interviews, newportrait photography and the digitisation of family photograph albums.A virtual exhibition was produced and new digital historical sources werecreated that transform intangible heritage by crystallising people’s voicesand images into ‘tangible’ digital objects. ‘Local People’ utilised Facebookhttps://www.facebook.com/localpeopleproject/?fref=ts and Vimeo https://vimeo.com/album/2518991. It is argued that the digital space provides a‘virtual contact zone’ in which diverse, unofficial and personal narrativescan be presented together
Water column productivity and temperature predict coral reef regeneration across the Indo-Pacific
No full textPredicted increases in seawater temperatures accelerate coral reef decline due to mortality by heat-driven coral bleaching. Alteration of the natural nutrient environment of reef corals reduces tolerance of corals to heat and light stress and thus will exacerbate impacts of global warming on reefs. Still, many reefs demonstrate remarkable regeneration from past stress events. This paper investigates the effects of sea surface temperature (SST) and water column productivity on recovery of coral reefs. In 71 Indo-Pacific sites, coral cover changes over the past 1-3 decades correlated negative-exponentially with mean SST, chlorophyll a, and SST rise. At six monitoring sites (Persian/Arabian Gulf, Red Sea, northern and southern Galápagos, Easter Island, Panama), over half of all corals were <31 years, implying that measured environmental variables indeed shaped populations and community. An Indo-Pacific-wide model suggests reefs in the northwest and central Indian Ocean, as well as the central west Pacific, are at highest risk of degradation, and those at high latitudes the least. The model pinpoints regions where coral reefs presently have the best chances for survival. However, reefs best buffered against temperature and nutrient effects are those that current studies suggest to be most at peril from future ocean acidification
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