Browsing by Subject "Sea water"

Now showing 1 - 3 of 3
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    Open Access
    Environmental influences on the abundance and sexual composition of white sharks Carcharodon carcharias in Gansbaai, South Africa
    (Public Library of Science, 2013) Towner, Alison V; Underhill, Les G; Jewell, Oliver J D; Smale, Malcolm J
    The seasonal occurrence of white sharks visiting Gansbaai, South Africa was investigated from 2007 to 2011 using sightings from white shark cage diving boats. Generalized linear models were used to investigate the number of great white sharks sighted per trip in relation to sex, month, sea surface temperature and Multivariate El Niño/Southern Oscillation (ENSO) Indices (MEI). Water conditions are more variable in summer than winter due to wind-driven cold water upwelling and thermocline displacement, culminating in colder water temperatures, and shark sightings of both sexes were higher during the autumn and winter months (March-August). MEI, an index to quantify the strength of Southern Oscillation, differed in its effect on the recorded numbers of male and female white sharks, with highly significant interannual trends. This data suggests that water temperature and climatic phenomena influence the abundance of white sharks at this coastal site. In this study, more females were seen in Gansbaai overall in warmer water/positive MEI years. Conversely, the opposite trend was observed for males. In cool water years (2010 to 2011) sightings of male sharks were significantly higher than in previous years. The influence of environmental factors on the physiology of sharks in terms of their size and sex is discussed. The findings of this study could contribute to bather safety programmes because the incorporation of environmental parameters into predictive models may help identify times and localities of higher risk to bathers and help mitigate human-white shark interactions.
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    Open Access
    gbpA as a Novel qPCR Target for the Species-Specific Detection of Vibrio cholerae O1, O139, Non-O1/Non-O139 in Environmental, Stool, and Historical Continuous Plankton Recorder Samples
    (Public Library of Science, 2015) Vezzulli, Luigi; Stauder, Monica; Grande, Chiara; Pezzati, Elisabetta; Verheye, Hans M.; Owens, Nicholas J. P.; Pruzzo, Carla
    The Vibrio cholerae N-acetyl glucosamine-binding protein A (GbpA) is a chitin-binding protein involved in V . cholerae attachment to environmental chitin surfaces and human intestinal cells. We previously investigated the distribution and genetic variations of gbpA in a large collection of V . cholerae strains and found that the gene is consistently present and highly conserved in this species. Primers and probe were designed from the gbpA sequence of V . cholerae and a new Taq-based qPCR protocol was developed for diagnostic detection and quantification of the bacterium in environmental and stool samples. In addition, the positions of primers targeting the gbpA gene region were selected to obtain a short amplified fragment of 206 bp and the protocol was optimized for the analysis of formalin-fixed samples, such as historical Continuous Plankton Recorder (CPR) samples. Overall, the method is sensitive (50 gene copies), highly specific for V . cholerae and failed to amplify strains of the closely-related species Vibrio mimicus . The sensitivity of the assay applied to environmental and stool samples spiked with V . cholerae ATCC 39315 was comparable to that of pure cultures and was of 10 2 genomic units/l for drinking and seawater samples, 10 1 genomic units/g for sediment and 10 2 genomic units/g for bivalve and stool samples. The method also performs well when tested on artificially formalin-fixed and degraded genomic samples and was able to amplify V . cholerae DNA in historical CPR samples, the earliest of which date back to August 1966. The detection of V . cholerae in CPR samples collected in cholera endemic areas such as the Benguela Current Large Marine Ecosystem (BCLME) is of particular significance and represents a proof of concept for the possible use of the CPR technology and the developed qPCR assay in cholera studies.
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    Reconstructing local redox conditions, mineral precipitation processes and nutrient availability in seawater during deposition of the Transvaal Supergroup, South Africa
    (2025) Nke, Ansahmbom; Tostevin, Rosalie; Tsikos, Harilaos
    Iron formations (IF) and carbonate rocks serve as geochemical archives, which can be used to reconstruct marine environments in the Archean and Proterozoic Eons. The chemistry of ancient oceans influenced iron redox states and primary mineral precipitation, affecting the cycling of other trace elements and nutrients. While carbonate minerals are commonly used as geochemical archives, reconstructions using IF have proved more challenging, with many studies analysing bulk powders. However, reconstructing ancient conditions is challenging due to post-depositional alteration, fine-grained mineral composition, and complex mineralogy. Recent studies highlight greenalite, an Fe(II)-silicate mineral, as a primary phase in IF and a potential proxy for ancient seawater chemistry. This study combines geochemical reconstructions from carbonate rocks with mineral-specific data from greenalite. The Transvaal Supergroup in South Africa spans the Great Oxidation Event (GOE), and provides an ideal setting for studying ancient marine chemistry due to its exceptional preservation across a range of facies. This study aims to uncover early ocean conditions by investigating carbonate and IF sequences from across a shelf environment using laser ablation inductively coupled plasma-mass spectrometry. Specifically, it explores Archean oxygen oases by studying redox-sensitive rare earth element (REE) data from contorted microbial laminae and adjacent carbonate cement from microbial carbonates, alongside a new compilation of existing data to explore the implications for pre-GOE molecular oxygen availability. A novel methodology that involves cutting along bedding planes to maximize exposure of fine-grained primary seawater phases like greenalite, combined with MATLAB code to isolate greenalite data from the enclosing chert, is used to extract accurate trace metal and REE content from primary precipitates. The trace metal content from Paleoproterozoic greenalite is then used to predict Paleoproterozoic ocean metal content. The findings from this study show that the microbial carbonates from the Campbellrand Subgroup exhibit seawater-like post-Archean Australian Shale patterns, characterized by heavy REE enrichment, small positive Eu and La anomalies, super-chondritic Y/Ho ratios, but lack Ce anomalies, indicating deposition in anoxic marine conditions. These results provide no evidence for an oxygen oasis in the Transvaal basin. However, Fe-speciation data from these carbonates show evidence for pre-GOE free molecular oxygen. This suggests that one of the proxy records is not recording primary conditions, or that cyanobacteria were producing oxygen, but it was either being consumed by aerobic processes or the environmental conditions might be too fine-scaled to be recorded by the laser ablation technique. Greenalite from the Paleoproterozoic Kuruman Formation shows heavy REE enrichment, small positive Eu anomalies, super-chondritic Y/Ho ratios, and low total REE, consistent with formation in a shelf environment. While greenalite precipitation in vent settings is possible, significant formation likely occurred on the shelf, potentially triggered by the presence of minor Fe3+, local pH increases, or warmer temperatures. High resolution data from the greenalite in this study provide quantitative constraints on marine metal concentrations in an ~2.46 Ga shelf environment, revealing drastically different patterns compared to today. Specifically, Zn and V were scarce, Ni levels were similar, Co was enriched, and Mn was highly abundant. These patterns align with thermodynamic models and other geological archives, suggesting significant impacts on early microbial evolution. This supports phylogenomic and proteomic data indicating early microbes' preference for Mn and Co over Zn. This research highlights greenalite's value as a paleo-archive and lays the groundwork for exploring the Archean and Late Proterozoic Eons to reconstruct metal concentrations across various settings and geological epochs.