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    ABSTRACT: The balance of evidence suggests that oxygenic photosynthesis had evolved by 3.0–2.7 Ga, several hundred million years prior to the Great Oxidation ≈2.4 Ga. Previous work has shown that if oxygenic photosynthesis spread globally prior to the Great Oxidation, this could have supported widespread aerobic ecosystems in the surface ocean, without oxidising the atmosphere. Here we use a suite of models to explore the implications for carbon cycling and the Great Oxidation. We find that recycling of oxygen and carbon within early aerobic marine ecosystems would have restricted the balanced fluxes of methane and oxygen escaping from the ocean, lowering the atmospheric concentration of methane in the Great Oxidation transition and its aftermath. This in turn would have minimised any bi-stability of atmospheric oxygen, by weakening a stabilising feedback on oxygen from hydrogen escape to space. The result would have been a more reversible and probably episodic rise of oxygen at the Great Oxidation transition, consistent with existing geochemical evidence. The resulting drop in methane levels to ≈10 ppm is consistent with climate cooling at the time but adds to the puzzle of what kept the rest of the Proterozoic warm. A key test of the scenario of abundant methanotrophy in oxygen oases before the Great Oxidation is its predicted effects on the organic carbon isotope (δ13Corg) record. Our open ocean general circulation model predicts δCorg13≈−30 to −45‰ consistent with most data from 2.65 to 2.45 Ga. However, values of δCorg13≈−50‰ require an extreme scenario such as concentrated methanotroph production where shelf-slope upwelling of methane-rich water met oxic shelf water.
    Full-text · Article · Nov 2015 · Earth and Planetary Science Letters
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    ABSTRACT: Changes in woodland management practices are implicated in observed population changes of many European woodland birds, yet the long-term effects of woodland management on bird demographics is poorly understood. Using detailed long-term (55 year) datasets of both woodland management to plot level, and breeding birds from nest box monitoring, from an upland oak woodland in southwest England, I investigated effects of conservation management aimed at restoring abandoned oak coppice to a more natural and varied vertical structure, and hence its suitability for hole nesting birds, through singling and thinning. Effects of management on nest site occupation and breeding parameters for four hole nesting birds; blue tit, great tit, pied flycatcher and common redstart were examined. Blue tit nest site occupation was higher in managed plots irrespective of time since management. Common redstart nest site occupation was lowest in plots managed >8 years previously. No convincing effects of management on nest site occupancy were found for great tit or pied flycatcher, with inter-specific competition most important. Management had no influence on clutch size or productivity of any of the four species; instead weather variables had some influence on clutch size and productivity. Blue tit clutch size was influenced by spring weather with smaller clutches associated with higher temperatures and increased rainfall. Productivity of blue tit, great tit, pied flycatcher and common redstart was influenced by weather, with lower productivity tending to be associated with rainfall in the months when they were provisioning young. Together this suggests management, at the intensity undertaken within the study site, has a very limited role in determining nest site occupation and demographic rates of hole nesting woodland birds and that other factors such as weather, particularly rainfall, is of greater importance.
    Full-text · Article · Oct 2014 · Forest Ecology and Management
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    ABSTRACT: We recently reported the genome sequence of a free-living strain of Vibrio furnissii (NCTC 11218) harvested from an estuarine environment. V. furnissii is a widespread, free-living proteobacterium and emerging pathogen that can cause acute gastroenteritis in humans and lethal zoonoses in aquatic invertebrates, including farmed crustaceans and molluscs. Here we present the analyses to assess the potential pathogenic impact of V. furnissii. We compared the complete genome of V. furnissii with 8 other emerging and pathogenic Vibrio species. We selected and analyzed more deeply 10 genomic regions based upon unique or common features, and used 3 of these regions to construct a phylogenetic tree. Thus, we positioned V. furnissii more accurately than before and revealed a closer relationship between V. furnissii and V. cholerae than previously thought. However, V. furnissii lacks several important features normally associated with virulence in the human pathogens V. cholera and V. vulnificus. A striking feature of the V. furnissii genome is the hugely increased Super Integron, compared to the other Vibrio. Analyses of predicted genomic islands resulted in the discovery of a protein sequence that is present only in Vibrio associated with diseases in aquatic animals. We also discovered evidence of high levels horizontal gene transfer in V. furnissii. V. furnissii seems therefore to have a dynamic and fluid genome that could quickly adapt to environmental perturbation or increase its pathogenicity. Taken together, these analyses confirm the potential of V. furnissii as an emerging marine and possible human pathogen, especially in the developing, tropical, coastal regions that are most at risk from climate change.
    Full-text · Article · Aug 2014 · Frontiers in Microbiology
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