OREGON GOVERNMENT ETHICS LAW REFORM
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OREGON GOVERNMENT ETHICS LAW REFORM
Dynamic redox conditions control late Ediacaran metazoan ecosystems in the Naina Group, NamibiaWood, R. A.1*, Poulton, s.w.2, Prave, A.R.3, Hoffmann, OREGON GOVERNMENT ETHICS LAW REFORM K-H.4, Clarkson, M.o.1’*.Guilbaud, R.2, Lyne, J.w.1, Tostevin, R.5, Bowyer, F. Penny, A.M.1, Curtis, A.1, andKasemann, S.A.6• School of Geosciences, University of Edinburgh, West Mains Road, Edinburgh,EH93JW, UK:School of Earth and Environment. University of Leeds. Leeds, LS2 9JT,UKdepartment of Ea OREGON GOVERNMENT ETHICS LAW REFORMrth Sciences, University of St Andrews. St Andrews. KY16 9AL. UKGeological Survey of Namibia, Private Bag 13297, Windhoek, Namibiadepartment of EarthOREGON GOVERNMENT ETHICS LAW REFORM
Sciences, University College London, Gower Street, London, WC1E 6BT, UKdepartment of Geosciences, University of Bremen, P.O. Box 330 440, 28334 BremenDynamic redox conditions control late Ediacaran metazoan ecosystems in the Naina Group, NamibiaWood, R. A.1*, Poulton, s.w.2, Prave, A.R.3, Hoffmann, OREGON GOVERNMENT ETHICS LAW REFORM.WQodiffed.ac.ukABSTRACT1https://khothuvien.cori!The first appearance of skeletal metazoans in the late Ediacaran (~550 million years ago; Ma) has been linked to the widespread development of oxygenated oceanic conditions, but a precise spatial and temporal reconstruction of their evolution has not OREGON GOVERNMENT ETHICS LAW REFORMbeen resolved. Here we consider the evolution of ocean chemistry from ~550 to ~541 Ma across shelf-to-basin transects in the Zaris and Witputs Sub-BasOREGON GOVERNMENT ETHICS LAW REFORM
ins of the Nama Group, Namibia. New carbon isotope data capture the final stages of the Shuram/Wonoka deep negative C-isotope excursion, and these areDynamic redox conditions control late Ediacaran metazoan ecosystems in the Naina Group, NamibiaWood, R. A.1*, Poulton, s.w.2, Prave, A.R.3, Hoffmann, OREGON GOVERNMENT ETHICS LAW REFORM insight into the potential role of ocean redox chemistry during this pivotal interval of major biological innovation.The strongly negative 013c values in the lower parts of the sections reflect both a secular, global change in the C-isotopic composition of Ediacaran seawater, as well as the influen OREGON GOVERNMENT ETHICS LAW REFORMce of ‘local’ basinal effects as shown by the most negative 013c values occurring in the transition from distal to proximal ramp settings. Critical, tOREGON GOVERNMENT ETHICS LAW REFORM
hough, is that the transition to positive ô13c values which marks the end of the Shuram/Wonoka excursion postdates the appearance of calcified metazoaDynamic redox conditions control late Ediacaran metazoan ecosystems in the Naina Group, NamibiaWood, R. A.1*, Poulton, s.w.2, Prave, A.R.3, Hoffmann, OREGON GOVERNMENT ETHICS LAW REFORM column conditions persist after the excursion. Thus, if the c isotope trend reflects the transition to global-scale oxygenation in the aftermath of the oxidation of a large-scale, isotopically light organic carbon pool, it was not sufficient to fully oxygenate the deep, or indeed, very shallow ocea OREGON GOVERNMENT ETHICS LAW REFORMn.2Both sub-basins reveal highly dynamic redox structures, where deep areas were anoxic and shallow, inner ramp settings often experienced transient oOREGON GOVERNMENT ETHICS LAW REFORM
xygenation. Here anoxic horizons were caused by either episodic upwelling of deeper anoxic waters or higher rates of productivity. .Metazoans are founDynamic redox conditions control late Ediacaran metazoan ecosystems in the Naina Group, NamibiaWood, R. A.1*, Poulton, s.w.2, Prave, A.R.3, Hoffmann, OREGON GOVERNMENT ETHICS LAW REFORMcific skeletal metazoan communities of small individuals. By contrast, microbial (thrombolite) reefs found in inner- and mid-ramp settings where accommodation space was available and oxygenation was persistent supported large skeletal metazoans, and more biodiverse communities with complex ecologies OREGON GOVERNMENT ETHICS LAW REFORM. These long-lived reef communities, as well as Ediacaran soft-bodied biotas, are found particularly within transgressive systems. We suggest that a mOREGON GOVERNMENT ETHICS LAW REFORM
id-ramp position enabled physical ventilation mechanisms for shallow water oxygenation to operate, particularly during flooding and transgressive sea-Dynamic redox conditions control late Ediacaran metazoan ecosystems in the Naina Group, NamibiaWood, R. A.1*, Poulton, s.w.2, Prave, A.R.3, Hoffmann, OREGON GOVERNMENT ETHICS LAW REFORM ecology of Ediacaran skeletal metazoan communities.Keywords: Oxygenation; Neoproterozoic; Biomineralisation; Metazoans; Ediacaran; Ecosystems31. IntroductionThe Ediacaran (635-541 Ma) witnessed a profound biological shift from a world with minimal multicellular diversity and evolutionary' stasis, t OREGON GOVERNMENT ETHICS LAW REFORMo one of new body plans, skeletal types and novel ecologies, culminating in the appearance of modern-style communities by the early Cambrian (ButterfiOREGON GOVERNMENT ETHICS LAW REFORM
eld, 2007; Erwin et al., 2011). Complex, multicellular, body fossils appeared about 575 million years ago (Ma), represented by the soft-bodied EdiacarDynamic redox conditions control late Ediacaran metazoan ecosystems in the Naina Group, NamibiaWood, R. A.1*, Poulton, s.w.2, Prave, A.R.3, Hoffmann, OREGON GOVERNMENT ETHICS LAW REFORMtazoans are known from at least ~600-580 Ma (Xiao et al., 1998), while the first unequivocal calcified metazoans were present by ~550 Ma (Germs, 1972). The subsequent rapid diversification of metazoans with hard parts around the Precambrian-Cambrian boundary (541 Ma) marks a step change in biodivers OREGON GOVERNMENT ETHICS LAW REFORMity, the complexity of marine ecosystems, and in the workings of the global carbon cycle. Metazoans demand oxygen to support aerobic metabolisms and sOREGON GOVERNMENT ETHICS LAW REFORM
keletal hard-parts, and so it has been presumed that a rise in oxygen, perhaps incrementally, facilitated the evolution of this complexity (Fike et alDynamic redox conditions control late Ediacaran metazoan ecosystems in the Naina Group, NamibiaWood, R. A.1*, Poulton, s.w.2, Prave, A.R.3, Hoffmann, OREGON GOVERNMENT ETHICS LAW REFORMles during the Ediacaran, such as the global Shuram'Wonoka deep negative C-isotope excursion (Bums and Matter, 1993). This has variously been interpreted as being due to oxidation of a substantial reservoir of organic carbon dissolved in the deep ocean (Rothman et al., 2003; Fike et al., 2006), to a OREGON GOVERNMENT ETHICS LAW REFORM large flux of methane released from clathrates (Bjerrum and Canfield, 2011), or to diagenetic phenomena (Derry, 2010). The models of Bristow and KennOREGON GOVERNMENT ETHICS LAW REFORM
edy (2008), however, suggest that there were not enough oxidants available for the model proposed by Fike et al.4(2006), and thus that the Shuram coulDynamic redox conditions control late Ediacaran metazoan ecosystems in the Naina Group, NamibiaWood, R. A.1*, Poulton, s.w.2, Prave, A.R.3, Hoffmann, OREGON GOVERNMENT ETHICS LAW REFORMs and shelves may all have significantly different values (Canfield, 1998). Indeed, the global response of ocean redox chemistry to rising oxygen levels through this period has been shown to be complex (Fike et al., 2006; Canfield et al., 2008; Johnston et al., 2010, 2012b; 2013; Sperling et al., 20 OREGON GOVERNMENT ETHICS LAW REFORM13a), including in South China the presence of metastable zones of euxinic (anoxic and sulfidic) waters impinging on the continental shelf and sandwicOREGON GOVERNMENT ETHICS LAW REFORM
hed within ferruginous IFe(II)-enriched] deep waters (Li et al., 2010). Detailed reconstructions of ocean chemistry suggest that a globally anoxic andDynamic redox conditions control late Ediacaran metazoan ecosystems in the Naina Group, NamibiaWood, R. A.1*, Poulton, s.w.2, Prave, A.R.3, Hoffmann, OREGON GOVERNMENT ETHICS LAW REFORMCanfield, 2011), whereas surface-water oxygenation is thought to be a near-continuous feature throughout the latter half of the Ediacaran (Canfield et al., 2008). Indeed some have argued that pervasive and persistent oxygenation of the deep ocean did not occur until the later Palaeozoic (e.g. Canfie OREGON GOVERNMENT ETHICS LAW REFORMld el al., 2008). There is also growing evidence to suggest that mid-depth euxinia (free-sulphide in the water column) may have been a feature (but poOREGON GOVERNMENT ETHICS LAW REFORM
ssibly temporally restricted) along some continental shelves at certain times in the Neoproterozoic (Canfield et al. 2008; Johnston et al., 2010; Li eDynamic redox conditions control late Ediacaran metazoan ecosystems in the Naina Group, NamibiaWood, R. A.1*, Poulton, s.w.2, Prave, A.R.3, Hoffmann, OREGON GOVERNMENT ETHICS LAW REFORMturbations to the c, Fe and s cycles (Des Marais el al.1992; Logan et al. 1995; Rothman et al., 2003; Fike et al., 2006; Canfield et al., 2007) which are all potentially linked to rising oxygen.Oxygen requirements in metazoans vary widely, as a consequence of size, metabolism, mobility, and the pres OREGON GOVERNMENT ETHICS LAW REFORMence or absence of a circulatory system (Vaquer-Sunyer and Duarte,52008). Some have argued that the presence of diverse, mitochondrial-based anaerobicOREGON GOVERNMENT ETHICS LAW REFORM
respiratory pathways in metazoans suggests that at least some may be able (0 function under low-oxygen conditions (Budd, 2008). Such metazoans toleraDynamic redox conditions control late Ediacaran metazoan ecosystems in the Naina Group, NamibiaWood, R. A.1*, Poulton, s.w.2, Prave, A.R.3, Hoffmann, OREGON GOVERNMENT ETHICS LAW REFORM has been proposed that metazoans may have been limited to small size (<3 mm), thin body plans, and low diversity communities with simple foodwebs by the relatively low levels of oxygen of the Proterozoic, with the explosion of larger and ecologically diverse organisms in the late Ediacaran and Camb OREGON GOVERNMENT ETHICS LAW REFORMrian related, in part, to increasing oxygen levels (e.g. Cloud, 1968; Runnegar, 1982). Experimental work has also shown that the oxygen levels necessaOREGON GOVERNMENT ETHICS LAW REFORM
ry (0 support small, primitive metazoans such as sponges (Porifera) are far lower (Mills et al., 2014) than those required for large, active, and ecolGọi ngay
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