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Controls on the spatio-temporal distribution of microbialite crusts on the Great Barrier Reef over the past 30,000 years
Marine Geology ( IF 2.9 ) Pub Date : 2020-08-05 , DOI: 10.1016/j.margeo.2020.106312
Zs. Szilagyi , Jody M. Webster , Madhavi A. Patterson , Kinga Hips , Robert Riding , Matthew Foley , Marc Humblet , Yusuke Yokoyama , Liyuan Liang , Eberhard Gischler , Lucien Montaggioni , Douglas Gherardi , Juan C. Braga

Calcification of microbial mats adds significant amounts of calcium carbonate to primary coral reef structures that stabilizes and binds reef frameworks. Previous studies have shown that the distribution and thicknesses of late Quaternary microbial crusts have responded to changes in environmental parameters such as seawater pH, carbonate saturation state, and sediment and nutrient fluxes. However, these studies are few and limited in their spatio-temporal coverage. In this study, we used 3D and 2D examination techniques to investigate the spatio-temporal distribution of microbial crusts and their responses to environmental changes in Integrated Ocean Drilling Program (IODP) Expedition 325 (Great Barrier Reef Environmental Changes) fossil reef cores that span 30 to 10 ka at two locations on the GBR reef margin. Our GBR microbialite record was then combined with a meta-analysis of 17 other reef records to assess global scale changes in microbialite development (i.e., presence/absence, thickness) over the same period. The 3D results were compared with 2D surface area measurements to assess the accuracy of 2D methodology. The 2D technique represents an efficient and accurate proxy for the 3D volume of reef framework components within the bounds of uncertainty (average: 9.45 ± 4.5%). We found that deep water reef frameworks were most suitable for abundant microbial crust development. Consistent with a previous Exp. 325 study (Braga et al., 2019), we also found that crust ages were broadly coeval with coralgal communities in both shallow water and fore-reef settings. However, in some shallow water settings they also occur as the last reef framework binding stage, hundreds of years after the demise of coralgal communities. Lastly, comparisons of crust thickness with changes in environmental conditions between 30 and 10 ka, show a temporal correlation with variations in partial pressure of CO2 (pCO2), calcite saturation state (Ωcalcite), and pH of seawater, particularly during the past ~15 kyr, indicating that these environmental factors likely played a major role in microbialite crust development in the GBR. This supports the view that microbialite crust development can be used as an indicator of ocean acidification.



中文翻译:

过去30,000年中对大堡礁上的微辉石结壳的时空分布的控制

微生物垫的钙化为主要的珊瑚礁结构增加了大量碳酸钙,从而稳定并束缚了珊瑚礁的骨架。先前的研究表明,晚期第四纪微生物结壳的分布和厚度已经对环境参数的变化做出了响应,例如海水的pH值,碳酸盐饱和状态以及沉积物和养分通量。但是,这些研究很少,而且时空覆盖范围有限。在这项研究中,我们使用3D和2D检查技术调查了跨越30层的综合海洋钻探计划(IODP)远征325(大堡礁环境变化)化石礁岩心中微生物结壳的时空分布及其对环境变化的响应在GBR礁边缘的两个位置达到10 ka。然后将我们的GBR微生物岩记录与对其他17条珊瑚礁记录的荟萃分析相结合,以评估同一时期微生物岩发育的整体规模变化(即存在/不存在,厚度)。将3D结果与2D表面积测量值进行比较,以评估2D方法的准确性。2D技术代表了在不确定性范围内(平均:9.45±4.5%)礁石框架组件的3D体积的高效,准确的代理。我们发现深水礁框架最适合于丰富的微生物结壳发育。与先前的Exp。325研究(Braga et al。,2019),我们还发现在浅水和前礁环境中,地壳年龄与珊瑚群落大致相同。然而,在某些浅水环境中,它们也是珊瑚礁群落消亡后数百年的最后一个礁石框架绑定阶段。最后,对地壳厚度与环境条件在30和10 ka之间变化的比较,表明与CO分压变化存在时间相关性2(pCO 2),方解石饱和状态(Ω方解石)和海水的pH值,尤其是在过去约15年来,这表明这些环境因素可能在GBR中的微辉石结壳形成中起了重要作用。这支持了微辉石结壳的发展可以用作海洋酸化指标的观点。

更新日期:2020-08-05
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