Benthic Foraminiferal Assemblages from the Laurentian Channel in the Lower Estuary and Gulf of ST. Lawrence, Eastern Canada: Tracers of Bottom-Water Hypoxia

IF 0.9 4区 地球科学 Q4 PALEONTOLOGY
T. Audet, A. de Vernal, A. Mucci, M. Seidenkrantz, C. Hillaire‐Marcel, Vladislav Carnero-Bravo, Y. Gélinas
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引用次数: 1

Abstract

Over the past century, an increase in temperatures and a decrease in dissolved oxygen concentrations have been observed in the bottom waters of the Laurentian Channel (LC), throughout the Lower St. Lawrence Estuary (LSLE) and the Gulf of St. Lawrence (GSL), eastern Canada. To document the impact of these changes, we analyzed the benthic foraminiferal assemblages and geochemical signatures of four sediment cores taken in the LC. Radiometric measurements (210Pb, 226Ra, 137Cs) indicate that the studied cores encompass the last 50 years of sedimentation in the LSLE and the last ∼160 years in the GSL. The sedimentary record shows a 60 to 65% decrease in benthic foraminiferal taxonomic diversity in the LC since the 1960s. An accelerated change in the foraminiferal assemblages is observed at approximately the same time at all studied sites, around the late 1990s and the early 2000s, towards populations dominated by the hypoxia-tolerant indicator taxa Brizalina subaenariensis, Eubuliminella exilis, and Globobulimina auriculata. This evolution of assemblages reflects incursions of the hypoxic zone into the western GSL over the last decades. The results of our multivariate analyses highlight the potential of benthic foraminiferal assemblages as a proxy of bottom-water hypoxia.
加拿大东部劳伦斯湾和下河口劳伦斯海峡的底栖有孔虫组合:底层水缺氧的痕迹
在过去的一个世纪里,在劳伦斯海峡(LC)的底层水域,整个下圣劳伦斯河口(LSLE)和加拿大东部的圣劳伦斯湾(GSL),都观察到了温度的升高和溶解氧浓度的降低。为了记录这些变化的影响,我们分析了LC中采集的四个沉积物岩芯的底栖有孔虫组合和地球化学特征。辐射测量(210Pb、226Ra、137Cs)表明,所研究的岩芯涵盖了LSLE最后50年的沉积和GSL最后~160年的沉积。沉积记录显示,自20世纪60年代以来,LC的底栖有孔虫分类多样性减少了60%至65%。大约在20世纪90年代末和21世纪初,在所有研究地点,几乎同时观察到有孔虫组合向耐缺氧指示类群Brizalina subaenariensis、Eubuliminella exilis和Globobulimina aurculata主导的种群加速变化。这种组合的演变反映了过去几十年来缺氧带对西部GSL的入侵。我们的多元分析结果突出了海底有孔虫组合作为底层水缺氧指标的潜力。
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来源期刊
Journal of Foraminiferal Research
Journal of Foraminiferal Research 地学-古生物学
CiteScore
2.10
自引率
9.10%
发文量
32
审稿时长
>12 weeks
期刊介绍: JFR publishes original papers of international interest dealing with the Foraminifera and allied groups of organisms. Review articles are encouraged.
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