Disentangling natural vs. anthropogenic induced environmental variability during the Holocene: Marambaia Cove, SW sector of the Sepetiba Bay (SE Brazil)
Disentangling natural vs. anthropogenic induced environmental variability during the Holocene: Marambaia Cove, SW sector of the Sepetiba Bay (SE Brazil)
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DOI：
10.1007/s11356-020-12179-9
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发表时间：
2021-01
影响因子：
5.8
通讯作者：
Wellen Fernanda Louzada Castelo;Maria Virgínia Alves Martins;M. Martínez-Colón;J. V. Guerra;Tatiana Pinheiro Dadalto;D. Terroso;Maryane Filgueiras Soares;F. Frontalini;W. Duleba;Orangel Antonio Aguilera Socorro;M. Geraldes;F. Rocha;Sérgio Bergamaschi
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作者：
Wellen Fernanda Louzada Castelo;Maria Virgínia Alves Martins;M. Martínez-Colón;J. V. Guerra;Tatiana Pinheiro Dadalto;D. Terroso;Maryane Filgueiras Soares;F. Frontalini;W. Duleba;Orangel Antonio Aguilera Socorro;M. Geraldes;F. Rocha;Sérgio Bergamaschi
基于对 176 厘米长岩心 (SP8) 的结构、矿物学、地球化学和微型动物分析的多代理方法已应用于重建塞佩蒂巴湾（巴西东南部）Marambaia 湾的全新世古环境变化并理清自然与人为变化。由于全新世期间马兰巴亚障壁岛的演化和发展以及广阔的河流盆地的存在，塞佩蒂巴湾成为了一个泻湖系统。附近 SP7 岩心的人类活动前层的元素浓度已用于估计该区域的基线元素浓度，并确定金属富集因子 (EF)、污染负荷指数 (PLI) 和沉积物污染指数 (SPI)。 SP8 核心的记录提供了泻湖演化的令人信服的证据，区分了过去约 9.5 ka BP 自然强迫和人为强迫下潜在有毒元素 (PTE) 的影响。研究区域可能是约 9.5 至 7.8 ka BP（放射性碳测年）之间的沿海沙脊的一部分。约 8.6 至 7.8 ka 之间沉积的异源物质和有机物的冲刷事件。 8.2 ka BP 气候事件中，南美夏季风在巴西加强，导致降雨量和湿度增加，并出现缺氧事件。有机物的积累导致沉积物中氧气耗尽，甚至缺氧，从而激活生物地球化学过程，从而导致潜在有毒元素（PTE）的保留。全新世海平面开始上升约 7.8 ka BP 后，海洋入侵淹没了 Marambaia 湾地区（之前暴露在地面条件下）。环境条件变得有利于底栖有孔虫的定殖。有孔压力指数 (FSI) 和 Exp(H’bc) 表明，在全新世中期相对海平面高位期间，自约 7.8 ka BP 起，环境条件从恶劣转为有利，最大健康度在约 5 ka BP 时达到。从那时起，沉积学和生态学指标表明该系统的限制程度不断增加。约1975年以来，人类活动引起的淤积、镉、锌和有机物急剧增加，导致有孔虫组合发生重大变化，Ammonia/ElphidiumIndex（AEI）、EF和SPI值显着增加，FSI和Exp（H'bc）（生态指标）下降，表明环境从“中度污染”向“重度污染”（生态条件恶劣）演变，在可变的低氧条件下。因此，岩心 SP8 说明了人为强迫对沉积物地球化学和相关污染负荷的最显着事件及其对底栖生物的负面影响。
Multiproxy approach based on textural, mineralogical, geochemical, and microfaunal analyses on a 176-cm-long core (SP8) has been applied to reconstruct the Holocene paleoenvironmental changes and disentangling natural vs. anthropogenic variability in Marambaia Cove of the Sepetiba Bay (SE Brazil). Sepetiba Bay became a lagoonal system due to the evolution and development of the Marambaia barrier island during the Holocene and the presence of an extensive river basin. Elemental concentrations from pre-anthropogenic layers from the nearby SP7 core have been used to estimate the baseline elemental concentrations for this region and to determine metals enrichment factors (EF), pollution load index (PLI), and sediment pollution index (SPI). Record of the core SP8 provides compelling evidence of the lagoon evolution differentiating the effects of potentially toxic elements (PTEs) under natural vs. anthropic forcing in the last ~ 9.5 ka BP. The study area was probably part of coastal sand ridges between ≈ 9.5 and 7.8 ka BP (radiocarbon date). Events of wash over deposited allochthonous material and organic matter between ≈ 8.6 and 7.8 ka. Climatic event 8.2 ka BP, in which the South American Summer Monsoon was intensified in Brazil causing higher rainfall and moisture was scored by an anoxic event. Accumulation of organic matter resulted in oxygen depletion and even anoxia in the sediment activating biogeochemical processes that resulted in the retention of potentially toxic elements (PTEs). After ≈ 7.8 ka BP at the onset of the Holocene sea-level rise, a marine incursion flooded the Marambaia Cove area (previously exposed to subaerial conditions). Environmental conditions became favorable for the colonization of benthic foraminifera. The Foram Stress Index (FSI) and Exp(H’bc) indicate that the environmental conditions turned from bad to more favorable since ≈ 7.8 ka BP, with maximum health reached at ≈ 5 ka BP, during the mid-Holocene relative sea-level highstand. Since then, the sedimentological and ecological proxies suggest that the system evolved to an increasing degree of confinement. Since ≈ 1975 AD, a sharp increase of silting, Cd, Zn, and organic matter also induced by anthropic activities caused major changes in foraminiferal assemblages with a significant increase of Ammonia/ElphidiumIndex (AEI), EF, and SPI values and decreasing of FSI and Exp(H’bc) (ecological indicators) demonstrating an evolution from “moderately polluted” to “heavily polluted” environment (bad ecological conditions), under variable suboxic conditions. Thus, core SP8 illustrates the most remarkable event of anthropogenic forcing on the geochemistry of the sediments and associated pollution loads and its negative effect on benthic organisms.