We investigated the long-term effects (6 years) of sediment improvement and submerged plant restoration of a subtropical shallow urban lake, Hangzhou West Lake China. To reveal the lake ecosystems variations, we analyzed the sediment properties, submerged macrophyte characteristics, sediment microorganisms, and benthic macroinvertebrate communities from 2015 to 2020. The ecological restoration project decreased sediment TP and OM, increased submerged macrophyte biomass and sediment microbial diversity, and improved the benthic macroinvertebrate communities in the restored area. The sediment TP decreased from 2.94 mg/g in 2015 to 1.33 mg/g in 2020. The sediment OM of the restored area decreased from 27.44 % in 2015 to 8.08 % in 2020. Principal component analysis (PCA) confirmed that the restoration improved the sediment conditions, making it suitable for the growth of submerged macrophytes, and then sped up the restoration and reconstruction of the lake ecosystem. These results have significant implications on the ecological management of shallow lakes.

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甲壳素纳米晶体和纳米纤维对水泥浆凝结时间、流变性能和力学性能的相关性研究

Insights into Setting Time, Rheological and Mechanical

Properties of Chitin Nanocrystals- and Chitin Nanofibers-cement Paste

作者: Md Mostofa Haider, GuoqingJian, Tuhua Zhong, Hui Li, Carlos A., Fernandez, Leonard S.Fifield, Michael Wolcott, and Somayeh Nassiri 

期刊: Cement and Concrete Composites 

甲壳素是自然界中产量第二丰富的生物聚合物，可提取自海产品行业的废水。在这项开创性的研究中，废弃虾壳中的甲壳素被加工成甲壳素纳米晶体和纳米纤维（Ch-NCs和Ch-NFs），用以评估水泥浆体中的甲壳素。结果显示，可能是由于水泥颗粒的静电排斥，纳米晶体将最终凝固时间推迟至106分钟，但纳米纤维只将延迟时间推迟至78分钟。此外，新鲜水泥浆的粘度随着纳米纤维的加入而增加，而纳米晶体对于水泥浆的粘度未造成显著影响。结果的差异是由于纳米晶体棒与纳米纤维网络相比具有更大的流动性。此外，在质量百分比为0.05的水泥中，形成的纳米甲壳素显著提高了28d的抗弯强度（约40%）以及抗压强度（约12%）。这项研究结果令人欢欣鼓舞，纳米甲壳素在为目标应用定制水泥基材料的新鲜和硬化性能方面具有远大前景。

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（实习生朱月编译）

Chitin, the second most abundant biopolymer in nature, is available in the seafood industry's waste streams. In this pioneering study, chitin from waste shrimp shells was processed into chitin nanocrystals and nanofibers (Ch-NCs and Ch-NFs) for evaluation in the cement paste. The results show Ch-NCs delayed the final set time by up to 106 min, likely by electrostatic repulsion of cement particles, but Ch-NFs imparted only a max 78-min delay. Furthermore, the viscosity of fresh cement paste increased with Ch-NFs but did not significantly change with Ch-NCs. These different outcomes are attributed to more mobility of Ch-NCs rods versus the Ch-NFs network. In addition, nanochitin forms at 0.05 wt% of cement significantly increased 28d flexural strength by ∼40% and compressive strength by up to ∼12%. The encouraging results of this study indicate the promise of nanochitins in tailoring fresh and hardened properties of cement-based materials for target applications.

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板鳃亚纲类物种在运动生态学垂直维度的深入研究

Diving into the Vertical Dimension of Elasmobranch Movement Ecology

作者: Samantha Rzejaczek, Maurice C. Goodman, Nigel E. Hussey, Amelia J. Armstrong, Aaron Carlisle, Daniel M. Coffey, Adrian C. Gleiss, and Charlie Huveneers et Al.

期刊: Science Advances 

了解板鳃亚纲类物种的三维运动模式对理解它们的生态作用和人类压力至关重要。迄今为止，全球范围内的物种比较研究主要集中在水平运动上。我们的研究填充了垂直运动的知识空缺，基于38种板鳃纲物种部署989个生物遥感标签获得的数据，首次编制了板鳃纲垂直栖息地使用的全球合成。板鳃亚纲类物种在垂直运动模式中表现出很高的种内和种间变异性。经观察发现，许多上浮游板鳃类在垂直方向上存在大量重叠，这表明它们更有可能出现空间重叠、生物相互作用，并对垂直梯度上的人类活动造成类似的威胁。我们强调，下一步的关键步骤是将垂直移动纳入板鳃亚纲类物种的全球管理和监测战略，强调需要解决部署时的地理和分类偏差，并同时考虑水平和垂直移动。

（实习生朱月编译）

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Fig. 2 Deployment and pop-up and/or recapture locations of tracked elasmobranchs.

Yellow triangles indicate deployment and red circles indicate pop-up and/or recapture of the 989 elasmobranchs included within the analysis for this study. Numbers refer to the ocean biogeographic realms as defined by Costello et al. (22) (see table S3). Pop-up locations were not available for 144 tags.

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements.

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海洋热浪与海洋极端酸化的复合

Compound Marine Heatwaves and Ocean Acidity Extremes

作者: Friedrich A. Burger, Jens Terhaar, and Thomas L. Frölicher

期刊:  Nature Communications



海洋热浪（MHW）与海洋极端酸化事件（OAX）的共同出现对海洋生态系统可以产生比单个事件的出现更强的影响。对1982-2019年期间每月的开放海观测结果显示，以现今为基线，全球每100个月就发生1.8次MHW-OAX事件，如此频繁，几乎是90%极端事件发生频数的两倍之多（MHWs和OAX事件分别统计）。复合MHW-OAX事件最可能发生在亚热带地区(100个月2.7次；纬度10°−40°)，不太可能发生在赤道太平洋和中高纬度地区(100个月0.7次；纬度>40°)。该模式是温度和溶液无机碳对[H+]相反作用的结果。当MHWs期间升温造成的[H+]正反馈大于溶液无机碳降低对[H+]造成的负反馈，复合MHW-OAX事件发生的可能性较大。大型集成模拟系统分析了地球系统模型，评估了在气候变化背景下MHW-OAX事件发生的可能性。长时间尺度上，若以工业化之前为基线，每年全球升温2℃，会使每年发生MHW-OAX事件的天数从12天增加至265天。即使忽略长周期趋势，全球气温升高2℃，[H+]的增大会导致MHW-OAX事件天数增加60%。这些预测将会对海洋生态系统造成严重影响。

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Fig. 3 Map of the likelihood multiplication factor (LMF) based on the global monthly gridded observation-based SST and surface [H+] data. The baseline period 1982–2019 was used to define the extreme events. Warm colors indicate LMF > 1 and cold colors indicate LMF < 1. These regions are separated by the thin gray contour line. The color bar also indicates the respective number of compound event months per year. The colored dots indicate the location and the estimated LMFs from 15 observation stations (see “Methods”). SST and [H+] anomalies and the Pearson correlation coefficient (r) from eight SST and [H+] time series are shown around the map. All data were linearly detrended prior to the analysis.

Compound MHW-OAX events, during which marine heatwaves (MHWs) co-occur with ocean acidity extreme (OAX) events, can have larger impacts on marine ecosystems than the individual extremes. Using monthly open-ocean observations over the period 1982–2019, we show that globally 1.8 in 100 months (or about one out of five present-day MHW months) are compound MHW-OAX event months under a present-day baseline, almost twice as many as expected for 90th percentile extreme event exceedances if MHWs and OAX events were statistically independent. Compound MHW-OAX events are most likely in the subtropics (2.7 in 100 months; 10°−40° latitude) and less likely in the equatorial Pacific and the mid-to-high latitudes (0.7 in 100 months; >40° latitude). The likelihood pattern results from opposing effects of temperature and dissolved inorganic carbon on [H+]. The likelihood is higher where the positive effect on [H+] from increased temperatures during MHWs outweighs the negative effect on [H+] from co-occurring decreases in dissolved inorganic carbon. Daily model output from a large-ensemble simulation of an Earth system model is analyzed to assess changes in the MHW-OAX likelihood under climate change. The projected long-term mean warming and acidification trends have the largest effect on the number of MHW-OAX days per year, increasing it from 12 to 265 days per year at 2 °C global warming relative to a fixed pre-industrial baseline. Even when long-term trends are removed, an increase in [H+] variability leads to a 60% increase in the number of MHW-OAX days under 2 °C global warming. These projected increases may cause severe impacts on marine ecosystems.

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Source - https://mp.weixin.qq.com/s/ywckZAMyUp3KcTJZ5lFJQQ

英国专属经济区内沉积有机碳在海底捕捞活动下的稳定性和潜在脆弱性的评估

Assessing the Potential Vulnerability of Sedimentary Carbon Stores to Bottom Trawling Disturbance within the UK EEZ

作者: Kirsty E. Black, Craig Smeaton, William R. Turrell, and William E. N. Austin

期刊: Frontiers in Marine Science

据估计，在英国“专属经济区”内，储存在海底沉积物中的有机碳（OC）存量约为5.24亿吨。这些沉积物中的有机碳在人为压力(如海底捕捞活动)下的稳定性和潜在脆弱性仍然难以定量。为了更好地了解沉积物有机碳在海底捕捞活动中易受到威胁的区域，我们开发了一个碳脆弱性排名（CVR）来定位海底区域。在这些区域采取预防性保护措施将有助于维持现有有机碳储量，从而进一步探寻并解释海底捕捞后有机碳的轨迹（如再矿化、转化和消耗）。我们在ArcGIS内利用模糊集合理论生成了目前捕捞强度、有机碳和沉积物分布以及沉积物有机碳稳定性的预测图。我们的研究结果表明，苏格兰西海岸是沉积物有机碳可能受到海底捕捞活动影响的关键地区之一。其中主要原因在于这些富含有机碳的沉积物的高反应性，以及近海水域内重复性捕捞活动的压力。研究表明，鉴于这些有机碳热点地区受海底捕捞活动干扰的潜在风险，应该优先考虑未来的保护(管理)措施，以确保最低程度的碳排放，以及更佳的自然碳资源保护。

（实习生朱月编译）

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Fig. 4 Declining year-to-year ocean memory through the 21^st century.

(A) Simplified five classification scheme sediment map of the UK EEZ, (B) Estimated Organic Carbon (OC) content (%) of marine sediments in the UK EEZ. Raster pixel resolution in both figures have been decreased for this study. For higher resolution rasters, see Smeaton et al. (2021a)

It is estimated that within the UK exclusive economic zone (UK EEZ), 524 Mt of organic carbon (OC) is stored within seabed sediment . However, the stability and potential vulnerability of OC in these sediments under anthropogenic stressors, such as bottom trawling activity , remains poorly quantified. To improve our understanding of the areas where sedimentary OC is likely to be at greatest risk from trawling events, we have developed a carbon vulnerability ranking (CVR) to identify areas of the seabed where preventative protection may be most beneficial to help maintain current OC stocks while further research continues to shed light on the fate of OC after trawling (e.g., remineralization, transport, and consumption). Predictive maps of currently available fishing intensity, OC and sediment distribution, and sediment OC lability have been generated within ArcGIS using fuzzy set theory . Our results show that the west coast of Scotland represents one of the key areas where sedimentary OC is potentially at greatest risk from bottom trawling activity. This is due mainly to the high reactivity of these OC rich sediments combined with the pressures of repetitive trawling activity within inshore waters. Our research shows that these OC hotspots are potentially at risk of disturbance from bottom trawling activity and should be prioritized for the consideration of future safeguarding (management) measures to ensure emissions are minimized and to provide greater protection of this natural carbon capital resource.

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红狮鱼（斑鳍蓑鲉）的"持续捕食策略"

The Persistent-predation Strategy of the Red Lionfish (Pterois Volitans)

作者: Ashley N. Peterson, and Matthew J. McHenry

期刊: Proceedings of the Royal Society B: Biological Sciences 



追逐猎物对捕食者的生物学至关重要，对于捕食行为的许多方面展开了深入研究。然而，尚未厘清的是，当猎物的速度快于非隐蔽的捕食者时，如何才能有效进行追捕。利用运动学测量，我们观测了红狮鱼（斑鳍蓑鲉）在实验室条件下追逐速度更快的青魔鱼（蓝绿光鳃鱼）的策略。尽管斑鳍蓑鲉的游泳速度只有蓝绿光鳃鱼的一半，但在61%的实验中，斑鳍蓑鲉成功地捕获了猎物。这种成功的追捕行为是由三个关键特征决定的。首先，斑鳍蓑鲉以纯粹的追击为目标，通过调整它们的航向，使其朝着猎物的位置而不是预期的拦截点前进。第二，斑鳍蓑鲉凭借不间断的运动来追逐猎物。相比之下，蓝绿光鳃鱼的运动是间歇性的，其速度变化包括缓慢的游泳。这样的时间段使斑鳍蓑鲉能够拉近与猎物的距离，并在相对较近的距离（小于9厘米）发动吸食性攻击。最后，斑鳍蓑鲉表现出很高的攻击成功率，在所有的捕食活动中，74%的狮斑鳍蓑鲉子鱼捕获了猎物。这些特征构成了一种行为，被称之为 "持续捕食策略"，通常见于各种运动相对缓慢的捕食者。

（实习生朱月编译）

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Fig. 5 The kinematics of prey targeting. (a) Photos of the red lionfish (Pterois volitans) and prey fish (Chromis viridis), shown from a lateral perspective, scaled to mean total fish length. (b) The heading of the predator (red) and prey (blue) may depend on the line-of-sight (grey line), the predator’s bearing (ϕ) and the prey’s relative heading (β). (c,d) Trajectories of predators (red curves) targeting prey (dotted blue curves) by either (c) ‘pure pursuit’ or (d) ‘parallel navigation’. The two sets of trajectories are predicted from common starting positions (filled circles), with the line-of-sight (grey lines) drawn at an even interval. (c) Deviated pursuit is characterized by a predator maintaining a near-zero bearing. (d) Parallel navigation yields a non-zero bearing to direct the predator toward the point of interception with the prey. (Online version in colour.)

The pursuit of prey is vital to the biology of a predator and many aspects of predatory behaviour are well-studied. However, it is unclear how a pursuit can be effective when the prey is faster than a non-cryptic predator. Using kinematic measurements, we considered the strategy of red lionfish (Pterois volitans) as they pursued a faster prey fish (Chromis viridis) under laboratory conditions. Despite swimming about half as fast as C. viridis, lionfish succeeded in capturing prey in 61% of our experiments. This successful pursuit behaviour was defined by three critical characteristics. First, lionfish targeted C. viridis with pure pursuit by adjusting their heading towards the prey’s position and not the anticipated point of interception. Second, lionfish pursued prey with uninterrupted motion. By contrast, C. viridis moved intermittently with variation in speed that included slow swimming. Such periods allowed lionfish to close the distance to a prey and initiate a suction-feeding strike at a relatively close distance (less than 9 cm). Finally, lionfish exhibited a high rate of strike success, capturing prey in 74% of all strikes. These characteristics comprise a behaviour that we call the ‘persistent-predation strategy’, which may be exhibited by a diversity of predators with relatively slow locomotion.

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浮游植物的垂直迁移大幅“泵升”海洋初级生产力

Vertically Migrating Phytoplankton Fuel High Oceanic Primary Production

作者：Kai Wirtz, S. Lan Smith, Moritz Mathis, and Jan Taucher

期刊：Nature Climate Change 



海洋净初级生产力(NPP)非常高，因为光照和营养物质充足的深度区之间通常有50-150米的垂直跨度。我们在此列出的证据表明，许多自养生物通过向下和向上的迁移弥合了这一跨度，从而促进了生物营养泵和海洋净初级生产力的高比率。我们的模型表明，浮游植物垂直迁移(PVM)可产生高达40% (>28 tg yr⁻¹ N)的新产物，并直接贡献了海洋总净初级生产力的25%(此处估计为56 PgC yr⁻¹)。海洋净初级生产力的季节性、垂直和地理变化的良好再现佐证了这些预估的可信度。然而与常见的预测相反，垂直迁移模式的敏感性研究表明，在全球变暖的情况下，当层结增强减少海洋表面的物理营养输送时，海洋净初级生产力会更呈现更高的数值。我们的研究结果表明，垂直迁移模式是推动海洋生物地球化学的关键机制，因此全球碳预算应对此加以考虑。

（实习生朱月编译）

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Fig. 6 Empirically derived zN and both simulated and observed zSCM are shown for individual events at the marine time-series stations K2, S1, HOT and BATS. The relationship has been fitted using the function y=x/(1+(x/x∗)2)y=x/(1+(x/x∗)2) (black line). a, zSCM reconstructed from reported CHL profiles. Optimal fit parameter x∗=242mx∗=242m. b, zSCM calculated by the model and fit function with x* = 240 m.

Marine net primary production (NPP) is remarkably high given the typical vertical separation of 50–150 m between the depth zones of light and nutrient sufficiency, respectively. Here we present evidence that many autotrophs bridge this gap through downward and upward migration, thereby facilitating biological nutrient pumping and high rates of oceanic NPP. Our model suggests that phytoplankton vertical migration (PVM) fuels up to 40% (>28 tg yr⁻¹ N) of new production and directly contributes 25% of total oceanic NPP (herein estimated at 56 PgC yr^-1 ). Confidence in these estimates is supported by good reproduction of seasonal, vertical and geographic variations in NPP. In contrast to common predictions, a sensitivity study of the PVM model indicates higher NPP under global warming when enhanced stratification reduces physical nutrient transport into the surface ocean. Our findings suggest that PVM is a key mechanism driving marine biogeochemistry and therefore requires consideration in global carbon budgets.

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大气静止现象和气候变暖对蓝藻类水华的影响：一个基于个体的建模方式

Impacts of Atmospheric Stilling and Climate Warming on Cyanobacterial Blooms: An Individual-based Modelling Approach

作者：Mohammad Hassan Ranjbar, David P.Hamilton, Amir Etemad-Shahidi, and Fernanda Helfera

期刊：Water Research 

淡水蓝藻属微囊藻形成的有害藻类水华是一个全球性问题，且将随着气候变化而愈演愈烈。在目前的气候变化对微囊藻华影响的研究中，还尚未考虑到大气静止现象。随着气候变暖，世界某些地区将随之出现大气静止现象，并将影响到湖泊分层制度。我们采用了一个新的基于个体的模型（IBM）来测试静止是否会对水体微囊藻的分布产生影响。我们利用IBM与一个三维流体力学模型的耦合，评估未来气候下微囊藻生物量对风速下降和空气温度上升的反应。IBM模型提及的湍流关系来自过往的文献，并利用来自城市浅水湖泊的输入数据，包括光线、温度和营养物质对微囊藻生长的影响，改变了微囊藻的群落大小。模型结果显示，菌落大小的动态变化对于准确预测蓝藻水华的发展和衰变至关重要。与空气温度上升2℃相比，风速下降20%时，菌落大小（平均值和变异性）增加了6倍以上。研究结果表明，在预测气候变化下浮力型、菌落形成型蓝藻水华的频率、分布和规模的变化时，需要将大气静止现象的因素加以考虑。

（实习生朱月编译）

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Fig. 7

Harmful algal blooms of the freshwater cyanobacteria genus Microcystis are a global problem and are expected to intensify with climate change. In studies of climate change impacts on Microcystis blooms, atmospheric stilling has not been considered. Stilling is expected to occur in some regions of the world with climate warming, and it will affect lake stratification regimes. We tested if stilling could affect water column Microcystis distributions using a novel individual-based model (IBM). Using the IBM coupled to a three-dimensional hydrodynamic model, we assessed responses of colonial Microcystis biomass to wind speed decrease and air temperature increase projected under a future climate. The IBM altered Microcystis colony size using relationships with turbulence from the literature, and included light, temperature, and nutrient effects on Microcystis growth using input data from a shallow urban lake. The model results show that dynamic variations in colony size are critical for accurate prediction of cyanobacterial bloom development and decay. Colony size (mean and variability) increased more than six-fold for a 20% decrease in wind speed compared with a 2 °C increase in air temperature. Our results suggest that atmospheric stilling needs to be included in projections of changes in the frequency, distribution and magnitude of blooms of buoyant, colony-forming cyanobacteria under climate change.

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内重力波引发的珊瑚礁潜在热避难所的全球图谱

A Global Atlas of Potential Thermal Refugia

for Coral Reefs Generated by Internal Gravity Waves

作者：Scott D. Bachman, Joan A. Kleypas, Mark Erdmann, and Edy Setyawan

期刊：Frontiers in Marine Science

受到海洋变暖的严重威胁，在未来不到三十年的时间里，大部分珊瑚礁可能会濒临灭绝。在这一时期最大限度地保护珊瑚礁的第一步是确定在海洋温度上升的地方珊瑚礁更有可能存活下来，比如温度较周围地区低、温度变化大、食物供应充裕的地方。这种情况通常由自然发生的内重力波(IGWs)所致，这是一种振动性的地下扰动，它可以导致较冷和/或富含营养的地下水，并造成高频的温度波动。这些特征通常不为人知，因为它们发生在地下和O(1千米)或更小的空间尺度。为了阐明内部重力波对珊瑚礁地区的温度产生的影响，我们对LLC4320的数据进行了分析，LLC是一个大规模的高分辨率（1/48˚；<2.5公里）全球海洋数值模拟。研究结果突出了内重力波引起的温度变率的区域差异。该分析还显示，热避难所仅限于高温度变化与实际珊瑚礁深度相吻合的深度，并不会全年一直持续。假设名义珊瑚礁深度为十米，由内重力波引起的冷却的珊瑚礁区域出现在东南亚和珊瑚三角区、加拉帕戈斯、中美洲太平洋大陆架沿线以及世界各地的孤立地点。这样的避难所在大西洋的珊瑚礁区是非常罕见的。

（实习生朱月编译）

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Fig. 8 (A) Regional map and (B) bathymetric contours near Miang Island, the site of the Wall et al. (2015) study. (C) Model output of hourly temperature (blue) and filtered temperature (red) profiles from the west (top) and east (bottom) sides of the island, the differences of which are broadly consistent with the observations in Wall et al. (2015).

Coral reefs are highly threatened by ocean warming and the majority are likely to be lost in less than three decades. A first step in maximizing reef conservation through this period is to identify where coral reefs are more likely to survive rising ocean temperatures, such as locations that experience lower temperatures than surrounding regions, high temperature variability, and high food supply. Such conditions are often the result of naturally occurring internal gravity waves (IGWs), oscillatory subsurface disturbances that can entrain cooler and/or nutrient-rich subsurface waters and cause high frequency temperature fluctuations. These features usually remain undetected because they occur subsurface and at spatial scales of O(1 km) and smaller. To shed light on where IGWs are likely to impact temperature conditions within coral reef regions, we present an analysis of data from the LLC4320, a massive high resolution (1/48˚; < 2.5 km) numerical global ocean simulation. The results highlight strong regional differences in the incidence of IGW-induced temperature variability. The analysis also reveals that thermal refugia are limited to depths where high temperature variability coincides with the actual reef depth and may not persist year-round. Assuming 10-m depth as the nominal reef depth, reef regions likely to benefit from IGW-induced cooling occur in SE Asia and the Coral Triangle, the Galápagos, along the Pacific shelf of Central America, and isolated locations worldwide. Such refugia are rare within the Atlantic reef sector.

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过去2000年长江三角洲多百年尺度

沉积物堆积量的变化-气候与人类活动的交织影响

Multi-Centennial Variability of Yangtze Delta Growth

Over the Last 2000 Years: Interplay of Climate and People

作者：Xiaomei Nian, Weiguo Zhang, Xiaoting Wang, Simon M. Hutchinson, Xuanqi Zhao, and Kam-biu Liu

期刊：Earth’s Future

全新世河流三角洲沉积物堆积量的重建，可帮助我们深入理解气候变化、人类活动与三角洲发育之间的关系，为预测未来提供机制认识。然而，相比全新世千年尺度和年代际尺度的研究，过去2000年间三角洲多百年尺度上的演变过程和机制仍然缺乏研究。作者团队基于最新的OSL年代学研究及研究区已有发表的年代数据，首次计算了长江三角洲过去2000年以500年为时间间隔的沉积物堆积量的变化。结果表明，2.0–1.5 ka和0.5–0 ka时期的沉积物堆积量高于1.5–1.0 ka和1.0–0.5 ka时期，最大值约为最小值的2倍。对比流域洪水和干旱事件的历史记录表明，较湿润的气候导致了三角洲沉积物堆积量的增加，反映了河流输沙量在三角洲生长中的作用。然而，过去500年最高的沉积物堆积量 (205±29×10⁶m³/a)不仅与小冰期的湿润条件有关，而且与区域人口的急剧增长有关。作者认为，在过去的五个世纪里，人类活动在三角洲增长方面的影响已经超过了自然强迫。以堆积量最低的中世纪暖期作为当前气候变暖的相似型，并考虑近些年来的筑坝和水土流失治理造成的河流入海泥沙量下降，作者预测，在未来几个世纪，长江三角洲可能面临更严重的泥沙供应不足及更高的侵蚀风险。

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Fig. 9 Location of the Yangtze River basin (a), and the red square depicts the location of the Yangtze River Delta (YRD) which is detailed in (b). a, The trajectories of the East Asian summer monsoon and Indian summer monsoon are shown by the white arrows. The white circles are historic water level markers on the Yangtze River at Baiheliang (Qin et al., 2020) and Datong Hydrological Station which gauges fluvial sediment flux to the sea. b, The red/magenta and green circles represent the cores dated by the optically stimulated luminescence and AMS 14C techniques, respectively. Red circles represent published cores while magenta new dated cores. Detailed core information can be found in Table S1 in Supporting Information S1, Table S2 and Table S3. Cores along three transects (white lines, A-A’, B-B’, C-C’) are used to construct the stratigraphy shown in Figure 2. The paleo-coastlines of the YRD over the last 2 ka follow previous studies (Chen et al., 1979; Delta Research Group, 1978) with modification according to the compilation of recent dating results. The blue-shaded zone indicates the area for which sediment deposition volume has been calculated.

Reconstruction of sediment accumulation in river deltas over the Holocene provides a basis for understanding the relationship between climate change, human activities and delta growth. However, variations in deposition rates on a centennial-scale over the last 2000 years remain poorly studied for mega-deltas. Based on optically stimulated luminescence and AMS ¹⁴C ages, we calculated deposited sediment volumes in the Yangtze River Delta (YRD) for 500-year intervals over the last two millennia for the first time. Our results reveal that the 2.0–1.5 and 0.5–0 ka periods had higher sediment deposition rates than in 1.5–1.0 and 1.0–0.5 ka, with maximum value about two times that of the minimum. A comparison with historical records of flooding and drought events indicates that a wetter climate led to a higher sediment deposition, reflecting the role of fluvial discharge in delta growth. However, the highest sediment deposition (205 ± 29 × 10⁶ m³/a) over the last 500 years is not only related to the wetter conditions of the Little Ice Age, but also linked to dramatic regional population growth. We suggest that human activities have predominated over natural forcing in determining the deltaic growth over the last five centuries. Taking the Medieval Climate Anomaly with the lowest deposition volume as an analog of current climate warming, and considering the decline in sediment loads due to recent damming and soil conservation, the YRD is likely to face an even more severe deficit in sediment supply and higher risk of delta destruction in the coming centuries.

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Source - https://mp.weixin.qq.com/s/9ZWewmpWQnuHmxIC9tly2g

声明：本版块为尝试性栏目，旨在传播分享最新科研动态。中文翻译仅供参考，中英文若有不符之处，请以英文为准。如有不妥之处，请联系 imber@ecnu.edu.cn 进行订正或要求撤稿。

Disclaimer: This column is a new trial to share cutting-edge research with wider academic community. The Chinese is not an official translation, while the English is invoked from original publication. If there is anything inappropriate, please contact imber@ecnu.edu.cn to correct us or request for a retraction.

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