基于深海采矿过程的环境影响分析与管理对策建议

深海矿产开发所产生的环境影响是目前制约深海采矿的重要问题之一,了解开发全过程的环境影响和生态响应是商业化开采的前提。本文以多金属结核、富钴结壳和多金属硫化物三种具有代表性的深海固体矿产资源为例,分析了开发前赋存环境、开发过程中及开发后的环境影响。结果表明：①不同深海固体矿产资源的分布规律、深度以及生物特征等赋存环境存在较大差异,因采矿活动带来的赋存环境改变、对环境的影响以及采矿潜在影响区域、影响时长和恢复潜力也有所不同。②多金属结核开采的环境影响着重考虑了沉积物羽流的影响,结壳开采活动从沉积物扰动、外壳去除以及栖息地改变三个方面考虑环境影响,多金属硫化物开采的环境影响还要增加对有毒物质的释放以及栖息地移除两个方面的考虑。③深海采矿对底栖生物种群的数量和物种组成皆会造成不同程度的影响。最后,从持续跟进监测评估、充实数据、提升采矿技术与设备、顶层设计与决策管理、规则制定等方面提出了环境保护与可持续发展对策建议,为深海采矿的环境影响评价及规则制定提供参考。     

Chemical profile of the secondary metabolites produced by a deep-sea sediment-derived fungus Penicillium commune SD-118

Bioassay-guided fractionation of the crude extract from Penicillium commune SD-118, a fungus obtained from a deep-sea sediment sample, resulted in the isolation of a known antibacterial compound, xanthocillin X (1), and 14 other known compounds comprising three steroids (2-4), two ceramides (5 and 6), six aromatic compounds (7-12), and three alkaloids (13-15). Xanthocillin X (1) was isolated for the first time from a marine fungus. In the bioassay, xanthocillin X (1) displayed remarkable antimicrobial activity against Staphylococcus aureus and Escherichia coli, and significant cytotoxicity against MCF-7, HepG2, H460, Hela, Du145, and MDA-MB-231 cell lines. Meleagrin (15) exhibited cytotoxicity against HepG2, Hela, Du145, and MDA-MB-231 cell lines. This is the first report of the cytotoxicity of xanthocillin X (1).     

Deep-Sea Impact Experiments and their Future Requirements

In recent years, several experiments to assess the potential impacts due to deep-sea mining in the Pacific as well as the Indian Oceans have indicated the immediate changes and restoration patterns of environmental conditions in the marine ecosystem. The large volume of sediment(~ 500 × 10⁷ m³ per year) estimated to be resuspended would be the major influencing factor in environmental impact in the mining area, leading to changes in availability of certain nutrients and composition of biomass, followed by gradual restoration. Important results have been obtained from these experiments, but in order to have a better understanding of the impacts and restoration processes, it will be necessary to improvise future experiments to resemble actual deep-sea mining in terms of scale and methodology.     

Comment on “Evaluation of palaeo-oxygenation of the ocean bottom cross the Permian–Triassic boundary” by Kakuwa (2008): Was the Late Permian deep-superocean really oxic?

Nearly 15 years after the proposal of the superanoxia concept (Isozaki, Y., 1994. Superanoxia across the Permo–Triassic boundary: record in accreted deep-sea pelagic chert in Japan. In: Embry, A.F., Beauchamp, B., Glass, D.J. (Eds.), Pangea: Global Environments and Resources. Memoir, Canadian Society of Petroleum Geologists, 17, pp. 805–812.), it is an appropriate timing to re-evaluate its geological context with the updated dataset. Kakuwa (Kakuwa, Y., 2008. Evaluation of palaeo-oxygenation of the ocean bottom across the Permian–Triassic boundary. Global and Planetary Change 63, 40–56.) lately discussed that the deep-sea anoxia across the Permian–Triassic boundary (P–TB) may have been much shorter than previously proposed, on the basis of ichnofabrics and geochemical data; however, his interpretations of the data do not appear straightforward nor persuading, and thus his claim is likely misled. Here we raise comments to his explanation on the following four issues: 1) invalid application of ichnofabric indices for shallow sea sediments to deep-sea cherts, 2) misinterpretation of Ce anomaly as a redox indicator, 3) improper application of various redox sensitive trace elements, and 4) questionable interpretations of δ³⁴S data of pyrites.     

热带北太平洋深海小型底栖生物大尺度空间分布

通过对2001年热带北太平洋深海小型底栖生物大尺度空间的数量分布的初步调查,共发现了15个类群的小型底栖生物,其平均丰度为34.1个/10 cm2,东太平洋区的东小区小型底栖生物类群数明显高于其它区域,小型底栖生物量比例随着沉积物厚度的增加而降低,生物量比例为68%~87%的小型底栖生物集中在沉积物0~2 cm层(表层)内。食物是深海小型底栖生物分布的限制因子,沉积物类型和底层流对小型底栖生物空间分布也有一定的影响。     

Microbial community structure and diversity in deep-sea hydrothermal vent sediments along the Eastern Lau Spreading Centre

The aim of this study is to investigate microbial structures and diversities in five active hydrothermal fields’ sediments along the Eastern Lau Spreading Centre (ELSC) in the Lau Basin (southwest Pacific). Microbial communities were surveyed by denatured gradient gel electrophoresis (DGGE) and clone library analysis of 16S rRNA genes. The differences in microbial community structures among sediment samples from the five deep-sea hydrothermal sites were revealed by DGGE profiles. Cluster analysis of DGGE profiles separated the five hydrothermal samples into two groups. Four different 16S rRNA gene clone libraries, representing two selected hydrothermal samples (19-4TVG8 and 19-4TVG11), were constructed. Twenty-three and 32 phylotypes were identified from 166 and 160 bacterial clones respectively, including Proteobacteria, Bacteroidetes, Firmicutes, Nitrospirae and Planctomycetes. The phylum Proteobacteria is dominant in both bacterial libraries with a predominance of Gamma-Proteobacteria. A total of 31 and 25 phylotypes were obtained from 160 and 130 archaeal clones respectively, including Miscellaneous Crenarchaeotic Group, Marine Group Ⅰ and Ⅲ, Marine Benthic Group E, Terrestrial Hot Spring Crenarchaeota and Deep-sea Hydrothermal Vent Euryarchaeota. These results show a variety of clones related to those involved in sulfur cycling, suggesting that the cycling and utilization of sulfur compounds may extensively occur in the Lau Basin deep-sea hydrothermal ecosystem.     

Deep-Sea Nodules and Co-rich Mn Crusts

The mining of deep-sea manganese nodules has been a topic of interest since J.L. Mero undertook his preliminary studies in the 1960s to evaluate the prospects for mining deep-sea nodules. Despite the great deal of investment in deep-sea mining over more than 40 years, there has still been no successful attempt to mine the deep-sea nodules on a commercial scale. One of the major problems is that the nodules cannot be brought to the surface with the necessary amounts of recoverable nickel, cobalt and zinc to warrant the initial high investment necessary for this operation. It therefore appears that in the short term, deep-sea manganese and Co-rich Mn crusts will not be mined on a commercial scale in the foreseeable future. Nonetheless, investigations of deep-sea mineral deposits by a number of nations will continue and enable us to understand the deep-sea environment in increasing detail, which is necessary in view of the great extent of the deep oceans which cover an area of about 66% of the Earth's surface.     

Hummocky cross-stratification-like structures in deep-sea turbidites: Upper Cretaceous Basque basins (Western Pyrenees, France)

Hummocky cross-stratification is a sedimentary structure which is widely interpreted as the sedimentary record of an oscillatory current generated by energetic storm waves remobilizing surface sediment on the continental shelf. Sedimentary structures named hummocky cross-stratification-like structures, similar to true hummocky cross-stratification, have been observed in the Turonian–Senonian Basque Flysch Basin (south-west France). The bathymetry (1000 to 1500 m) suggests that the observed sedimentary structures do not result from a hydrodynamic process similar to those acting on a continental shelf. The morphology of these three-dimensional structures shares similarities with the morphology of hummocky cross-stratification despite a smaller size. The lateral extent of these structures ranges from a few decimetres to many decimetres; they consist of convex-up domes (hummock) and concave-up swales with a non-erosive base. Four types of hummocky cross-stratification-like geometries are described; they occur in association with structures such as climbing current ripple lamination and synsedimentary deformations. In the Basque Flysch, hummocky cross-stratification-like structures are only found in the Tc interval of the Bouma sequence. Hummocky cross-stratification-like structures are sporadic in the stratigraphic series and observed only in few turbidite beds or bed packages. This observation suggests that hummocky cross-stratification-like structures are linked genetically to the turbidity current but form under a very restricted range of parameters. These structures sometimes show an up-current (upslope) migration trend (antidunes). In the described examples, they could result from standing waves forming at the upper flow interface because of Kelvin–Helmholtz instability.     

深海热液活动环境场参数及模型分析

深海热液活动是当今科学研究的热点,本文基于近年有关热液活动的各种模型,系统分析比较了热液柱的上升高度与热通量等参数变化规律,并对现有的热液羽状流模型和考虑洋壳特性的经验模型进行了分析。主要研究结果有:(1)热液柱上升高度与底部横向流和热源特性密切相关,单个热液喷口热通量和羽状热液柱中性浮力层模型热液热通量达109W/m2;(2)热液羽状流受多种因素影响,热液柱面积的轮廓,羽状热液柱各处的含盐量、潜在温度、速度可随深度改变发生变化;(3)考虑洋壳特性后,其浮力通量和热液柱最大的上升高度均有变化,上升高度可达1000多m,热通量达108W/m2。上述模型和参数可为进一步深入研究热液羽流运动机制和建立热液活动正演和反演模型提供参考。     

深海沉积理论发展及其在油气勘探中的意义

深海沉积理论的进展主要涉及“鲍玛序列”、浊流、砂质碎屑流和深海层序地层四方面。以Shanmugam为代表认为:“鲍玛序列”并非唯一浊流产物,可含有砂质碎屑流、浊流、内潮汐、内波、等深流多种流体作用的结果;过去识别的“鲍玛序列”A段有浊流也有相当部分是砂质碎屑流成因,B—D段交错层理则是底层牵引流沉积产生的;只有浊流的沉积物才能称为浊积岩;“高密度浊流”是指砂质碎屑流而不是浊流;浊流是一种有牛顿流和紊乱状态的沉积物重力流;浊积岩没有复杂的颗粒悬浮层和碎石浮层,不发育逆粒序。Shanmugam等关于“鲍玛序列”这一新解是深海沉积学理论的一个进步。深海牵引流过去数十年取得了较大进步,但理论与实践脱节。深海层序地层是深海沉积理论进展的另一个方面,层序界面类型、体系域沉积有自身的独特性:层序界面至少存在斜坡侵蚀面、低水位下超面和水下沉积间断面三种;当沉积背景以陆源碎屑为主时,LST主要为盆底扇,TST和早期HST表现为非钙质远洋沉积,晚期HST一般不发育;当碳酸盐沉积为沉积背景时,LST主体为碎屑流和跨塌蹦落沉积或淡水透镜体,TST和早期HST为钙质细粒沉积,晚期HST可能存在有较小规模的钙屑海底扇。建议慎重解释“鲍玛序列”,审视“浊积扇”理论,废弃“浊积扇”概念,加强深海牵引流沉积机理方面的研究;LST浊积砂体、砂质碎屑流形成的块状不规则砂体、深海牵引流砂体可在深海储层预测方面具有巨大潜势,深海沉积作用及其过程的精细研究在指导深海油气勘探方面将会发挥越来越为重要的作用。