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首先介绍Warwick和Clarke(1995)提出的等级生物多样性指数以及在自由生活海洋线虫中的应用,重点以1998年9～10月和1999年4～5月两个航次的沉积物样品,用物种数目(S)、Margalef物种丰富度指数(d)、优势度Simpson指数(λ)、多样性Shannon-Wiener指数(H')、Pielou的均匀度指数(J)、Hill多样性系列指数(N1,N2和N+∞)、分类多样性指数(△)、分类差异指数(△*)、等级多样性指数(△+)对渤海自由生活海洋线虫的多样性进行了研究。结果表明,黄河输入的泥沙对渤海自由生活海洋线虫多样性的变化有一定的作用,距离黄河口越近的站位,群落具有的物种多样性和均匀性越低,优势度越高;距离黄河口越远的站位,群落具有的物种多样性和均匀性越高,优势度越低。 相似文献
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东海陆架外缘隆褶带是菲律宾海板块俯冲带陆侧弧后裂陷盆地(陆架盆地与冲绳海槽)之间的水下残留火山弧.其地球物理特征、地层组成、岩浆活动及地质构造等均具有“东西分带、南北分块”之特征.本隆褶带的形成始于第三纪初,当时为陆缘弧;中新世末以后,由于琉球弧后冲绳海槽的张裂作用,遂成为古琉球弧的残留弧.其形成机理受东海构造格局控制,与菲律宾海板块的俯冲作用及俯冲带的东向迁移有关,东海隆褶带的形成和构造演化大致经历了四个阶段:(1)断隆火山弧(E1+2)、(2)褶隆火山弧(E3)、(3)褶隆残留弧(N1)和(4)消亡残留弧(N2～Q).最后一个阶段隆褶带与陆架盆地整体沉降,接受了厚约1500m的上新世-第四纪浅海相沉积. 相似文献
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南海环礁发育过程中形成了开放程度不同的环礁类型,依据环礁不同地貌部位的几何因子作为反映环礁开放程度的指标可以定量划分环礁开放程度类型。如果将澙湖潮汐通道作为环礁地貌结构要素用来反映环礁开放程度,则潮汐通道可以成为新的度量因子。利用高分辨率遥感影像结合GIS技术,以澙湖潮汐通道的几何参数为主构建反映环礁开放程度的模型,结果表明,以口门宽度与礁体中轴线长度之比为指标建立的经验式,可用来划分环礁开放程度类型,封闭型环礁的开放度为0,准封闭型环礁的开放度为0~0.06,半开放型环礁的开放度为0.06~0.25,开放型岛礁的开放度为0.25~1。因此,采用这一量化表达式反映南海环礁的开放程度类型,可为珊瑚环礁的开放程度发育规律研究提供科学工具。 相似文献
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生活于珊瑚礁区的大型海藻可以与珊瑚一起为礁栖生物提供食物和栖息地, 它们在维护珊瑚礁生态系统生物多样性中起着极为重要的作用。本论文比较研究了生活于我国南海中沙大环礁区4种优势海藻的生化组分、光合特征及其对海水升温的生理响应,其中厚膜藻(Grateloupia ellipitica)和粉枝藻(Liagora samaensis)为红藻, 钙扇藻(Udotea flabellum)和仙掌藻(Halimeda discoidea)为绿藻。结果显示, 与绿藻相比, 红藻藻体叶绿素(Chl a)和类胡萝卜素含量更低且含有藻胆素, 红藻的光补偿点(EC)和呼吸速率(Rd)均显著低于绿藻。海水升温提高了4种海藻的光能利用效率(α)、EC、Rd和日净光合固碳量; 同时, 升温还降低红藻的饱和光强(EK)、提高绿藻的最大光合放氧速率(Pmax)。结果还显示, 海水升温在光强较低时提高红藻的光合放氧速率, 光强较高时则降低其放氧速率; 升温也提高绿藻的光合放氧速率, 但光强变化对升温效应的影响不显著。基于4种海藻的光生理特征以及升温效应的种间差异性可见, 短时间升温(~4℃)有利于中沙大环礁区海藻的光合作用; 与绿藻相比, 该升温效应更有利于红藻。 相似文献
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Mangrove forests are under the stress of sea level rise(SLR) which would affect mangrove soil biogeochemistry.Mangrove soils are important sources of soil-atmosphere greenhouse gas(GHG) emissions,including carbon dioxide(CO2),methane(CH4) and nitrous oxide(N2O).Understanding how SLR influences GHG emissions is critical for evaluating mangrove blue carbon capability.In this study,potential effects of SLR on the GHG emissions were quantified through static closed c... 相似文献
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为了解西沙群岛珊瑚礁海域浮游动物的群落特征, 于2015年5月末至7月初在西沙群岛8个岛礁(七连屿、永兴岛和东岛3个岛屿以及浪花礁、盘石屿、玉琢礁、华光礁和北礁5个环礁)进行了浮游动物采样, 分析了浮游动物的多样性、丰度和群落结构特征, 并比较了5个环礁潟湖内和向海礁坡区浮游动物群落组成的差异。调查海域共鉴定浮游动物180种(包括浮游幼虫13个类群), 其中桡足类最多, 达83种, 其次是水母类(38种)、浮游软体类(14种)、毛颚类(11种)和浮游被囊类(7种); 浮游动物平均丰度为256.4±117.8个·m-3, 桡足类占总丰度的51.08%, 其次是浮游幼虫(16.30%)、浮游被囊类(13.22%)和毛颚类(7.70%)。浮游动物种数、多样性和均匀度指数、丰度在岛屿和环礁之间以及环礁的潟湖区和向海礁坡区均存在差异; 浮游动物多样性和丰度在东岛、玉琢礁和华光礁较高, 而在七连屿和北礁较低; 5个环礁向海礁坡区的浮游动物多样性和丰度皆高于潟湖区的。多元统计分析结果表明调查岛礁的浮游动物可划分两个聚群(相似水平85%); 岛屿近岸及环礁的潟湖群落(Ⅰ)和岛屿远岸及环礁的向海礁坡群落(Ⅱ); 两个聚群浮游动物组成差异较显著(r=0.832, p<0.001); 前者的种数、多样性指数、总丰度和主要浮游动物类群如桡足类、毛颚类和浮游幼虫的丰度显著低于后者。环礁潟湖区和向海礁坡区的空间异质性和生态环境差异可能是导致浮游动物群落结构呈现不同特征的主要因素。 相似文献
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为探究不同凡纳滨对虾(Litopenaeus vannamei)池塘养殖系统养殖期间水-气界面CO2通量及其环境影响因素,以凡纳滨对虾池塘单养系统(L)和凡纳滨对虾-硬壳蛤(Mercenaria mercenaria)池塘综合养殖系统(低密度硬壳蛤LM-L、中密度硬壳蛤LM-M、高密度硬壳蛤LM-H)为研究对象,采用静态箱气相色谱法逐月监测了养殖期间(5—9月)池塘的水-气界面CO2通量,分析了CO2通量与环境因子的关系。研究表明：(1)对虾单养系统养殖期间水-气界面平均CO2通量为-12.66 mg·m-2·h-1,整体表现为CO2的汇;(2) LM-L、LM-M和LM-H综合养殖系统养殖期间水-气界面平均CO2通量分别为-16.02、-16.48和-36.70 mg·m-2·h-1,整体表现为CO2的汇,随着硬壳蛤放养密度的增加其碳汇能力增强;... 相似文献
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于2007年5月份(枯水期)和8月份(丰水期)采集辽河口区域大气样品及水样,应用气相色谱及静态顶空法测定大气及海水中溶解N2O的浓度,并计算不同站位的N2O通量。结果表明:辽河口区域水体中溶解N2O浓度存在着明显的时空变化,5月份河口区域水体中N2O浓度高于8月份,且河流段溶解N2O浓度大于近海岸海域。水中溶解N2O浓度及溶解氧浓度呈显著的负相关关系。在枯水期和丰水期,所有站位的N2O均处于过饱和状态,N2O气体从水体向大气排出,辽河口区域是大气中N2O的一个排放源。 相似文献
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灰色系统理论在建立海面石油烃风化模式中的应用 总被引：3，自引：2，他引：3
本文以n-C17/n-C20、Pr/n-C20、n-C18/n-C20、Ph/n-C20为指标,用最大矩阵元模糊聚类法探讨了风化一个月的任丘原油和30#重柴油与其他常见的7种油间的油种鉴别问题,确定了4种石油烃为表征油种的风化指标,并对其风化指标建立了灰色风化模式GM(1,1).研究结果表明,GM(1,1)风化模式的精度优于指数回归法,可用于一个月内的海面石油烃风化的预测. 相似文献
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The remote sensing composite information entropyand types of Nansha coral reef atolls 总被引：1，自引：1，他引：0
INTRODUCTIONTherearemorethan60atollsintheNanshaIslandsofChina.AInongtheemergedatollsofthem,thelargestreeftopareaisabout620kmZ,thesmallestisaboutIkmZ.TheresearchontheirgrowthisimPOrtantfromthescientificandrealisticperspectives.Duringthegeologicalhistory,undertheconditionthatthesealevelisrelativelysteady,theatoll'sformationisatypeofmarinetranSgression.Onthebasisoftheatollreef-ring'sopen-degree,theemergedatollsareclassifiedintofourtypes:opentype,half-opentype,quasi-closedtypeandclosedtyp… 相似文献
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Dinitrogen (N2) fixed by a group of prokaryotes (diazotrophs) is the dominant process adding bioavailable nitrogen into the ocean. Although it has been intensively studied how N2 fixation is controlled by resources (bottom-up factors), it is unclear whether the grazing (top-down control) effectively impacts growth and distribution of different diazotroph groups. In this study, we evaluate this question by conducting log-log regression of diazotroph biomass onto corresponding N2 fixation rates in the global ocean. The slope of the regression for Trichodesmium is ~0.8, indicating that a small portion of the increase in N2 fixation does not accumulate as its biomass. This leads to a conclusion that Trichodesmium is under a substantial top-down control, although bottom-up control still dominates. We also analyze the residuals of the regression in the North Atlantic, concluding that free trichomes of Trichodesmium are subject to stronger top-down control than its colonies. The weak correlation between the biomass and N2 fixation of unicellular cyanobacterial diazotrophs indicates that the degree of top-down control on this type of diazotrophs varies greatly. The analyses obtain unrealistic results for diatom-diazotroph assemblages due to complicated nitrogen sources of these symbioses. Our study reveals the variability of top-down control among different diazotroph groups across time and space, suggesting its importance in improving our understandings of ecology of diazotrophs and predictions of N2 fixation in biogeochemical models. Measurements of size-specific N2 fixation rates and growth rates of different diazotroph groups can be useful to more reliably analyze the top-down control on these key organisms in the global ocean. 相似文献
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Danyang Li Minfang Zheng Yusheng Qiu Limin Lai Nengwang Chen Hongmei Jing Run Zhang Min Chen 《海洋学报(英文版)》2023,42(1):75-82
Nitrogen fixation is one of the most important sources of new nitrogen in the ocean and thus profoundly affects the nitrogen and carbon biogeochemical processes. The distribution, controlling factors, and flux of N2 fixation in the global ocean remain uncertain, partly because of the lack of methodological uniformity. The 15N2 tracer assay (the original bubble method → the 15N2-enriched seawater method → the modified bubble method) is the mainstream method for field measurements of N2 fixation rates (NFRs), among which the original bubble method is the most frequently used. However, accumulating evidence has suggested an underestimation of NFRs when using this method. To improve the availability of previous data, we compared NFRs measured by three 15N2 tracer assays in the South China Sea. Our results indicate that the relationship between NFRs measured by the original bubble method and the 15N2-enriched seawater method varies obviously with area and season, which may be influenced by incubation time, diazotrophic composition, and environmental factors. In comparison, the relationship between NFRs measured by the original bubble method and the modified bubble method is more stable, indicating that the N2 fixation rates based on the original bubble methods may be underestimated by approximately 50%. Based on this result, we revised the flux of N2 fixation in the South China Sea to 40 mmol/(m2·a). Our results improve the availability and comparability of literature NFR data in the South China Sea. The comparison of the 15N2 tracer assay for NFRs measurements on a larger scale is urgently necessary over the global ocean for a more robust understanding of the role of N2 fixation in the marine nitrogen cycle. 相似文献
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During N2-O2 simulated saturation at a depih of 36.5 m the frequency, amplitude and index of a waves decreased and the activities of β and θ wave increased on the EEGs at rest. After the pressure was decompressed to normal, they could recover to the predive level. During the air excursion diving at depths of 60 and 70 m , the paramenters of EEG approximated to those of N2-O2 exposure. But at that time of the air excursion diving at a depth of 75 m they appeared the maximum. This showed that the changes related to the nitrogen partial pressure. There was an increase in slow waves during the simulated N2-O2 saturation. The activities of slow wave decreased on the EEGs in case of hyperventilation. The photic scimulation to the eyes caused the slow wave to disappear, and a rhythm could recover temporarily. When the photic stimulation was over the slow rhythm reappeared on the EEG. All the changes in EEG indicated that the encephalon function of the human body showed a gradual adaptation process during the 相似文献
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In the present study, we report N_2 fixation rate(~(15)N isotope tracer assay) and the diazotroph community structure(using the molecular method) in the western tropical North Pacific Ocean(WTNP)(13°–20°N, 120°–160°E). Our independent evidence on the basis of both in situ N_2 fixation activity and diazotroph community structure showed the dominance of unicellular N_2 fixation over majority of the WTNP surface waters during the sampling periods.Moreover, a shift in the diazotrophic composition from unicellular cyanobacteria group B-dominated to Trichodesmium spp.-dominated toward the western boundary current(Kuroshio) was also observed in 2013. We hypothesize that nutrient availability may have played a major role in regulating the biogeography of N_2 fixation.In surface waters, volumetric N_2 fixation rate(calculated by nitrogen) ranged between 0.6 and 2.6 nmol/(L·d) and averaged(1.2±0.5) nmol/(L·d), with 10 μm size fraction contributed predominantly(88%±6%) to the total rate between 135°E and 160°E. Depth-integrated N_2 fixation rate over the upper 200 m ranged between 150 μmol/(m~2·d)and 480 μmol/(m~2·d)(average(225±105) μmol/(m~2·d). N_2 fixation can account for 6.2%±3.7% of the depthintegrated primary production, suggesting that N_2 fixation is a significant N source sustaining new and export production in the WTNP. The role of N_2 fixation in biogeochemical cycling in this climate change-vulnerable region calls for further investigations. 相似文献
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海洋沉积体系的定量模拟可分为仿真和勘察式模拟,后者的目标是建立沉积特征的连续谱、凝练新的科学问题。本文提出一个勘察式模拟的方法论框架,即根据控制方程确定自变量的定义域,进而由模拟计算给出应变量的值域,并结合物质收支平衡原理和“圆台状环礁”几何模型,以此方法预估环礁及其海底阶地物质输运和堆积格局。环礁是珊瑚礁的独特类型,其礁盘区提供了礁体生长和礁外坡、海底阶地堆积的几乎全部物源。结果表明,环礁自身生长受控于生物碎屑生产,而海底阶地的范围和沉积速率不仅决定于离礁悬沙通量,而且受到环礁外水深和海盆环流的制约。悬沙输运和重力流过程形成常态沉降和水下滑坡的交替沉积。此模型所预测的环礁沉积体系高程-面积曲线与南海环礁的实际曲线相对照,可获得环礁演化的机制信息。模拟结果还提示了需进一步研究的科学问题,如环礁生长规模及其控制机制、环礁沉积体系中周期性沉积的时间尺度、环礁外坡由于珊瑚生长自组织机制形成的重力流事件与地震等极端事件的对比和机制识别、环礁群的海底阶地沉积记录多样性、海面变化对环礁演化的影响和沉积记录、环礁人居环境安全等。 相似文献
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This paper demonstrates a practical step-wise method for modelling wave energy at the landscape scale using GIS and remote sensing techniques at Alphonse Atoll, Seychelles. Inputs are a map of the benthic surface (seabed) cover, a detailed bathymetric model derived from remotely sensed Compact Airborne Spectrographic Imager (CASI) data and information on regional wave heights. Incident energy at the reef crest around the atoll perimeter is calculated as a function of its deepwater value with wave parameters (significant wave height and period) hindcast in the offshore zone using the WaveWatch III application developed by the National Oceanographic and Atmospheric Administration. Energy modifications are calculated at constant intervals as waves transform over the forereef platform along a series of reef profile transects running into the atoll centre. Factors for shoaling, refraction and frictional attenuation are calculated at each interval for given changes in bathymetry and benthic coverage type and a nominal reduction in absolute energy is incorporated at the reef crest to account for wave breaking. Overall energy estimates are derived for a period of 5 years and related to spatial patterning of reef flat surface cover (sand and seagrass patches). 相似文献
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沉积物中的异化硝酸盐还原过程对于海洋氮循环起着至关重要的作用。基于15N标记的培养技术是目前测定沉积物异化硝酸盐还原的主要手段。准确快速测定15N标记的产物(29N2、 30N2)是量化异化硝酸盐还原各个过程速率的关键。本研究自行组装膜进样质谱系统用于29N2和30N2的测定,对其测量条件进行了优化。结果表明,进样蠕动泵进样流速0.80 mL/min,进样时间3~3.5 min,恒温槽温度20~25℃,同时铜还原炉温度在300~600℃的条件下,^29N2/^28N2和^30N2/^28N2的测试精密度分别可以控制在0.1%和1%以内,比较适合29N2和30N2的测定。利用自组装的膜进样质谱系统结合15N标记的培养技术研究了青岛石老人沙滩沉积物中的异化硝酸盐还原过程。石老人沙滩沉积物不存在将硝酸盐完全还原为氮气好氧的反硝化。厌氧铵氧化、厌氧反硝化和异化硝酸盐还原为铵(Dissimilatory Nitrate Reduction to Ammonium,DNRA)的潜在速率(以湿沉积物N计)分别为(0.05±0.01) nmol/(cm^3·h),(2.32±0.21) nmol/(cm^3·h)和(1.02±0.15) nmol/(cm^3·h)。厌氧反硝化是硝酸盐异化还原主要的贡献者,其比例接近70%,其次是DNRA,比例可达30%,而厌氧铵氧化的贡献最低,仅为1%。在N2产生过程中,主要贡献者是反硝化,厌氧铵氧化的贡献仅为2%。 相似文献
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Several boreholes drilled by the Commissariat à l'Energie Atomique have reached and passed through the volcanic bedrock of Fangataufa atoll. The sampled volcanic rocks under the coral ring were produced during both aerial and submarine activity, whereas rocks drilled under the lagoon were erupted during submarine volcanism only. The bathymetric data show that the atoll has a “starfish” shape. The rift zones are elongated in N-S, N70–80 and N120 directions; these three main directions are also the directions of structural discontinuities in the lithosphere. Reconstruction of the atoll's topography before erosion using a slope angle of about 16° shows that the maximum height reached by the volcano was about 1300 m above sea level. For comparison, the maximum height of Méhetia island (southeast of Tahiti) is approximately 435 m. The successive construction stages are: (1) initiation of volcanism along the rift zones and construction of a central volcano; (2) production of brecciated lavas; (3) emergent volcanism; and (4) central and aerial activity. The present day position of the aerial volcanic rocks under the coral reef and the submarine products under the lagoon is discussed with reference to two hypotheses. The first is based on sea level changes and the second on a tectonic origin (collapse of the atoll's flanks). Using recent geochronological data, the submarine construction of the atoll related to the hot-spot activity lasted about 1.1 Ma. The accumulation rate was approximately 0.7 cm/yr (1.5 × 10−3 km3/yr) and the aerial volcanic activity lasted about 2 Ma (1.5 × 10−5 km3/yr). 相似文献