渤海莱州湾表层沉积物中底栖有孔虫分布特征及其环境意义

对渤海莱州湾海域240个站位表层沉积物中底栖有孔虫群落进行了分析,共鉴定常见的底栖有孔虫42种。结果表明,莱州湾表层沉积物中底栖有孔虫主要以玻璃质壳为主(平均丰度达70.9%),瓷质壳含量次之,胶结壳含量最低;玻璃质壳占有孔虫全群的百分含量,随水深的增加而增加;从黄河口向外海方向,有孔虫分异度和丰度都逐渐增大。该海域底栖有孔虫平面分布的主要控制因素为盐度和底质沉积物类型,大体可分为两个组合分区,I区为Ammonia beccarii-Quinqueloculina spp.组合,代表盐度较低的近岸海陆过渡浅水环境;II区为Cribrononionsub-incertum-Protelphidium tuberculatum组合,代表盐度较高的远岸内陆架环境。     

大丰野鹿荡中全新世以来有孔虫群落及古环境变化

对江苏省盐城市大丰区野鹿荡DF20钻孔21 m长沉积物岩芯开展了详细微体古生物学定量分析研究,结果显示,沉积物中浮游有孔虫仅在下部部分层位少见,含丰富的底栖有孔虫化石。研究共识别出47属66种底栖有孔虫,尤其以Ammonia beccarii var.,Cribrononion vitreum,Cribrononion subincertum,Elphidium advenum,Pseudononionella variabilis,Stomoloculina multangula,Elphidium magellanicum,Pararotalia nipponica,Elphidium hispidulum和Ammonia compressiuscula等近岸和内陆架浅水分子高含量为主。其中Ammonia beccarii var.最高达87.5%,平均含量超过50%。结合钻孔底部沉积物中贝壳的初步测年资料,该钻孔底栖有孔虫组成和变化揭示了野鹿荡地区近七千年来沉积环境存在一个由相对较深的近岸浅水海洋环境向海陆过渡相半咸水环境的演化过程。     

台湾海峡西北部平潭岛海域表层沉积物中底栖有孔虫分布及其环境控制因素

对台湾海峡西北部平潭岛海域337个站位表层沉积物中底栖有孔虫进行分析鉴定,结果表明底栖有孔虫丰度、分异度变化较大,所出现的属种类型以玻璃质壳体为主,其次为瓷质壳,胶结壳最少。底栖有孔虫分布受水深、盐度、底质类型、底流和沿岸上升流等因素共同影响。应用‘PAST’软件的因子分析结果表明,该海域底栖有孔虫可划分为四个组合:组合Ⅰ(Hanzawaia-Pseudorotalia-Bolivina)主要分布于水深大于20m的深水区,受水深和底流影响明显;组合Ⅱ(Ammonia beccarii-Elphidiumspp.)主要分布于近岸浅水环境;组合Ⅲ(Quinqueloculina-Ammonia annectens-Spiroloculina)主要分布于海湾内高盐度区,推测受到沿岸上升流影响;组合Ⅳ(Elphidium advenum-Ammonia annectens)分布于组合Ⅰ与组合Ⅲ之间的局部区域,可能受浙闽沿岸流影响较强。     

浙江舟山岛礁潮间带有孔虫种群季节性生态特征研究

作者选择位于舟山长峙岛西南淤泥质潮间浅滩,通过为期一年的采样(2014年7月—2015年6月),尝试探讨淤泥质岛礁潮间带有孔虫种群的季节性生态特征。共鉴定出有孔虫14属18种。有孔虫种群以玻璃质壳为主,占全群95%以上。优势种为Ammonia beccarii vars.,Elphidiella kiangsuensis,Cribrononion vitreum。研究结果显示:1)区域有孔虫总体平均丰度为850个/10cm~3,活体平均丰度为504个/10cm~3。丰度季节变化显著,秋冬季节总生物量仅为春夏季节的38%;2)活体与总体属种组成基本一致,以本地埋葬群为主,显示研究区潮流动力输送作用不强;3)区域潮间带有孔虫分带性不明显,国外研究中常见的属种Trochammina macrescens,Trochammina inflata和Miliammina fusca,在本区也有出现,但丰度显著减少;4)研究区有孔虫组合个体畸形率不超过5%,畸形个体以Ammonia beccarii vars.最为常见,可作为区域环境指示的敏感种。     

海南岛近岸沉积物中的有孔虫特征与分布

对位于海南岛近岸7-170 m水深、180个站位沉积物表层样的有孔虫分析表明,研究区浮游有孔虫类型较少、共发现浮游有孔虫19种,单个站位最多含有浮游有孔虫16种,而且浮游有孔虫含量(丰度)亦较低.底栖有孔虫则较为丰富,仅在较粗砂中底栖有孔虫丰度相对较低.常见近40多个底栖有孔虫属种,多数样品中以含有螺旋式与平旋式玻璃质底栖有孔虫为主,少数样品以胶结壳、列式玻璃质壳或大型底栖有孔虫为优势特征.本研究在详细阐述了底栖有孔虫主要特征属种的基础上进行了有孔虫分区,从而揭示其所包含的环境意义.     

北部湾中部海域底质沉积物中的有孔虫

本文对北部湾中部海域水深2.4m到61m、共计184个站位表层沉积物中的有孔虫进行研究。结果显示浮游有孔虫丰度非常低,种类也较稀少,仅在南侧水深较大的少数站位有发现,且含量不超过5%;而底栖有孔虫则较丰富,多数样品中以含有螺旋式与平旋式的玻璃质壳类型为主,暖水或大型底栖有孔虫分子常见。和其它海区相较而言,该海域底栖有孔虫中胶结壳类含量偏高,可能与沉积物底质颗粒较粗及海水盐度较低有关。该研究详细报道了底栖有孔虫主要属种在北部湾的分布特征。与海洋环境对比显示,水深和沉积物底质类型是影响这些属种平面分布的主要因素,而湾外温暖水团则是控制暖水种分子分布的另一重要因素。     

长江三角洲DY03孔有孔虫群落演化及其古环境意义

文中对上海奉贤DY03孔222m长的沉积物柱状样样品进行有孔虫定量统计分析,结合颗石藻、孢粉等其它古生物学资料,重建了晚新生代长江三角洲南部沉积环境变化。钻孔孔深60m以上发现有孔虫产出,包括60—40m与24.6—2m两层位,尤以24.6—2m有孔虫丰度较高。孔深60m附近有孔虫丰富,底栖有孔虫主要属种为Ammonia beccarii vars.,Nonionella stella,Protelphidium tuberculatum,Elphidium advenum和Astrononion tasmanensis等,而58.8—49.2m则不含有孔虫;孔深48.8—40m,有孔虫丰度、分异度均从下而上降低,从以Ammonia beccarii vars.-Elphidium advenum组合为主,Ammonia compressiuscula,Florilus decorus,Pseudononionella variabilis及Nonionella stella等繁盛的面貌,变为仅含少量的Ammonia beccarii vars.和Elphidium limpidum等。有孔虫群落在60—40m层位呈现了其沉积环境由滨岸演变为浅海、又转变为滨岸的演化序列。另一有孔虫丰富层位(埋深为24.6—2m)中,有孔虫分布连续、丰度高、属种分异度高,其中下部21.4—8.8m含有大量的低盐种Pseudononionella variabilis,Stomoloculinasp.以及少量Heterolepaspp.和Lagena hispida;中部8.4—5.0m产出大量深水型分子Ammonia compressiuscula及代表高温、高盐环境的瓷质类型Quinqueloculina seminula,Triloculina rotunda和Spiroloculina laevigata;上部4.8—2m中深水类型缺失,从下至上显示了一个海水由浅到深再变浅、海水盐度由低到高再变低、海水温度由低到高再变低的海侵-海退过程,且本次海侵较上次海侵水深更深、范围更广。对比显示,DY03孔24.6—2m地层相当于中国东部广泛存在的第一海侵层(全新世),而60—40m地层则相当于第二海侵层(晚更新世),有孔虫等生物群落演化反映了该地区晚更新世以来的两次较大海水进退过程。     

苏北海岸带有孔虫Ammonia beccarii微环境分布的初步研究

本文通过对苏北海岸从北到南采样,统计有孔虫的个数,着重分析Ammonia beccarii(毕克卷转虫),并结合样品粒度分析、化学分析,试图寻找这单一属种的分布规律,发现．Ammonia beccarii的丰度、活体百分含量、优势度沿海岸线变化与有孔虫群的变化有较好的对应关系,但优势度在有孔虫群落中并不明显,基本在20％以下;Ammonia beccarii在分布上有如下特征：滩面上丰度与活体百分含量较大,在海滩、河口环境较小,在人工泻湖中极大;在南北方向上的分布变化没有显著规律;在沉积物中,一般在中值粒径较小(Mdφ≤0.8)或较大(Mdφ≥5．44)的沉积物中,Ammonia beccarii是不适宜生长的;另外,有机质含量可能是限制．Ammonia beccarii生长的一个条件。     

东沙西南海域表层沉积物底栖有孔虫群落特征及其对冷泉活动的指示意义

底栖有孔虫群落及其地球化学组成是海底冷泉区发育的重要指示标志之一。对南海北部东沙西南海域4个含碳酸盐结核表层沉积物样品进行了底栖有孔虫群落分析,以探讨该区底栖有孔虫对冷泉活动的响应特征。结果表明,该区底栖有孔虫群落组合总体具有玻璃壳含量高、胶结壳含量低的特征,主要属种以Cibicides pseudoungerianus,Globocassidulina subglobosa为主,其次Discanomalina semipunctata,Gyroidina soldani,Lenticulina orbicularis和Cibicides lobatulus也有较高含量。该区底栖有孔虫群落组成与邻近正常沉积区有显著差异,总体上含碳酸盐结核区底栖有孔虫以玻璃壳表生种为主,而正常沉积区的胶结壳和内生种则相对有较高含量。Cibicides属底栖有孔虫和D.semipunctata通常附生于蠕虫管壁、珊瑚枝或碳酸盐结核表面,它们在东沙西南区域大量出现可能与该区硬底质沉积密切相关。我们提出D.semipunctata可作为南海北部硬底质类型冷泉活动的指示标志。     

浙江钱塘江冰后期有孔虫化石记录及其古环境意义

本研究对浙江萧山SE2钻孔近50m沉积物岩心进行了详细的有孔虫定量统计分析,并结合测年资料重建了冰后期以来钱塘江沉积河谷的环境演化过程。有孔虫群落特征反映的古环境变化与沉积相分析结果一致。有孔虫资料显示:大约1万年以来该地区受到海水的影响、以胶结质壳Textularia-Reophax组合为特征,并在中全新世海水深度到达最大、以近岸浅水组合Ammonia beccarii-Elphidium magellanicum为代表,而晚全新世以来在全球海平面下降的影响下、该地区海水变浅的同时,却由于狭窄的特殊河口地形,水动力相对较强,显示强潮型河口地区特有的近岸分子Ammonia beccarii,Elphidium advenum和相对较深水分子Ammonia compressiuscula共存的底栖有孔虫群落特征。     

Development of modern benthic ecosystems in eutrophic coastal oceans: The foraminiferal record over the last 200 years,Osaka Bay,Japan

The ecosystem dynamics of a modern benthic community in Osaka Bay was studied by analyzing sediment cores and fossil foraminifera deposited during the past 200 years. The results suggest that the high-density/low-diversity assemblage has appeared in the early 1900s, coinciding with the eutrophication of the bay resulting from the Japanese industrial revolution. This assemblage proliferated during the period 1960 to 1970 when the eutrophication and bottom-water hypoxia were most pronounced. The development of the assemblage has been characterized by an increase in the relative and absolute abundance of eutrophication-tolerant species (Ammonia beccarii, Eggerella advena, and Trochammina hadai) and a decrease in many other foraminiferal species, such as Ammonia tepida, Elphidium, Miliolinella subrotunda, and Valvulineria hamanakoensis, that are unable to tolerate low-oxygen conditions. Approximately thirty years after the imposition of discharge restrictions in the 1970s, this assemblage continues to predominate in the inner part of the bay, and E. advena is currently found across the entire bay. These records make a significant contribution to understanding the long-term relationship between anthropogenic impact and ecosystem change.     

奥茅卷转虫Ammonia aomoriensis(Asano,1951)与毕克卷转虫Ammonia beccarii(Linnaeus,1758)(有孔虫)的分类学以及在黄东海分布的温盐深特征比较研究

Ammonia aomoriensis(Asano,1951)和Ammonia beccarii(Linnaeus,1758)是两个形态学易混淆,但被广泛使用并具有重要环境指示意义的有孔虫。通过对渤海、黄海和东海陆架区60个站位表层沉积物的水平分布调查,并连续17个月对潮间带分低潮区和高潮区进行了季节调查,对二者的形态分类、生态分布和环境关系进行比较研究。结果表明A.aomoriensis和A.beccarii在潮间带的丰度都有季节性变化,体现冬高夏低的特点,前者一般在高潮区较多,后者在低潮区较多。二者的丰度从潮间带到陆架区随着水深的增加呈阶梯式锐减:平均含量分别达22%和39%;在水深<20m的陆架区平均含量分别降至15%和6%;在水深>20m的陆架区平均含量分别再次降至0.6%和1.4%。统计分析表明二者对盐度和水深的响应相似,但对温度的反应存在差异:在潮间带环境,二者的丰度都与盐度显著正相关;在浅海陆架环境,二者的丰度都与水深呈显著负相关;无论在潮间带还是陆架海区,A.beccarii的丰度都与海水温度呈显著负相关,但A.aomoriensis与温度相关性不显著。本研究结果显示A.aomoriensis和A.beccarii对滨岸浅海都具有优越的指示作用,在古环境分析中,首先可根据二者的含量进行环境推测(潮间带或者陆架浅海),再利用不同环境下本文所建立的线性方程对海水温、盐、深进行大体的估算。     

Heterosteginapapyracea Seguenza du Miocène du Corridor Sud-Rifain (Maroc) : biométrie et particularités paléoécologiques

Biometric study of the inner features of Heterostegina specimens preserved in tortonian sediments of the oued Yhoudi member allows to confirm the presence of species Heterostegina papyracea Seguenza, 1880. Analysis of both large and small components of the foraminiferal assemblage in all examined samples establishes the dominant character of species Heterostegina papyracea Seguenza (more than 60% of total benthic foraminifera). The assemblage of small benthic foraminifera associated with the Heterostegina is different from that described from Recent sediments, as well as from Miocene sediments of Calabria and Spain. In order to explain this result, two hypotheses can be put forward: (1) the Tortonian Heterostegina from Morocco proliferated abundantly in very shallow environments in association with small foraminifera (i.e. abundant Ammonia beccarii). (2) Because of powerful tidal currents in the South Rifian Corridor, Heterostegina tests were probably transferred after death. This transfer could possibly be due to the narrowness of the South Rifian Corridor in the Early Late Tortonian and its position between the Atlantic and the Mediterranean. Similar cases foraminiferal displacements are also known from modern basins. This study illustrates the difficulties in reconstructing the paleogeography of the studied area and the importance of considering all available components of the assemblage.     

山东新汶煤田太原组小有孔虫动物群及石炭-二叠系界线的探讨

通过对山东新汶煤田太原组小有孔虫动物群的系统研究,共鉴定出小有孔虫化石24属66种,根据小有孔虫在太原组中的垂向分布和含量的变化,自下而上分为3个小有孔虫组合：1．Brad yina samarica- Palaeotextularia angusta elongata组合,2．Nodosaria sinensis- Tetrataxis组合,3．Geinitzina postacarbonica组合。通过与邻区及华北部分地区的对比,本区太原组小有孔虫动物群的地质时代应归属于早二叠世,其层位大致相当于华北各地太原组(ting)类的Pseudoschwagerina带。     

南海北部琼东南盆地BD-2井中新世有孔虫生物地层及沉积环境

南海北部琼东南盆地BD-2井中新世地层沉积连续,是琼东南盆地中新统较典型的钻井剖面之一。该井中新世地层中含丰富的有孔虫化石,共鉴定有孔虫62属98种,其中浮游有孔虫13属41种,底栖有孔虫49属57种。根据有孔虫标志种及螺旋浮游有孔虫旋向优势度的变化,对该井的有孔虫生物地层进行了详细划分,从早中新世至晚中新世共识别出11个有孔虫化石带或联合化石带。探讨了下中新统与中中新统,中中新统与上中新统界线的有孔虫划分标志。依据有孔虫丰度、分异度及组合特征,讨论了BD-2井从早中新世至晚中新世沉积环境演化特征。     

Metabarcoding reveals high diversity of benthic foraminifera linked to water masses circulation at coastal Svalbard

Arctic marine biodiversity is undergoing rapid changes due to global warming and modifications of oceanic water masses circulation. These changes have been demonstrated in the case of mega- and macrofauna, but much less is known about their impact on the biodiversity of smaller size organisms, such as foraminifera that represent a main component of meiofauna in the Arctic. Several studies analyzed the distribution and diversity of Arctic foraminifera. However, all these studies are based exclusively on the morphological identification of specimens sorted from sediment samples. Here, we present the first assessment of Arctic foraminifera diversity based on metabarcoding of sediment DNA samples collected in fjords and open sea areas in the Svalbard Archipelago. We obtained a total of 5,968,786 reads that represented 1384 amplicon sequence variants (ASVs). More than half of the ASVs (51.7%) could not be assigned to any group in the reference database suggesting a high genetic novelty of Svalbard foraminifera. The sieved and unsieved samples resolved comparable communities, sharing 1023 ASVs, comprising over 97% of reads. Our analyses show that the foraminiferal assemblage differs between the localities, with communities distinctly separated between fjord and open sea stations. Each locality was characterized by a specific assemblage, with only a small overlap in the case of open sea areas. Our study demonstrates a clear pattern of the influence of water masses on the structure of foraminiferal communities. The stations situated on the western coast of Svalbard that are strongly influenced by warm and salty Atlantic water (AW) are characterized by much higher diversity than stations in the northern and eastern part, where the impact of AW is less pronounced. This high diversity and specificity of Svalbard foraminifera associated with water mass distribution indicate that the foraminiferal metabarcoding data can be very useful for inferring present and past environmental conditions in the Arctic.     

Modern foraminiferal record of alternating open and restricted environmental conditions in the Santo André lagoon,SW Portugal

Benthic foraminifera from eleven stations sampled seasonally were analyzed in order to examine the biological response to rapid and intense environmental changes taking place in the Santo André coastal lagoon. Foraminiferal assemblages show a very low species diversity and a high dominance of three euryhaline species throughout the year. Under closed-inlet conditions, foraminiferal assemblages exhibit low abundance of foraminiferal tests, whereas under open-inlet conditions absolute abundance greatly increases due to sea water entrance. Present-day dramatic environmental changes are thought to be responsible for deformed foraminiferal tests that are commonly found. Comparison of modern assemblages with those obtained from the Holocene sedimentary record indicates persistent restrictive environmental conditions after sandy barrier formation, circa 5000 years ago.     

Experimental dissolution of a fossil foraminiferal assemblage (Paleocene–Eocene Thermal Maximum,Dababiya, Egypt): Implications for paleoenvironmental reconstructions

Dissolution experiments were carried out on a foraminiferal assemblage from the Paleocene–Eocene Thermal Maximum (PETM) at Dababiya, Egypt, in order to: 1) reveal the effects of differential dissolution on the composition of the foraminiferal assemblage and 2) develop objective criteria for the evaluation of dissolution in foraminiferal assemblages used in early Paleogene paleoenvironmental reconstructions, particularly with respect to neritic Midway-type assemblages from the Paleocene/Eocene transition. Our results confirm two general observations on modern foraminifera: 1) planktic foraminifera are much more vulnerable to dissolution than benthic foraminifera, leading to depressed P/B ratios and 2) dissolution susceptibility differs between size fractions, with the smaller specimens dissolving more rapidly than the bigger ones, leading to a larger average size of the remaining assemblage. Within a size fraction, wall structure and thickness are considered to be the main factors controlling differential dissolution susceptibility. We propose a ranking scheme for taxa with respect to dissolution resistance. Among the benthic taxa, Lenticulina is most resistant, followed by the agglutinated Gaudryina cf. ellisorae and Alabamina midwayensis. Biserial and triserial hyaline taxa and the porcelaneous Spiroloculina sp. are most susceptible to dissolution, whereas rotaliines, such as Cibicidoides and Anomalinoides have an intermediate susceptibility. This implies that mild dissolution of a Midway-type benthic assemblage leads to a relative enrichment in Lenticulina, Gaudryina and rotaliines. Amongst planktic foraminifera, the muricate taxa Acarinina and Morozovella are most resistant, followed by the cancellate Subbotina. The smooth and generally small Globanomalina and Zeauvigerina are least resistant to dissolution. Our data enable to objectively evaluate various degrees of dissolution in benthic and planktic foraminiferal assemblages retrieved from the lower Paleogene Tethyan outcrops. In this way taphonomic artifacts can be readily distinguished from paleoenvironmental signals affecting the primary composition of the assemblages. More generally, we propose that the combined use of foraminiferal numbers, P/B ratio and relative abundances of non-calcareous agglutinated taxa and Lenticulina may provide a powerful proxy for assessing dissolution in hemipelagic assemblages from Cenozoic and upper Cretaceous continental margins. In order to achieve more robust pre-Quaternary paleoenvironmental reconstructions based on quantitative foraminiferal data, application of dissolution proxies, like proposed here, or in slightly modified form, should become a more widely used micropaleontologic procedure. Particularly continental margin studies dealing with major biotic events (e.g. PETM) or employing P/B ratios for sea-level reconstructions should benefit from such an approach.     

The niche of benthic foraminifera,critical thresholds and proxies

Ecological studies of benthic foraminifera are carried out to explain patterns of distribution and the dynamics of communities. They are also used to provide data to establish proxy relationships with selected factors. According to niche theory, the patterns of distribution of benthic foraminifera are controlled by those environmental factors that have reached their critical thresholds. For each species, in variable environments, different factors may be limiting distributions both temporally and spatially. For a species or an assemblage to be useful as a proxy its abundance must show a strong correlation with the chosen factor. Since numerous factors influence each species, it is only in those environments where the majority of factors show little variation but one particular factor shows significant variation that the proxy relationship for that factor can be determined. On theoretical grounds, the reliability of using foraminiferal abundance as a proxy of a selected environmental factor should be restricted to the range close to the upper and lower thresholds. For oxygen, foraminifera are potential proxies for the lower limits but once oxygen levels rise to values of perhaps >1 or 2 ml l⁻¹, there is no longer a relationship between oxygen levels and abundance. By contrast, the flux of organic matter over a large range shows a sufficiently close relationship with foraminiferal assemblages so that transfer functions can be derived for the deep sea. However, the relationship at species level is far less clear cut. Much more accurate estimates of primary productivity and modern organic flux rates are required to improve the determination of past flux rates.