Trophic ecology of Pomatoschistus microps within an intertidal bay (Roscoff,France), investigated through gut content and stable isotope analyses

The diet of Pomatoschistus microps has been studied using both gut content and stable isotope analyses. In the Roscoff Aber Bay (Brittany, France), this fish is commonly found on sandy muddy intertidal flats. Gut content analyses were also interpreted using trophic indices. Owing to the large diversity of prey consumed, these indices emphasised the opportunistic feeding behaviour of P. microps. Here, this species fed mainly on endofauna with meiofauna being of high relative importance. The main biotic components of its trophic habitat, characterized by δ¹³C and δ¹⁵N, provided evidence of a major trophic pathway based on drift Enteromorpha sp. Trophic positions estimated by both diet analyses and isotopic analyses led to similar results. In this bay, P. microps is a first‐order predator with a low degree of omnivory. Despite a preferential consumption of the amphipod Corophium arenarium, we assumed that this goby behaves as a generalist feeding on a uniform variety of endofauna taxa.     

珠江口盆地西江凹陷南部文昌组层序地层及沉积体系研究

珠江口盆地西江凹陷南部包括两个相邻洼陷：西江36洼和番禺4洼,钻探结果却揭示了截然不同的油气勘探前景,其中,番禺4洼探明储量已过亿吨,而西江36洼却未有商业发现,导致勘探上对西江36洼烃源潜力有所顾虑。为了揭示这种差异油气地质条件产生的原因,亟待开展两个洼陷的对比研究。以主要烃源层系文昌组为切入点,通过开展精细的层序-沉积研究,进一步系统评估西江36洼烃源潜力。依据地震、钻井及分析化验等资料,在西江36洼与番禺4洼文昌组共识别了6个三级层序。西江36洼和番禺4洼文昌组发育扇三角洲、辫状河三角洲、湖底扇及湖泊沉积等沉积相类型,垂向上沉积相带具有旋回特征。伴随裂陷不同阶段和边界断层活动差异,陡坡带和缓坡带三角洲沉积体系规模呈现差异演化特征,而湖盆和半深湖-深湖相规模总体呈现出先增大后减小的规律。沉积相带在横向上也具有明显的迁移特征,表现为文六段时期先在西江36洼开始沉积,文五段开始再扩展到番禺4洼,同时文一段时期西江36洼湖盆已经消失,只在番禺4洼沉积充填。进一步对比两个洼陷各三级层序反映优质烃源岩条件的半深湖-深湖规模及物源供给量,结果显示在文六段至文四段时期两个洼陷烃源条件基本一致。鉴于该层段作为番禺4洼的主力源岩,其巨大的生烃潜力已经被勘探所证实,因此认为不能低估具有相似烃源条件的西江36洼生烃潜力。     

Spatiotemporal aspects of silica buffering in restored tidal marshes

Losses of pelagic diatom production resulting from silica limitation have not only been blamed for toxic algal blooms, but for the reduction in ability of coastal food webs to support higher trophic levels. Recent research has shown the importance of advective seepage water fluxes of dissolved silica (DSi) from freshwater marshes to pelagic waters during moments of riverine Si-limitation. In this study, we investigated the potential impact of recently installed new tidal areas along the Schelde estuary, located in former polder areas and characterized by so-called controlled reduced tidal regimes (CRT). Nine mass-balance studies were conducted in a newly constructed CRT in the freshwater Schelde estuary. During complete tidal cycles both DSi and amorphous silica (ASi) concentrations were monitored at the entrance culverts and in different habitats in the marsh. A swift DSi-delivery capacity was observed despite the shifted spatiotemporal frame of exchange processes compared to reference marshes. As silica-accumulating vegetation is not yet present, and difference with reference marshes’ deliveries is surprisingly small, we indicate diatomaceous debris and phytoliths to be the main silica source. Although further research is necessary on the driving forces of the different processes involved, restoration of former agricultural areas under CRT-regime provide the potential to buffer silica in the estuary.     

南海北部C4站柱状沉积中的孢粉组合及其古环境意义

对南海北部C4站柱状沉积剖面进行了高分辨率孢粉、藻类成分的分析和研究,同时测定了部分样品的AMS14C年代,划分了该站柱状沉积物地层时代,相应恢复了南海北部9 800 a B P以来植被、气候、环境的3个演替阶段.南海北部C4站从下至上可划分成3个孢粉组合带,依次为:1带(258～194 cm):以Pinus-Quercus(常绿)-Polypodiaceae-Pterdium-Pteris-Dicranopteris-Adiantum为主孢粉带;2带(194～94 cm):以Pinus-Quercus(常绿)-Pteridium-Polypodiaceae-Microlepia-Dicranopteris为主孢粉带;3带(94～4 cm):以Pinus-Pteridium-Polypodiaceae-Quercus(常绿)-Microlepia-Dicranopteris为主孢粉带.与3个孢粉带相对应的古植被阶段依次为:伴有针叶树的常绿阔叶、落叶阔叶混交林,热带半常绿季雨林,热带常绿阔叶、落叶阔叶混交林,与周边地区的植被演替相一致.由此可见,研究区经历了全新世早期气候转暖,中期气候炎热、干湿季明显、海平面上升以及晚期气候暖热、湿润3个古环境演变阶段.     

Relationship between Cd and PO4 in the Subtropical Sea near the Ryukyu Islands

The relationship between dissolved cadmium (Cd) and phosphate (PO₄) was examined at three stations in the subtropical area near the Ryukyu Islands in May 1999. Preformed PO₄ was obtained using the Redfield ratio in order to separate the surface water and the other layers in this study area. Almost 0 μM (−0.043 μM to 0.094 μM) was estimated in the layers above 300 m and 250 m at Sts. 1 and 3 and at St. 2, respectively. Up to these depths, water was considered to be uniform, and these layers were defined as the surface water in this study area. In the surface water, the slopes of the regression lines of the Cd-PO₄ plot were 0.162, 0.156, and 0.226 (nM/μM) at Sts. 1, 2, and 3, respectively, and these values were much closer to the estimated regenerated ratio of Cd to PO₄ from the Apparent Oxygen Utilization (AOU)-Cd/PO₄ plots, which was 0.197 (nM/μM) in this study area. Below surface layers, the slopes of the Cd-PO₄ plot changed to 0.371, 0.352, and 0.362 (nM//μM) at Sts. 1, 2, and 3, respectively. In the relationships between Cd and PO₄, clear deviations or kinks were observed at three stations at a PO₄ concentration of approximately 0.2 μM in the plot, which was attributable to the discontinuity of surface water and the other layers across the North Pacific subtropical mode water. In studies of the interaction between surface water and biogenic particles concerning the Cd/PO₄ ratio, separate analyses of seawater (surface water and the other layers) should be carried out to obtain the individual surface water ratio because the Cd/PO₄ ratio in the surface water is expected to differ from that of the underlying water. Furthermore, the biological fractionation of these constituents is based on the surface water ratio. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spectral properties of the X-ray binary pulsar LMC X-4 during different Intensity states

We present spectral variations of the binary X-ray pulsar LMC X-4 observed with the RXTE/PCA during different phases of its 30.5 day long third period. Only out-of-eclipse data were used for this study. The 3–25 keV spectrum, modeled with high energy cut-off power-law and iron line emission is found to show strong dependence on the intensity state. Correlations between the Fe line emission flux and different parameters of the continuum are presented here.     

4U 1957+11: a persistent low-mass X-ray binary and black hole candidate in the high state?

We report on several pointed Rossi X-ray Timing Explorer observations of the enigmatic low-mass X-ray binary (LMXB) 4U 1957+11 at different X-ray luminosities. The luminosity of the source varied by more than a factor of 4 on time-scales of months to years. The spectrum of the source tends to become harder when its luminosity increases. Only very weak  (1–2  per cent rms amplitude,  0.001–10 Hz  ,  2–60 keV)  rapid X-ray variability was observed during the observations. A comparison of the spectral and temporal behaviour of 4U 1957+11 with other X-ray binary systems, in particular LMC X-3, indicates that 4U 1957+11 is likely to be a persistent LMXB harbouring a black hole and it is persistently in the black hole high state. If confirmed, it would be the only such system known.     

Climate Change of 4°C Global Warming above Pre-industrial Levels

Using a set of numerical experiments from 39 CMIP5 climate models, we project the emergence time for 4°C global warming with respect to pre-industrial levels and associated climate changes under the RCP8.5 greenhouse gas concentration scenario. Results show that, according to the 39 models, the median year in which 4°C global warming will occur is 2084. Based on the median results of models that project a 4°C global warming by 2100, land areas will generally exhibit stronger warming than the oceans annually and seasonally, and the strongest enhancement occurs in the Arctic, with the exception of the summer season. Change signals for temperature go outside its natural internal variabilities globally, and the signal-to-noise ratio averages 9.6 for the annual mean and ranges from 6.3 to 7.2 for the seasonal mean over the globe, with the greatest values appearing at low latitudes because of low noise. Decreased precipitation generally occurs in the subtropics, whilst increased precipitation mainly appears at high latitudes. The precipitation changes in most of the high latitudes are greater than the background variability, and the global mean signal-to-noise ratio is 0.5 and ranges from 0.2 to 0.4 for the annual and seasonal means, respectively. Attention should be paid to limiting global warming to 1.5°C, in which case temperature and precipitation will experience a far more moderate change than the natural internal variability. Large inter-model disagreement appears at high latitudes for temperature changes and at mid and low latitudes for precipitation changes. Overall, the inter-model consistency is better for temperature than for precipitation.     

Methane-rich fluid inclusions and their hosting volcanic reservoir rocks of the Songliao Basin, NE China

Methane-rich fluids were recognized to be hosted in the reservoir volcanic rocks as primary inclusions.Samples were collected from core-drillings of volcanic gas reservoirs with reversed δ12C of alkane in the Xujiaweizi depression of the Songliao Basin. The volcanic rocks are rhyolite dominant being enriched in the more incompatible elements like Cs, Rb, Ba, Th, U and Th with relative high LREE, depleted HREE and negative anomalies of Ti and Nb,suggesting a melt involving both in mantle source and crustal assimilation. Primary fluids hosted in the volcanic rocks should have the same provenance with the magma. The authors concluded that the enclosed CH4 in the volcanics are mantle/magma-derived alkane and the reversed δ13C of alkane in the corresponding gas reservoirs is partly resulted from mixture between biogenic and abiogenic gases.     

麻黄山西区延长组长4+5至长6储层成岩作用及成岩演化史研究

麻黄山西区长4＋5至长6储层为一套三角洲前缘亚相的细砂岩,研究证明砂岩目前处于中成岩A期。机械压实与胶结作用是孔隙减少的主要作用,也是本区原生孔隙少、储集物性差的直接原因;而大气淡水的淋滤作用及有机酸溶蚀作用,尤其是有机酸溶蚀作用,是产生次生孔隙的主要作用,使局部储层物性有所改善,因此次生孔隙是本区油气的主要储集空间,下一步油气勘探开发应注重对有利次生孔隙空间的预测。