Assessment of <i>Posidonia Oceanica</i>(L.) Delile conservation status by standard and putative approaches: the case study of Santa Marinella meadow (Italy, W Mediterranean)

The conservation status of the Posidonia oceanica meadow at Santa Marinella (Rome) was evaluated through both standard (bed density, leaf biometry, "A" coefficient, Leaf Area Index, rhizome production) and biochemical/genetic approaches (total phenol content and Random Amplified Polymorphic DNA marker). The bio-chemical/genetic results are in agreement with those obtained by standard approaches. The bed under study was ranked as a disturbed one, due to its low density, and high heterogeneity in leaf biometry, LAI values, "A" coefficient and primary production. This low quality ranking is confirmed by both mean phenol content in plants, quite high and scattered, and by the low genetic variability in the meadow, with a very high similarity of specimen at a local scale. Hence, these two putative approaches clearly identify the endangered conservation status of the meadow. They link plant biodiversity and ecophysiology to ecosystem 'health'. Furthermore, they are repeatable and standardizable and could be usefully introduced in meadows monitoring to check environmental quality.

Trace metals in <i>Posidonia oceanica</i>in a coastal area of the Ionian Sea (Calabria, Italy)

As, Cd, Cu and Pb concentrations were measured in Posidonia oceanica sampled from meadows located in two sites along the calabrian coast (Ionian Sea, South-eastern Mediterranean). By dating the scales and the rhizome using retrospective procedures (lepidochronology), a time series over a period of nine years (1995-2004) was analysed. Throughout the whole lepidochronological period, the arsenic content in the scales was tenfold higher than that measured in the rhizome with a peak in the lepidochronological year 1996-1997 and a general decrease in the years after. Pb concentration also showed a tendency to decrease with time, whereas the Cd and Cu concentration were increasing. A comparison of the metal level in dead sheaths (scales) and living tissue (leaves) was also performed. The detailed distribution of the trace metals along the leaf axis and in the leaves at different developmental stages (adult, intermediate and juvenile) showed some differences in the metal content. The results also indicate that the arsenic content measured in the leaf blade reflects the high As content measured at the superficial sediments at one of the two sampled sites, demonstrating, for the first time, that P. oceanica would be a good indicator for this element.

Epiphytic Diatom Communities on Sub-Fossil Leaves of <i>Posidonia oceanica</i>Delile in the Graeco-Roman Harbor of Neapolis: A Tool to Explore the Past

The Graeco-Roman harbor of Neapolis (Naples, Italy), chronologically constrained between the late 4th century BC and the 6th century AD, offers a unique sight on relationship between past and present into the history of the marine biodiversity. In fact, the digs expose fossil leaf of Posidonia oceanica with epiphytic communities of microorganisms. Posidonia oceanica is a seagrass endemic to theMediterraneanthat forms large meadows whose remains can persist in the sediment for thousands of years. In this communication, we report results of analyses carried out using both molecular and morphological techniques on sub-fossil leaves of P. oceanica and their associated epiphytic communities.

Comparative analysis of bed density, total phenol content and protein expression pattern in <i>Posidonia oceanica</i>(L.) Delile

Posidonia oceanicameadows are experiencing a progressive decline, and monitoring their status is crucial for the maintenance of theseecosystems. We performed a comparativeanalysis of bed density, total phenol content and protein expression pattern to assess the conservation status ofPosidoniaplants from the S. Marinella (Rome, Italy) meadow. The total phenol content was inversely related to maximum beddensity, confirming the relationship betweenhigh phenol content and stressful conditions. In addition, protein expression pattern profilesshowed that the number of differentially expressed proteins was dramatically reduced in the latest years compared to previous analyses. Our results support the usefulness of integrating solid descriptors, such as phenol content, with novel biochemical/molecular approaches in the monitoring of meadows.

Diet of fish populations in posidonia oceanica meadows off the Island of Ischia (Gulf of Naples, Italy):

The gut contents of fish in three Posidonia oceanica meadows off the island of Ischia (Bay of Naples, Italy) were investigated. A total of 926 individual fish belonging to 28 species was sampled by bottom trawl in the leaf canopy. Labridae, Pomacentridae, Scorpaenidae, and Serranidae were the best represented families (41%, 38%, 8% and 6% of the total number of individuals, respectively). Of the 94 taxa detected in the gut contents, 42 were identified to the species level. The most common food items were decapod crustaceans (15% of the gut contents, on average), copepods (13%), amphipods (14%), brown fragments of P. oceanica (6%), and ostracods (6%). The most abundant species of labridae, Symphodus ocellatus and S. rostratus, showed a broad spectrum of prey. This generalist feeding may positively influence their numerical abundance. Seasonal variations in the diets of fish, also at prey-species level, were demonstrated. The fish taxon plays essentially a macro-carnivore trophic role. In the investigated seagrass meadows the main trophic fluxes start from plant detritus, macrophyta, and microphyta (as primary producers) towards crustacean decapods, copepods, ostracods, and gammarid amphipods (as secondary producers) to fish. A low recycling rate (4%) within the fish community was observed. Larger fish predators (e.g., Sparidae), swimming over the leaf canopy, are the main exporters to adjacent coastal systems.

生油岩特征和测井参数之间的关系——以德国西北部早侏罗纪Posidonia页岩为例

本文确定了中欧最发育的油源岩。下侏罗统Posidonia页岩的特征与电测井参数之间的关系。其中所使用的电缆测井有r-射线光谱测定法,密度、声波和各种电阻率测井。所考虑的有机地球化学参数包括有机碳含量、氢指数和热解烃产量。研究过程是对一个完整的、尚未成熟的Posidonia页岩段进行连续取芯。研究中查明并且避免了由钻孔的不光滑和裂缝影响样品和测井值。良好的相关关系只在由r-射线光谱测定法所测得的铀的含量和有机碳含量之间所看到。而铀含量和用氢指数所确定的干酪根类型之间没有关系。在本次研究中,由于多种原因,密度、声波和电阻率测井没有提供有用的资料。不同的环境是造成岩石是铀含量高低不规则的可能原因岩作用和裂缝作用下使得铀重新分配。

Effect of Fiber Weight Ratio and Fiber Modification on Flexural Properties of Posidonia-Polyester Composites

The main objective of this research is to study the effect of fiber weight ratio and chemical fiber modification on flexural properties of composites reinforced with Posidonia fiber. An unsaturated polyester matrix reinforced with untreated and treated Posidonia fibers was fabricated under various fiber weight ratios. Results showed that the combined chemical treatment provided better mechanical properties of composites in comparison with untreated fiber. The fiber weight ratio influenced the flexural properties of composites. Indeed, a maximum value of flexural modulus was observed for 10% fiber weight ratio for composites reinforced with treated fibers. SEM photographs revealed a different fracture surface between Posidonia fibers reinforced polyester composites.

Effect of Combined Chemical Treatment on Physical, Mechanical and Chemical Properties of Posidonia Fiber

The aim of this study is to investigate the effect of chemical treatment method on the properties of Posidonia fibers. The chemical treatment which is carried out is a combined hydrogen peroxide and sodium hydroxide treatment. First, an investigation of the treatment processes was undertaken. Secondly, the physical properties (linear density, diameter and ratio length per diameter), the mechanical properties (tenacity, elongation) and chemical properties (FT-IR spectra and X ray diffraction) of posidonia fibers were investigated. The optimum operating conditions were identified using a factorial design.

Variability in patterns of macro-epiphytic leaf community of Posidonia oceanica in the Islands of Kuriate:Western coast of Tunisia

Objective:To test the response of the epiphyte community structure and biomass of the Posidonia oceanica(P.oceanica)leaves to natural disturbance.Methods:Sampling of P.oceanica was carried in winter and summer on three sites in Kuriate Islands(western coast of Tunisia)subject to different environments disturbances.Shoots of P.oceanica were preserved in seawater-formalin(5%)solution for macro-epiphytes species identification in the laboratory.The samples were examined for leaf surface per shoot and the coverage(expressed as a percentage of leaf surface)of each morphological group,then carefully scraped with a razor blade.Epiphytes and scraped leaves were oven-dried at 60℃for 48 h.Biomass was expressed as g dry weight/shoot.Results:The biomass and the percentage cover of macro-epiphytic leaves showed seasonal variation.The highest values of epiphytic leaves were detected in summer whereas the lowest values were registered during winter.ANOVA showed that Kuriate Islands functioned as a single ecosystem in terms assemblage of macro-epiphytic leaves since no significant variation was detected for biomass and percentage cover at the scale site.Our study showed that natural disturbance had no effect on the assemblage distribution and the biomass of macro-epiphyte on the leaves of P.oceanica between the scales of site,whereas variability at the smallest scale was detected.ANOVA showed that exposure to wind and current had no effect on the biomass of macro-epiphytes leaves.Conclusions:Biomass and assemblages of macro-epiphytic leaves of P.oceanica were high in summer and homogenous between all sites investigated.Natural disturbances such as exposure to wind have no effect on the distribution and the biomass of epiphytes on the shallow meadow.

青藏高原羌塘盆地早侏罗世晚期海螂蛤页岩及其年代地层学意义

发现于德国南部的早侏罗世土亚辛期的海螂蛤页岩相沉积是中生代最早一次,也是唯一保存在大陆地层中的全球性大洋缺氧事件的典型代表。近年中国羌塘盆地已相继发现4处海螂蛤页岩相地层。北羌塘天然气水合物钻探试验井QK-5井钻遇含海螂蛤页岩相特有化石组合的地层,厚度逾150m,是迄今所知羌塘盆地纬度最高的海螂蛤页岩相产地,其他3处分布在羌塘盆地中间隆起带以南的双湖和色哇等地。海螂蛤页岩相的分布纵贯南、北羌塘,意味着羌塘盆地在早侏罗世并没有受到中间隆起带的制约而分成南、北2个独立的沉积凹陷。北羌塘西部白龙冰河、半岛湖一带与东部雀莫措、雁石坪一带的早侏罗世沉积相截然不同,形成早侏罗世西海东陆的沉积格局。海螂蛤页岩相在羌塘盆地的发现,有助于进一步认识中生代羌塘盆地沉积和古海洋演化历史。该区以海螂蛤黑色页岩为代表的富碳沉积无论是分布面积还是沉积厚度都十分可观,对盆地的天然气水合物、页岩气及常规油气勘探具有重要的意义。

深海超短基线定位系统现状及展望

水声定位技术具备稳定的高精度定位能力,能够为各类深海探测装备直接提供绝对位置信息。超短基线定位系统的声学换能器阵安装在船底,便于大范围机动作业,成为现代远洋科考船必不可少的水声定位设备。首先介绍了超短基线定位的基本原理,然后系统介绍了法国iXblue、挪威Kongsberg、英国Sonardyne、美国LinkQuest和德国Evologics等公司的深海远程超短基线定位系统,并以哈尔滨工程大学远程超短基线定位系统为例分析了国内发展情况,最后展望了深海远程超短基线定位系统的发展趋势。