Over 10 years of variation in Mediterranean reef benthic communities          下载免费PDF全文

Federico Betti  Giorgio Bavestrello  Marzia Bo  Valentina Asnaghi  Mariachiara Chiantore  Simone Bava  Riccardo Cattaneo‐Vietti 《Marine Ecology》2017,38(3)

During the last several decades, the Mediterranean littoral shallow water benthic communities have suffered significant changes in their structure and taxa composition. Despite numerous studies conducted to characterize these changes at various levels, it has always been very difficult to disentangle the effects of natural factors from anthropic ones. The main purpose of this work was to evaluate possible changes, over a 10‐year scale, in diversity and abundance of the most representative species of the benthic communities considered to be primarily and potentially affected by natural stressors in a highly protected area. Sets of macro‐photographs were taken in 2002–2003 of three sites inside a small bay called Ca’ dell'Oro, which is the “no entry—no take” zone of the Marine Protected Area of Portofino, in order to analyse the structure of the benthic communities at different depths over a short time scale. The same sampling was repeated 10 years later in 2013. In the 10‐year span, a significant change in the macroalgal coverage and composition was observed, while the overall richness and coverage of species remained almost unchanged. This process resulted in a significant reduction of the habitat complexity of the three‐dimensional algal components. Likewise, a remarkable change in terms of presence and abundance occurred among all zoobenthic components. The benthic communities seem to have suffered from detrimental effects probably caused by climatic events that have been occurring in recent years in the Ligurian Sea.  相似文献   

The <Emphasis Type="Italic">M</Emphasis><Subscript>w</Subscript> 4.3 January 17, 2014, earthquake: very rare seismic event on the Siberian platform     

Alena I. Seredkina  Valentina I. Melnikova  Nadezhda A. Gileva  Yan B. Radziminovich 《Journal of Seismology》2015,19(3):685-694

We described the 2014 January 17 earthquake (M _w?=?4.3) occurred on the Siberian platform in the area of sublongitudinal part of the Angara river in the zone of possible influence of two large reservoirs—Ust-Ilimsk and Boguchan. This is the first event of such magnitude recorded in this previously aseismic area during the whole period of instrumental observations. A seismic moment, a moment magnitude, a hypocentral depth, and a focal mechanism of the event were calculated on the basis of surface wave amplitude spectra. Analysis of the geological and geophysical data showed that the earthquake origin is connected with high-velocity gradient zone located at the border of the Late Proterozoic cover and the Precambrian basement of the Siberian platform. Some evidences for a natural character of the earthquake were considered.  相似文献   

Assessing the impact of climate change on flood in an alpine catchment using multiple hydrological models   总被引：3，自引：3，他引：0  

Xiaoyan Wang  Tao Yang  Valentina Krysanova  Zhongbo Yu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(8):2143-2158

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Drowning history of a Miocene carbonate platform (Zhujiang Formation, South China Sea)   总被引：4，自引：0，他引：4  

Ute Sattler  Adrian Immenhauser  Wolfgang Schlager  Valentina Zampetti   《Sedimentary Geology》2009,219(1-4):318-331

The identification and interpretation of drowning events in the geologic record can aid significantly to the reconstruction of the depositional, tectonic and eustatic history of a study area and often improve reservoir and seal prediction in carbonate rocks. The differentiation between drowned platforms showing a record of continuous deepening and those with a record of exposure followed by rapid deepening remains, however, problematic. The Zhujiang carbonate platform (Liuhua 11-1 field, South China Sea) study shown here provides an example of an integrated approach combining high-resolution geochemistry, microfacies analyses and foraminiferal biostratigraphy in order to improve the reconstruction of environmental conditions prior, during and after platform demise and drowning. The Zhujiang carbonate platform displays the following vertical succession of four facies types i) skeletal grain facies with a miogypsinid/lepidocyclinid-dominated fauna deposited in a moderately deep (< 50 m), oligotrophic back-reef setting; ii) in situ corals in patch-reef facies in an oligotrophic lagoon (< 10 m); iii) rhodoid facies with in situ red algal crusts, dominated by Heterostegina sp. and spiroclypeids, possibly capped by a subaerial exposure surface. Well-rounded rhodoids representing a mesotrophic lagoon dominate the upper portions of the rhodoid facies; iv) pelagic marine shales of the Hanjiang Formation burying the carbonate platform after drowning. This facies succession, in combination with geochemical evidence suggests a deepening-upward trend. This trend might have been interrupted by transient subaerial exposure but no evidence for meteoric diagenesis was found at the drowning unconformity topping the carbonate platform. Instead, microfacies analyses suggest that platform demise may be related to progressive changes in environmental conditions, including increasing nutrient-levels and/or decreasing temperature up-core towards the drowning unconformity. These findings are of significance for those concerned with Miocene carbonate factories and, more specifically, the demise of carbonate platforms in general.  相似文献   

Age and palynological characteristic of the Dongning Formation (Eastern Heilongjiang,China)     

Tatiana A. Kovaleva  Valentina S. Markevich  Ge Sun

《Russian Journal of Pacific Geology》2017,11(3):178-190

The taxonomic composition of the palynological assemblage of the Dongning Formation is supplemented. The palynological assemblage corresponds to those from the Lipovtsy Formation (Aptian) in the Razdolnaya Basin of Primorye (Russia) and the Muling Formation (Aptian) in the Jixi Basin of eastern Heilongjiang (China). It is found that the age of the Dongning Formation is Aptian. The palynological assemblage is characterized by dominance of spores of Gleicheniaceae; they are accompanied by spores of Cyatheaceae. The most important feature of the palynological assemblage of the Dongning Formation is the presence of angiosperm pollen (Tricolpites sp., T. micromunus, T. vulgaris, Retitricolpites georgiensis, R. vulgaris, Clavatipollenites hughesii, Quercites sparsus, Fraxiniopollenites variabilis).  相似文献   

Estimation of net ecosystem metabolism of seagrass meadows in the coastal waters of the East Sea and Black Sea using the noninvasive eddy covariance technique     

Jae Seong Lee  Dong-Jin Kang  Elitsa Hineva  Violeta Slabakova  Valentina Todorova  Jiyoung Park  Jin-Hyung Cho 《Ocean Science Journal》2017,52(2):243-256

We measured the community-scale metabolism of seagrass meadows in Bulgaria (Byala [BY]) and Korea (Hoopo Bay [HP]) to understand their ecosystem function in coastal waters. A noninvasive in situ eddy covariance technique was applied to estimate net O₂ flux in the seagrass meadows. From the high-quality and high-resolution time series O₂ data acquired over > 24 h, the O₂ flux driven by turbulence was extracted at 15-min intervals. The spectrum analysis of vertical flow velocity and O₂ concentration clearly showed well-developed turbulence characteristics in the inertial subrange region. The hourly averaged net O₂ fluxes per day ranged from -474 to 326 mmol O₂ m^-2 d^-1 (-19 ± 41 mmol O₂ m^-2 d^-1) at BY and from -74 to 482 mmol O₂ m^-2 d^-1 (31 ± 17 mmol O₂ m^-2 d^-1) at HP. The net O₂ production rapidly responded to photosynthetically available radiation (PAR) and showed a good relationship between production and irradiance (P-I curve). The hysteresis pattern of P-I relationships during daytime also suggested increasing heterotrophic respiration in the afternoon. With the flow velocity between 3.30 and 6.70 cm s^-1, the community metabolism during daytime and nighttime was significantly increased by 20 times and 5 times, respectively. The local hydrodynamic characteristics may be vital to determining the efficiency of community photosynthesis. The net ecosystem metabolism at BY was estimated to be -17 mmol O₂ m^-2 d^-1, which was assessed as heterotrophy. However, that at HP was 36 mmol O₂ m^-2 d^-1, which suggested an autotrophic state.  相似文献   

Mud‐rich delta‐scale compound clinoforms in the Triassic shelf of northern Pangea (Havert Formation,south‐western Barents Sea)     

Valentina Marzia Rossi  Niall William Paterson  William Helland‐Hansen  Tore Grane Klausen  Christian Haug Eide 《Sedimentology》2019,66(6):2234-2267

In recent years it has become clear that many shallow‐marine heterolithic and mudstone‐dominated successions are deposited as mud belts forming part of subaqueous deltas that are related to major fluvial sources either upstream or along shore. Here the Havert Formation is presented as an ancient example of this kind of system. The Havert Formation in the south‐western Barents Sea represents shelf margin clinoforms consisting predominantly of heterolithic deposits. Sediments were mainly derived from the east (Ural Mountains), but a smaller system prograded northward from Fennoscandia. The Havert Formation holds a lot of interest due to: (i) its stratigraphic position, directly above the Permo–Triassic boundary and contemporaneous to the emplacement of the Siberian Traps; (ii) the fact that it represents the first siliciclastic input in the south‐western Barents Sea and it shows interaction between Uralian‐derived and Fennoscandian‐derived sediments; and (iii) its hydrocarbon potential. This study is focused on a detailed sedimentological analysis of cored intervals of the (Ural‐derived) Havert Formation, in combination with seismic interpretation, well‐log correlations and palynological analysis of the Havert and overlying Klappmyss formations. The cored intervals belong to the shelf environment of the Havert shelf‐margin clinoforms (300 to 500 m thick). This sedimentological analysis distinguishes six facies associations, spanning from tidally‐influenced channels at the shoreline to mud‐rich subaqueous platform and foresets of the subaqueous delta. Seismic lines and well‐log correlations show the larger‐scale evolution of the Ural‐derived Havert Formation, characterized by episodes of low‐accommodation and high‐accommodation. The palynological analyses provide the first detailed study of the Havert Formation in the Nordkapp Basin, revising its depositional age in the region as Induan to early Olenekian (Smithian). Furthermore, they strengthen the environmental interpretation; palynofacies present on the shelf record flora of tidally‐influenced coastal plains, whereas the palynofacies in the deep‐water slope contain only amorphous organic matter.  相似文献   

Depth distribution of earthquakes in the Baikal rift system and its implications for the rheology of the lithosphere   总被引：7，自引：0，他引：7  

Jacques Déverchère  Carole Petit  Nadejda Gileva  Natalia Radziminovitch  Valentina Melnikova  Vladimir San'Kov 《Geophysical Journal International》2001,146(3):714-730

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Impact of climate change on staple food crop production in Nigeria     

Valentina Mereu  Gianluca Carboni  Andrea Gallo  Raffaello Cervigni  Donatella Spano 《Climatic change》2015,132(2):321-336

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远震数据显示贝加尔裂谷带北穆伊斯克(Severomuysk)段地壳和上地幔的精细结构     

Valentina V. MORDVINOVA  Maria A. KHRITOVA  Elena A. KOBELEVA  Mikhail M. KOBELEV  Evgeniy Kh. TURUTANOV  Victor S. KANAYKIN 《地学前缘》2022,29(2):378-392

通过贝加尔裂谷系统北穆伊斯克(Severomuysk)段的密集地震台站线性网络获得的远距离强震记录,并利用P波接收函数技术,揭示了地壳和上地幔顶部的复杂分层块状结构。横波速度的分布表明构成北穆伊斯克地壳的地块具有不同性质。这些地块的西部聚散和地壳下部的分层证实了该地区隆起的堆积-碰撞起源。位于西伯利亚克拉通变薄的倾斜边缘上的北穆伊斯克段解释了该地区地壳碰撞效应的强度。2015年地震的震中深度与Muyakan 凹陷地壳上部的明显速度差异存在令人信服的相关性。  相似文献