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1.
We deployed five broadband three-components seismic stations in the Iles Eparses in the south-west Indian Ocean and on Mayotte Island, between April 2011 and January 2014. These small and remote oceanic islands suffer the effects of strong ocean swells that affect their coastal environments but most islands are not instrumented by wave gauges to characterize the swells. However, wave action on the coast causes high levels of ground vibrations in the solid earth, so-called microseismic noise. We use this link between the solid earth and ocean wave activity to quantify the swells locally. Spectral analyses of the continuous seismic data show clear peaks in the 0.05–0.10 Hz frequency band (periods between 10 and 20 s), corresponding to the ocean wave periods of the local swells. We analyze an example of austral swell occurring in August 2013 and a cyclonic event (Felleng) that developed in January 2013, and quantify the ground motion at each station induced by these events. In both cases, we find a linear polarization in the horizontal plane with microseismic amplitude directly correlated to the swell height (as predicted by the global swell model WaveWatchIII), and a direction of polarization close to the predicted swell propagation direction. Although this analysis has not been performed in real time, it demonstrates that terrestrial seismic stations can be efficiently used as wave gauges, and are particularly well suited for quantifying extreme swell events. This approach may therefore provide useful and cheaper alternatives to wave buoys for monitoring swells and the related environmental processes such as beach erosion or coral reef damages.  相似文献   

2.
Coral reef environments are generally recognized as being the most threatened of marine ecosystems. However, it is extremely difficult to distinguish the effects of climate change from other forcing factors, mainly because it is difficult to study ecosystems that are isolated from human pressure. The five Iles Eparses (Scattered Islands) are located in the Western Indian Ocean (WIO) and can be considered to be “pristine” ecosystems not subject to anthropogenic pressure. This study characterized their plankton assemblages for the first time, by determining the abundances of microbial (virus, bacteria, heterotrophic protists and phytoplankton) and metazooplankton communities in various lagoon and ocean sites around each island. The Europa lagoon has extensive, productive mangrove forests, which have the highest nutrient concentrations (nitrogen forms, dissolved organic carbon) and whose microbial communities present a peculiar structure and functioning. By means of bioassay experiments, we observed that bacterial production and growth rates are higher in Europa than those reported for the other islands. Tromelin, which lies outside the Mozambique Channel, had the lowest biological productivity, nutrient concentrations, and bacterial growth rates. Multivariate analysis indicated that distinct microbial assemblages occur in association to varying nutrient concentrations. Molecular fingerprinting showed clear discrimination of the structure of the archaea, bacteria and eukaryotes community between the sites. Our results suggest that the geographical distance can influence the diversity of dominant microbial taxa in the WIO.  相似文献   

3.
TAAF ensures since 2007 the management of 5 small tropical islands lying in the southwestern Indian Ocean: the Iles Eparses. These islands share an exceptional natural heritage including many marine and terrestrial endemic species. At a regional scale the Iles Eparses are some of the most pristine ecosystems, largely preserved from anthropogenic impacts due to their geographical isolation and a historically very limited human occupation. In this context, TAAF wished that Iles Eparses become unique natural laboratories for earth scientists and environmental process observation – like climate change impacts - but also sustainable biodiversity sanctuaries for which the scientific community should provide baseline ecological data to inform on appropriate conservation tools. An inter-agency research consortium emerged in 2009 to meet this commitment for the Iles Eparses. This program was intended to set a science framework in accordance with France' objectives for Research and Conservation. It enabled between 2009 and 2014 the implementation of 18 cross-disciplinary research projects ranging from geology to ecology and represented by the variety of the proposed articles in this special issue. Altogether research projects have dramatically increased knowledge on the Iles Eparses' ecosystems and have provided the first overview of their diversity, their functions and their dynamics and its determinants. In particular applied research efforts have supplied a significant amount of ecological evidence that is now available to develop optimal conservation strategy to ensure the Iles Eparses' long-term biodiversity value. These findings point out that the continuation of research activity in the Iles Eparses should be considered a priority.  相似文献   

4.
A new species of treefrog of the Boophis rappiodes group (Anura, Mantellidae) is described from the Sahamalaza – Iles Radama National Park in northwest Madagascar. This new species is green in colour with bright red speckling across its head and dorsum; similar in morphology to other species of this group including: B. bottae, B. rappiodes, B. erythrodactylus and B. tasymena. The new species can be distinguished by its advertisement call and by a genetic divergence of more than 4.9% in the analysed mitochondrial 16S rRNA gene fragment. Its call consists of two note types: a trill and a click; although similar sounding to B. bottae, the trill note of the new species has a faster pulse rate while the click note is predominantly two-pulsed rather than three. All individuals were detected from the banks of two streams in Ankarafa Forest. The new species represents the only member of the B. rappiodes group endemic to Madagascar’s western coast, with the majority of other members known from the eastern rainforest belt. Despite its conspicuous call, it has not been detected from other surveys of northwest Madagascar and it is likely to be a local endemic to the peninsula. The ranges of two other amphibian species also appear restricted to Sahamalaza, and so the area seems to support a high level of endemicity. Although occurring inside a National Park, this species is highly threatened by the continuing decline in the quality and extent of its habitat. Due to these threats it is proposed that this species should be classified as Critically Endangered according to the IUCN Red List criteria.  相似文献   

5.
We studied the dispersion of 4-year-old southern elephant seals (Mirounga leonina) along a 75.5 km coastal area at the Courbet Peninsula, Iles Kerguelen, relative to their birth site when they were ashore to moult in early 1984. The seals were mostly faithful to their natal sites, but availability of suitable moulting habitat (e.g. wallows, vegetated areas) influenced seal dispersion. As moult progressed, the seals moved farther away from their initial moult sites and natal sites, but remained largely on the easterly beaches of the Courbet Peninsula. This behaviour would facilitate mark-recapture estimates of age and sex specific survival.  相似文献   

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报道了在广西发现的2个百合科蜘蛛抱蛋属Aspidistra新种,即乳突蜘蛛抱蛋A. papillata G. Z. Li和环江蜘蛛抱蛋A. huanjiangensis G. Z. Li&Y. G. Wei。乳突蜘蛛抱蛋与大花蜘蛛抱蛋A. tonkinensis(Gagner. )F. T. Wang&K. Y. Lang近缘。它们的共同特征是:花单生;花被裂片两侧彼此覆盖;柱头盾状,边缘3裂,上表面具3条辐射状沟缝。不同点是:乳突蜘蛛抱蛋植株较大花蜘蛛抱蛋的粗大;叶柄较粗;叶片椭圆形或长椭圆形;花被阔钟  相似文献   

9.
设计了用于扩增梭绒盘菌ITS rDNA片段的特异性引物。研究发现,梭绒盘菌不仅存在于被侵染植物的茎部病斑中,而且存在于寄主Medeola virginiana未被感染的叶片、茎及根部。由于寄主植物通过克隆繁殖,因此病害发生与营养体的系统性侵染有关。文中评述了寄主植物的生长模式以及该菌在其寄主群体中长期生存的状况。  相似文献   

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eterachopsis was proposed by the senior author as an independent genus of the family Aspleniaceae in 1940 with 2 species. Since then much study on its morphology, anatomy, gametophyte and palynology has been carried out by Nayar, Bir, Chandra & Nayar and Chang et al., and they are of the opinion that the genus like Ceterach, is a comparatively primitive element in the family Aspleniaceae. The queer zigzag patern of cutting of lanceolate fronds appears extraordinary in the family Aspleniaceae, and also suggests its antiquity in evolution. So far only 3 species (C. dalhousiae, C. paucivenosa and C. magnifica) are recognized, the former from W. Himalayas, also known from Africa, while the latter two from W. S. China (Yunnan). However, in the past forty years the Chinese botanists have discovered 2 more species as new in N. W. Yunnan, thus bringing the total known species of the genus up to 5. The present paper is a brief summary on the genus Ceterachopsis, which will be published in detail in the Flora Sinica vol. 4. Pteridologists are also divided in their views regarding the generic status of Ceterachopsis with 5 well-defined species in Yunnan and the East Himalayas. We prefer to mintain it as a genus separate from Asplenium on account of its distinct morphological features. It is to be hoped that more species may come to light in the mountainsin N. W. Yunnan through further exploration now under way.  相似文献   

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Three new species in Polygonum section Polygonum (Polygonaceae) from Xinjiang, China, are described and illustrated. Polygonum urumqiense F. Z. Li, Y. T. Hou & F. J. Lu is similar to P. aviculare L. in habit, but differs by having flowers densely clustered and spicate in the upper part of branches, stamens 5–6, and two types of achenes (the longer one densely and irregularly granulate on surface). Polygonum tachengense F. Z. Li, Y. T. Hou & F. J. Lu is similar to P. aviculare in the flowers not forming a raceme in the upper part of branches, the stamens 8, and the achenes striate-granulate on surface, but differs by the leaf blades linear-lanceolate, the midvein and lateral veins conspicuously raising abaxially, the ochreae longer, up to 1.1 cm, 15–20-veined, the flowers 3–6 clustered together in the upper axils of branches. This species is also similar to P. patulum M. Bieb. in the erect stem, and the flowers 3–6 clustered together in the axils of the upper part of branches, but differs by the midvein and lateral veins of leaves conspicuously raising abaxially, the ochreae longer, up to 1.1 cm, 15–20-veined, the leaves in the upper part of branches not becoming smaller gradually, and the flowers clustered in the upper axils of branches not forming a raceme, and the achenes striate-granulate on surface. Polygonum shiheziense F. Z. Li, Y. T. Hou & F. J. Lu is similar to P. argyrocoleon Steud. ex Kunze in the erect stem, the 3–6 flowers clustered in the upper axils of branches, the stamens 8, and the slightly smooth achenes, but differs by the midvein and lateral veins of leaves conspicuously raising abaxially, the ochreae longer, up to 1.1 cm, 15–20-veined, and the flowers clustered in the upper axils of branches not forming a raceme. This species is also similar to P. tachengense in habit, but differs in the leaves borne in the upper part of branches becoming smaller gradually and the smooth, slightly shiny achenes. The pollen morphology, leaf epidermal characters and achene micromorphology of the three new species and their relatives were comparatively observed under the scanning electron microscope (SEM).  相似文献   

14.
The levels of the major sterols of the starfish Asterias vulgaris collected at one location in Nova Scotia varied considerably from month to month. After spawning in June the levels of the sterols in the starfish were very low, but a rapid assimilation of dietary sterols allowed the total sterol level to increase approximately two-hundred-fold to the annual maximum in July. The levels of a few minor sterols were unaffected by the spawning process, and during this period they emerged as the major components of the sterol mixture. The sterol mixtures from samples collected at different locations were compared.  相似文献   

15.
Three new species of Lichomolgidae, Cerioxynus moluccensis, Cerioxynus bandensis , and Rakotoa ceramensis , are described from the scleractinian corals Favites pentagona (Esper) and Favites virens (Dana) in Ceram and Banda.  相似文献   

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秤锤树属(安息香科)的一个新异名   总被引:3,自引:0,他引:3  
将怀化秤锤树Sinojackia oblongicarpa C. T. Chen & T. R. Cao处理为肉果秤锤树 Sinojackia sarcocarpa L. Q. Luo的新异名。  相似文献   

18.
This paper reports a diatom assemblage found by the author from the Upper Tertiary continental strata in Shangdu County in Niemongol Autonomous Region and Dunhua County in Jilin Province of China. The diatom assemblage in Shangdu County comprises 4 new species and 2 new varieties: Tetracyclus ellipticus var. ovalifolium Li; Tetracyclus ellipticus var. rostrata Li; Tetracyclus jaoi Li; Tetracyclus navicularis Li; Tetracyclus shangduensis Li and Tetracyclus sinensis Li. From the Miocene of Dunhua County; JilinProvince are recorded 2 new species: Tetracyclus dunhuanensis Li and Tetracyclus ovaliformis Li.  相似文献   

19.
The leaflet architecture of Cyclocarya cf. paliurus (Batal.) Iljinskaja from the Hunchun Formation (Middle Eocene) shows similarity to that of modem C. paliurus (Batal.) Iljinskaja and the specimen is the oldest fossil record in Europe and Asia. The distributions of C. cf. paliurus and other fossil records, such as Glyptostrobus, Metasequoia, Nyssa, and Liquidambar, in Hunchun flora show that it would have been a warmer-temperature to subtropical climate in Hunchun District during the Eocene period.  相似文献   

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