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排序方式: 共有375条查询结果,搜索用时 15 毫秒
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Guinevere Kauffmann Timothy M. Heckman Simon D. M. White Stéphane Charlot Christy Tremonti Jarle Brinchmann Gustavo Bruzual Eric W. Peng Mark Seibert Mariangela Bernardi Michael Blanton Jon Brinkmann Francisco Castander Istvan Csábai Masataka Fukugita Zeljko Ivezic Jeffrey A. Munn Robert C. Nichol Nikhil Padmanabhan Aniruddha R. Thakar David H. Weinberg Donald York 《Monthly notices of the Royal Astronomical Society》2003,341(1):33-53
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Abstract. Rhodoliths provide a stable and three-dimensional habitat to which other seaweeds and invertebrates can attach. Although ecological factors affecting rhodolith beds have been studied, little is known about the effect of rhodolith species and growth-form on associated fauna. Experiments were conducted at three rhodolith beds in the central-west Gulf of California. Faunal abundance differed significantly in relation to rhodolith-forming species, but no significant differences were observed between different growth-forms. Rhodolith structure differs between the species Lithophyllum margaritae and Neogoniolithon trichotomum , and the combination of structure differences and rhodolith abundances may be responsible of the significant differences in faunal abundance and richness. Crustaceans, polychaetes and molluscs were the most important taxa in all three rhodolith beds. The amphipod species Pontogeneia nasa and the cnidarian Aiptasia sp. were dominant in both rhodolith beds, El Requesón and Isla Coyote, in Bahía Concepción. The Isla Coronados rhodolith bed was dominated by an unidentified harpacticoid copepod (Copepoda sp.1). Rhodolith species is more important than growth-form in determining abundance and richness of the associated fauna. Nevertheless, factors such as wave motion, depth, bioturbation and others should be considered when studying organisms associated with rhodolith beds. 相似文献
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Florencia Botto Agustina Mendez-Casariego Macarena Valiñas Oscar Iribarne 《Estuaries and Coasts》2008,31(1):134-143
We show that, as previously described, there are conflicts between areas used by people and shorebirds. However, we propose
that burrowing organisms add complexity to the shorebird–human interaction that should be taken into account for management
and conservation. This is because SW Atlantic mudflats are dominated by high densities (up to 60 crabs m−2) of a strong bioturbator, the burrowing crab Neohelice granulata (=Chasmagnathus granulatus). These crabs affect the habitat use and foraging performance of shorebird species. The two-banded plover Charadrius falklandicus feed more in burrow areas whereas the yellowlegs Tringa spp. and the white-rumped sandpiper Calidris fuscicollis tend to avoid burrow areas. We evaluated the effect of human recreational activities on shorebirds, taking into account shorebird–crab
interaction, during shorebird migratory periods (November to April) of 2001, 2002, and 2003. This study was performed at the
Mar Chiquita coastal lagoon (37° 40′ S, Argentina). Results showed that people only rarely used the extensive soft bottom
intertidals dominated by burrowing assemblages of N. granulata because the soft sediments make walking difficult. Therefore, human impact is reduced for the two-banded plover. However,
for several migratory shorebirds that also avoid burrow areas, these areas act as suboptimal alternative areas when human
impact is important in their preferred habitats. When human activity is low, shorebirds remain foraging in the area but they
decrease their feeding intakes. The extensions of burrow areas differ among estuaries and are likely to generate between-estuaries
differences as stopover sites for shorebirds. Also, other species that form large burrowing assemblages can have a similar
impact on shorebird–human interactions. 相似文献
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Stephen V. Smith Silvia E. Ibarra-Obando Victoria Díaz-Castañeda Francisco Javier Aranda-Manteca José D. Carriquiry Brian N. Popp Oscar Gonzalez-Yajimovich 《Estuaries and Coasts》2008,31(4):719-727
Sediment grain size and organic carbon (OC) data collected over the past 50 years, together with δ13C values of OC in recently collected samples, were analyzed to improve understanding of sediment OC distribution and abundance in Todos Santos Bay. Sediments in the submarine canyon at the mouth of the bay and in quiet-water locations along the shore are fine grained, high in OC, and have generally low δ13C values; sediments in high-energy environments are low in OC and have high δ13C values. A bivariate isotopic mixing model indicates that none of the sediments contain >50% terrigenous OC (average ~30%), and that the terrigenous OC content of the sediments is a small proportion of the OC content of local soils. Sediment OC composition is apparently controlled by energy-related sorting and deposition, oxidation of much of the original terrigenous OC, and replacement of some terrigenous OC by marine OC. 相似文献
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Alejandro R. Carlini Gustavo A. Daneri Ricardo Casaux María E. I. Márquez 《Polar research》2006,25(2):139-144
The seasonal haul-out pattern of itinerant male Antarctic fur seals ( Arctocephalus gazella ) was determined by regular counts at Mossman Peninsula, Laurie Island, South Orkney Islands, from 1996 to 2005. Small numbers of animals began to arrive at the beach in late December/early January (mean date 28 December Ø 15 days, n= 10). Peak numbers of animals ashore changed considerably between seasons. In 1996, 1998 and 2001, peak numbers were registered in March (6/3, 18/3 and 6/3, respectively). Numbers peaked in 1997, 1999 and 2005 at the end of January/beginning of February (26/1,2/2 and 28/1, respectively). In 2000, 2002, 2003 and 2004 peaks were registered in the third week of February (15/2, 22/2, 14/2 and 20/2, respectively). Peaks in numbers of seals ashore also varied between years, being minimum during 2001 (2531 individuals) and maximum during 2006 (16 610 individuals). In March 1998 the coasts of Laurie Island were surveyed by navigating inflatable boats near the shoreline; 18 haul-out places were identified. The big differences in peak numbers, as well as in the dates of peak events among years, suggest that local conditions could have an effect on the numbers of animals hauled out in a given year. It may therefore be difficult to predict trends from summer censuses in non-breeding places. 相似文献
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Axel K Schmitt Marty Grove Oscar Lovera Mark Walters 《Geochimica et cosmochimica acta》2003,67(18):3423-3442
Combined U-Pb zircon and 40Ar/39Ar sanidine data from volcanic rocks within or adjacent to the Geysers geothermal reservoir constrain the timing of episodic eruption events and the pre-eruptive magma history. Zircon U-Pb concordia intercept model ages (corrected for initial 230Th disequilibrium) decrease as predicted from stratigraphic and regional geological relationships (1σ analytical error): 2.47 ± 0.04 Ma (rhyolite of Pine Mountain), 1.38 ± 0.01 Ma (rhyolite of Alder Creek), 1.33 ± 0.04 Ma (rhyodacite of Cobb Mountain), 1.27 ± 0.03 Ma (dacite of Cobb Valley), and 0.94 ± 0.01 Ma (dacite of Tyler Valley). A significant (∼0.2-0.3 Ma) difference between these ages and sanidine 40Ar/39Ar ages measured for the same samples demonstrates that zircon crystallized well before eruption. Zircons U-Pb ages from the underlying main-phase Geysers Plutonic Complex (GPC) are indistinguishable from those of the Cobb Mountain volcanics. While this is in line with compositional evidence that the GPC fed the Cobb Mountain eruptions, the volcanic units conspicuously lack older (∼1.8 Ma) zircons from the shallowest part of the GPC. Discontinuous zircon age populations and compositional relationships in the volcanic and plutonic samples are incompatible with zircon residing in a single long-lived upper crustal magma chamber. Instead we favor a model in which zircons were recycled by remelting of just-solidified rocks during episodic injection of more mafic magmas. This is consistent with thermochronologic evidence that the GPC cooled below 350° C at the time the Cobb Mountain volcanics were erupted. 相似文献