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1.
High calcium ion and low magnesium ion concentrations in sediment pore waters in cores from the Galápagos Mounds Hydrothermal Field on the flank of the Galápagos Spreading Center are believed to be due to a calcium-magnesium exchange reaction between circulating seawater and basement basalt. The nonlinearity of the calcium ion and magnesium ion gradients indicates that these discharging hydrothermal solutions on the ridge flank are upwelling at the rate of about 1 centimeter per year through the pelagic sediments of the Mounds Field and at about 20 centimeters per year through the hydrothermal mounds themselves. 相似文献
2.
Carbon-13 depletion in a hydrothermal vent mussel: suggestion of a chemosynthetic food source 总被引：1，自引：0，他引：1
Tissues of a mytilid mussel from the Clambake I hydrothermal vent in the Galápagos Rift zone are strikingly depleted in carbon-13 relative to the tissues of other marine organisms. The stable carbon isotope composition of this mussel suggests that chemoautotrophic bacteria present in the hydrothermal waters are a major food source for filter-feeding organisms in this abyssal environment. 相似文献
3.
Rau GH 《Science (New York, N.Y.)》1981,213(4505):338-340
The stable carbon isotope ratios in clam mantle tissues taken from both Galápagos and 21 degrees N hydrothermal vent sites were similar to the unusually low ratios of carbon-13 to carbon-12 previously reported for a Galápagos hydrothermal vent mussel. In marked contrast to these bivalves, vestimentiferan worm tissues from a Galápagos vent had isotope ratios that were higher than those of open ocean biota. These observations suggest that more than one nonpelagic and nonphotosynthetic carbon fixation pathway is of nutritional importance to vent animals, and that at least one of these pathways is common to two geographically separated vent sites. 相似文献
4.
Direct measurements of shell growth of an unclassified mussel from active hydrothermal vents along the Galápagos Rift reveal growth rates of approxmately 1 centimeter per year for mature specimens. The largest mussel collected (with shell length of 18.4 centimeters) was estimated to be 19 +/- 7 years old at the time of sampling. Recorded growth rates are among the highest documented for deep-sea species. 相似文献
5.
Johnson KS Beehler CL Sakamoto-Arnold CM Childress JJ 《Science (New York, N.Y.)》1986,231(4742):1139-1141
Large changes in the concentration of sulfide around a hydrothermal vent in the Galápagos Rift provide direct evidence for the consumption of sulfide by the organisms of the vent community. These changes were detected with a new chemical analyzer capable of measuring silicate, sulfide, oxygen, and temperature on the sea floor at depths of 2500 meters. More than 10,000 measurements showed systematic variations in the sulfide and oxygen concentrations due to biogenic oxidation of sulfide in the hydrothermal solutions. Silicate concentration was highly correlated with temperature, but different trends were observed at different locations. 相似文献
6.
A heterodont bivalve mollusk Calyptogena magnifica, from the East Pacific Rise and the Galápagos Rift hydrothermal vent areas, contains abundant hemoglobin in circulating erythrocytes. No other known heterodont clam contains a circulating intracellular hemoglobin. The hemoglobin is tetrameric and has a relatively high oxygen affinity, which varies only slightly between 2 degrees and 10 degrees C. The presence of hemoglobin in the clam may facilitate the transport of oxygen to be used in chemoautotrophic hydrogen sulfide metabolism. 相似文献
7.
Helium-3/helium-4 ratios in submarine basalt glasses from the Galapagos Archipelago range up to 23 times the atmospheric ratio in the west and southwest. These results indicate the presence of a relatively undegassed mantle plume at the Galápagos hot spot and place Galápagos alongside Hawaii, Iceland, and Samoa as the only localities known to have such high helium-3/helium-4 ratios. Lower ratios across the rest of the Galápagos Archipelago reflect systematic variations in the degree of dilution of the plume by entrainment of depleted material from the asthenosphere. These spatial variations reveal the dynamics of the underlying mantle plume and its interaction with the nearby Galápagos Spreading Center. 相似文献
8.
Bailey K 《Science (New York, N.Y.)》1976,192(4238):465-467
Potassium-argon ages of eight volcanic rocks from some of the geologically oldest flows exposed in the Galápagos Archipelago indicate that the Galápagos Islands have a probable maximum age of 3 million years. Rocks from six islands were dated; the oldest are from Espa?ola (3.2 +/- 0.2), Sante Fe (2.7 +/- 0.1), and Plazas (4.2 +/- 1.8 million years). The new data suggest that the Galápagos Islands are younger than previously supposed on the basis of marine magnetic anomaly dating, but they are older than most previously dated rocks from the Galápagos. 相似文献
9.
10.
Natland JH Rosendahl B Hekinian R Dmitriev Y Fodor RV Goll RM Hoffert M Humphris SE Mattey DP Petersen N Roggenthen W Schrader EL Srivastava RK Warren N 《Science (New York, N.Y.)》1979,204(4393):613-616
The Galápagos mounds sea-floor hydrothermal system is at least 300,000 years old and once produced manganese-poor sediments, which nearly blanketed the area of the present mounds field. Present-day mound deposits are limited manganese-rich exposures, suggesting that the system has changed from rock-to water-dominated and has diminished in intensity with time. 相似文献
11.
The regular echinoid Eucidaris thouarsii is a conspicuous omnivore on coral bottoms in the Galápagos. Unlike Eucidaris in Panama and mainland Ecuador, Galápagos Eucidaris are large and abundant and graze heavily in the open on live corals day and night. These differences are probably due in large part to more intense predation by fishes on mainland compared with island urchin populations. An assessment of coral growth versus coral attrition from grazing shows that Eucidaris interferes with the establishment of pocilloporid reef frame and therefore reduces reef growth in the Galápagos. 相似文献
12.
Hall ML 《Science (New York, N.Y.)》1983,221(4610):545-547
Geological studies of Espa?ola (Hood) Island, Galápagos, Ecuador, indicate that the island had a subaerial rather than a submarine origin. Because the younger lava flows are dated at 3 million years, Espa?ola has apparently existed as an island for at least that long. Thus terrestrial life may have existed or arrived on the Galápagos Islands at least 3 million years ago, more than twice as long as had been assumed. 相似文献
13.
The shell of a 19-centimeter-long vesicomyid clam, collected live at the Galápagos spreading center hydrothermal field, was sampled along growth lines and analyzed for members of the (238)U and (232)Th decay series. The growth rate, determined from the (210)Po/(210)Pb and (228)Th/(228)Ra couples, is about 4 centimeters per year along the axis of maximum growth, which is 12 centimeters long. This yields an age of 3 to 4 years for this clam. 相似文献
14.
Regression analyses to determine plant species number are repeated for the Galápagos Islands with new data. The multiple curvilinear regression gives the best prediction of species number, with island area making the only significant contribution. The proportion of species endemic to the Galápagos is highest in the arid, transition zone and on small islands, and lowest in the littoral and mesic zones. This is explained in terms of zone-specific immigration and extinction rates and the very recent appearance of moist upland climates in the archipelago. 相似文献
15.
Spiess FN Macdonald KC Atwater T Ballard R Carranza A Cordoba D Cox C Garcia VM Francheteau J Guerrero J Hawkins J Haymon R Hessler R Juteau T Kastner M Larson R Luyendyk B Macdougall JD Miller S Normark W Orcutt J Rangin C 《Science (New York, N.Y.)》1980,207(4438):1421-1433
Hydrothermal vents jetting out water at 380 degrees +/- 30 degrees C have been discovered on the axis of the East Pacific Rise. The hottest waters issue from mineralized chimneys and are blackened by sulfide precipitates. These hydrothermal springs are the sites of actively forming massive sulfide mineral deposits. Cooler springs are clear to milky and support exotic benthic communities of giant tube worms, clams, and crabs similar to those found at the Galápagos spreading center. Four prototype geophysical experiments were successfully conducted in and near the vent area: seismic refraction measurements with both source (thumper) and receivers on the sea floor, on-bottom gravity measurements, in situ magnetic gradiometer measurements from the submersible Alvin over a sea-floor magnetic reversal boundary, and an active electrical sounding experiment. These high-resolution determinations of crustal properties along the spreading center were made to gain knowledge of the source of new oceanic crust and marine magnetic anomalies, the nature of the axial magma chamber, and the depth of hydrothermal circulation. 相似文献
16.
A residual negative free-air and Bouguer anomaly of at least 80 milligals, superimposed on a broader high, occurs over the Galápagos Islands The axis of the anomaly trends roughly east and plunges eastward. Thus, a low-density mass in the crust or upper mantle must underlie the archipelago. This anomaly may be caused by thermal expansion over a crust-mantle " hot spot". 相似文献
17.
During the 1975 El Ni?o expedition an array of conventional and electric field type near-bottom current recorders was deployed at the equator 300 kilometers west of the Galápagos Islands. While hydrographic observations were indicating El Ni?o activity off the South American coast, the current meters recorded an oscillation with a 25-day period, a wavelength of about 1000 kilometers, and an amplitude of 0.04 meter per second propagating westward at approximately 0.5 meter per second. These characteristics agree with theoretical models of a first-mode baroclinic Rossby wave trapped at the equator. 相似文献
18.
Boersma PD 《Science (New York, N.Y.)》1978,200(4349):1481-1483
Surface water changes associated with El Ni?o have been known to affect deleteriously top carnivores along coastal South America. Data on the breeding strategies of Galápagos penguins and other seabirds indicate that the biological effects of El Ni?o extend much farther west. The breeding biology of these seabirds is adapted to frequent changes in productivity which are associated with El Ni?o. 相似文献
19.
Dramatic changes in the patterns of satellite-derived pigment concentrations around the Galápagos Islands during February and March 1983 are associated with unusual oceanographic conditions observed during the 1982-1983 El Ni?o. The redistribution of food resources might have contributed to the reproductive failure of seabirds and marine mammals on these islands during this El Ni?o. 相似文献
20.
Halpern D Hayes SP Leetmaa A Hansen DV Philander SG 《Science (New York, N.Y.)》1983,221(4616):1173-1175
Moored current meter, sea level, hydrographic, and surface drifter measurements show the large changes that took place in the eastern tropical Pacific during the onset of the warm episode of 1982. In August the near-surface flow at 0 degrees , 110 degrees W reversed direction to eastward. By October the sea surface temperature in the equatorial zone increased by 5 degrees Celsius above the long-term monthly mean value, sea level rose by 22 centimeters at the Galápagos Islands, and the thermocline was displaced downward by 50 to 70 meters along the equator and the South American coast. 相似文献