Export stoichiometry and migrant-mediated flux of phosphorus in the North Pacific Subtropical Gyre     

Cecelia C.S. Hannides  Michael R. Landry  Claudia R. Benitez-Nelson  Renée M. Styles  Joseph P. Montoya  David M. Karl 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(1):73-88

Export processes play a major role in regulating global marine primary production by reducing the efficiency of nutrient cycling and turnover in surface waters. Most studies of euphotic zone export focus on passive fluxes, that is, sinking particles. However, active transport, the vertical transfer of material by migrating zooplankton, can also be an important component of carbon (C) and nitrogen (N) removal from the surface ocean. Here we demonstrate that active transport is an especially important mechanism for phosphorus (P) removal from the euphotic zone at Station ALOHA (Hawaii Ocean Time-series program; 22°45′N, 158°W), a P-stressed site in the North Pacific Subtropical Gyre. Migrant excretions in this region are P-rich (C₅₁:N₁₂:P₁) relative to sinking particles (C₂₅₀:N₃₁:P₁), and migrant-mediated P fluxes are almost equal in magnitude (82%) to P fluxes from sediment traps. Migrant zooplankton biomass and therefore the importance of this P removal pathway relative to sinking fluxes has increased significantly over the past 12 years, suggesting that active transport may be a major driving force for enhanced P-limitation of biological production in the NPSG. We further assess the C:N:P composition of zooplankton size fractions at Station ALOHA (C₈₈:N₁₈:P₁, on average) and discuss migrant-mediated P export in light of the balance between zooplankton and suspended particle stoichiometries. We conclude that, because active transport is such a large component of the total P flux and significantly impacts ecosystem stoichiometry, export processes involving migrant zooplankton must be included in large-scale efforts to understand biogeochemical cycles.  相似文献   

Eight-hundred years of summer temperature variations in the southeast of the Iberian Peninsula reconstructed from tree rings     

Isabel Dorado Liñán  Eduardo Zorita  Jesús Fidel González-Rouco  Ingo Heinrich  Filipe Campello  Elena Muntán  Laia Andreu-Hayles  Emilia Gutiérrez 《Climate Dynamics》2015,44(1-2):75-93

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Erratum to: Distribution and thickness of sedimentary facies in the coastal dune, beach and nearshore sedimentary system at Maspalomas, Canary Islands     

Angela Fontán Bouzas  Javier Alcántara-Carrió  Isabel Montoya Montes  Andrés Barranco Ojeda  Silvia Albarracín  Jaime Rey Díaz de Rada  Jorge Rey Salgado 《Geo-Marine Letters》2013,33(2-3):231-231

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The impact of spatial resolution on area burned and fire occurrence projections in Portugal under climate change     

Anabela Carvalho  Mike D. Flannigan  Kim A. Logan  Lynn M. Gowman  Ana Isabel Miranda  Carlos Borrego 《Climatic change》2010,98(1-2):177-197

In this study, we investigated the impact of future climate change on fire activity in 12 districts across Portugal. Using historical relationships and the HIRHAM (High Resolution Hamburg Model) 12 and 25 km climate simulations, we assessed the fire weather and subsequent fire activity under a 2 × CO₂ scenario. We found that the fire activity prediction was not affected by the spatial resolution of the climate model used (12 vs. 25 km). Future area burned is predicted to increase 478% for Portugal as a whole, which equates to an increase from 1.4% to 7.8% of the available burnable area burning annually. Fire occurrence will also see a dramatic increase (279%) for all of Portugal. There is significant spatial variation within these results; the north and central districts of the country generally will see larger increases in fire activity.  相似文献   

Isoductile strengths and strength reduction factors of elasto‐plastic SDOF systems subjected to simple waveforms     

Isabel Cuesta  Mark A. Aschheim 《地震工程与结构动力学》2001,30(7):1043-1059

The inelastic response of elasto‐plastic SDOF oscillators subjected to 24 simple waveforms was studied. The waveforms contain linear, quadratic, sinusoidal, and triangular acceleration components that repeat for not more than several cycles. Similarities and differences in oscillator response characteristics are presented, organized by a characteristic period. The strengths and corresponding strength reduction factors required for constant ductility responses are discussed. Response data are compared with expectations based on the concepts of equal energy, equal displacement, and preservation of force. Limitations on the applicability of the equal energy concept are identified. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

A field study of orographic precipitation anomalies during high velocity winds using an aerofoil rain gauge     

C. J. G. Morris  M. Nunez  S. Montes 《Theoretical and Applied Climatology》1995,51(3):139-151

Summary This study was prompted by a need to explain an anomaly in the apparent precipitation distribution over a prominent mountain subject to a high velocity westerly airstream. Historical data reveal that the lee receives 58% more precipitation than the summit. A novel rain gauge with a vertically orientated collecting orifice, 3 standard rain gauges and complementary wind data were procured from 3 sites on the mountain to assess the effect of the airstream on the precipitation distribution. The catch efficiency of standard rain gauges decrease after the wind velocity exceeds 2.5 ms^–1 Results indicate that the summit actually receives 59% more precipitation than the lee, where a vortex directly affects the precipitation distribution over, and east, of the mountain.With 11 Figures  相似文献   

Dollard canal thwarted     

Aristides Hall  Isabel Valente 《Marine pollution bulletin》1974,5(11):165-171

The inner bay of Lourenço Marques receives the untreated sewage of the city, the run-off from five rivers and metal and hydrocarbon pollution from the activities of the port. Iron ore handling results in an increase in iron and copper concentrations in the water, particularly since loading by slurry was introduced. Large quantities of metal pollutants are probably accumulating in muds and are likely to contaminate shellfish which are an important food source in the area. Untreated sewage discharges are at such a level that eutrophication of the bay is threatened, besides constituting a public health risk on bathing beaches.  相似文献   

Hydrocarbon contamination in mussels from Guanabara Bay     

Azevedo LA  de Andrade Brüning IM  Moreira I 《Marine pollution bulletin》2004,49(11-12):1120-1122

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Closure of a seaway: stratigraphic record and facies (Guadix basin, Southern Spain)     

Christian Betzler  Juan Carlos Braga  José M. Martín  Isabel M. Sánchez-Almazo  Sebastian Lindhorst 《International Journal of Earth Sciences》2006,95(5):903-910

During the late Tortonian (upper Miocene), the Guadix Basin in S Spain formed one of the Betic corridors that connected the Mediterranean Sea with the Atlantic Ocean. The closure of this connection occurred in a series of steps, documented by three sedimentary units. A lower unit, consisting of basinal marls, shallow-water calcarenites and sands records the formation of a wide seaway. During deposition of the following unit this narrowed to a strait no more than 2 km in wide, triggering an intensification of currents that caused migration of submarine dunes preserved as giant cross-beds in bioclastic sands and conglomerates. Current flowed from the Mediterranean to the Atlantic. The third unit constitutes the youngest marine episode of the filling of the Guadix Basin. At this stage, the connection between the Mediterranean Sea and the Atlantic Ocean was broken, and a system of coastal coral reefs was established in the northern part of the Basin.  相似文献   

A Wetland Simulation Module for the MODFLOW Ground Water Model   总被引：8，自引：0，他引：8  

Jorge I. Restrepo  Angela M. Montoya  Jayantha Obeysekera 《Ground water》1998,36(5):764-770

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