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81.
Ecological status assessment in the lower Eo estuary (Spain). The challenge of habitat heterogeneity integration: a benthic perspective 总被引:2,自引:1,他引:1
The implementation of the European Water Framework Directive (WFD) requires evaluation of the ecological status (ES) of benthic communities in coastal and transitional water systems, and the intercalibration of assessment methodologies therefore becomes a research challenge. Our aim was to test the suitability of applying the M-AMBI index to assess the status of the Eo estuary (northern coast of Spain). Our results showed that M-AMBI was influenced by the natural variability of benthic communities, and presented an apparent dependence on habitat characteristics. Consequently, the definition of homogeneous areas in transitional water systems should be based on the salinity gradient combined with other factors. To achieve an accurate ES assessment, habitat-specific reference conditions should then be defined prior to the application of M-AMBI; this necessitates dividing an estuary into several sections, which may be classified as different ESs. From this perspective, a novel approach to integrate habitat heterogeneity in a global ES assessment was tested. 相似文献
82.
José M. Mirás‐Avalos Antonio Paz‐González Jorge Dafonte‐Dafonte Eva Vidal‐Vázquez Montserrat Valcárcel‐Armesto 《地球表面变化过程与地形》2009,34(15):2087-2095
Knowledge of soil loss rates by water erosion under given climate, soil, topography, and management conditions is important for establishing soil conservation schemes. In Galicia, a region with Atlantic climatic conditions in Spain, field observations over the last decade indicate that interrill, rill and ephemeral gully erosion may be an important sediment source. The aim of this work was to assess concentrated erosion rates, describe types of rills and ephemeral gullies and determine their origin, evolution and importance as sediment sources. Soil surface state and concentrated flow erosion were surveyed on medium textured soils, developed over basic schists of the Ordenes Complex series (Coruña province, Spain) from 1997 to 2006. Soil surface state was characterized by crust development, tillage features and roughness degree. Soil erosion rate was directly measured in the field. Concentrated flow erosion took place mainly on seedbeds and recently tilled surfaces in late spring and by autumn or early winter. During the study period, erosion rates were highly variable and the following situations could be distinguished: (a) no incision or limited rill incision, i.e. below 2 Mg ha?1 year?1; (b) generalized rill and ephemeral gully incision in the class of mean values between 2·5 and 6·25 Mg ha?1 year?1, this was the most common erosion pattern; and (c) heavy erosion as observed during an extremely wet winter period, between October 2000 and February 2001, with erosion figures that may be about ten orders of magnitude higher, up to 55–60 Mg ha?1 year?1. Therefore, low values of soil losses are dominant, but also large values of rill and ephemeral gully erosion occurred during the study period. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
83.
84.
Sylvia Bonilla Daniel Conde Luis Aubriot María del Carmen Pérez 《Estuaries and Coasts》2005,28(6):884-895
A survey was carried out to investigate the relationship of phytoplankton biovolume, structure, and species life strategies
with major abiotic factors in a subtropical choked coastal lagoon (34°33′S, 54°22′W) naturally connecting with the Atlantic
Ocean several times a year. Marine and limnetic influence areas were sampled on a monthly basis during two periods, one of
low rainfall and high conductivity (August 1996 to February 1998) and a second period with the opposite tendency (December
1998 to March 2000). Photosynthetically active radiation availability was high and reached the bottom (>1% of the incident
light), while dissolved inorganic nitrogen (0.6–18.4 μM), soluble reactive phosphorus (<0.3–2.7 μM), and reactive silica (5–386
μM) were highly variable. Life strategies were identified in the phytoplankton as a function of morphology. C-strategists,
invasive planktonic and epipelic species of small size, and R-strategists, mixing-dependent species of medium size, characterized
this permanently mixed system. High frequency of exchange with the ocean prevented high biomass accumulation. Phytoplankton
biomass was lower in the second period of high rainfall (2.3 and 1.1 mm3 1−1 for period 1 and 2 respectively). A canonical correspondence analysis showed that conductivity, nitrogen, phosphorus, and
silica were the main environmental variables explaining phytoplankton species composition patterns. During the first period,
Bacillariophyceae (mostly pennate species) and the potentially toxicPrococentrum minimum were dominant; during the second period a higher contribution of flagellates (Cryptophyceae, Euglenophyceae, Prasinophyceae,
and flagellates <7 μm) was found. Differences of phytoplankton biomass, main taxonomic groups, and strategies were found between
periods but not between limnic and marine areas, suggesting that hydrological dynamic is more relevant than seasonal and spatial
differences. 相似文献
85.
Hardi Peter L. Abbo V. Andretta F. Auchère A. Bemporad F. Berrilli V. Bommier A. Braukhane R. Casini W. Curdt J. Davila H. Dittus S. Fineschi A. Fludra A. Gandorfer D. Griffin B. Inhester A. Lagg E. Landi Degl’Innocenti V. Maiwald R. Manso Sainz V. Martínez Pillet S. Matthews D. Moses S. Parenti A. Pietarila D. Quantius N. -E. Raouafi J. Raymond P. Rochus O. Romberg M. Schlotterer U. Schühle S. Solanki D. Spadaro L. Teriaca S. Tomczyk J. Trujillo Bueno J. -C. Vial 《Experimental Astronomy》2012,33(2-3):271-303
The magnetic field plays a pivotal role in many fields of Astrophysics. This is especially true for the physics of the solar atmosphere. Measuring the magnetic field in the upper solar atmosphere is crucial to understand the nature of the underlying physical processes that drive the violent dynamics of the solar corona—that can also affect life on Earth. SolmeX, a fully equipped solar space observatory for remote-sensing observations, will provide the first comprehensive measurements of the strength and direction of the magnetic field in the upper solar atmosphere. The mission consists of two spacecraft, one carrying the instruments, and another one in formation flight at a distance of about 200 m carrying the occulter to provide an artificial total solar eclipse. This will ensure high-quality coronagraphic observations above the solar limb. SolmeX integrates two spectro-polarimetric coronagraphs for off-limb observations, one in the EUV and one in the IR, and three instruments for observations on the disk. The latter comprises one imaging polarimeter in the EUV for coronal studies, a spectro-polarimeter in the EUV to investigate the low corona, and an imaging spectro-polarimeter in the UV for chromospheric studies. SOHO and other existing missions have investigated the emission of the upper atmosphere in detail (not considering polarization), and as this will be the case also for missions planned for the near future. Therefore it is timely that SolmeX provides the final piece of the observational quest by measuring the magnetic field in the upper atmosphere through polarimetric observations. 相似文献
86.
Denis Duda Costa Cintia B. Uvo Adriano Rolim Da Paz Frede De Oliveira Carvalho Carlos R. Fragoso Jr 《水文科学杂志》2013,58(11):1636-1652
ABSTRACTThe high variability in the hydrological regime of the Eastern Hydrological Region (EHR) of Northeast Brazil often results in floods and droughts, leading to serious socio-economic issues. Therefore, this work aimed to investigate connections between spatiotemporal hydrological variability of the EHR and large-scale climate phenomena. Multivariate statistical techniques were applied to relate climate indices with hydrological variables within two representative river basins in the EHR. The results indicated a multi-annual relationship between the state of the sea surface temperature of the Atlantic and Pacific oceans and anomalous hydrological variability in the basins. In addition, the northern Tropical Atlantic conditions were shown to play an important role in modulating the long-term variability of the hydrological response of the basins, whilst only extreme ENSO anomalies seemed to affect the rainy season. This knowledge is an important step towards long-term prediction of hydrological conditions and contributes to the improvement of water resources planning and management in the EHR. 相似文献