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561.
Jesús M. Mercado Carmen B. de los Santos J. Lucas Pérez-Lloréns Juan J. Vergara 《Estuarine, Coastal and Shelf Science》2009
The 13C signature of forty-five macroalgal species from intertidal zones at Cádiz Bay was analysed in order to research the extension of diffusive vs. non-diffusive utilisation of dissolved inorganic carbon (DIC) and to perform a comparison with data published for other bio-geographic regions. The ∂13C values ranged from −6.8‰ to −33‰, although the span of variation was different depending on the taxa. Thus, ∂13C for Chlorophyta varied from −7‰ (Codium adhaerens) to −29.6‰ (Flabellia petiolata), while all the Phaeophyceae (excepting Padina pavonica with ∂13C higher than −10‰) had values between −10‰, and −20‰. The widest variation range was recorded in Rhodophyta, from values above −10‰ (Liagora viscida) to values lower than −30‰ obtained in three species belonging to the subclass Rhodymeniophycidae. Accordingly, the mean ∂13C value calculated for red algae (−20.2‰) was significantly lower than that for brown (−15.9‰) and green algae (−15.6‰). Most of the analysed red algae were species inhabiting crevices and the low intertidal fringe which explains that, on average, the shaded-habitat species had a ∂13C value lower than those growing fully exposed to sun (i.e. in rockpools or at the upper intertidal zone). The comparison between the capacity for non-diffusive use of DIC (i.e. active or facilitated transport of HCO3− and/or CO2) and the ∂13C values reveals that values more negative than −30‰ indicate that photosynthesis is dependent on CO2 diffusive entry, whereas values above this threshold would not indicate necessary the operation of a non-diffusive DIC transport mechanism. Furthermore, external carbonic anhydrase activity (extCA) and ∂13C values were negatively correlated indicating that the higher the dependence of the photosynthesis on the CO2 supplied from HCO3− via extCA, the lower the ∂13C in the algal material. The comparison between the ∂13C values obtained for the analysed species and those published for species inhabiting other bio-geographic areas (warm-temperate, cold and polar) suggests that globally (at least for the red and brown algae) the non-diffusive entry of DIC is more widely spread among the species from Cádiz Bay than among those of polar regions. If it is assumed that non-diffusive use of DIC implies saturation of photosynthesis at the present-day CO2 concentration in seawater, our data indicate that the potential impact of the acidification on photosynthesis in the seaweed communities will be different depending on the latitude. 相似文献
562.
Almeida DV Trindade GS Geracitano LA Barros DM Monserrat JM Marins LF 《Marine environmental research》2008,66(1):158-160
563.
Presence of Anthropogenic Markers in Water: A Case Study of the Guaporé River Watershed,Brazil
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564.
Atahebson B. Santos Milton J. Porsani Manuelle S. Góis 《Geophysical Prospecting》2019,67(7):1720-1731
The determination of three-dimensional geometry and acquisition parameters, the seismic acquisition survey design, is constantly subject of studies in obtaining data with the highest seismic quality, operational efficiency and cost minimization. In this paper, we propose a methodology for inverting geometry parameters of three-dimensional orthogonal land seismic surveys based on a direct search method using a mixed-radix based algorithm. In this algorithm, the search space is discretized on a mixed-radix base, which depends on the extreme values and the search resolution of each parameter. We will show how to reparametrize the orthogonal acquisition geometry elements in order to obtain the independents and integers parameters that are necessary to construct the mixed-radix base. For the optimization purpose, we define an objective function to contemplate target parameters associated with the elements of the acquisition geometry directly related to the geophysical and operational constraints. Taking in account that the mathematical functions and the objective function we define for the problem have no significant computational cost, all model space parameters are fast and efficiently tested. We applied the algorithm, using as input data, provided by a one-line roll orthogonal reference geometry, assuming a pair of geological objectives as shallow and deep targets. All selected models that meet both the proposed objectives and the constraints are organized by decreasing order of fitness so that with the mixed-radix inversion algorithm we found not only the best model, but also a set of suitable models. Likewise, with the best set of geometries, it is possible to establish a direct comparison between them, analysing their adherence to the technical and operational requirements according to the availability and degree of detail of each one. We show the top 10 best results as a table, allowing a direct comparison between all aspects of these geometries, and we summarize the results showing graphically the fitness of all selected geometries and the inverted geometry elements for the 1000 best geometries. These graphical displays provide a direct way to understand how each model behaves as the fitness decreases. The algorithm is very flexible and its application can be extended to any environment and type of acquisition geometry, and in any phase study of an area be it regional, exploratory or development. 相似文献
565.
Eduarda B. H. Santos Olga M. S. Filipe Regina M. B. O. Duarte Helena Pinto Armando C. Duarte 《洁净——土壤、空气、水》2001,28(7):364-371
Three‐dimensional fluorescence spectra of water samples from an eucalyptus bleached kraft pulp mill and from a river, upstream and downstream of the discharge of the effluent, revealed the existence of a peak at δexc = 280 nm and δem = 340 nm Δδ = 60 nm), characteristic of effluentπs organic matter. Humic substances were isolated from the effluent by sequential adsorption onto resins XAD‐8 and XAD‐4 in series. Their synchronous fluorescence spectra with Δδ = 60 nm do also exhibit an intense signal at δexc = 280 nm (≈ 300 nm in the humic acid fraction). The peak is absent in the spectra of humic substances isolated from a non‐polluted site of the river, but it is clearly seen in the spectra of the humic substances from a site downstream of the discharge of the effluent. Synchronous fluorescence spectra (Δδ = 60 nm) of water samples from the river and its lagoon were recorded and revealed to be an easy and fast way of tracing the organic contamination from the effluent. 相似文献
566.
Spatial distribution and estimation of rainfall trends and erosivity in the Epitácio Pessoa reservoir catchment,Paraíba,Brazil 总被引:1,自引:0,他引:1
da Silva Richarde Marques Santos Celso Augusto Guimarães da Costa Silva Jorge Flávio Cazé Braga Silva Alexandro Medeiros Brasil Neto Reginaldo Moura 《Natural Hazards》2020,102(3):829-849
Natural Hazards - The main goals of this study are to better understand the spatial and temporal variabilities in rainfall and to identify rainfall trends and erosivity for the period from 1963 to... 相似文献
567.
Nilza Maria Dos Reis Castro Anne‐Vronique Auzet Pierre Chevallier Jean‐Claude Leprun 《水文研究》1999,13(11):1621-1628
In the region of the basaltic plateau in Southern Brazil, problems of runoff and erosion on the deep ferrallitic soils are becoming increasingly recognized. Land use change from conventional tillage using disk plough to no‐tillage on residues without terracing occurred at the beginning of the 1990s and it spread very quickly. Measurements of runoff and sediment concentrations on 1 m2 plots receiving natural rainfall and simulated rainfall under different crops with different stages of growth and different tillage systems, field surveys and measurements of rills and gullies in nested experimental catchments indicate a relative decrease of runoff on slopes but an increase of subsurface flow, and a marked decrease of sheet and rill erosion and soil loss from plot to catchment scales. Nevertheless, the extension of parts of the gully system is still continuing, strongly influenced by extreme rainfall. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
568.
The population dynamics of the seagrass Cymodocea nodosa was investigated in three meadows differently affected by the artificial relocation of an inlet in the western sector of the Ria Formosa lagoon, southern Portugal. One meadow was subjected to increasing currents that caused erosion, another one was subjected to an initial episode of burial and a third meadow was undisturbed by the inlet opening. The hydrodynamic/sedimentary condition of meadows was assessed through comparative sediment analysis between the meadow and the adjacent unvegetated area. 相似文献
569.
570.
de Freitas Pedro Paulo Amorim Felipe de Luca Lopes Mill Guilherme Nogueira da Costa Vladimir Santos Gabioux Mariela Cirano Mauro Paiva Afonso de Moraes 《Ocean Dynamics》2019,69(10):1203-1215
Ocean Dynamics - Near-inertial oscillations (NIO) are intermittent motions with a frequency close to the inertial frequency and represent an important fraction of the energy to the currents in the... 相似文献