Epibenthic megacrustaceans from the continental margin, slope and abyssal plain of the Southwestern Gulf of Mexico: Factors responsible for variability in species composition and diversity     

Elva G. Escobar-Briones  Adriana Gaytn-Caballero  Pierre Legendre 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(24-26):2667

The community structure of megacrustaceans (orders Lophogastrida, Isopoda, and Decapoda) collected in trawls on the continental margin, upper slope and abyssal plain of the southern Gulf of Mexico was studied to determine to what extent broad-scale variation in community composition and diversity was influenced by geographic regions environmental variability and depth. Trawls were collected in the Mexican Ridges, the Campeche Bank, and the Sigsbee abyssal plain. There was variability in species composition, density and diversity among geographic regions and along the depth gradient. A total of 106 species were identified and grouped in three orders; five infraorders, 40 families, and 70 genera. This study extends the known geographic ranges of the species Homolodromia monstrosa and Ephyrina benedicti. The largest number of species was recorded in the Mexican Ridges and on the upper continental shelf; lower values were found on the continental margin and in the abyssal plain. The largest densities were recorded on the continental margin in the Mexican Ridges. Megacrustaceans show in general low frequencies and low abundances in trawls, characterizing them as rare components of benthic assemblages. Contrary to an accepted paradigm about deep-sea biodiversity, the highest H′ diversity values were recorded in the Sigsbee abyssal plain, followed by values from the upper continental slope; diversity values were correlated with evenness. Canonical Redundancy analysis results showed a significant affinity to regions for 18 crustacean species; 33 species showed a significant affinity to both regions and depth zones within regions.  相似文献   

Particulate organic matter uptake rates of two benthic filter-feeders (Sabella spallanzanii and Branchiomma luctuosum) candidates for the clarification of aquaculture wastewaters     

Cavallo D  Pusceddu A  Danovaro R  Giangrande A 《Marine pollution bulletin》2007,54(5):622-625

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Center-to-Limb Variation of Solar Microwave Bursts     

Silva  Adriana V.R.  Valente  Marcelo M. 《Solar physics》2002,206(1):177-188

Statistical studies of hard X-ray flares position on the solar disk have shown that the more energetic hard X-rays have a tendency to be more concentrated near the limb rather than at disk center, whereas lower-energy hard X-ray emission seems isotropic. Since the high-frequency radio emission is believed to be produced by the same energetic electron population responsible for the high-energy hard X-rays, we searched the microwave/millimeter emitting bursts for center-to-limb variation in their emission. A total of 499 bursts observed by the radio telescopes in Bern at the frequencies of 3.1, 5.2, 8.4, 11.8, 19.6, 35.0, and 50.0 GHz were analyzed. Simultaneous Hα flares were used for determination of the radio burst position on the solar disk. For each of the 7 frequencies, the peak flux and duration were studied as a function of heliocentric position. For 312 bursts, spectral parameters such as spectral index, peak frequency, and flux at spectral maximum were analyzed. For a subset of 43 bursts with emission at all frequencies, the emission and spectral parameters were analyzed. Center-to-limb variations of the spectral parameters for all bursts were sought. In order to interpret the observational results, we have performed a numerical simulation of gyrosynchrotron spectra. We find that high-frequency events, which are also the more energetic ones, have larger center-to-limb variations in their parameters than do the overall flares. Moreover, this behavior agrees with theoretical predictions.  相似文献   

Light curve analysis of the short period eclipsing binary RT and     

S. Mancuso  L. Milano  G. Russo  C. Sollazzo 《Astrophysics and Space Science》1979,66(2):475-486

We have analysed the 1978 UBV photoelectric observations of the short-period (RS CVn type) binary system RT And, using the rectifiable methods of Russell and Merrill (1952) and Kitamura (1965). The primary minimum is a transit. The solutions allow us to classify the system as a detached one, but a certain disagreement results with respect to solutions of previous epochs. A graphical test of the reliability of the solution is given.  相似文献   

Toxicity assessment of sediments associated with various land-uses in coastal South Carolina, USA, using a meiobenthic copepod bioassay     

Bejarano AC  Maruya KA  Chandler GT 《Marine pollution bulletin》2004,49(1-2):23-32

Coastal urbanization supplies surrounding estuarine environments with urban-related contaminants such as polycyclic aromatic hydrocarbons (PAHs), metals and pesticide mixtures. In our study, adult female and male copepods (Amphiascus tenuiremis) were chronically exposed to 18 sediment samples collected from sites influenced by different land-uses. Sediment samples were collected from three major suburban areas (Hilton Head, Kiawah Island and the Okatee River watershed) and a pristine site (North Inlet) in coastal South Carolina. Three-sediment bioassays (six sites per bioassay) were conducted by culturing copepods for 14 days in quadruplicate test sediments under flow-through conditions at 20 degrees C and 12:12 LD cycles. Adult survival and copepod reproductive output were quantified. Sediment samples were also analyzed by GC-MS for low and high molecular weight PAHs. Minimal adult mortality was observed in most sediment samples. However, sediments from Hilton Head Island and the Okatee River showed significant effects on copepod reproductive output (i.e., nauplii, copepodites and clutch size). Thus, we determined that reproductive endpoints rather than adult copepod survivorship were more sensitive to effects of contaminated sediments on A. tenuiremis. Furthermore, six (33%) of the 18 sites had a >25% reduction in copepod bioassay endpoints relative to controls, suggesting a high risk to long term A. tenuiremis population maintenance.  相似文献   

Origin of the Multiple Metric Type II Radio Burst Structure Associated with the 2002 July 23 CME     

Salvatore Mancuso  Davide Avetta 《Earth, Moon, and Planets》2009,104(1-4):105-108

We report on the analysis of a fast (>2,000 km/s) CME-driven shock event observed with the UVCS telescope operating aboard SoHO on 23 July 2002. The same shock was also detected in the metric band by several ground-based radiospectrographs. The peculiarity of this event is the presence in the radio spectra of two intense metric type II bursts features drifting at different rates, together with clear shock/related broadenings of the O VI doublet lines observed by UVCS that were found to be temporally associated with the above radio features. The nature of these multiple radio lanes in the metric band is still under debate. One possible explanation is that they are produced by multiple shock waves generated by different ejections or, alternatively, by the flare and the associated CME. Also, emission from the upstream and downstream shock regions can produce split bands. By adopting a plausible CME model, together with a detailed analysis of the white-light, UV, and radio data associated with this event, we are able to conclude that both the radio and the UV shock signatures were produced by a single shock wave surface generated by the expanding CME.  相似文献   

Vulnerability assessment in urban areas exposed to flood risk: methodology to explore green infrastructure benefits in a simulation scenario involving the Cañaveralejo River in Cali,Colombia     

López-Valencia  Adriana Patricia 《Natural Hazards》2019,99(1):217-245

Natural Hazards - Building resilient infrastructure is one of the major challenges faced by cities due to increasing urbanization rates and climate change. Furthermore, the application of...  相似文献   

Effects of intensive aquifers exploitation on groundwater salinity in coastal wetlands     

Malva Mancuso  Lucía Santucci  Eleonora Carol 《水文研究》2020,34(11):2313-2323

The coastal plain of the Río de la Plata constitutes a large wetland which develops on the right margin of the river estuary. Anthropic activities such as intensive exploitation of groundwater carried out in the vicinity of the wetland can modify the natural hydrological regime. The aim of this work is to asses the effects of intensive aquifer exploitation in coastal wetlands using hydrogeological models. Such models allow to evaluate changes in the environmental conditions of wetland at regional level. The hydrogeological model exposed in this work shows how the intensive groundwater exploitation affects the wetland area, generating important variations both in the groundwater flows and in the salinity of the groundwater. Identification of these modifications to the environment is important to generate guidelines leading to minimize these affectations.  相似文献   

Quaternary charophytes from Salina del Bebedero, Argentina: their relation with extant taxa and palaeolimnological significance     

Adriana García 《Journal of Paleolimnology》1999,21(3):307-323

Charophyte (Charales, green macroscopic algae) assemblages found in Quaternary shoreline sediments from Salina del Bebedero, Argentina, are described in detail, illustrated, and statistically analysed. Fossil gyrogonites, Late Pleistocene and Holocene in age, of Chara cf. hispida var. major (Hartman) Wood, Chara halina García, Chara hornemannii Wallmann, Chara bulbillifera (Donterberg) García, Lamprothamnium haesseliae Donterberg and Lamprothamnium succinctum (Braun ex Ascherson) Wood were identified. A comparison with extant charophyte species of similar ecological requirements allowed for an accurate systematical determination and provided useful data for complementary palaeoecological and palaeobiogeographical approaches. On this basis, a reconstruction of palaeo-salinities for the Salina del Bebedero lake, represented by eleven palaeo-beaches, is proposed. Also the associations of charophytes with the ostracods Cyprideis sp., Limnocythere sp., Pampacythere sp., Cypridopsis sp., Darwinula sp., Ilyocypris gibba (Randohr) Brady and Norman, and the foraminifers Ammonia sp., Elphidium gunteri Cole, Quinqueloculina sp., and one species of Discorbacea are analysed, since they are present in both the fossil and modern environments.  相似文献   

Analysis of suspended sediment dynamics at event scale: comparison between a Mediterranean and an Alpine basin     

Stefano Giorgio Pagano  Adriana García-Rama  Francesco Gentile  Mario Aristide Lenzi 《水文科学杂志》2019,64(8):948-961

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