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101.
Invisible floral larcenies: microbial communities degrade floral nectar of bumble bee-pollinated plants 总被引:2,自引:0,他引:2
The ecology of nectarivorous microbial communities remains virtually unknown, which precludes elucidating whether these organisms play some role in plant-pollinator mutualisms beyond minor commensalism. We simultaneously assessed microbial abundance and nectar composition at the individual nectary level in flowers of three southern Spanish bumble bee-pollinated plants (Helleborus foetidus, Aquilegia vulgaris, and Aquilegia pyrenaica cazorlensis). Yeasts were frequent and abundant in nectar of all species, and variation in yeast density was correlated with drastic changes in nectar sugar concentration and composition. Yeast communities built up in nectar from early to late floral stages, at which time all nectaries contained yeasts, often at densities between 10(4) and 10(5) cells/mm3. Total sugar concentration and percentage sucrose declined, and percentage fructose increased, with increasing density of yeast cells in nectar. Among-nectary variation in microbial density accounted for 65% (H. foetidus and A. vulgaris) and 35% (A. p. cazorlensis) of intraspecific variance in nectar sugar composition, and 60% (H. foetidus) and 38% (A. vulgaris) of variance in nectar concentration. Our results provide compelling evidence that nectar microbial communities can have detrimental effects on plants and/or pollinators via extensive nectar degradation and also call for a more careful interpretation of nectar traits in the future, if uncontrolled for yeasts. 相似文献
102.
Among pelagic fish, the Southwestern Atlantic menhaden genus Brevoortia (Clupeidae, Alosinae) constitutes an important species model to investigate the patterns of genetic differentiation. It is
abundant in the Río de la Plata estuary and in the Atlantic coastal lagoons system from Uruguay and Southern Brazil. To access
in the taxa discrimination and population structure in Brevoortia we perform a phylogeographic approach based on mitochondrial cytochrome b (cyt-b) sequences including 240 individuals from 16 collecting sites. Among the 720 bp cyt-b sequenced, 199 correspond to variables and 88 to phylogenetically informative sites. High values of haplotype diversity (h = 1.000) and nucleotide diversity (π = 0.061), as well as an average of 0.084 polymorphic segregating sites and 46 different haplotypes were found. Maximum likelihood
analysis based on the GTR + I + G model and Bayesian inference strongly support the idea that B. aurea is the only species of the genus inhabiting the Southwestern Atlantic region. Our analyses revealed a complex population
pattern characterized by the existence of long-term highly structured genetic assemblages of mixed stocks. Each monophyletic
entity included individuals from different collecting sites, different age groups and collected in different years. Our data
also suggest that the recruitment of unrelated mtDNA haplotypes carried out by individuals within schools could be occurring
in the same nursery areas revealing the existence of many different maternal lineages. A scenario where different simultaneously
and successively mixed mtDNA lineages remain historically connected through basal haplotypes among different clades could
explains more accurately the complex and ordered metapopulation dynamic found in this pelagic fish. 相似文献
103.
Gilad Heinisch Aldo Corriero Antonio Medina Francisco J. Abascal Jose-Miguel de la Serna Robert Vassallo-Agius Antonio Belmonte Ríos Antonio García Fernando de la Gándara Christian Fauvel Christopher R. Bridges Constantinos C. Mylonas Saadet F. Karakulak Isik Oray Gregorio De Metrio Hanna Rosenfeld Hillel Gordin 《Marine Biology》2008,154(4):623-630
Atlantic bluefin tuna (BFT; Thunnus thynnus) is a migrating species straddling the North Atlantic Ocean and Mediterranean Sea. It is assumed that this species is divided
into a western and an eastern stock, which spawn in the Gulf of Mexico and the Mediterranean Sea, respectively. To learn more
about the reproductive behavior of the eastern BFT stock, we tracked gonadal development in adult fish that were sampled between
April and July during three consecutive years (2003–2005). Sampling campaigns were carried out using common fishing methods
at selected locations within the Mediterranean Sea, namely Levantine Sea, Malta, and Balearic Islands. An additional sampling
point, Barbate, was situated northwest of the Straits of Gibraltar along the Atlantic coast. Morphometric parameters such
as the total body mass (M
B) and the weights of the gonads (M
G) were recorded, and the respective gonadosomatic index (GSI) values were calculated. The data collected revealed two important
trends: (1) GSI values are higher in fish caught in the eastern rather than the western locations across the Mediterranean
Sea, and (2) the GSI reaches maximum values between late May and early June in Levantine Sea (eastern Mediterranean Sea),
and only 2 and 4 weeks later in the central (Malta) and western (Balearic Islands) locations, respectively. The advanced gonadal
development in BFT correlates well with higher sea surface temperatures. Our findings also distinguish the northern Levantine
Sea BFT population (mean M
B 78.41 ± 4.13 kg), and the Barbate BFT population with the greatest M
B (all fish sampled > 100 kg). These data reflect a situation in which the eastern Mediterranean basin may function as a habitat
for young BFT, until they gain a larger M
B and are able to move to the Atlantic Ocean. However, the existence of genetically discrete BFT populations in the Mediterranean
Sea cannot be ruled out. 相似文献
104.
de Guzmán Báez A Villoria Sáez P del Río Merino M García Navarro J 《Waste management (New York, N.Y.)》2012,32(5):920-924
In the last years, the European Union (EU) has been focused on the reduction of construction and demolition (C&D) waste. Specifically, in 2006, Spain generated roughly 47million tons of C&D waste, of which only 13.6% was recycled. This situation has lead to the drawing up of many regulations on C&D waste during the past years forcing EU countries to include new measures for waste prevention and recycling. Among these measures, the mandatory obligation to quantify the C&D waste expected to be originated during a construction project is mandated. However, limited data is available on civil engineering projects. Therefore, the aim of this research study is to improve C&D waste management in railway projects, by developing a model for C&D waste quantification. For this purpose, we develop two equations which estimate in advance the amount, both in weight and volume, of the C&D waste likely to be generated in railway construction projects, including the category of C&D waste generated for the entire project. 相似文献
105.
J M López-Gutiérrez M García-León C Schnabel M Suter H A Synal S Szidat 《Journal of environmental radioactivity》2001,55(3):269-282
Iodine-129 (T1/2 = 1.57 x 10(7) yr) concentrations have been determined by accelerator mass spectrometry in rainwater samples taken at Seville (southwestern Spain) in 1996 and 1997. This technique allows a reduction in the detection limits for this radionuclide in comparison to radiometric counting and other mass spectrometric methods such as ICP-MS. Typical 129I concentrations range from 4.7 x 10(7) 129I atoms/l (19.2%) to 4.97 x 10(9) 129I atoms/l (5.9%), while 129I depositions are normally in the order of 10(8)-10(10) atoms/m2d. These values agree well with other results obtained for recent rainwater samples collected in Europe. Apart from these, the relationship between 129I deposition and some atmospheric factors has been analyzed, showing the importance of the precipitation rate and the concentration of suspended matter in it. 相似文献
106.
Combined photo-Fenton and biological oxidation for pesticide degradation: effect of photo-treated intermediates on biodegradation kinetics 总被引:2,自引:0,他引:2
Ballesteros Martín MM Sánchez Pérez JA Acién Fernández FG Casas López JL García-Ripoll AM Arques A Oller I Malato Rodríguez S 《Chemosphere》2008,70(8):1476-1483
Biodegradability of a partially photo-oxidized pesticide mixture is demonstrated and the effect of photo-Fenton treatment time on growth and substrate consumption of the bacteria Pseudomonas putida CECT 324 is shown. Four commercial pesticides, laition, metasystox, sevnol and ultracid, usually employed in citric orchards in eastern Spain, were chosen for these experiments. The active ingredients are, respectively, dimethoate, oxydemeton-methyl, carbaryl and methidathion. Judging by biomass measurements, dissolved organic carbon measurements and biodegradation efficiency, it may be concluded that 90min相似文献
107.
Anaerobic biodegradability and toxicity on anaerobic bacteria of di(hydrogenated tallow) dimethyl ammonium chloride (DHTDMAC) and two esterquats have been investigated. A batch test system containing municipal digester solids as a source of anaerobic bacteria, based on the method proposed by the ECETOC, has been applied. To evaluate the potential toxicity of such surfactants on anaerobic sludge, a co-substrate, an easily biodegradable compound in anaerobic conditions, has been added to the samples to test and the effects on biogas production have been determined. For the esterquats studied high biodegradation levels were obtained and no toxic effects on anaerobic bacteria were observed even at the highest concentrations tested, 100 and 200 mg C/l, respectively. On the contrary, DHTDMAC was not degradated at the same test conditions. However, no inhibitory effects on the biogas production were detected for this surfactant at concentrations <100 mg C/l. 相似文献
108.
Study of metal fractionation in river sediments. A comparison between kinetic and sequential extraction procedures 总被引:6,自引:0,他引:6
Gismera MJ Lacal J da Silva P García R Teresa Sevilla M Procopio JR 《Environmental pollution (Barking, Essex : 1987)》2004,127(2):175-182
The extraction kinetic of trace metals (Cd, Cu, Pb, and Zn) in river sediments by four extraction agents was studied. As extractants ammonium acetate, acetic acid, hydroxylamine and EDTA solutions were assayed. These reagents can leach the metals more or less selectively from several metal compartments of sediments. The metal leaching kinetic model permits classification of the metal species in labile and moderately-labile ones. The combination of two or more non specific reagents permits a high characterisation of metal distribution and leachability. The results obtained with this model in four river sediments were compared with data obtained by the SM&T sequential extraction procedure, in order to characterise the chemical nature of leached metal. 相似文献
109.
An important gap has been detected in the application of the European framework for the evaluation of pesticide active substances constituted by enantiomeric and other kind of stereoisomeric mixtures. Up to date, little attention has been paid to the different biological properties of these compounds. Considering efficacy, toxicity, environmental fate and behaviour and ecotoxicity of separated isomers is necessary to fulfil Directive 91/414/EEC objectives of health and environment protection. Here, a critical review of this question for pesticide active substances is presented. An evaluative scheme for considering this question in the framework of Directive 91/414/EEC is also proposed. 相似文献
110.
The presence of toxic metals on paper pulp and the migration of these metals to food from the food package is receiving significant attention. The final exposure levels for consumers depend on two main processes. First the potential of metals to bind paper pulp during manufacture. Second, the metal potential to migrate from paper to food during storage and use. Binding and unbinding processes are modelled for cadmium kinetics through kinetic approaches. The cadmium concentration in paper pulp is estimated from the cadmium concentration in the water-pulp liquor during manufacture, the temperature, and contact time. Two food simulants have been employed for desorption studies, water and acetic solution (3%, w/w). As expected, under acidic conditions desorption is total and rapid (close to 100% desorption reached in a few minutes). However, the desorption of cadmium into the neutral food simulant depends on the initial cadmium concentration in the paper pulp, temperature and contact time. Surface response curves for each combination are presented. Temperature did not affect cadmium binding, but played a significant role for the desorption processes into the neutral food simulant. The proposed equations offer a good fitting of the experimental values, with p < 0.001 and residuals within a factor of 3 for over 99% of the measured data. These models allow estimations of the expected exposure levels in consumers, on the basis of manufacture and use conditions. Linking the expected exposure with toxicity thresholds, such as the admissible daily intake (ADI), would allow a scientific assessment of the maximum acceptable cadmium levels in water-pulp liquors during manufacture and in the final paper pulp on the basic of the use patterns of each food packaging material. 相似文献