958 resultados para marine water
Resumo:
Previous work has suggested that seasonal and inter-annual upwelling of deep, cold, radiocarbon depleted waters from the South Atlantic has caused variations in the reservoir effect (R) through time along the southern coast of Brazil. This work aims to examine the possible upwelling influence on the paleo-reservoir age of Brazilian surficial coastal waters based on paired terrestrial/marine samples obtained from archaeological remains. On the Brazilian coast there are hundreds of shell-middens built up by an ancient culture that lived between 6500 to 1500 years ago, but there are few located on open coast with a known upwelling influence. Three archaeological sites located in a large headland in Arraial do Cabo and Ilha de Cabo Frio, southeastern coast of Brazil with open ocean conditions and a well-known strong and large upwelling of the Malvinas/Falkland current were chosen for this study. The 14C age differences between carbonized seed and marine samples varied from 281 ± 44 to 1083 ± 51 14C yr. There are also significant age differences between carbonized seed samples (977 14C yr) and marine samples (200 and 228 14C yr) from the same archaeological layer that cannot be explained by a reservoir effect or an old-wood effect for charcoal. Therefore the present data from the southeastern Brazilian coast are inconclusive for identifying an upwelling effect on R. To do so it would be necessary to more precisely define the present-pre-bomb R in upwelling regions and to analyze paired marine/terrestrial samples that are contemporaneous beyond doubt.
Resumo:
The chemical structure of refractory marine dissolved organic matter (DOM) is still largely unknown. Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR-MS) was used to resolve the complex mixtures of DOM and provide valuable information on elemental compositions on a molecular scale. We characterized and compared DOM from two sharply contrasting aquatic environments, algal-derived DOM from the Weddell Sea (Antarctica) and terrigenous DOM from pore water of a tropical mangrove area in northern Brazil. Several thousand molecular formulas in the mass range of 300-600 Da were identified and reproduced in element ratio plots. On the basis of molecular elemental composition and double-bond equivalents (DBE) we calculated an average composition for marine DOM. O/C ratios in the marine samples were lower (0.36 ± 0.01) than in the mangrove pore-water sample (0.42). A small proportion of chemical formulas with higher molecular mass in the marine samples were characterized by very low O/C and H/C ratios probably reflecting amphiphilic properties. The average number of unsaturations in the marine samples was surprisingly high (DBE = 9.9; mangrove pore water: DBE = 9.4) most likely due to a significant contribution of carbonyl carbon. There was no significant difference in elemental composition between surface and deep-water DOM in the Weddell Sea. Although there were some molecules with unique marine elemental composition, there was a conspicuous degree of similarity between the terrigenous and algal-derived end members. Approximately one third of the molecular formulas were present in all marine as well as in the mangrove samples. We infer that different forms of microbial degradation ultimately lead to similar structural features that are intrinsically refractory, independent of the source of the organic matter and the environmental conditions where degradation took place.
Resumo:
The Water Framework Directive (WFD) establishes Environmental Quality Standards (EQS) in marine water for 34 priority substances. Among these substances, 25 are hydrophobic and bioaccumulable (2 metals and 23 organic compounds). For these 25 substances, monitoring in water matrix is not appropriate and an alternative matrix should be developed. Bivalve mollusks, particularly mussels (Mytilus edulis, Mytilus galloprovincialis), are used by Ifremer as a quantitative biological indicator since 1979 in France, to assess the marine water quality. This study has been carried out in order to determine thresholds in mussels at least as protective as EQS in marine water laid down by the WFD. Three steps are defined: - Provide an overview of knowledges about the relations between the concentrations of contaminants in the marine water and mussels through bioaccumulation factor (BAF) and bioconcentration factor (BCF). This allows to examine how a BCF or a BAF can be determined: BCF can be determined experimentally (according to US EPA or ASTM standards), or by Quantitative Activity-Structure Relationship models (QSAR): four equations can be used for mussels. BAF can be determined by field experiment; but none standards exists. It could be determined by using QSAR but this method is considered as invalid for mussels, or by using existing model: Dynamic Budget Model, but this is complex to use. - Collect concentrations data in marine water (Cwater) in bibliography for those 25 substances; and compare them with concentration in mussels (Cmussels) obtained through French monitoring network of chemicals contaminants (ROCCH) and biological integrator network RINBIO. According to available data, this leads to determine the BAF or the BCF (Cmussels /Cwater) with field data. - Compare BAF and BCF values (when available) obtained with various methods for these substances: BCF (stemming from the bibliography, using experimental process), BCF calculated by QSAR and BAF determined using field data. This study points out that experimental BCF data are available for 3 substances (Chlorpyrifos, HCH, Pentachlorobenzene). BCF by QSAR can be calculated for 20 substances. The use of field data allows to evaluate 4 BAF for organic compounds and 2 BAF for metals. Using these BAF or BCF value, thresholds in shellfish can be determined as an alternative to EQS in marine water.
Resumo:
A diagnostic survey of the incidence of mayfly (Povilla sp.) infestation of wooden infrastructures of the artisanal fishers in ten (10) lagoons and marine fishing villages of Ogun States (Nigeria) was carried out through the application of structured questionnaire and participatory Rural Appraisal interviews. The demographic, infrastructural and socioeconomic characteristics of the ten fishing villages sampled were derived and analyzed. The infestation which occurs all year round is found to be most prevalent (70%) in the wet season, increasing proportionally with salinity from 56% (brackish water); to 63% (marine water). The life-span of Povilla sp. is reduced from 55% to 62% (freshwater); 41% (brackish water) and 38% (marine water). Annual financial loss of N10,000.00 per fisher or N80,000,000.00 to the 8000 artisanal fishers affected in Ogun State is discussed. It is recommended that fishers should preferably use non-wood crafts and infrastructures while adopting appropriate management strategies for containing the existing infestation
Resumo:
Pathogenic microorganisms such as Bacillus cereus, Listeria Monocytogenes and Staphylococcus sp have caused serious diseases, and consequently contributed to considerable economic loss in the food and agricultural industries. Antibiotics have been practically used to treat these pathogens since penicillin G was discovered more than half a century ago. Many different types of antibiotics have been discovered or synthesized to control pathogenic microorganisms. Repetitive use and misuse of antibiotics by the agricultural and pharmaceutical industries have caused the emergence of multidrug-resistant microorganisms, even to the strongest antibiotics currently available; therefore, the rapid development of more effective antimicrobial compounds is required to keep pace with demand. Bacteria were isolated from marine water and sediment samples collected from various locations off the coast of Cochin and salt pans of Tuticorin using pour plate technique. One hundred and twelve isolates were obtained. Seventeen isolates exhibiting antimicrobial activity were segregated after primary screening. The secondary screening which was aimed at selection of bacteria that produce proteinaceous inhibitory compounds, helped to select five strains viz. BTFK101, BTHT8, BTKM4, BTEK16 and BTSB22. The five isolates inhibited the growth of six Gram positive test organisms viz. B. cereus, B. circulans, B. coagulans, B. pumilus, Staphylococcus aureus and Clostridium perfringens. After quantitative estimation of the bacteriocin production, the two strains BTFK101 and BTHT8 were selected for further study.
Resumo:
Density, species composition and antimicrobial resistance in bacteria of the Enterococcus genus were evaluated in seawater and sands from 2 marine recreational beaches with different levels of pollution. The 2 beaches showed predominance of Enterococcus faecalis and Enterococcus faecium, in the water and the sand. Dry sand presented higher densities of Enterococcus sp. and higher frequency of resistant strains than wet sand and seawater. The beach with a higher degree of pollution presented higher percentages of resistant strains (66.7% and 61.5%, in sand and in water, respectively) and resistance to a larger number of antimicrobials compared with the less polluted beach, Ilha Porchat (35.7% and 31.25% of resistant strains in sand and water, respectively). in water samples, the highest frequencies of resistance were obtained against streptomycin (38.5%) and erythromycin (25%), whilst in sand, the highest frequencies were observed in relation to erythromycin and tetracycline (38.1% and 14.3%, respectively). These results show that water and sands from beaches with high indexes of faecal contamination of human origin may be potential sources of contamination by pathogens and contribute to the dissemination of bacterial resistance. (C) 2007 Elsevier Ltd. All rights reserved.
Resumo:
Species of Fusarium were isolated from water samples collected from the Andarax River and coastal sea water of the Mediterranean in Granada and Almería provinces of southeastern Spain. In total, 18 water samples were analyzed from the Andarax River, and 10 species of Fusarium were isolated: Fusarium anthophilum, F. acuminatum, F. chlamydosporum, F. culmorum, F. equiseti, F. verticillioides, F. oxysporum, F. proliferatum, F. solani, and F. solani. When considering the samples by their origins, 77.8% of the river water samples yielded at least one species of Fusarium , with F. oxysporum comprising 72.2% of the total isolates. In the case of marine water, 45.5% of the samples yielded at least one species of Fusarium, with F. solani comprising 36.3% of the total isolates. The pathogenicity of 41 isolates representing nine of the species collected from river an sea water during the study ws evluated on barley, kohlrabe, melon, and tomato. Inoculation with F. acuminatum, F. chlamydosporum, F. culmorum, F. equiseti, F. verticillioides, F. oxysporum, F. proliferatum F. solani, and F. sambucinum resulted in pre-and post-emergence damping off. Pathogenicity of Fusarium isolates did not seem to be related to the origin of the isolates (sea water or fresh water). However, the presence of pathogenic species of Fusarium in river water flowing to the sea could indicate long-distance dispersal in natural water environments
Resumo:
Density, species composition and antimicrobial resistance in bacteria of the Enterococcus genus were evaluated in seawater and sands from 2 marine recreational beaches with different levels of pollution. The 2 beaches showed predominance of Enterococcus faecalis and Enterococcus faecium, in the water and the sand. Dry sand presented higher densities of Enterococcus sp. and higher frequency of resistant strains than wet sand and seawater. The beach with a higher degree of pollution presented higher percentages of resistant strains (66.7% and 61.5%, in sand and in water, respectively) and resistance to a larger number of antimicrobials compared with the less polluted beach, Ilha Porchat (35.7% and 31.25% of resistant strains in sand and water, respectively). in water samples, the highest frequencies of resistance were obtained against streptomycin (38.5%) and erythromycin (25%), whilst in sand, the highest frequencies were observed in relation to erythromycin and tetracycline (38.1% and 14.3%, respectively). These results show that water and sands from beaches with high indexes of faecal contamination of human origin may be potential sources of contamination by pathogens and contribute to the dissemination of bacterial resistance. (C) 2007 Elsevier Ltd. All rights reserved.
Resumo:
Variation in strontium (Sr) and barium (Ba) within otoliths is invaluable to studies of fish diadromy. Typically, otolith Sr : Ca is positively related to salinity, and the ratios of Ba and Sr to calcium (Ca) vary in opposite directions in relation to salinity. In this study of jungle perch, Kuhlia rupestris, otolith Sr : Ca and Ba : Ca, however, showed the same rapid increase as late-larval stages transitioned directly from a marine to freshwater environment. This transition was indicated by a microstructural check mark on otoliths at 35–45 days age. As expected ambient Sr was lower in the fresh than the marine water, however, low Ca levels (0.4 mg L–1) of the freshwater resulted in the Sr : Ca being substantially higher than the marine water. Importantly, the otolith Sr : Ba ratio showed the expected pattern of a decrease from the marine to freshwater stage, illustrating that Sr : Ba provided a more reliable inference of diadromous behaviour based on prior expectations of their relationship to salinity, than did Sr : Ca. The results demonstrate that Ca variation in freshwaters can potentially be an important influence on otolith element : Ca ratios and that inferences of marine–freshwater habitat use from otolith Sr : Ca alone can be problematic without an understanding of water chemistry.
Resumo:
Parameters of the von Bertalanffy growth function are presented for 42 fish stocks belonging to 16 families, 22 genera and 27 species. The growth performance index, Phi '(= log K + 2logL sub( infinity )), was computed for each stock and was found to be highest in male Gymnarchus niloticus (Gymnarchidae) from Lake Chad and lowest in Chrysichthys auratus (Bagridae) from the Cross River. Mean Phi ' for major fish genera and families are also presented and was highest in brackishwater fishes, closely followed by freshwater and inshore marine water fishes.
Resumo:
Este estudo teve como objetivo contribuir com as informações ecológicas e paleoecológicas geradas para a Baía de Guanabara com base na distribuição das assembléias de foraminíferos bentônicos. Para tal foram coletadas 30 amostras de sedimento superficial, ao longo de três perfis distribuídos pela baía e um testemunho (BG28) de 6 m de comprimento retirado próximo a Ilha do Governador. Nas amostras superficiais foram identificados 30 gêneros e 52 espécies das quais as espécies mais constantes foram Amonia tepida e Bolivina translucens que apresentaram a maior constância. Espécies de habitat de plataforma foram identificadas em diversas estações indicando uma boa eficiência no transporte das correntes de fundo para dentro da baía. Das estações superficiais analisadas, 10 localizadas ao redor da Ilha do Governador não continham testas de foraminíferos, possivelmente como resultado da acidificação do sedimento causado pelo derrame de óleo ocorrido em 2000. O índice de confinamento associado às análises de agrupamento e ao DCA indicaram a presença de três setores ambientais influenciadas por COT e granulometria. O primeiro setor entre Copacabana-Itatipú e Aeroporto Santos Dumont Ilha de Boa Viagem foi o ambiente marinho, o segundo setor entre o Aeroporto Santos Dumont - Ilha de Boa Viagem e Ilha do Governador Ilha de Paquetá Litoral de São Gonçalo pode se classificado como um ambiente de estuário inferior ou baía com grande influência marinha e o terceiro setor entre a Ilha do Governador Ilha de Paquetá Litoral de São Gonçalo e fundo da baía como o ambiente mais confinado. No testemunho foram feitas 7 datações indicando uma idade de aproximadamente 5180 40 anos BP. As datações também mostraram que nos últimos anos a taxa de sedimentação aumentou muito podendo estar relacionada com o período de colonização européia. Foram encontradas 18 gêneros e 30 espécies de foraminíferos das quais a espécie mais constante foi a Ammonia tepida seguida pela Buliminella elegantissima. O padrão de distribuição dessas espécies ocorreu com a maior abundância de B. elegantissima nas porções mais inferiores do testemunho e uma abundância maior de A. tepida nas porções mais superiores. Os índices de confinamento junto com as análises de agrupamento e com as curvas de isótopos mostraram que houve poucas oscilações no aporte de água marinha naquela região. As análises dos isótopos de C13 e C14 e O16 e O18 não seguiram um padrão inverso comum em outros estudos, possivelmente influenciado pela proximidade da costa. As análises de agrupamentos indicaram que nos últimos 5180 anos BP a baía não sofreu grandes variações ambientais, ou seja, a região oeste da baía mesmo apresentando alterações ao longo dos anos não foi suficiente para modificar as características de confinamento. As análises nos padrões de distribuição das assembléias de foraminíferos demonstraram ser eficientes ferramentas na caracterização ambiental e paleoambiental da Baía de Guanabara.
Resumo:
Deterioration of water quality clearly indicated a moderate to severe coastal pollution around Mahim whereas a relatively healthy marine environment towards offshore was noticed. Foraminifera, polychaetes, crustaceans and pelecypods were the dominant macro faunal groups encountered in the area. The occasional inhabitants like pennatularians, nemertines, sipunculids, ophiuroids and fish larvae were mostly restricted to offshore regions. Biomass and population density of macro fauna were moderate and showed fluctuating trend. Similarity coefficients of foraminifera (0.89) and polychaetes (0.81) were high for offshore unpolluted stations (3 and 4) as compared to near shore coastal stations (1 and 2). Faunal diversity was relatively more in unpolluted zone. The diversity index (H) was more at station 3 for polychaetes (1.39) and at station 4 for foraminifers (0.54). In general, biomass was high during post monsoon excepting station 1 which was invariably under severe pollution stress throughout the study period. Foraminifera were abundant at sandy bottom while polychaetes preferred muddy (clayey silt) bottom. A noticeable ecological modification associated with faunal abundance and diversity were related to deteriorating marine water quality due to anthropogenic waste disposals. The prevailing water quality around Mahim is unsuitable for any kind of culture practices and also for harvesting economically important marine species.
Resumo:
Salinity, temperature and pressure are parameters which govern the oceanographic state of a marine water body and together they make up density of seawater. In this contribution we will focus our interest on one of these parameters, the salinity: accuracy in relation to different purposes as well as observation technique and instrumentation. We will also discuss the definition of salinity. For example most of the Indian Ocean waters are within the salinity range from 34.60-34.80, which emphasize the importance of careful observations and clear definitions of salinity, in such a way that it is possible to define water masses and predict their movements. In coastal waters the salinity usually features much larger variation in time and space and thus less accuracy is sometimes needed. Salinity has been measured and defined in several ways over the past century. While early measurements were based on the amount of salt in a sea water sample, today the salinity of seawater is most often determined from its conductivity. As conductivity is a function of salinity and temperature, determination involves also measurement of the density of seawater is now more precisely estimated and thus the temperature. As a result of this method the Practical Salinity Scale (PSS) was developed. The best determination of salinity from conductivity and the temperature measurements gives salinity with resolution of 0.001 psu, while the accuracy of titration method was about ± 0.02‰. Because of that, even calculation of movements in the ocean is also improved.