894 resultados para Diurnal
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A decade-long time series recorded in southern Monterey Bay, California demonstrates that the shallow, near-shore environment (17 m depth) is regularly inundated with pulses of cold, hypoxic and low pH water. During these episodes, oxygen can drop to biologically threatening levels, and pH levels were lower than expected. Weekly water chemistry monitoring revealed that the saturation state of aragonite (the more soluble form of calcium carbonate) was often below saturation and had a moderate positive relationship with pH, however, analytical and human error could be high. Pulses of hypoxia and low pH water with the greatest intensity arise at the onset of the spring upwelling season, and fluctuations are strongly semidurnal (tidal) and diurnal. Arrival of cold, hypoxic water on the inner shelf typically occurs 3 days after the arrival of a strong upwelling event and appears to be driven by upwelling modulated by internal tidal fluctuations. I found no relationship between the timing of low-oxygen events and the diel solar cycle nor with terrestrial nutrient input. These observations are consistent with advection of hypoxic water from the deep, offshore environment where water masses experience a general decline of temperature, oxygen and pH with depth, and inconsistent with biochemical forcing. Comparisons with concurrent temperature and oxygen time series taken ~20 km away at the head of the Monterey Canyon show similar patterns but even more intense hypoxic events due to stronger semidiurnal forcing there. Analysis of the durations of exposure to low oxygen levels establishes a framework for assessing the ecological relevance of these events. Increasing oceanic hypoxia and acidification of both surface and deep waters may increase the number, intensity, duration and spatial extent of future intrusions along the Pacific coast. Evaluation of the resiliency of nearshore ecosystems such as kelp forests, rocky reefs and sandy habitats, will require consideration of these events.
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As explained in the title, this campaign aimed to assess the diurnal vertical variations in abundance of demersal species off the Côte d'Ivoire
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Diurnal variation in trawl catches and its influence on energy efficiency of trawler operations are discussed in this paper, based on data on landings of a Japanese factory trawler which operated in the Indian waters during 1992-93. The factory vessel equipped for stern trawling had a length overall of 110 m, GT of 5460 and installed engine power of 5700 hp. Operations were conducted off west coast of India between 31 and 278 m depth contours, using a 80.4 m high opening bottom trawl with an adjusted vertical opening of 7.60.9 m. The catch data was grouped according to the median towing hour, by the time of the day. CPUE obtained was 3713.4 kg.h-1 for day time operations and 1536.6 kg.h-1 for night-time operations. Mean daily catches were 31367 kg.day-1 (SE: 2743) for day time operations and 9430 kg.day-1 (SE: 966) for night-time operations. Fuel consumption were 0.399 and 0.982 kg fuel.kg fish-1, respectively for day and night-time operations. Total catch and catch components such as threadfin bream, bulls eye, hairtails, trevelly, lizard fish showed significant improvement during day-time operations while swarming crabs showed a significant improvement in the night-time operations. The difference in catch rates between day and night could be attributed to diurnal variation in the spatial distribution and schooling behaviour of the catch categories, their differential behaviour in the vicinity of trawl systems under varying light levels of day and night and consequent effect on catching efficiency and size selectivity at different stages in the capture process. The results obtained in addition to its importance in the operational planning of trawling in order to realise objectives of maximising catch per unit effort and minimising fuel consumption per unit volume of fish caught, has added significance in the use of bottom trawl surveys in stock abundance estimates.
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O objeto de estudo foi o estresse no trabalho e os níveis de cortisol salivar. O objetivo geral foi avaliar a associação entre estresse no trabalho e variações de cortisol salivar de trabalhadores de Enfermagem inseridos na assistência hospitalar no Rio de Janeiro. A hipótese do estudo foi que existe associação entre trabalhadores expostos à alta exigência no trabalho e as variações de cortisol salivar. Trata-se de estudo epidemiológico observacional analítico seccional, realizado em hospital estadual localizado no Rio de Janeiro com amostra de 103 trabalhadores. Para avaliação dos aspectos psicossociais do trabalho, utilizou-se o questionário Job Content Questionnaire. O cortisol salivar foi medido através da coleta de 04 amostras de cada participante em um dia do plantão: ao acordar, 30 minutos depois, às 12h e 18 h. A coleta de dados foi realizada entre março e abril de 2012. Utilizou-se o programa SPSS 18.0 para análise dos dados. As dimensões demanda psicológica e controle e a subtração foram utilizadas sob a forma contínua nas análises de correlação com as covariáveis e desfecho. Os níveis de cortisol foram quantificados por meio de cinco índices: o cálculo da área sob a curva em relação ao zero ou base (AUCg), área sob a curva em relação ao aumento (AUCi), o aumento médio (MnInc), a excreção do cortisol no período pós acordar (AUCtrab) e a área sob a curva em relação ao zero ou base do ciclo diurno (AUCCD). Para avaliar a associação entre as covariáveis e exposição e desfecho utilizou-se os testes de Mann Whitney e Kruskall-Wallis. As covariáveis associadas à exposição ou ao desfecho com nível de significância de 20% (p≤0,20) foram testadas no modelo de regressão linear. Realizada análise de correlação utilizando-se o coeficiente de correlação de Spearmans. Como resultado encontrou-se que os trabalhadores de Enfermagem obtiveram médias para demanda psicológica e controle que tendem para o limite superior, bem como para a subtração, caracterizando alta demanda e alto controle, ou seja, trabalho ativo. O valor médio de cortisol observado ao acordar, 30 minutos após, 12h e 18h foi de 5,82 nmol/L) (4,86), 16,60 nmol/L ( 8,31), 7,49 nmol/L ( 6,97) e 3,93 nmol/L ( 3,15), respectivamente. O aumento do cortisol entre o acordar e 30 minutos após foi em média de 64%. Já para os índices de cortisol adotados observa-se o valor médio da MnInc, AUCg, AUCi, AUCtrab e AUCCD foi de 10,78 nmol/L (6,99), 5,61 nmol/L ( 2,92) 2,69 nmol/L ( 1,75), 32,51 nmol/L ( 21,99) e 107,99 nmol/L ( 61,63), respectivamente. Este estudo demonstrou que os níveis de cortisol salivar livre não estão associados à alta exigência no trabalho, mesmo quando ajustadas pelas possíveis variáveis de confusão ou modificadoras de efeito. A hipótese do estudo não foi confirmada. Os dados obtidos neste estudo revelaram aspectos importantes dos riscos psicossociais a que estão expostos os trabalhadores de Enfermagem durante o processo de trabalho, oferecendo subsídios para que sejam implementados programas de orientação e promoção à saúde do trabalhador e fornecem um contributo para entender os caminhos biológicos pelos quais o estresse no trabalho influencia a saúde.
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Seasonal variations of abundance and vertical distribution over the shelf are investigated for Ostracoda, Cladocera and Cirripede larvae. The main characteristics of the environment are the periodical enrichments mainly caused by upwellings, secondly by the river floods. Ostracoda abundance variations approximately follow phytoplankton outburst. Breeding occurs all over the year. Their vertical distribution is correlated with a discontinuity layer. Diurnal migration, when it occurs in warm season consists in an upward movement during the night towards surface layers. The Ostracoda inhabit bottom layers during the day and migrate at night in intermediate and surface layers. For the main two species of Cladocera, Penilia avirostris and Evadne tergestina, abundance periods follow upwellings, especially during the main cool season. However, Cladocera can grow in low salinity but rich waters. On average Penilia inhabits more superficial waters in cold than in warm seasons. Cirripede nauplii and cypris are more abundant off rocky coasts. Their maxima are in the upwelling periods.
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Diurnal variations and geographic distribution of zooplankton and micronekton are studied in the Angola Dome. The small zooplankton species (Copepodids, Copepods, Amphipods, Ostracods, Chaetognaths, etc.) undertake vertical migrations within a 100 m water layer. Most of the micronekton species are below this layer during the day and move towards the surface during the night. The whole region prospected is rich in zooplankton and micronekton species that are present in the upper 100 m layer during the day. Only the South-West region is poor. On the contrary, this latter region is abundant in species that migrate below this layer during the day. The authors think there are 3 main difficulties in establishing good relationships between micronekton and tunas distribution: 1 - inability of micronekton nets to catch the tunas preys; 2 - the great diversity of tunas food; and 3 - the too large delay between micronekton studies and those of stomach contents of tunas.
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Hydroclimatic conditions in the Gulf of Guinea between Senegal and Nigeria are briefly described emphasizing the seasonal variations of transparency. Analysis of the Abidjan based shrimp fleet allowed to the description of the seasonal variations of activity rhythms for Côte d'Ivoire, Ghana, and Nigeria. These rhythms are different between seasons, between fishing grounds, and sometimes even between depths on a given ground. These variations follow the turbidity ones. Diurnal activity is observed in very turbid waters, nocturnal and transition activity in clearer ones. The authors assume that the basic behaviour is a nocturnal one, but that the shrimp-trawlers catches reflect some apparently different ones resulting from diel variations in the stock availability. To explain the apparently diurnal behaviour observed most of the year over the whole Gulf of Guinea it is suggested that these generally benthic shrimps become nectonic at night when turbidity is very high. The results obtained in Ivory Coast, Ghana and Nigeria are compared to those from Senegal where hydroclimatic conditions are different. The similarities are emphasized. The differences in observed behaviour are supposedly caused by the cold season water temps which are sufficiently low to disturb the nor mal activity rhythm.
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In February-March 1971 the hydrological conditions off Angola did not display the thermal dome mapped by Mazeika's averages (1967). Cold water cells observed are connected at the surface to a sinuous boundary between low-salinity coastal waters and high-salinity tropical oceanic waters. That boundary coincides rather regularly with an area where trades and SW winds alternate; photosynthesis growths rapidly in a thermoclinal layer that rises until 10 m of the surface but never outcrops. Below a poor and permanent homogeneous surface layer, chlorophyll concentrations show a distribution which is typical of divergence areas. Geostrophical and measured currents show off a transient process in horizontal and vertical movements, however the general curvature of the circulation is propitious to upwelling. Oxygen oversaturations of about 110%, suggest a moderate potential primary production which confirms slowness and alternation of movements. Also, the regular range of the various chemical and biological levels and moderate chlorophyll concentrations suggest an ecosystem where nutrients supply rapidly equilibrate phytoplankton consumption and not at all a 'phytoplankton bloom' area as that which exists in coastal upwelling. Values of Richardson's number show that instability becomes visible at the bottom of the euphotic layer. An evaluation of the vertical motion is inferred by the peculiar distribution and diurnal alternance of the winds shows that 'doming' structures may be sustained by local meteorological events.
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Most shallow-dwelling tropical marine fishes exhibit different activity patterns during the day and night but show similar transition behavior among habitat sites despite the dissimilar assemblages of the species. However, changes in species abundance, distribution, and activity patterns have only rarely been examined in temperate deepwater habitats during the day and night, where day-to-night differences in light intensity are extremely slight. Direct-observation surveys were conducted over several depths and habitat types on Heceta Bank, the largest rocky bank off the Oregon coast. Day and night fish community composition, relative density, and activity levels were compared by using videotape footage from a remotely operated vehicle (ROV) operated along paired transects. Habitat-specific abundance and activity were determined for 31 taxa or groups. General patterns observed were similar to shallow temperate day and night studies, with an overall increase in the abundance and activity of fishes during the day than at night, particularly in shallower cobble, boulder, and rock ridge habitats. Smaller schooling rockfishes (Sebastes spp.) were more abundant and active in day than in night transects, and sharpchin (S. zacentrus) and harlequin (S. variegatus) rockfish were significantly more abundant in night transects. Most taxa, however, did not exhibit distinct diurnal or nocturnal activity patterns. Rosethorn rockfish (S. helvomaculatus) and hagfishes (Eptatretus spp.) showed the clearest diurnal and nocturnal activity patterns, respectively. Because day and night distributions and activity patterns in demersal fishes are likely to influence both catchability and observability in bottom trawl and direct-count in situ surveys, the patterns observed in the current study should be considered for survey design and interpretation.
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A demarcação de Unidades de Conservação é uma forma supostamente eficaz para a conservação da biodiversidade. A Mata Atlântica é caracterizada por apresentar uma elevada biodiversidade e altos níveis de ameaça. O estado do Rio de Janeiro encontra-se totalmente inserido nesse bioma e seus remanescentes florestais são considerados um hotspot dentro de outro hotspot. O Rio de Janeiro pode ser considerado um dos estados melhor amostrados, porém ainda existem lacunas de conhecimentos geográficos sobre a ocorrência de morcegos. Esta tese foi desenvolvida em três capítulos com o objetivo de contribuir com conservação de morcegos no estado do Rio de Janeiro, focando em como e onde eles já foram amostrados e que locais ainda carecem de atenção. Para este estudo foram utilizados dados referentes a buscas bibliográficas e dados de amostragens do Laboratório de Diversidade de Morcegos da Universidade Federal Rural do Rio de Janeiro. No primeiro capítulo pode-se observar que as localidades com mais de 30 espécies de morcegos são resultado de grande esforço de captura e amostragens usando diversas metodologias. Para uma melhor amostragem da riqueza local, devem-se armar redes não somente em trilhas e próximas a árvores em frutificação, mas também sobre corpos de água. Fazer busca em refúgios diurnos também é aconselhável. Devem ser realizadas amostragens durante a noite toda e variar a fase do ciclo lunar, não restringindo a apenas uma ou partes das fases do ciclo lunar. No segundo capítulo observou-se que 43% das Unidades de Conservação aqui estudadas apresentam 20 ou mais espécies. Localidades que apresentam de 20 a 40 espécies de morcegos na Mata Atlântica podem ser consideradas bem amostradas. Isso demonstra que mais da metade das Unidades de Conservação não podem ser consideradas bem inventariadas. Muitos projetos de pesquisas dão prioridade para a localidade estudada ser uma Unidade de Conservação, porém existem poucos trabalhos de longa duração. No Rio de Janeiro ainda existem diversas Unidades de Conservação não amostradas, principalmente aquelas de difícil acesso e em altitudes elevadas. No terceiro capítulo foi possível observar que há uma maior proporção de espécies que apresentam distribuição geográfica restrita. Esse padrão constitui uma informação importante em termos de conservação, visto que indiretamente poderia indicar uma menor capacidade de dispersão desses animais em médias e grandes distâncias. Entretanto existem lacunas de conhecimento em decorrência da falta de amostragem em algumas regiões, sendo imperativos maiores esforços de captura. Importantes municípios para a conservação e/ou preservação de morcegos como Varre-Sai, Cambuci, Miracema, Carmo, Cantagalo, Valença, Barra do Piraí e Piraí não estão sob proteção legal, mesmo constituindo possíveis corredores entre Unidades de Conservação ou mesmo fragmentos importantes que ainda detém espécies que não estão representadas em Unidades de Conservação já estabelecidas. É imperativo que mais estudos e esforços de conservação sejam direcionados para essas áreas
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本论文由三部分组成: 1) 大豆高产品种黑农40与低产品种黑农37不同发育时期叶片光合生理生态特性的研究;以不同产量水平的东北大豆黑农40和对照品种黑农37为试验材料,研究了从幼苗期到衰老期五个不同发育时期叶片光合作用特性的变化。尤其是系统的研究了光合作用、蒸腾作用和水分利用效率的变化之间的联系,以及气孔导度和胞间CO2浓度的相随变化。发现净光合速率和产量之间存在明显的正相关关系,各个光合生理生态参数之间也有密切的关系。 2) 在大豆生长过程的重要时期结荚期,对大豆品种黑农37和黑农40的光合和水分特性的日变化研究;测定结荚期黑农37和黑农40的光合作用、蒸腾作用、气孔导度和水分特征(水分利用效率和水势)的日变化以及它们之间可能存在的联系,并分析了光抑制的现象,研究表明在晴朗的一天中,光合速率的日变化呈双峰曲线,在整个日变化中,黑农40的净光合速率都比黑农37的要高。黑农40和黑农37相比,在水分亏缺的情况下黑农40能维持较高的水势和水分利用效率,特别是在中午的时候,差别更加明显。 3) 比较研究了1970s 、1980s 和1990s 期间不同大豆 (Glycine max (L) Merr.)品种的生理生态特性:光合作用、蒸腾作用、水分利用效率和叶片水势,分析了各生理生态特性之间以及与产量的关系。研究表明光合速率和产量之间存在显著的相关关系,大豆叶片水势和净光合速率之间也存在明显正相关关系,高产大豆在水分亏缺的情况下仍能维持较高的的水分利用效率和水势。
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本论文对草地群落地上/地下生物量构成、根冠比特征及其影响因子以及土壤呼吸测定方法比较等的国内外研究进展和主要成果进行了综述,在此基础之上对地处我国北方农牧交错带中段的内蒙古多伦县境内的18种草地群落(包括天然草地和人工草地群落)进行了相关内容的研究工作。 在2002年生长季期间,对这18个植物群落中选取的16个进行了群落学调查,测定了其地上、地下生物量,同时测定了土壤含水量、土壤容重、土壤全氮含量和土壤有机质含量。分别分析了地上、地下生物量以及根冠比(root to shoot ratio)与这些立地因子间的相关关系。同期,从18个群落中选定10个代表性群落测定其土壤呼吸速率,测定方法选用了动态红外气体分析法 (Infra red gas analysis, abbreviated as IRGA)和碱液吸收法(Alkali absorption, abbreviated as AA)。对这两种方法的测定结果进行了比较分析,同时分析了不同群落间土壤呼吸变化与土壤水分和养分状况等的相关关系。主要结论如下: ①16种植物群落的地上和地下生物量差异明显,地上生物量变化范围在80~500 g•m-2之间;相比之下,地下生物量的变化范围要大得多,16个群落中地下生物量最小的为猪毛菜群落,最大的为拂子茅群落,分别为533 g•m-2和2590 g•m-2。群落的根冠比在1.5~11.21之间,平均根冠比为 5.69。 ②土壤含水量对地上和地下生物量有着重要的影响,土壤含水量高的样地(羊草样地)较含水量低(小米蒿样地)的样地地上生物量高,反之亦然。但含水量与地下生物量之间的这种关系却不明显,即土壤含水量高的样地其地下生物量并不一定比含水量低的样地地下生物量高;根冠比与土壤含水量之间基本上呈负相关。土壤全氮含量和有机质含量与地上、地下生物量也存在着一定的正相关关系,而土壤容重却与生物量存有负相关关系;根冠比与土壤全氮、有机质和容重的关系正好与此相反,即根冠比与全氮和有机质含量呈负相关,与容重为正相关。 ③10种植物群落土壤呼吸的昼夜变化比较明显,均为单峰型曲线,主要受土壤温度的驱动,但同时也受到当日降水情况和云量、风速等气象因子的较大影响。因此,影响到这些群落土壤呼吸日动态的一致性,使得规律性并不明显。 ④用碱液吸收法和动态密闭气室法测定的10个群落的土壤呼吸速率变化范围分别为394~894mg C•m-2•d-1和313~2043 mg C•m-2•d-1,其中碱液吸收法测定结果平均为动态气室法的67.5%,明显低于动态密闭气室法。 ⑤两种测定方法具有很好的相关性,R2为0.8739。本研究中发现,在土壤呼吸速率低的情况下,两种方法的测定结果十分接近,甚至碱液吸收法的测定结果稍大于动态密闭气室法;而在土壤呼吸速率较高的情况下,动态密闭气室法测定结果则显著高于碱液吸收法。上述结果与国内外同类研究的结果高度一致,从而为校正我们以往采用碱液吸收法在该区域的测定结果提供了可靠依据。 ⑥各个群落间的土壤呼吸变化与立地土壤水分和土壤养分之间存有一定的相关关系,但并不显著,可能与这些群落土壤呼吸测定不是在同一天进行有关。
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Relative abundance and diurnal variations of zooplankton from six anchor stations along Kerala coast were investigated. Samples were collected during April-May 1988 at three hour intervals from depths varying between 15 and 40 m from the traditional fishing grounds of Kerala coast. Average biomass values ranged from 45-95 ml 100/mˉ³. Increase in zooplankton at night was discernible at most of the stations and the highest biomass noticed was 131 ml 100/mˉ³. Copepods formed the most abundant group, of which calanoids predominated. A swarm of the hydromedusan species, Aequorea conica, (181/mˉ³) was seen at night. Quantitative and qualitative variations of various zooplankton groups from six stations in relation to selected physicochemical factors are discussed. Maximum fish larvae were observed in the night samples. Relatively high abundance of sardines, carangids and flat fish larvae in the collections is in agreement with the predominance of fish catch from the area of study.
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The larvae of bothids were found to be sparsely distributed in the Gulf of Thailand and South China Sea being only 11.9% in the Naga Expedition Collections. They were confined mostly to the coastal waters and were found in near shore stations situated between Bangkok and Saigon. Their density was high in the Gulf of Thailand. The larvae seem to prefer darkness with greater incidence during April 16 to October 15 period, with a peak in the collections taken during April. This report includes the occurrence of 17 species belonging to 6 genera collected from the Gulf of Thailand and South China Sea, along with their regional, seasonal as well as diurnal variations
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The southern part of the Sofala Bank (in Mozambique) was investigated. A net of closely spaced hydrographic stations were obtained and a current meter mooring consisting of two current meters and a bottom pressure recorder was deployed. High salinity shelf water was observed near shore with a maximum salinity above 36.6 ppt. Both average and tidal currents are discussed. The mean currents are steered by the continental slop and seem to be influenced by the wind. The tides have strong semidiurnal components, with a major axis of 53 cm/s perpendicular to the coast at 60m depth. The possibility that the tides may transport passive drifters with a diurnal vertical migration pattern up to a few kilometers a day is considered.