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731.
太湖日本沼虾、秀丽白虾现存量的周年动态研究——以梅梁湾、贡湖湾为例 总被引:1,自引:0,他引:1
太湖日本沼虾与秀丽白虾资源较为丰富,在太湖渔业中占有非常重要的地位,但对两种虾类资源动态的研究较少。对梅梁湾和贡湖日本沼虾、秀丽白虾现存量进行了周年调查,结果表明,梅梁湾和贡湖湾日本沼虾丰度和现存量一年内出现波动,冬季较低,春季开始增加,夏季达到高峰,9月后丰度和现存量大幅下降,随后随着个体的生长又有所上升,说明其资源量在短期内受繁殖和捕捞的影响会大幅震荡。不同湖区日本沼虾丰度和现存量存在差异,夏季沿岸带的丰度和现存量明显比敞水区大,主要是6~9月沿岸带分布量增多,说明日本沼虾繁殖季节的亲虾及当年繁殖的幼虾大量栖息于沿岸带,而非敞水区。贡湖秀丽白虾水草区丰度和现存量最高,说明秀丽白虾喜栖息于有沉水植物分布的水域。为合理利用太湖虾类资源提供依据 相似文献
732.
In this study we assessed the degree of copper (Cu) tolerance in two common lichen species (Cladonia furcata and Cladina arbuscula subsp. mitis) that grow on both uncontaminated substrata and the surface of waste heaps from abandoned old Cu-mines. Regardless of their locality, populations of these lichens contain identical strains of photobionts (Asterochloris clade A in C. arbuscula subsp. mitis and clade D in C. furcata). Therefore, it was expected that if there were differences in Cu toxicity or tolerance between populations, that the photobiont could not be a key element of Cu tolerance in these two lichen species. In laboratory experiments samples of both lichen species (from contaminated and control sites) were incubated in Cu solutions (500 μM) for 24 h. We attempted to determine whether Cu tolerance in these lichens was constitutive, or inducible form. Based on measurements of Cu accumulation, chlorophyll a integrity, chlorophyll a fluorescence, photosynthesis, respiration, measurements of the content of thiobarbituric acid reactive substances (TBARS), the content of soluble proteins, reactive oxygen species (ROS) and the amount of extracellular secondary metabolites of both lichens we found that there were no significant differences in the response of all selected populations of both lichen species to short-term exposure to these high levels of Cu. As a result, we conclude that Cu tolerance in these two lichen species is the constitutive rather than the inducible. 相似文献
733.
燃煤电厂烟气脱硫装置实际运行的稳定性和可靠性并不理想,由于设计、运行维护经验少及设备选型不合理等原因使脱硫系统维护工作量大。浆液pH值、密度等关键工艺参数设计范围较广,不利于系统稳定运行。目前国内缺少从化学反应理论和工艺控制角度对湿法脱硫系统的研究,对脱硫系统运行经济性的研究也较少。鉴于以上脱硫运行现状,开展了旨在优化湿法脱硫工艺控制、提高系统运行的可靠性和经济性的优化研究。 相似文献
734.
735.
Jayaraj KA Jayalakshmi KV Saraladevi K 《Environmental monitoring and assessment》2007,127(1-3):459-475
The paper deals with the standing stock of macrobenthic infauna and associated environmental factors influencing the benthic
community in the shelf region of the northwest Indian coast. The data were collected onboard FORV Sagar Sampada during the
winter monsoon (January–February, 2003) to understand the community structure and the factors influencing the benthic distribution.
The environmental parameters, sediment characteristics and macrobenthic infauna were collected at 26 stations distributed
in the depths between 30 and 200 m extending from nobreak{Mormugao} to Porbander. Total benthic abundance was high in lower
depths (50–75 m), and low values noticed at 30 m depth contour was peculiar. Polychaetes were the dominant group and were
more abundant in shallow and middle depths with moderate organic matter, clay and relatively high dissolved oxygen. On the
other hand crustaceans and molluscs were more abundant in deeper areas having sandy sediment and low temperature. High richness
and diversity of whole benthic groups observed in deeper depths counter balanced the opposite trend shown by polychaete species.
Generally benthos preferred medium grain sized texture with low organic matter and high organic matter had an adverse effect
especially on filter feeders. Deposit feeding polychaetes dominated in shallow depths while carnivore species in the middle
depths. Ecologically, benthos were controlled by a combination of factors such as temperature, salinity, dissolved oxygen,
sand and organic matter and no single factor could be considered as an ecological master factor. 相似文献
736.
We investigated the influence of known correlates of parasitism, namely fish density, body size and social behaviour, on three
highly variable aspects of the interactions between cleaning gobies (Elacatinus spp.) and their clients, on a Barbadian coral reef. We specifically considered (1) variability in client visit rate to cleaning
stations, (2) cleaning goby preference for specific clients and (3) variation in the time spent cleaning by cleaners. Using
phylogenetically independent contrasts, we found that client species that were abundant on the reef visited cleaning stations
more often than rarer client species. This could be due to the positive relationship between ectoparasite load and client
density, or alternatively may simply reflect the frequency of contact between cleaners and clients. Cleaning gobies spent
more time cleaning large-bodied clients, which usually have higher ectoparasite loads, although cleaning goby preference for
clients was influenced by none of the correlates of client parasitism. Overall, factors assumed to correlate with ectoparasite
load had a limited influence on the variability observed in the interactions between cleaning gobies and their clients.
Received: 27 October 1999 / Received in revised form: 11 January 2000 / Accepted: 24 January 2000 相似文献
737.
Line transect sampling is an effective survey method for estimating butterfly densities because it provides unbiased estimates of site-density (provided key assumptions are met), and estimates are comparable among sites. For monitoring Karner blue butterflies in Wisconsin, USA, comparable estimates are required because each year a different selection of sites will be monitored. Annual state-wide indices of species abundance can be derived from the site-surveys and compared to previous year's indices to monitor trends. We advocate that line transect sampling is preferable to Pollard-Yates transects as a survey technique for monitoring Karner blue butter- flies. The Pollard-Yates surveys do not adjust for diferences in site detectability. As a consequence, estimates of among-site from Pollard-Yates surveys can be biased. © Rapid Science 1998 相似文献
738.
Sperm competition and sexual selection: a meta-analysis of paternity studies of birds 总被引:8,自引:0,他引:8
Sperm competition (the competition among the sperm of different males for fertilization of the eggs of a female) has been
suggested to be an important component of sexual selection, but no general assessment has been made of this proposition. We
used a meta-analytic approach to assess the extensive literature on paternity (the proportion of offspring in a focal nest
sired by an attending male) in birds based on allozyme and molecular techniques. The relative variance in male mating success
was on average increased by a factor of 4.6 over the variance in apparent male success. Males with more extravagant secondary
sexual characters had higher paternity in their own nests than less adorned males. There was a weak effect of male age being
positively associated with paternity in own nests. Male body size measured as the length of wing and tarsus was weakly positively
associated with paternity in own nests. Male survival prospect was positively associated with paternity in own nests. Polygynous
males generally had decreased paternity of their broods compared to monogamous males. Paternity of the resident male decreased
with increasing population density and breeding asynchrony. The intensity of paternity guards such as within-pair copulation
rate and mate guarding were not significantly related to extra-pair paternity. Sperm competition was thus an important component
of sexual selection by increasing the variance in male mating success, and by being associated with the expression of secondary
sexual characters, in particular in dense and asynchronously breeding populations of birds.
Received: 12 February 1998 / Accepted after revision: 31 May 1998 相似文献
739.
Astrid M. Heiling 《Behavioral ecology and sociobiology》1999,46(1):43-49
The nocturnal orb-web spider Larinioides sclopetarius lives near water and frequently builds webs on bridges. In Vienna, Austria, this species is particularly abundant along the
artificially lit handrails of a footbridge. Fewer individuals placed their webs on structurally identical but unlit handrails
of the same footbridge. A census of the potential prey available to the spiders and the actual prey captured in the webs revealed
that insect activity was significantly greater and consequently webs captured significantly more prey in the lit habitat compared
to the unlit habitat. A laboratory experiment showed that adult female spiders actively choose artificially lit sites for
web construction. Furthermore, this behaviour appears to be genetically predetermined rather than learned, as laboratory-reared
individuals which had previously never foraged in artificial light exhibited the same preference. This orb-web spider seems
to have evolved a foraging behaviour that exploits the attraction of insects to artificial lights.
Received: 8 June 1998 / Received in revised form: 18 January 1999 / Accepted: 19 January 1999 相似文献
740.
论我国酒精工业推行清洁生产的潜力和机会 总被引:14,自引:0,他引:14
通过分析我国酒精工业现状和存在的清洁生产潜力,针对我国酒精工业主要的工艺环节提出其潜在的清洁生产机会、相应的污染预防措施、技术要求与环境和经济效益。 相似文献