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201.
栉孔扇贝Chlamys farreri(Jones et preston)肉细嫩鲜美,营养丰富,经济价值很高,在国外市场上深受欢迎,为海珍品之一。 我所在连续四年进行扇贝半人工采苗试验和两年半人工采苗生产的基础上,于1981年承担了山东省水产局下达的“扇贝大面积半人工采苗生产技术”的研究课题。通过不断的实践和改进,目前已系统地摸索出提高扇贝半人工采苗率的技术措施。 相似文献
202.
志留纪是显生宙内,除第四纪和新近纪外,历程最短的一个纪,是奥陶纪大灭绝后生物多样性快速复苏、板块聚合、大洋消失或变窄、气候和海平面多变、生物地理区系弱化和植物开始占据陆地的一个重要而特殊的时期.志留系又是第一个建立全球年代地层标准(四统、七阶)的系,但在20世纪80年代中期开展的"后层型"研究后发现,一些阶的底界层型,由于定义不精准和/或层型剖面的先天缺陷、关键标准化石始终未曾发现等,精时对比受到制约.本文剖析中国志留系发育特点,综述近些年来在生物地层、年代地层、事件地层(如沉积相分异,黑色页岩、海相红层和碳酸盐岩与生物礁的时空分异)、化学地层、构造地层(如华南志留纪晚期地层的广布及其构造意义)等方面取得的主要研究进展,指出目前存在的和今后需重点关注的问题.年代地层学研究不宜只集中在一条界线上,需注重界线上下的生物、化学、磁性、环境、年龄等多领域的综合交叉,提高层型的优质度,延伸在区域和全球的对比价值.期盼我国志留系研究在兰多维列统生态地层、盆地分析及综合地层的精时对比,温洛克世至普里道利世年代地层框架的确立和对比,化学和磁性地层研究及关键层段绝对年龄的测定,古地理与大地构造研究的深化,陆地生态系统早期演化等方面取得重要成果,并在个别统、阶的底界层型的再研究中发挥重要作用. 相似文献
203.
To investigate whether the biological toxicity of aquatic hypercapnia is due to the direct effects of CO2 or to the effects of acidification of seawater by CO2, the Japanese flounder (Paralichthys olivaceus) was subjected to seawater equilibrated with a gas mixture of air containing 5% CO2 (pH 6.18) or seawater acidified to the same pH with 1 N H2SO4. All the fish died within 72 h in the CO2 exposure group, whereas no mortality occurred in the acid group. Acid-base parameters as well as plasma ion concentrations were severely perturbed in the CO2 exposure group, whereas they were minimally affected in the acid group. These results clearly demonstrate that the mortality in the CO2 group is a direct result of the elevated levels of dissolved CO2 and not to the effects of the reduced water pH. 相似文献
204.
Variation in the concentrations of iodine-129 (129I, T1/2=15.7 Myr), a low-level radioactive component of nuclear fuel waste, is documented in surface waters and depth profiles collected during 2001 along a transect from the Norwegian Coastal Current to the North Pole. The surface waters near the Norwegian coast are found to have 20 times higher 129I concentration than the surface waters of the Arctic Ocean. The depth profiles of 129I taken in the Arctic Ocean reveal a sharp decline in the concentration to a depth of about 300-500 m followed by a weaker gradient extending down to the bottom. A twofold increase in the 129I concentration is observed in the upper 1000 m since 1996. Based on known estimates of marine transient time from the release sources (the nuclear reprocessing facilities at La Hague, France, and Sellafield, UK), a doubling in the 129I inventory of the top 1000 m of the Arctic Ocean is expected to occur between the years 2001 and 2006. As 129I of polar mixed layer and Atlantic layer of the Arctic Ocean is ventilated by the East Greenland Current into the Nordic Seas and North Atlantic Ocean, further dispersal and increase of the isotope concentration in these regions will be encountered in the near future. 相似文献
205.
In order to develop a viable foraminiferal proxy for heavy metal pollutants, juvenile specimens of Rosalina leei were subjected to different mercury concentrations (0-180 ng/l). Initially considerable growth was observed in specimens kept in saline water having a mercury concentration up to 100 ng/l. But with the gradual increase in concentration of mercury the growth rate started decreasing. Total growth achieved was significantly lower in case of specimens kept at relatively higher mercury concentrations then those maintained in normal saline water. The most significant result of this experiment was the addition of abnormal chambers in the specimens kept at higher mercury concentration. Later the specimens kept at highest concentration (180 ng/l) were subjected to progressively increasing concentration of mercury to see the further effects and it was found that the specimens were still living at as high a mercury concentration as 260 ng/l although there was no growth. 相似文献
206.
P. Alfaro J. Delgado F. J. Garcia-Tortosa L. Lenti J. A. Lopez C. Lopez-Casado S. Martino 许冲译 吕春来校 《世界地震译丛》2013,(3):66-80
2011年5月11日,一个中等震级地震(Mw5.1)袭击了西班牙东南部洛尔卡城和邻近地区,造成了显著的破坏和人员伤亡。通过地震影响区的野外考察对250多处主要是碎裂型(岩/土崩塌、碎裂的土质滑坡和岩崩)诱发滑坡进行了定点和特征描述。与以前该区域相似震级(Mw4.7~5.0)的地震事件,以及以前预测地震期间斜坡表现的模型结果相比,本次地震诱发滑坡的数量相当大。提出了几个原因来解释这种差异:(1)地震序列中相对高震级(Mw4.5)的前震可能弱化了区域内的斜坡强度;(2)这些事件产生了高的地震动峰值;(3)发生了地形场地效应。本研究的结果指出了在改进区域斜坡特征研究模型时考虑这些影响的重要性。 相似文献
207.
针对隔震改造后叠层橡胶隔震支座与地下室下支柱组成的串联隔震体系的地震稳定性问题,采用理论推导与数值模拟方法开展系统研究。将叠层橡胶支座简化为一种具有水平刚度和抗弯刚度的特殊铰支座,RC柱简化为弯曲型竖杆,建立橡胶支座和RC柱串联隔震体系的理论模型,推导地下室下支柱的临界承载力方程;通过实际案例求解出该串联隔震体系的临界承载力具体表达式,并对典型参数的影响进行分析;采用数值模拟方法建立下支柱截面尺寸不同的6种柱顶隔震模型,对下支柱柱顶、隔震支座、下支柱与隔震支座串联后整体位移响应以及上部结构层间位移角响应进行对比分析。结果表明:所推导的临界承载力表达式变化规律与柱顶隔震设计模型数值模拟相一致;下支柱截面增大对上部结构和隔震支座的动力响应影响并不明显,但是可以明显减小下支柱的位移;在既有建筑隔震改造实际工程中,增加下支柱的截面尺寸是保证下部结构的抗震能力高于上部结构既简单且行之有效的方法,但实际工程中截面增量普遍较大且偏于保守,造成了一定的浪费。 相似文献
208.
Renaud F Oberhänsli F Teyssié JL Miramand P Temara A Warnau M 《Marine pollution bulletin》2011,62(5):942-947
Linear Alkylbenzene Sulfonates (LAS) are ubiquitous surfactants. Traces can be found in coastal environments. Sorption and toxicity of C12-LAS congeners were studied in controlled conditions (2-3500 μg C12LAS/L) in five marine phytoplanktonic species, using standardized methods. IC50 values ranged from 0.5 to 2 mg LAS/L. Sorption of 14C12-6 LAS isomer was measured at environmentally relevant trace levels (4 μg/L) using liquid scintillation counting. Steady-state sorption on algae was reached within 5 h in the order dinoflagellate > diatoms > green algae. The sorption data, fitted a L-type Freundlich isotherm, indicating saturation. Desorption was rapid but a low LAS fraction was still sorbed after 24 h. Toxic cell concentration was 0.38 ± 0.09 mg/g for the studied species. LAS toxicity results from sorption on biological membranes leading to non-specific disturbance of algal growth. Results indicate that LAS concentrations in coastal environments do not represent a risk for these organisms. 相似文献
209.
210.
Accoroni S Romagnoli T Colombo F Pennesi C Di Camillo CG Marini M Battocchi C Ciminiello P Dell'Aversano C Dello Iacovo E Fattorusso E Tartaglione L Penna A Totti C 《Marine pollution bulletin》2011,62(11):2512-2519
Intense blooms of the benthic dinoflagellate Ostreopsis cf. ovata have occurred in the northern Adriatic Sea since 2006. These blooms are associated with noxious effects on human health and with the mortality of benthic organisms because of the production of palytoxin-like compounds. The O. cf. ovata bloom and its relationships with nutrient concentrations at two stations on the Conero Riviera (northern Adriatic Sea) were investigated in the summer of 2009. O. cf. ovata developed from August to November, with the highest abundances in September (1.3 × 106 cells g−1 fw corresponding to 63.8 × 103 cells cm−2). The presence of the single O. cf. ovata genotype was confirmed by a PCR assay. Bloom developed when the seawater temperature was decreasing. Nutrient concentrations did not seem to affect bloom dynamics. Toxin analysis performed by high resolution liquid chromatography-mass spectrometry revealed a high total toxin content (up to 75 pg cell−1), including putative palytoxin and all the ovatoxins known so far. 相似文献