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991.
992.
The present study tested for density-dependent effects of the invasive drift macroalgae Gracilaria vermiculophylla (Ohmi) Papenfuss on growth and survival of the native eelgrass, Zostera marina L., under different temperature levels. Three weeks laboratory experiments were conducted in Odense, Denmark, combining three algae densities (control, low 1.9 kg WW m−2, high 4.5 kg WW m−2) with typical Danish summer temperatures (18 °C) and elevated temperatures (21 °C and 27 °C). There was a significant effect of temperature on shoot survival with on average 68% mortality in the high temperature treatment but almost no mortality at the two lower temperatures. The higher mortality was probably caused by high sulphide levels in the sediment pore water (0.6 mmol l−1 at 18 °C compared to 3.7 mmol l−1 at 27 °C). Above-ground growth of the surviving shoots was also significantly affected by temperature, with leaf elongation rates being negatively affected, while the leaf plastochrone interval increased. Relative growth rate was significantly higher at 21 °C than at 18 °C or 27 °C, whereas rhizome elongation was significantly lowest at 27 °C. Elemental sulphur content in the plant tissues increased significantly with temperature and was up to 34 times higher (S0 in rhizomes) at 27 °C compared to the lower temperatures. In contrast to the temperature effects, cover by G. vermiculophylla did not cause significant effects on any seagrass responses. However, there was a (non-significant) negative effect of algal cover at the highest temperature, where the seagrass is already stressed. The latter results suggest that more studies should test for interaction effects between temperature and other anthropogenic stressors given that temperature is predicted to increase in the near future. 相似文献
993.
Improving the economic performance of fisheries is becoming increasingly important in fisheries management, and in some cases, maximum economic yield (MEY) is set as a key management target. However, recent critics of MEY as a management target have argued that a decline in the level of fishing activity necessary to achieve the target will result in a subsequent loss of economic activity elsewhere in the economy and, potentially, a net loss to society. In this paper, an input–output framework is used to estimate the net economic effects of achieving MEY in several Australian fisheries for which there is information on their short- and long-term performances when moving towards MEY. While overall losses were found in the short term, achieving MEY was found to result in a net economic benefit to society in the longer term. Local coastal communities in particular were found to benefit, although some losses were incurred elsewhere in the economy. 相似文献
994.
995.
结合航海英语具有专业术语多、重复少、多长句,复合句和被动语态的特点,选用典型实例从词汇内涵、句式表达、语篇分析3个语言层面阐述等效翻译理论在航海英语翻译中的应用,为规范译员在航海英语资料翻译和口译过程中的原则和行为提供有益启示,进一步提高国内外海员的交流与合作层次。 相似文献
996.
耕地保护经济补偿运行机制及补偿效应分析 总被引:3,自引:0,他引:3
在对耕地保护经济补偿机制内涵界定的基础上,提出了"农业保险+社会保障+实物技术货币一体化的区内经济补偿机制"和"基于上级政府调控和财政转移支付的耕地保护区际经济补偿协商机制",并对区内和区际经济补偿方式、运行机理进行了分析.同时,在对耕地保护经济补偿效应概念、类型界定的基础上,结合农户问卷调查,对耕地保护经济补偿效应进行了系统分析.研究表明:(1)耕地利用生态社会效益的外部性是耕地非农化的根本原因,而构建耕地保护的经济补偿机制则是抑制耕地非农化的根本途径.(2)耕地保护的经济补偿体系由区内经济补偿和区际经济补偿共同组成,耕地保护经济补偿方式、补偿标准是影响其补偿效应的重要因素. 相似文献
997.
中部地区经济差异的空间尺度效应分析 总被引:1,自引:0,他引:1
为深入分析空间尺度选择对区域经济差异的影响,采用变异系数、基尼系数和锡尔系数等指标在省、市和县三级空间尺度重复使用的方法和尺度方差分析法,选取人口、GDP和人均GDP 3项指标,分析1990-2007年我国中部地区区域经济差异的空间尺度效应。1)采用同一指标在3个尺度上重复使用的方法分析结果存在很大差别,市、县尺度上区域经济差异都有扩大趋势,但与省尺度上的趋势相异,尤其2003年后市、县尺度上区域经济差异呈扩大趋势,而在省尺度却呈缩小趋势;2)尺度方差分析也显示市、县尺度上结果较为一致,并在1997年达到低值后均有明显扩大趋势,这与省尺度上的趋势相异,尤为明显的是,2003年后区域经济差异在省尺度呈缩小趋势。尺度方差分解和锡尔系数分解结果表明:市际和县际差异是造成中部地区经济差异的主要因素,省际差异的影响很小。因此,在进行区域经济差异分析时应尽量选择较小空间尺度。 相似文献
998.
Frédéric Zagury 《Journal of Astrophysics and Astronomy》2005,26(4):395-420
This paper presents an analysis of a series of spectra in the Red Rectangle nebula. Only the reddest part of the spectra can
safely be attributed to light from the nebula, and indicates Rayleigh scattering by the gas, in conformity with the large
angles of scattering involved and the proximity of the star. In the blue, light from HD 44179, refracted or scattered in the
atmosphere, dominates the spectra. This paper questions the reliability of ground-based broad-band spectra of extended objects
in the blue. 相似文献
999.
1000.
Zhongzhi CHEN Jiawei QU Zhende GUAN 《东北亚地学研究》2006,9(2):232-234
The interact of construction and circumstance becomes more and more obviously,and research on it is essentially urgent.The way to solve it,first it relies on quantifiable evaluation to the effects done by different construction techniques,then,choose related techniques which cause less damage according to the endurance of circumstance. 相似文献