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Guoyi Niu Dilok Wongsathein Sukolrat Boonyayatra Rutch Khattiya 《Aquaculture Research》2019,50(12):3643-3652
Edwardsiella tarda is a pathogen that causes edwardsiellosis in aquatic animals. The emergence of multiple antibiotic‐resistant strains makes antibiotic treatment difficult. This study aimed to investigate the antibiotic susceptibility patterns and the genotypic characterization of E. tarda isolated from cage‐cultured red tilapia in Thailand. A total of 30 isolates were identified as E. tarda using biochemical and molecular analysis. The disc diffusion method for testing antibiotic susceptibility showed all the isolates were resistant to colistin sulphate and oxolinic acid. High levels of resistance to amoxicillin, ampicillin, ceftazidime, oxytetracycline and sulphamethoxazole/trimethoprim were observed as well. The multiple antibiotic resistance index ranged from 0.25 to 0.92, indicating that these isolates had been exposed to high risk sources of contamination where antibiotics were commonly used. All the isolates carried the blaTEM gene based on polymerase chain reaction (PCR). The tetA and sul3 genes were detected in 90% (27/30) and 26.7% (8/30) of the isolates respectively. Nine different genetic groups of isolates were obtained using enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC‐PCR). A correlation between genetic types and multiple antibiotic‐resistant patterns was found. These results highlight the potential risks of multiple antibiotic‐resistant isolates for humans and the environment. 相似文献
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1984-2017年洪泽湖湿地植被覆盖度变化及对水位的响应 总被引:1,自引:0,他引:1
为揭示洪泽湖湿地植被覆盖度变化状况,探讨其变化趋势,并分析植被覆盖度与水位的相关关系。本文基于1984-2017年间42期的TM/ETM+/OLI数据,采用像元二分模型估算洪泽湖湿地植被覆盖度,分析研究区域近34年来植被覆盖度的整体特征及动态变化趋势。利用归一化差异水体指数提取洪泽湖的水体信息,同时结合植被覆盖度与其对应的水位监测数据,运用统计分析的方法构建洪泽湖四季的植被覆盖度-水体面积-水位关系模型。结果表明:(1) 研究时段上,洪泽湖湿地的整体植被覆盖度呈略微降低的趋势,中高和高植被覆盖区主要分布于研究区域的西北部及南部。(2) 1984-2017年间,洪泽湖的植被覆盖情况以退化为主,退化面积约为576.1km2,其中不显著退化(82.3%)所占比重最大。(3) 整体上看,研究区的植被覆盖度、水体面积与水位呈极显著性相关,根据三者关系模型得出四季的最适宜水位为春季12.3m、夏季12.9m、秋季12.1m和冬季12.2m。研究结果可为洪泽湖湿地生态环境的科学管理提供理论支撑与技术参考。 相似文献
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Paul C. Stoy Mathew Williams Mathias Disney Ana Prieto-Blanco Brian Huntley Robert Baxter Philip Lewis 《Landscape Ecology》2009,24(7):971-986
Transferring ecological information across scale often involves spatial aggregation, which alters information content and
may bias estimates if the scaling process is nonlinear. Here, a potential solution, the preservation of the information content
of fine-scale measurements, is highlighted using modeled net ecosystem exchange (NEE) of an Arctic tundra landscape as an
example. The variance of aggregated normalized difference vegetation index (NDVI), measured from an airborne platform, decreased
linearly with log(scale), resulting in a linear relationship between log(scale) and the scale-wise modeled NEE estimate. Preserving
three units of information, the mean, variance and skewness of fine-scale NDVI observations, resulted in upscaled NEE estimates
that deviated less than 4% from the fine-scale estimate. Preserving only the mean and variance resulted in nearly 23% NEE
bias, and preserving only the mean resulted in larger error and a change in sign from CO2 sink to source. Compressing NDVI maps by 70–75% using wavelet thresholding with the Haar and Coiflet basis functions resulted
in 13% NEE bias across the study domain. Applying unique scale-dependent transfer functions between NDVI and leaf area index
(LAI) decreased, but did not remove, bias in modeled flux in a smaller expanse using handheld NDVI observations. Quantifying
the parameters of statistical distributions to preserve ecological information reduces bias when upscaling and makes possible
spatial data assimilation to further reduce errors in estimates of ecological processes across scale. 相似文献
76.
荒漠草原植被覆盖对土壤水分的影响 总被引:2,自引:0,他引:2
以希拉穆仁草原为研究对象,通过对不同植被覆盖下土壤水分进行测定,研究了荒漠草原植被覆盖对土壤水分的影响,结果表明:植被覆盖度与土壤水分之间具有显著的相关关系,尤其是10 cm深度范围内土壤水分随植被盖度呈二次抛物线性趋势增加(R2=0.904 9);由于根系层分布的差异使得土壤剖面不同深度上对这种影响的水分响应不尽相同,灌丛植被覆盖的土壤水分含量在剖面0~40cm范围内明显大于其他植被类型,以坡顶土壤含水量最低;荒漠草原植被覆盖状况变化不仅影响土壤水分含量大小,而且显著影响土壤水分的空间分布,退化较轻的河滩草甸植被有利于维持相对均匀的土壤水分空间分布. 相似文献
77.
Abstract Norway lobster, Nephrops norvegicus (L.), in the Bay of Biscay exhibited diel activity patterns with more individuals outside their burrows at dawn and dusk, increasing catchability at these times. Data from an on board observer programme on Nephrops trawlers between 2002 and 2005 were used to assess variability in catchability in commercial catches. Catch numbers per haul varied spatially and between months, but no signal for diel variations was found. Fishing strategies developed by the Nephrops trawlers had several components. On a seasonal level, they started around sunrise. On a haul level, haul duration decreased from haul to haul, with the longest hauls taking place at the time of the highest catchability. By-catch of hake, Merluccius merluccius (L.), increased more than proportionally with haul duration. 相似文献
78.
20世纪中叶以前,高黎贡山森林植被茂密,生态良好.如今,大面积的原始森林被砍伐,滑坡、泥石流自然灾害不时发生,生态环境恶化.通过对高黎贡山地区的生态环境恶化的原因进行分析,提出了5个方面的生态环境建设对策:(1)恢复植被;(2)开发替代能源以降低薪材消耗;(3)调整土地利用结构以发展社区经济;(4)发展生态旅游;(5)借助保护区的优势,争取国内外支持援助. 相似文献
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