Growth and proximate composition of the Chaetoceros calcitrans f. pumilus under different temperature, salinity and carbon dioxide levels

The marine diatom Chaetoceros calcitrans f. pumilus has been examined for its potential source as live feed in aquaculture. The present study investigated effects of temperature (20, 25 and 30 °C), salinity (25 and 35) and carbon dioxide addition (air+CO₂) on the growth and proximate composition of C. calcitrans under laboratory conditions. The growth and biomass of C. calcitrans were primarily affected by carbon dioxide addition, and to a lesser extent by temperature and salinity. In general, lipid and carbohydrate contents were higher at lower temperatures (20 and 25 °C), while the protein content was unaffected. Carbon dioxide addition increased protein, while lowering carbohydrates, but had no effect on lipid content. Carbohydrates were increased while lipids and protein decreased at the highest salinity (35±0.9). These results should be taken into consideration when evaluating the dietary value of this micro alga for aquaculture.     

Paired-site approach for studying soil organic carbon dynamics in a Mediterranean semiarid environment

This work investigated the effects of land cover and land-use change (LUC) on the ability of a soil to store carbon (C) and reduce carbon dioxide (CO₂) emissions, in a Mediterranean area. Using a paired-site approach, we estimated the effect of land-cover change on the C stock from 1972 to 2008 in a natural reserve (Grotta di Santa Ninfa) in western Sicily. We selected 15 paired sites representative of five LUCs. We studied the effect of land use on soil organic C (SOC) content in bulk soil and in different particle-size fractions (2000-1000 μm, 1000-500 μm, 500-250 μm, 250-63 μm, 63-25 μm, and < 25 μm). Laboratory incubation of the soil samples was conducted to measure CO₂ evolution in bulk soil collected at two different depths from each paired site. We found that the conversion of natural vegetation to orchards (vineyards and olive groves) resulted in SOC decreases ranging from 27% to 50%. The conversion from vineyards to arable land led to a 9% decrease in SOC, whereas the opposite caused a 105% gain. When arable land was replaced by Eucalyptus afforestation, a 40% increase in SOC was observed. SOC decline occurred mainly in coarser soil fractions, whereas the finest fractions were not influenced by land use. We calculated an overall SOC reduction of 63% in the study area, corresponding to a 58 Mg ha^− 1 SOC loss in less than 30 years. Our results indicate that land-use conversion, vegetation type, and management practices that control the biogeochemical and physical properties of soil could help reduce CO₂ emissions and sequester SOC.     

Effect of CO2 enrichment on fruit growth and quality in Japanese pear (Pyrus serotina Reheder cv. Kosui)

Six year-old Japanese pear (Pyrus seratina Reheder cv. Kosui) trees grafted on P. serotina cv. Nihonyamanashi were grown in containers filled with Granite Regosol under glasshouse conditions. At different stages of fruit growth, pear trees were exposed to an elevated CO₂ concentration (130 Pa CO₂ ) along with a control (35 Pa CO₂). For one group of plants, CO₂ enrichment was applied for 79 d from 52 d after full bloom (DAB) to fruit maturity (long-term CO₂ enrichment) and for another group the same treatment was applied for 35 d from 96 DAB to fruit maturity (short-term CO₂ enrichment). The effects of the elevated CO₂ concentration on vegetative growth, mineral contents, and fruit production and quality were examined. Long-term CO₂ enrichment enhanced vegetative growth, without any significant effect on the mineral contents in either flower bud or fruit except for a remarkable increase in the K content. Long-term CO₂ enrichment increased the fruit size and fresh weight, but had no significant effect on the fruit quality. On the other hand, the short-term CO₂ enrichment did not induce any significant change in the fruit size but increased the fruit sugar concentration. Along with the reduction of the sorbitol concentration in fruit, the fructose and sucrose concentrations increased and these changes occurred earlier at elevated CO₂ than at ambient CO₂ concentrations. From these results, we concluded that the effect of CO₂ enrichment on fruit growth varies depending upon the growth stages of fruit: during the initial and fruitlet stages when fruit expansion occurs, CO₂ enrichment increases the fruit size, whereas, during maturation when fruit expansion has slowed down and sugar accumulation in fruit is active, it increases the fruit sugar concentration.     

寒区桥梁用自密实混凝土试验研究

通过对自密实混凝土进行快冻法和3%NaCI溶液的冻融循环试验,测定不同冻融循环次数后的质量损失率和相对动弹模量及其变化特点以及冻融损伤对氯离子扩散能力的影响。结果表明：自密实混凝土随着冻融次数的增加,其表观质量、力学性能均呈现不同下降趋势。可为寒区桥梁工程设计、养护及寿命预测提供依据。     

橡胶林土壤呼吸研究概述及展望

橡胶林生态系统是热带地区重要的人工生态系统,为热带地区的生态服务和经济发展做出了重要贡献,在世界森林生态系统中占有重要的位置。橡胶林土壤呼吸对调控大气CO2有着重要的作用,是全球变化背景下碳循环过程研究的一个重要环节。系统概述了橡胶林土壤呼吸的研究意义、研究方法、影响因素、时空变化以及对干扰的响应和组分区分,指出橡胶林土壤呼吸研究中存在的不确定性,并对后续研究的热点与方向进行展望。     

Efficacy of a Fructus mume Extract Combination with Stable Chlorine in Preventing Bacterial Contamination in Frozen Mackerel (Scomber japonicus) Fillets

ABSTRACT

A combination composed of Fructus mume extract and stable chlorine dioxide was investigated for its antibacterial activity, mechanism of action, and its application against Escherichia coli and Staphylococcus aureus in mackerel (Scomber japonicus) fillets. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values against E. coli and S. aureus ranged from 0.9–1.2 and 1.3–1.6 mg/mL for F. mume extract and 0.004–0.006 and 0.007–0.010 mg/mL for stable chlorine dioxide, respectively. We observed a mechanism of action against E. coli that involved a pore-formation role that led to cell membrane damage. In the case of S. aureus, the mechanism of action is believed to be mediated by the combination’s activity as a metabolite disrupting agent. Here, the amount of bacteria was greatly reduced in mackerel fillets treated with the combination. Moreover, the flavor and texture properties of fillets were not significantly affected by this treatment (p < 0.05). These findings suggested that the combination has promise in being used as an additive to a broader class of foodstuffs.     

贵州红枫湖溶解有机质不同分离组分的卤代活性研究

饮用水使用氯化消毒产生的消毒副产物给人类健康带来了极大危害。利用XAD树脂与阴、阳离子交换树脂对贵州红枫湖水体中溶解有机质进行了富集分离,分成腐植酸、富里酸、疏水中性物质及亲水酸性、碱性及中性物质6种组分,比较了各组分在加氯消毒过程中卤代活性的大小及其三卤甲烷的生成情况,揭示了有机组分卤代活性与其结构之间的关系,并探讨了它们可能的来源,提出了相应的控制措施。结果表明,红枫湖水体溶解有机质以富里酸组分为主,占分离出总有机碳的56%。氯化消毒实验发现消毒副产物以三氯甲烷和一溴二氯甲烷为主,富里酸的卤代活性最强。结构分析显示各有机组分的卤代活性与紫外吸光系数和酚羟基含量之间具有显著相关性。6种分离组分的消毒副产物生成量中,富里酸是生成三卤甲烷的主要前驱物质,占消毒副产物总量的76%。有机组分的碳稳定同位素值与C/N比值表明,富里酸主要来自陆源有机物,其余组分兼有陆源和内源两种来源。因此,控制陆源污染是减少红枫湖消毒副产物前驱物的有效途径。