Passive irrigation and functional morphology of crustacean burrows in a tropical mangrove swamp

Flushing measurements and a resin cast of a burrow inhabited by Sesarma messa and Alpheus cf macklay were taken from a Rhizophoraspp. forest. The burrow had 9 openings and occupied a swamp surface area of 0.64 m². Passive irrigation of the burrow was investigated by recording change in conductivity of burrow water in a chamber 45 cm below the swamp surface during tidal inundation of the swamp. The chamber was completely flushed within approximately one hour, i.e. by a single tidal event. Burrow morphology was determined by means of resin casting. The investigated burrow was of discrete structure, with an overall depth of 1.2 m and a total volume of 68 l, i.e. ca. 9% of the volume of swamp soil. The below ground surface area of chambers and tunnels was 3.8 m². The mean and maximum chamber/tunnel diameter was 7 cm and 11 cm respectively. The soil in the close vicinity of the burrow was extensively penetrated by roots, and any two parts of the burrow were located no further than 20 cm away from each other. By reducing diffusion distances within the soil and by being well flushed, the burrows provide an efficient mechanism for removal of excess salt accumulated in the soil around mangrove roots due to exclusion.     

Tidal flushing of ammonium from intertidal sediments of Ria Formosa,Portugal

Ammonium concentrations were determined in near-bottom water and intertidal surface sediments collected in February and July 1993 at five stations of Ria Formosa, a shallow meso-tidal coastal lagoon in southern Portugal. At each station, samples were taken a few minutes before tidal inundation, and subsequently 2, 10, 15 and 20 minutes thereafter. Ammonium concentration in near-bottom waters increased dramatically in the first 2 minutes followed by a decrease during the 18 minutes of flooding (maximum range 10.3-2.2 M). The highest levels in the flooding water were concomitant with a decrease of extractable ammonium recorded in the upper sediment layer (2 cm). Laboratory experiments indicated that ammonium is easily extracted from the sediment solids by physical perturbation, as one would expect when tidal water flushes over the intertidal area. This perturbation results in the export of ammonium from the sediment, by pulse mechanisms of short time intervals. On a daily scale this amount is two orders of magnitude higher than transport resulting from molecular diffusion.     

Influence of surface copper content on Stenotrophomonas maltophilia biofilm control using chlorine and mechanical stress

Abstract

This work aimed to evaluate the action of materials with different copper content (0, 57, 96 and 100%) on biofilm formation and control by chlorination and mechanical stress. Stenotrophomonas maltophilia isolated from drinking water was used as a model microorganism and biofilms were developed in a rotating cylinder reactor using realism-based shear stress conditions. Biofilms were characterized phenotypically and exposed to three control strategies: 10?mg l^?1 of free chlorine for 10?min, an increased shear stress (a fluid velocity of 1.5?m s^?1 for 30s), and a combination of both treatments. These shock treatments were not effective in biofilm control. The benefits from the use of copper surfaces was found essentially in reducing the numbers of non-damaged cells. Copper materials demonstrated better performance in biofilm prevention than chlorine. In general, copper alloys may have a positive public health impact by reducing the number of non-damaged cells in the water delivered after chlorine exposure.     

黄河调水调沙对黄河口海域双酚A的影响

于2011年6—7月黄河调水调沙前、中期、后对黄河口海域双酚A(BPA)污染情况进行调查,研究了调水调沙对黄河口海域双酚A的影响。结果表明:黄河口13个站位表层海水和沉积物中均有双酚A检出,以调水调沙前测得的海水和沉积物中双酚A含量评估黄河口附近双酚A的污染程度。海水中双酚A浓度范围为13.6—64.0 ng/L,平均浓度为26.2 ng/L;沉积物中双酚A的浓度为0.559—2.73μg/kg干重,平均浓度为1.19μg/kg,是海水中平均含量的48倍。黄河河口区域海水中双酚A浓度受调水调沙影响而呈现较大变化,调水调沙后双酚A浓度明显增加,调水调沙前、后呈显著性差异(P0.01),说明陆源输入是黄河口区域中双酚A的主要污染来源。离入海口近的站位沉积物中双酚A浓度受调水调沙影响较大,呈显著性差异(P0.01),调水调沙后含量显著降低。黄河口海域已经遭受双酚A污染,存在生态安全问题。     

Increased heat requirement for leaf flushing in temperate woody species over 1980–2012: effects of chilling,precipitation and insolation

Recent studies have revealed large unexplained variation in heat requirement‐based phenology models, resulting in large uncertainty when predicting ecosystem carbon and water balance responses to climate variability. Improving our understanding of the heat requirement for spring phenology is thus urgently needed. In this study, we estimated the species‐specific heat requirement for leaf flushing of 13 temperate woody species using long‐term phenological observations from Europe and North America. The species were defined as early and late flushing species according to the mean date of leaf flushing across all sites. Partial correlation analyses were applied to determine the temporal correlations between heat requirement and chilling accumulation, precipitation and insolation sum during dormancy. We found that the heat requirement for leaf flushing increased by almost 50% over the study period 1980–2012, with an average of 30 heat units per decade. This temporal increase in heat requirement was observed in all species, but was much larger for late than for early flushing species. Consistent with previous studies, we found that the heat requirement negatively correlates with chilling accumulation. Interestingly, after removing the variation induced by chilling accumulation, a predominantly positive partial correlation exists between heat requirement and precipitation sum, and a predominantly negative correlation between heat requirement and insolation sum. This suggests that besides the well‐known effect of chilling, the heat requirement for leaf flushing is also influenced by precipitation and insolation sum during dormancy. However, we hypothesize that the observed precipitation and insolation effects might be artefacts attributable to the inappropriate use of air temperature in the heat requirement quantification. Rather than air temperature, meristem temperature is probably the prominent driver of the leaf flushing process, but these data are not available. Further experimental research is thus needed to verify whether insolation and precipitation sums directly affect the heat requirement for leaf flushing.     

污染土壤淋洗修复技术研究进展

土壤淋洗修复技术是一种行之有效的污染土壤治理技术,适合于快速修复受高浓度重金属和有机物污染土壤与沉积物。本文综述了土壤淋洗修复技术的特点、技术流程、土壤淋洗剂的研究与应用进展,指出异位土壤淋洗修复技术因修复效果稳定,易于实现系统控制和废弃物减量化等优点而具有更广阔的应用前景,天然螯合剂和生物表面活性剂等环境友好型淋洗剂正逐渐取代人工螯合剂和化学表面活性剂成为土壤淋洗剂研究的主流方向,而现代超分子化学的引入和发展有可能对复合污染土壤的高效淋洗修复研究产生新的影响。     

Patterns of tree phenological diversity in dry tropics

Recent phenological studies in tropical deciduous forests revealed a mosaic of vegetation composed of several pheno-phases that are evolved as an adaptation by the species to overcome seasonal drought in different ways. These pheno-phases represent extent of annual deciduousness (～leaflessness) and triggering factors for buds break (e.g. vegetative and flower). Thus, studying patterns of various pheno-phases (phonological diversity) in tropical forest have been thought to provide a potential tool to address critical questions related to climate change modeling and monitoring. In tropics, tree species represent a gradient of deciduousness (from leaf-exchanging species to >6 months deciduous species) and flowering initiation (breaking of flower buds in various part of annual cycle). Both processes are mostly triggered by variation in day length and/or temperature during late dry season/autumn, and/or first significant rain during rainy season. In addition, few factors like drought induced leaf fall and sporadic winter rains are supposed to affect these processes temporarily. Besides, the abundances of pheno-phases (i.e. leafing and flowering) also vary among tropical deciduous forest trees. Presence of such variations in tropical tree pheno-phases and their abundances are reported to vary due to micro-climatic variables and has specific implications in tropical forests. Present paper discusses the existing information on various pheno-phases and their abundances in tropical forests and role of climatic factors on tree phonological diversity. Further, we emphasized the need to develop predicting understanding of impending climatic change (i.e. precipitation and temperature) on diversity of pheno-phases by collecting long-term data on tree pheno-phases through a network of phonological stations in dry tropics.     

Comparison Between Tidally Driven Groundwater Flow and Flushing of Animal Burrows in Tropical Mangrove Swamps

Tidal groundwater in a mangrove swamp can return to the mangrove creek by one of two mechanisms: (a) it can either flow through the swamp soil due to the water table difference between the creek and the groundwater in the swamp; or (b) it can flow via tidal flushing of animal burrows. This paper compares the magnitude of these two mechanisms for different regions of a mangrove swamp. Direct groundwater flow rates resulting from water stored in the sediment as a consequence of infiltration, especially during and after tidal inundation, were calculated for every square meter in the surface of a mangrove forest from piezometer data. Flow rates of water due to burrow flushing were determined based on published surveys, by estimating the burrow volume and the percentage of the burrow water that is flushed at each tidal inundation. Although direct groundwater flux was found to decrease further away from the creek compared to close to the creek, it was also found to have a similar range as burrow flushing flow. Specifically, direct groundwater flow ranged from 0.004 to 0.04 m³/m²/day, whilst burrow flushing flux ranged from 0.01 to 0.04 m³/m²/day.Considering the errors involved in the experiments and calculations, these ranges can be considered as being the same and neither of the two processes can be considered as negligible compared to the other. As a consequence, surveys of groundwater processes in mangrove areas, and more generally in swamp and tidal areas where animal burrows are present, will need to consider both mechanisms. Investigations of the influence over flushing mechanisms of different residence times of the water in burrows and in the sediment body would also be recommended in order to establish salt and nutrient budget in mangrove swamps.     

引种保护植物对西双版纳极端冷年的春季物候响应

气温被普遍认为是春季物候期最主要的控制因子之一,然而低温对植物物候的影响效应一直都存在不同的观点。西双版纳由于地处热带地区的北缘,其气温相对于赤道附近的热带地区较低。自1959年以来,西双版纳热带植物园引入了来自世界各个热带地区的4万余种植物进行保护,之前的研究证明西双版纳的低温对这些引种植物的生长有很大影响。因此,1974年西双版纳出现的极端低温势必对引种植物造成极大威胁,同时也是对这些植物低温适应能力的一个考验。通过对比43种引种植物物候期（生长抽梢期与开花期）在1974年与常年的差异情况,分析不同来源（热带亚洲、热带美洲与热带非洲）引种植物对西双版纳低温的适应性。结果表明,经历西双版纳1974年初的极端低温之后,使81%的引种植物生长抽梢期提前,同时也造成35%的引种植物在该年没有开花;而植物生长抽梢提前的主要原因则是极端低温以及低温过后气温迅速回升。引种植物均能顺利度过1974年的最冷时期,并出现生长抽梢物候,这意味着引种植物在经历极端低温之后都能够进行正常的生长活动,但极端低温对引种植物繁殖活动的不利影响大于其对生长活动的影响;引种植物对西双版纳极端低温的适应能力由大到小顺序依次为：亚洲来源植物〉美洲来源植物〉非洲来源植物。因此在迁地保护植物的选择过程中,应多选择亚洲热带植物,其次为美洲热带植物,而对非洲热带植物的引入则需谨慎考察。