Courting virtual rivals increase ejaculate size in sticklebacks (<Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis>)

Sperm competition occurs when sperm of two or more males compete to fertilize a given set of eggs. Game-theory models of sperm competition predict that males, which face an increased risk of sperm competition, will invest more sperm in a mating. In the pair-spawning three-spined stickleback ( Gasterosteus aculeatus), males attempt to steal fertilizations (i.e. to sneak) when they are in the courting phase, but not when they are parental. The behaviour of neighbouring males may therefore indicate the risk of sperm competition. We visually confronted males before spawning with computer animations of the same virtual stickleback showing two different behaviours: either courting (high risk of sperm competition) or brood-caring (low risk of sperm competition). We show that males invest significantly more sperm (absolutely and relatively with respect to available sperm in the testes) after the courting stimulus. The relative investment ratio between the courting and the brood-caring treatment was on average 1.75. Three-spined sticklebacks thus seem to assess the risk of sperm competition by the behaviour of neighbours and to adjust their ejaculate accordingly. This result suggests that the evolutionary force of sperm competition has led to precise mechanisms of future risk assessment.     

Total mercury determination in sand boxes from Montreal

Direct mercury analysis was successfully applied to determine trace levels of total mercury in samples from sand boxes in Montréal (Québec, Canada). Twenty sand boxes were sampled from across the city and divided into two size fractions, a fine fraction (<100 microm) and a whole fraction. The concentrations of mercury ranged from 1.6 to 35 microg Hg kg(-1) dry soil for the fine fraction and from 0.7 to 6 microg Hg kg(-1) dry soil for the whole fraction. The mercury concentrations correlated with the soil organic carbon content (R2= 0.67) in the sand. The ratio of the concentration of mercury in the fine over the whole fraction varied from 2.2 to 18. Using published soil ingestion rates for children, the calculated daily intake values varied from 0 to 0.5 ng Hg kg(-1) bw d(-1) with an estimated oral ingestion of 200 mg of sand and from 0.2 to 4.7 ng Hg kg(-1) bw d(-1) with an ingestion of 1750 mg of sand. None of the sand boxes contain sufficient amounts of mercury so as to exceed the currently accepted daily intake threshold of 0.105 microg Hg kg(-1) bw d(-1) established by Health Canada.     

Towards a roadmap for sustainable land use in Europe

Regional Environmental Change -     

Calcareous electrochemical precipitation,a new method to trap nickel in seawater

There are few efficient, rapid and cheap methods to remove toxic metals from contaminated waters. Here we hypothesised that cathodic protection, an existing method used to control the corrosion of metallic structures, may trap toxic metals. Indeed, in seawater, the application of a cathodic current on a metallic structure induces the precipitation of limestone (CaCO₃) and magnesium dihydroxyde (Mg(OH)₂), thus forming a calcareous deposit on the metal surface. We therefore presumed that such calcareous deposit may trap metals dissolved in waters. Actually calcareous deposit formation has never been studied in the presence of dissolved metallic contaminants such as nickel. Here we tested ionic nickel (Ni²⁺) precipitation in calcareous deposit with a galvanized steel electrode by spiking artificial seawater with a NiCl₂ salt during 7 days of applied current. We analysed deposit surface and cross section by µ-Raman spectroscopy and scanning electron microscopy (SEM) with X-ray microanalysis. Ni concentration in the deposit was quantified by inductively coupled plasma analysis, after deposit dissolution in 60% HNO₃. Results show that in 7 days up to 24% of nickel can be trapped in the calcareous deposit. Scanning electron microscopy reveals that Ni is trapped under a pure CaCO₃ layer of aragonite. Raman spectra show that nickel is incorporated as nickel dihydroxyde (Ni(OH)₂), as evidence by vibration bands at 446 and 510 cm^?1. Overall our findings disclose a new and efficient method, calcareous electrochemical precipitation, which has potential applications to remove toxic metals from contaminated waters.     

河岸蜘蛛——多样水生生态系统中PCB污染的指示生物

栖息在河岸的蜘蛛越来越多地被用来追踪水生生态系统中存在和流出污染物的空间格局。然而,我们对蜘蛛在何种情况下可有效标志水生污染的认识有限。本研究力证在具有高生境异质性的水生生态系统中,能够有效地利用河岸蜘蛛来追踪沉积物中多氯联苯(PCBs)污染的空间格局。2011年到2013年,在五大湖共同关注区(AOC)的Manistique河流域,对2类常见科属的河岸蜘蛛进行采样,结果表明生物体内的ΣPCB浓度的空间格局能够普遍地追踪采样点范围内沉积物中ΣPCBs的空间变化。该研究区域位于密歇根北部半岛南岸(Manistique,MI,US),是一个河口生态系统,包括港口、河流、回水和湖泊等栖息地。沉积物ΣPCB浓度用总有机碳浓度进行归一,解释了11个采样点中41%的以脂类归一的蜘蛛ΣPCB浓度变异。此外,2类常见河岸蜘蛛类群(园蛛科Araneidae和长脚蛛科Tetragnathidae)的ΣPCB浓度高度相关(r² > 0.78),并且按全年计算其平均ΣPCB浓度两者相似。结果表明,在异质性的水生生态系统中,例如在河流入海口,会因为栖息地和污染物变化在水生生物分类中的差别不明显,河岸蜘蛛就可能成为水生和河岸食物网中PCB有效性的标记物。此外,对于为不同种群大型结网蜘蛛提供生存条件的海岸线开发和沿岸植被的生境异质性,目前的方法具有很强的适用性。
精选自Kraus, J. M., Gibson, P. P., Walters, D. M. and Mills, M. A. (2017), Riparian spiders as sentinels of polychlorinated biphenyl contamination across heterogeneous aquatic ecosystems. Environmental Toxicology and Chemistry, 36: 1278–1286. doi: 10.1002/etc.3658
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.3658/full
     

Carbon border adjustment mechanism in the transition to net-zero emissions: collective implementation and distributional impacts

As an instrument to minimize carbon leakage, the effects and feasibility of Carbon Border Adjustments Mechanism (CBAM) will depend on multiple design options. While the EU has committed to introducing CBAM as part of its green climate deal, pursuing climate efforts to successfully limit global warming requires a collective implementation involving major emitters China and the US. This paper quantifies the distributional impacts of a joint CBAM implementation of in a climate alliance or a club of the EU, the US, and China. Differing from a myriad of studies that focus on unilateral CBAM, this analysis emphasizes collective implications on leakage, sectoral competitiveness, and welfare by projecting climate neutrality relative to current policies and climate targets. Our findings confirm that coalition reduces leakage, improves production on energy-intensive industries, and increases club’s welfare relative to a non-CBAM and a unilateral implementation. These are in contrast with some unilateral analytical studies, especially for the US. It is further proof of the potential of CBAM as collective instruments to facilitate mitigation and trade competitiveness.

     

Quantifying disturbance effects on vegetation carbon pools in mountain forests based on historical data

Although the terrestrial carbon budget is of key importance for atmospheric CO₂ concentrations, little is known on the effects of management and natural disturbances on historical carbon stocks at the regional scale. We reconstruct the dynamics of vegetation carbon stocks and flows in forests across the past 100 years for a valley in the eastern Swiss Prealps using quantitative and qualitative information from forest management plans. The excellent quality of the historical information makes it possible to link dynamics in growing stocks with high-resolution time series for natural and anthropogenic disturbances. The results of the historical reconstruction are compared with modelled potential natural vegetation. Forest carbon stock at the beginning of the twentieth century was substantially reduced compared to natural conditions as a result of large scale clearcutting lasting until the late nineteenth century. Recovery of the forests from this unsustainable exploitation and systematic forest management were the main drivers of a strong carbon accumulation during almost the entire twentieth century. In the 1990s two major storm events and subsequent bark beetle infestations significantly reduced stocks back to the levels of the mid-twentieth century. The future potential for further carbon accumulation was found to be strongly limited, as the potential for further forest expansion in this valley is low and forest properties seem to approach equilibrium with the natural disturbance regime. We conclude that consistent long-term observations of carbon stocks and their changes provide rich information on the historical range of variability of forest ecosystems. Such historical information improves our ability to assess future changes in carbon stocks. Further, the information is vital for better parameterization and initialization of dynamic regional scale vegetation models and it provides important background for appropriate management decisions.     

Habitat Loss and Changes in the Species-Area Relationship

Abstract: The species-area relationship (SAR) has been used successfully to predict extinction from extent of habitat reduction. These extinction estimates assume that species have uniformly distributed range requirements and a minimum abundance level required for persistence; how many species are lost depends solely on how much habitat is removed, not on where it is removed. We consider another limiting case in which range requirements, rather than abundances, determine extinctions. We used a new method for constructing SARs based on assumptions about geographic ranges of species. Our results show that habitat destruction can change the SAR and consequently the number of species predicted to be lost due to habitat destruction. Our method generates SARs that vary in shape according to the specific distributions of geographic range and occupancy but that have the common feature of being described by a power law with an exponent of <1. When the geographic range of species was included in the SAR, the way habitat was lost became important. Although the SAR before habitat destruction is often used to predict species loss after habitat destruction, assumptions must be clearly stated. To predict the damage caused by habitat loss with our model, it is necessary to know the fraction of aggregated species, the distribution of geographic ranges, the form of habitat destruction, and the sampling protocol. The remaining theoretical challenge is to develop a full theory that links abundance and range.     

大鼠类Alu重复序列的克隆及其在染色体DNA突变分析中的应用

从大鼠低Ｃｏｔ值ＤＮＡ文库分离到一种类Ａｌｕ的重复序列,命名为ＲＡＬＲＳ－１。对ＲＡＬＲＳ－１克隆并进行了测序,长度为２８３ｂｐ,发现其中含有单一的微卫星（ｍｉｃｒｏｓａｔｅｌｌｉｔｅ）序列ＡＧ,ＡＧＧ和ＡＧＧＧ。ＲＡＬＲＳ－１ＤＮＡ序列在大鼠单倍体基因组中的拷贝数为１５００００～３３００００。依ＲＡＬＲＳ－１中的一段序列合成了一２８寡核苷酸探针（ＡＧＧＧ）７,对大鼠正常组织和肿瘤组织ＤＮＡ指数谱