Cu在扇贝组织中的蓄积及其对酶活性的影响

采用暴露实验方法，研究了不同浓度的Cu（Cu^2＋）对栉孔扇贝（Chlamys farreri）鳃、肌肉、内脏团组织中Cu蓄积量及过氧化氢酶（CAT）活性的影响．结果表明：随水体中Cu浓度的升高，扇贝各组织中Cu蓄积量明显上升，Cu蓄积量顺序为：内脏〉鳃〉肌肉．Cu浓度对栉孔扇贝各组织中过氧化氢酶（CAT）活性均有明显影响，各组织中酶活性均随Cu浓度升高表现为抑制-诱导-抑制的规律．这表明，栉孔扇贝各组织中CAT酶对水体中Cu污染反映敏感，存在计量-效应关系，对海洋Cu早期污染具有指示作用．图2表1参19     

Effects of long-term nitrogen addition and precipitation changes on CH4 flux in an alpine steppe北大核心CSCD

土壤是甲烷(CH4)重要的源和汇.氮沉降和降水格局变化正在急剧改变土壤碳循环,进而可能对土壤CH4通量造成深刻影响.高寒生态系统是巨大的碳库,对氮沉降和降水变化十分敏感.然而,目前多数研究集中在短期实验上,缺乏对长期氮沉降和降水变化背景下CH4通量的响应及其调控因素的认识.以青藏高原高寒草原为研究对象,在2013年搭建模拟氮沉降和降水格局改变实验平台.基于静态箱–气相色谱法测定2020年生长季(5-10月)土壤CH4通量.结果显示,高寒草原土壤呈CH4的汇.氮添加没有显著改变生长季和植物生长高峰CH4通量.然而,降水变化显著改变了生长季和植物生长高峰CH4通量,其中降水增加(+50%降水)降低了CH4的吸收(分别为–16%和–45%),降水减少(–50%降水)增强了CH4的吸收(分别为+73%和+33%).进一步研究发现,与植物属性和功能基因丰度相比,土壤环境因子主导了CH4通量变化(解释率>90%).其中CH4通量与土壤含水量和温度显著正相关,与土壤pH显著负相关.综上所述,在未来全球变化情景下,降水格局改变更能调节青藏高原高寒草原CH4通量的变化.(图6表1参37)     

Empirical likelihood confidence intervals for adaptive cluster sampling

Adaptive cluster sampling (ACS) is an efficient sampling design for estimating parameters of rare and clustered populations. It is widely used in ecological research. The modified Hansen-Hurwitz (HH) and Horvitz-Thompson (HT) estimators based on small samples under ACS have often highly skewed distributions. In such situations, confidence intervals based on traditional normal approximation can lead to unsatisfactory results, with poor coverage properties. Christman and Pontius (Biometrics 56:503–510, 2000) showed that bootstrap percentile methods are appropriate for constructing confidence intervals from the HH estimator. But Perez and Pontius (J Stat Comput Simul 76:755–764, 2006) showed that bootstrap confidence intervals from the HT estimator are even worse than the normal approximation confidence intervals. In this article, we consider two pseudo empirical likelihood functions under the ACS design. One leads to the HH estimator and the other leads to a HT type estimator known as the Hájek estimator. Based on these two empirical likelihood functions, we derive confidence intervals for the population mean. Using a simulation study, we show that the confidence intervals obtained from the first EL function perform as good as the bootstrap confidence intervals from the HH estimator but the confidence intervals obtained from the second EL function perform much better than the bootstrap confidence intervals from the HT estimator, in terms of coverage rate.     

Life history costs of olfactory status signalling in mice

Large body size confers a competitive advantage in animal contests but does not always determine the outcome. Here we explore the trade-off between short-term achievement of high social status and longer-term life history costs in animals which vary in competitive ability. Using laboratory mice, Mus musculus, as a model system, we show that small competitors can initially maintain dominance over larger males by increasing investment in olfactory status signalling (scent-marking), but only at the cost of reduced growth rate and body size. As a result they become more vulnerable to dominance reversals later in life. Our results also provide the first empirical information about life history costs of olfactory status signals. Received: 15 December 1999 / Revised: 6 June 2000 / Accepted: 24 June 2000     

New aspect in seagrass acclimation: leaf mechanical properties vary spatially and seasonally in the temperate species Cymodocea nodosa Ucria (Ascherson)

Seagrasses may acclimate to environmental heterogeneity through phenotypic plasticity. In contrast to leaf morphology, which has been a central point in seagrass acclimation studies, plasticity in leaf biomechanics and fibre content is poorly understood, despite being crucial in plant ecological performance, especially regarding physical forces. We hypothesised that mechanical traits (e.g. breaking force, strength, toughness, and stiffness) and fibre content of seagrass leaves vary as morphology does under differential environments. Cymodocea nodosa was seasonally monitored at three locations around Cádiz Bay (southern Spain) with hydrodynamic regime as the most noticeable difference between them. Leaves showed plasticity in both morphology and mechanical traits, with wave-exposed individuals presenting short but extensible and tough leaves. Leaf fibre content was invariant along the year and with little spatial variability. Cross-sectional area rather than material properties or fibre content differentiates leaf mechanical resistance. Seagrass capacity to thrive under a range of mechanical forces may be dictated by their plasticity in morpho-biomechanical traits, a key element for the hydrodynamical performance and, hence, for species colonisation and distribution.     

Evidence for division of labor in the social caterpillar Eucheira socialis (Lepidoptera: Pieridae)

The caterpillars of Eucheira socialis westwoodi cooperatively spin and maintain a hollow silken nest and an elaborate network of silken foraging trails on their host plant, madrone (Arbutus spp.: Ericaceae). Nests typically contain several hundred larvae. Two populations are known to harbor a sex ratio distorter. The primary sex ratio in these two populations for four generations has been exceedingly male biased (64–79% male). Lepidoptera larvae are easily sexed using external morphology, allowing us to uniquely mark male and female larvae and to assemble larval groups of particular sex ratios. We report here the results of experiments on sex-specific larval behavior and physiology and the effect of colony sex ratio on individual behavior. We found that male larvae spent more time spinning silk on the nest and less time feeding than female larvae. Males were the first to emerge from the nest and the first to venture out along trails to feed. Male-biased nests had a significantly greater amount of silk deposited on their surfaces than female-biased nests. In the field, male-biased nests produced heavier male and female pupae than female-biased nests. Male and female larvae in 75% male nests became active earlier than males and females in other sex ratio treatments. Received: 11 September 1998 / Received in revised form: 24 February 1999 / Accepted: 27 March 1999     

Uncertainty, learning, and the optimal management of wildlife

Wildlife management is limited by uncontrolled and often unrecognized environmental variation, by limited capabilities to observe and control animal populations, and by a lack of understanding about the biological processes driving population dynamics. In this paper I describe a comprehensive framework for management that includes multiple models and likelihood values to account for structural uncertainty, along with stochastic factors to account for environmental variation, random sampling, and partial controllability. Adaptive optimization is developed in terms of the optimal control of incompletely understood populations, with the expected value of perfect information measuring the potential for improving control through learning. The framework for optimal adaptive control is generalized by including partial observability and non-adaptive, sample-based updating of model likelihoods. Passive adaptive management is derived as a special case of constrained adaptive optimization, representing a potentially efficient suboptimal alternative that nonetheless accounts for structural uncertainty.     

Persistent organochlorine compounds in soils and sediments of European high altitude mountain lakes

The composition of persistent organochlorine compounds (OC) in soils and sediments from two high altitude European mountain lakes, Redon in the Pyrenees and Ladove in the Tatra mountains, has been studied. Sediment cores from two additional lakes in the Tatra mountains, Starolesnianske Pleso and Dlugi Staw, have also been examined. DDTs (1.7-13 ng g(-1)) were the most abundant OC in soils followed by total polychlorobiphenyls (PCBs; 0.41-1.5 ng g(-1)) and hexachlorobenzene (HCB; 0.15-0.91 ng g(-1)). In sediments, the dominant OC were also DDTs (3.3-28 ng g(-1)) and PCBs (2.3-15 ng g(-1)). These concentrations are low, involving absence of major pollution sources in these high mountain regions. The downcore OC profiles in soils and sediments were similar but higher concentrations and steeper vertical gradients were observed in the latter. Radiometric determinations showed absence of significant OC transport from catchment to lake. The sediment-soil difference points therefore to a better retention of the OC load in sediments than soils which may be related to the low temperatures that are currently encountered at the bottom of the lake water column and the depletion of sediment bioturbation in these cold environments. Significant qualitative changes in the soil PCB distributions are observed downcore. These involve a dominance of the high molecular weight congeners in the top core sections and those of lower weight (i.e. less chlorinated) in the bottom. Anaerobic dechlorination of higher molecular weight congeners occurring in microsites, e.g. as observed in flooded or poorly drained soils, could be responsible for these changes. This process could be concurrent to bioturbation.     

The solid-phase controls on the mobility of heavy metals at the Copper Cliff tailings area, Sudbury, Ontario, Canada

The Copper Cliff Tailings Disposal Area, located near Sudbury, Ontario, covers an area of approximately 2200 ha and constitutes more than 10% of the total area of all mine tailings in Canada. The area has been utilized since 1936, receiving sulphide-containing tailings from the Inco Sudbury operations. Field measurements of pore-gas oxygen and carbon dioxide in the vadose zone indicate that sulphide oxidation has progressed to depths of 1.6 m to 1.7 m within the tailings. The oxidation of sulphide minerals within the vadose zone, and the accompanying dissolution of carbonate and aluminosilicate minerals within these tailings releases SO₄, Fe(II) and other metals to the pore water. In the vadose and saturated zones, concentrations of Fe and Ni exceed 10100 mg/l and 2210 mg/l, respectively. These high concentrations of dissolved metals are attenuated by a series of precipitation, coprecipitation and adsorption reactions. The precipitation of secondary sulphate and hydroxide phases also create hardpan layers at or near the oxidation front. Geochemical modelling of the pore-water chemistry suggests that pH-buffering reactions are occurring within the shallow oxidized zones, and that secondary-phase precipitation is occurring at or near the underlying hardpan and transition zones. Mineralogical study of the tailings confirmed the presence of jarosite, gypsum and goethite within the shallow tailings, suggesting that these phases are controlling the dissolved concentrations of Fe, SO₄ and Ca. Extraction experiments conducted on the tailings solids indicate that the constituents contained in the water-soluble fraction of the shallow, weathered tailings are derived from the original pore water and the dissolution of highly soluble phases such as gypsum. The acid-leachable fraction of the weathered tailings accounts for up to 25% of the heavy metals, and the reducible fraction may contain up to 100% of the heavy metals within the shallow, weathered tailings. Based on the pore water profiles and the geochemistry of the tailings solids, a relative mobility scale of Fe=Mn=Ni=Co>Cd Zn>Cr=Pb>Cu can be determined.