Comparative study of the effects of temperature,salinity and oxygen tension on the rates of oxygen consumption of nauplii of different strains of Artemia

The effects of temperature, salinity and oxygen tension on the rates of oxygen consumption of three different strains of Artemia nauplii have been studied. When acclimated to a salinity of 30, nauplii from each of the three strains were able to maintain approximately constant rates of oxygen consumption over a wide range of oxygen tension. The ability to maintain respiratory independence during hypoxia was reduced, however, with an increase in either temperature or salinity. Nauplii of two of the strains (parthenogenetic diploid and tetraploid) showed a progressive increase in the rate of oxygen consumption with increasing temperature up to 35°C. Nauplii of the bisexual strain appeared to be less tolerant of exposure to temperatures >30°C, since at higher temperatures their oxygen consumption declined slightly. The differences between the nauplii of the different strains in their physiological responses to changing environmental conditions appear to correlate well with their seasonal occurrence in the field.     

地下水水化学成分对类Fenton法氧化硝基苯的影响

实验主要研究了地下水水化学成分对类Fenton法氧化去除硝基苯的影响。采用天然细砂模拟地下含水层介质,利用砂样中的原位铁做催化剂进行类Fenton氧化硝基苯实验。通过不同硝基苯和过氧化氢摩尔比的类Fenton实验,确定两者的最优物质的量比。然后模拟配制Na-SO4、Na-Cl、Ca-HCO3和Ca-SO4型4种水化学成分不同的地下水,在硝基苯和过氧化氢最优物质的量比情况下,研究了地下水水化学成分对类Fenton法氧化去除地下水中硝基苯的影响。反应在棕色瓶中进行,并用20℃恒温培养振荡器,以120 r.min-1的频率对其振荡。分别在10、30、60、90和120 min时取样,用气相色谱法检测硝基苯的质量浓度。结果表明：硝基苯和过氧化氢的最佳物质的量比为1∶200;地下水的水化学成分对类Fenton反应有重要影响,Na-SO4、Na-Cl、Ca-HCO3和Ca-SO4型地下水中硝基苯的最终去除率分别约为91%、92%、75%、82%,反应所需的时间大约为90、30、120和30 min。因此,类Fenton法对硝基苯污染地下水的原位化学修复具有较好效果,研究结果可为硝基苯污染地下水的原位化学修复提供一定的理论依据。     

Effects of simulated deposition of dredged material on structure of nematode assemblages – the role of burial

A microcosm experiment was designed to evaluate the effects of the simulated deposition of uncontaminated dredged material on nematode assemblages from estuarine intertidal mud. The main objective was to assess the ability of nematodes to migrate vertically into native muddy and non-native sandy sediment deposited in different amounts and frequencies. Results from univariate and graphical methods of data-evaluation revealed that nematodes were capable of migrating over a wide depth range from the bottom mud layer into the top layer of deposited sand and mud. A diverse mud assemblage of nematodes was able to survive in non-native fine sand for the experimental period of 2 mo. Multivariate analyses showed that the amount of deposit and the frequency of deposition were interactive factors. A high amount of sediment deposited once at the beginning of the experiment caused more severe changes in assemblage structure than the same amount deposited in more frequent but smaller doses. The response of most species to the experimental treatments appeared to be an integrated response to the enhancing effect of food input accompanying the deposit and the negative effect of burial. Upward migration of nematodes is a process which has often been underestimated in its importance for recolonisation of areas where uncontaminated dredged material is deposited. Active migration of nematodes can significantly affect the recovery of a dredgings disposal site. Received: 29 July 1999 / Accepted: 17 January 2000     

云南地区种子植物区系属的多度及区系过渡性的空间分布格局

植物区系地理分布格局的研究有助于更好地理解植物区系的起源、迁移和分化。研究利用覆盖云南地区全境的植物区系分布信息,探讨了云南地区植物区系属的多度及区系过渡性的地理分布格局。结果表明,所有热带区系属的多度均随着纬度升高呈递减趋势;大多数温带区系属的多度随着纬度的升高呈递增趋势。中亚分布(T13)属的多度的高值主要出现在滇西北地区,尤其是在金沙江、澜沧江和怒江的上游地区,但在其它地区十分少见。地中海、西亚至中亚分布(T12)属的多度的高值也出现在滇西北地区,但在其它地区无明显空间分布规律;中国特有分布(T15)属在滇西北地区最为丰富,其次是滇东南地区,大致以"田中线"为界,界线以西地区的中国植物特有属的多度明显低于界线以东地区。从南到北,植物区系过渡性基本上呈单调递增格局,这一格局的形成可能与区系成分的迁移和地形格局有关。大理州以南的低海拔地区,热带区系成分占据主导地位,并占据了云南大部分的土地面积,这在一定程度上证实了云南地区总体上是一个"热带山原"的假说。本研究与其它研究的不同可能源于与源数据和取样尺度的差异。     

Optimal Marking of Threatened Species to Balance Benefits of Information with Impacts of Marking

Abstract: Marking animals so that they are uniquely identifiable provides information that may assist conservation efforts. Nevertheless, some methods used to mark animals can be harmful. We used mathematical methods to assess the trade‐off between the impact of marking threatened species and the value of the information gained. We considered the case where 2 management strategies, each aiming to improve a species' survival rate, are implemented in an experimental phase. The results of the experiment were applied in a postexperimental management phase. We expressed the expected number of survivors in both phases mathematically, accounting for any mortality caused by the experiment, and determined the proportion of animals to mark to maximize this number. The optimal number of animals to mark increased with the number of individuals available for the experiment and with the number of individuals to be managed in the future. The optimal solution was to mark only 25% of the animals when there were 1000 individuals available for the experiment, the results were used to manage 2000 individuals, and marking caused mortality of 1%. Fewer animals were marked when there were fewer animals in either phase or when marking caused higher mortality. In the case of the Helmeted Honeyeater (Lichenostomus melanops cassidix), the optimal proportion to mark was <1 if the mortality rate was >0.15%–1%, with the threshold depending on the number of animals in the experimental and postexperimental phases. The trade‐off between gaining more information about a species and possibly harming individuals of that species by marking them is difficult to assess subjectively. We show how to determine objectively the optimal proportion of animals to mark to enhance the management of threatened species.     

How the diversity of human concepts of nature affects conservation of biodiversity

Protecting nature has become a global concern. However, the very idea of nature is problematic. We examined the etymological and semantic diversity of the word used to translate nature in a conservation context in 76 of the primary languages of the world to identify the different relationships between humankind and nature. Surprisingly, the number of morphemes (distinct etymological roots) used by 7 billion people was low. Different linguistic superfamilies shared the same etymon across large cultural areas that correlate with the distribution of major religions. However, we found large differences in etymological meanings among these words, echoing the semantic differences and historical ambiguity of the contemporary European concept of nature. The principal current Western meaning of nature in environmental public policy, conservation science, and environmental ethics–that which is not a human artifact–appears to be relatively rare and recent and to contradict the vision of nature in most other cultures, including those of pre-Christian Europe. To avoid implicit cultural bias and hegemony–and thus to be globally intelligible and effective–it behooves nature conservationists to take into account this semantic diversity when proposing conservation policies and implementing conservation practices.     

Field assessment of effects of timing and frequency of copper pulses on settlement of sessile marine invertebrates

 CuSO₄-treated plaster blocks were used to create localised concentrations of copper significantly above ambient levels. Between October 1996 and March 1997 we used this system to manipulate the timing and frequency of transient copper-pollution events close to settlement plates. We assessed the impacts on the development of assemblages of sessile marine invertebrates that occur on hard substrates at Breakwater Pier in Williamstown, Victoria, Australia. Barnacle densities were reduced by up to one-third, while serpulid polychaetes were insensitive. Assemblages at different stages of development were differentially sensitive to short-term pulses. Reductions in sponge and scyphozoan polyp densities were greatest (50%) when pulse-pollution events occurred at times of high settlement. If a pulse copper-pollution event occurred in the first week of substrate becoming available for colonisation, then it had few observable impacts on recruitment for all invertebrates examined. When the first pulse occurred in the first week of the experiment there was no difference between the impacts of single or double-pulse exposures to the toxicant. Received: 4 January 2000 / Accepted: 1 August 2000     

Ecological Attributes of Extinction-Prone Species: Loss of Freshwater Fishes of Virginia

I examined patterns of extirpation among Virginia's 197 historically native freshwater fish species to address the following questions: (1) Are extinction-prone species ecologically distinct? and (2) Are distinctive features similar to those identified for extinction-prone species in terrestrial systems? All species were assigned to categories for a series of attributes reflecting geographical distribution, habitat use, trophic habits, life history, size, and reproductive behavior. Associations between species that had been extirpated and those that had not were examined for each attribute. Univariate associations were observed between extirpation and three ecological attributes: diadromy, limited physiographic range, and limited range of water sizes. Species specialized with respect to multiple ecological attributes also were especially likely to be extirpated. These associations reflected the effects of reduced habitat area and increased isolation (insularization), which are also important determinants of extinction in terrestrial systems. Multivariate analyses suggested that extirpated species were ecologically similar to each other, but were not completely distinct from the nonextirpated fauna. My results suggest that ecological knowledge of species can help identify extinction-prone species and provide a basis for proactive conservation. Current approaches to conservation, which are largely reactive and piecemeal, are inadequate to protect biodiversity. Because aquatic degradation is complex and pervasive, conservation of aquatic biodiversity requires proactive comprehensive approaches to water resource management, including emphasis on protecting the ecological integrity of entire systems.     

甲苯二异氰酸酯(TDI)致癌性的综合评估

甲苯二异氰酸酯(TDI)被数家机构分类为可能的人类致癌物,其主要依据为动物实验发现对啮齿动物经灌胃暴露TDI后肿瘤发生率升高。基于研究结果的可靠性以及一致性,综合评估了现有研究数据是否支持这一分类。结果显示现有的流行病学数据不足以有力证明TDI为人类致癌物。动物实验研究表明,吸入接触TDI并不导致肿瘤发生。经灌胃暴露后观察到的肿瘤很可能是由于TDI转化为已知的啮齿动物致癌物甲苯二胺(TDA)所致。在TDI吸入暴露的体内实验中,当由TDI转化生成的TDA不能达到具有显著生物学效应的浓度时,TDI对啮齿动物或人类都没有遗传毒性。由于哺乳动物在生理性接触条件下TDI不能转变成TDA,所以对人类而言,TDI接触与致癌效应之间无直接的显著因果关系。因此虽然在如灌胃等非生理暴露的条件下,TDI可能的人类致癌物的分类是正确的,但本文对其致癌研究数据的合理评估和正确理解有助于将产品监管力度集中于与职业暴露更相关的有害健康效应上。     

Ecological applications of multilevel analysis of variance

A Bayesian representation of the analysis of variance by A. Gelman is introduced with ecological examples. These examples demonstrate typical situations encountered in ecological studies. Compared to conventional methods, the multilevel approach is more flexible in model formulation, easier to set up, and easier to present. Because the emphasis is on estimation, multilevel models are more informative than the results from a significance test. The improved capacity is largely due to the changed computation methods. In our examples, we show that (1) the multilevel model is able to discern a treatment effect that is smaller than the conventional approach can detect, (2) the graphical presentation associated with the multilevel method is more informative, and (3) the multilevel model can incorporate all sources of uncertainty to accurately describe the true relationship between the outcome and potential predictors.     

赤红壤贮水量变化过程的聚类分析研究

根据长期定位观测资料．用多元数据分析的有序样本分类中的最优分割法对南亚热带地带性土壤──赤红壤的土壤水分贮水量的变化过程进行聚类分析并进行土壤水分的季节划分，结果表明．赤红壤贮水量最高贮量出现在3～7月，最低出现在1～2月和10～12月，而8～9月为干湿交替变化的过渡阶段．     

水稻对UV-B辐射响应的敏感性差异

综述了UV-B辐射对水稻（Oryza sativa L.）的影响和水稻对UV-B辐射的抗性机制。UV-B辐射对水稻生长、叶片形态、生物量、产量、光合系统、病害等产生一定的影响。水稻对UV-B辐射的敏感性因子主要有CPD光解酶、UV-B吸收物质、抗氧化酶等。UV-B辐射使水稻叶片中产生了ROS,导致Rubisco酶降解,光合色素含量变化,抑制了光合作用,最终影响水稻籽粒形成和产量。水稻对UV-B辐射响应存在着品种差异,CPD光解酶编码基因的自然突变会引起水稻UV-B敏感性的差异,CPD光解酶活性是水稻对UV-B敏感性的关键因素。通过建立响应指数公式,对水稻UV-B响应敏感性的品种差异进行评估,存在品种差异的原因主要是基因、生长、生理、生育期和环境背景的差异。最后对UV-B辐射对水稻的影响、水稻对UV-B响应的差异及机理有待深入研究的方向进行了展望。     

麻疯树种仁油粕脱毒

为获得经冷榨脱油后麻疯树油粕最佳的脱毒方法,采用超声提取,运用四因素三水平正交实验,考察了脱毒温度、脱毒时间、脱毒次数以及脱油后种仁与乙醇料液比对脱毒效果的影响.结果显示,最佳的脱毒方法为料液比8:1,40℃,超声3次,每次20 min.该方法处理后麻疯树油粕中佛波酯含量为0.011 mg g-1.脱毒后的麻疯树油粕对小鼠的急性毒性实验显示,小鼠无死亡,体重增长正常,未出现中毒症状,初步表明脱毒方法有效.图2表3参9     

Contribution of black carbon to nonlinearity of sorption and desorption of acetochlor on sediment

In order to investigate the contribution of various black carbon (BC) contents to nonlinearity of sorption and desorption isotherms for acetochlor on sediment, equilibrium sorption and desorption isotherms were determined to measure sorption and desorption of acetochlor in sediment amended with various amounts of BC. In this paper, two types of BC referred to as BC400 and BC500 were prepared at 400°C and 500°C, respectively. Higher preparation temperature facilitated the formation of micropores on BC to enhance its sorption capacity. Increase of the BC content obviously increased the sorption amount and reduced the desorption amount for acetochlor. When the BC500 contents in total organic carbon (TOC) increased from 0 to 60%, Freundlich sorption coefficient (K _f) increased from 4.07 to 35.74, and desorption hysteresis became gradually obvious.When the content of BC in TOC was lower than 23%, the sorption isotherm had a significant linear correlation (p = 50.05). In case of desorption, a significant nonlinear change could be observed when the content of BC was up to 13%. Increase of BC content in the sediment would result in shifting the sorption-desorption isotherms from linearity to nonlinearity, which indicated that contribution of BC to nonlinear adsorption fraction became gradually remarkable.     

A Critique of the Recovery of Greenback Cutthroat Trout

Abstract: There are no examples of recovery of fish listed under the U.S. Endangered Species Act, but the number of federally threatened greenback cutthroat trout (  Oncorhynchus clarki stomias ) populations is approaching the delisting goal. We evaluated recovery of this subspecies in light of developing theory in conservation biology and with regard to recovery of other salmonids in the inland western United States. Four of the five criteria used to define populations that would count toward delisting appeared to underestimate the risk of extinction of those populations. Typically, recovery goals for numbers of greenback cutthroat trout populations were less stringent than those for other inland salmonids petitioned for listing or listed as threatened under the Endangered Species Act and were comparable to those for a federally endangered species. Before delisting is considered, we propose that historical populations be replicated in additional waters to protect genetic diversity and that existing populations be enlarged to reduce their vulnerability to demographic variation, to increase their access to refugia, and to permit reestablishment of mobile life histories. Existing stocks should also be evaluated to determine whether they represent distinct population segments.     

Comparative measurement of the redox potential of marine sediments as a rapid means of assessing the effect of organic pollution

A rapid method for measuring the redox potential (Eh) values of marine sediments is described. This method has been used to relate changes in the areas of highly reduced sediment in a sea loch system to the continuously fluctuating inputs of organic waste from a pulp and paper mill. Subsequent faunal changes in these areas can be related to changes in the measured sedimentary redox level. The method is suggested as a rapid means of assessing the potential impact of an additional organic input to a marine sediment.     

Effects of predation risk and hunger on the behaviour of two species of tadpoles

Predation and hunger are threats for most organisms, and appropriate behavioural responses to both factors should be shaped by natural selection. In combination, however, the behavioural demands of predation avoidance and effective foraging often cannot be satisfied at the same time and lead to a conflict within organisms. We examined the behavioural responses of two closely-related species of tadpoles, Rana lessonae and R. esculenta, to simulated predation by fish and hunger. Tadpoles, hatched and reared in the laboratory, were tested in a three-way factorial (predation risk × hunger × species) experiment with four predation levels and four hunger levels. Both species decreased their swimming activity with increasing predation risk. Predation risk did not influence the amount of activity time invested in feeding but caused the tadpoles to spend less time in patches with food. Refuges were not used to avoid predation. R. esculenta was more sensitive to predation risk than R. lessonae. Hunger increased both the activity of tadpoles and the amount of activity time invested in feeding, thus indicating an increased energy intake. No interactions were observed between predation risk and hunger. These results show that tadpoles possess genetically-based behavioural mechanisms that allow them to respond in a graded manner to predation and hunger. However, they did not balance the two conflicting demands of predation avoidance and effective foraging; the two mechanisms appeared to act independently. Correspondence to: R.D. Semlitsch     

Observations on the function of the glands of the foot of the pediveliger of Ostrea edulis during settlement

The use during settlement of secretions of the 9 different types of gland in the foot of the pediveliger of Ostrea edulis L. was examined experimentally. During settlement, there is a progressive decrease in the crawling speed of the larva and a strengthening of its bond with the substratum. Both changes are related to (a) a change from ciliary to muscular pedal locomotion; (b) the increasing acidity and viscosity of the mucoid secretions used; (c) the secretion of a byssus thread by the glands of the byssus duet; (d) changes in the form and composition of this byssus. At the termination of settlement, the entire contents of 2 types of gland are discharged. Their secretions give rise to the cement which permanently fixes the larva to the substratum. The 9 types of gland are utilised sequentially in a manner closely related to the 6 phases recognised in settlement behaviour.     

Optimal management of strategic reserves of nonrenewable natural resources

This paper studies the stockpiling issue for an oil importing country that is likely to suffer embargoes, the occurrence and duration of which are uncertain. I show the existence of a decreasing reserves path that the country wants to attain in order to hedge against these disruptions. Allowing the importing country to invest in R&D in order to free itself from the embargo threat, I determine the optimal effort that should be engaged in research. The incentive to develop a backstop is shown to increase with the depletion of the reserves.     

Settlement-competency periods of larvae of three species of scleractinian corals

The pattern of settlement over time of three broadcast spawning coral species (Cyphastrea serailia, Acanthastrea lordhowensis, and Goniastrea australensis) from the Solitary Islands (30°00′S; 153°20′E) was studied in 1995 and 1996 in order to determine the maximum length of time these larvae could remain in the water column and still retain the ability to settle and metamorphose. Larvae were maintained in aquaria and the number which had settled on biologically-conditioned tile pairs was monitored every 5 to 10 d. While the majority of larvae settled quickly after becoming competent, some larvae survived and settled for extended periods after spawning. Competency periods ranged from 26 d for C. serailia to 56 d for G. australensis and 78 d for A. lordhowensis. These data greatly extend the known competency periods for larvae of broadcast-spawning corals and indicate the potential for transport of broadcast-spawned coral larvae over large distances. Medium to long-distance larval dispersal of the species studied provides a mechanism for their widespread distribution in subtropical regions, on reefs which are often widely spaced and relatively isolated. Received: 27 May 1997 / Accepted: 27 November 1997