Modeling effects of toxin exposure in fish on long-term population size, with an application to selenium toxicity in bluegill (Lepomis macrochirus)

A primary goal in ecotoxicology is the prediction of population-level effects of contaminant exposure based on individual-level response. Assessment of toxicity at the population level has predominately focused on the population growth rate (PGR), but the PGR may not be a relevant toxicological endpoint for populations at equilibrium. Equilibrium population size may be a more meaningful endpoint than the PGR because a population with smaller equilibrium size is more susceptible to the negative effects of environmental variability. We address the individual-to-population extrapolation problem with modeling utilizing classical mathematical theory. We developed and analyzed a general model applicable to many freshwater fish species, that includes density-dependent juvenile survival and additional juvenile mortality due to toxicity exposure, and we quantified effect on equilibrium population size as a means of assessing toxicity. Individual-level effects are typically greater than population-level effects until the individual effect is large, due to compensatory density-dependent relationships. These effects are sensitive to the recruitment potential of a population, in particular the low-density first-year survival rate S_b. Assuming high S_b could result in underestimating effects of population-level toxicity. The equilibrium size depends directly on S_b, the reproductive potential, the toxin concentration at which mean mortality is 50% (LC₅₀), and the rate at which individual mortality increases with increasing toxin concentration. More experimental data are needed to decrease the uncertainty in estimating these parameters. We then used existing data for selenium toxicity in bluegill sunfish to parameterize a simulation version of the model as an example to assess the effects of environmental stochasticity on toxicity response. Effects of environmental variability resulted in simulated extinctions at much lower toxin concentrations than predicted deterministically.     

Antarctic krill fishery effects over penguin populations under adverse climate conditions: Implications for the management of fishing practices

Fast climate changes in the western Antarctic Peninsula are reducing krill density, which along with increased fishing activities in recent decades, may have had synergistic effects on penguin populations. We tested that assumption by crossing data on fishing activities and Southern Annular Mode (an indicator of climate change in Antarctica) with penguin population data. Increases in fishing catch during the non-breeding period were likely to result in impacts on both chinstrap (Pygoscelis antarcticus) and gentoo (P. papua) populations. Catches and climate change together elevated the probability of negative population growth rates: very high fishing catch on years with warm winters and low sea ice (associated with negative Southern Annular Mode values) implied a decrease in population size in the following year. The current management of krill fishery in the Southern Ocean takes into account an arbitrary and fixed catch limit that does not reflect the variability of the krill population under effects of climate change, therefore affecting penguin populations when the environmental conditions were not favorable.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01386-w) contains supplementary material, which is available to authorized users.     

三峡库区区域经济发展状况的实证研究

以三峡工程重庆库区为例．依据比较详实的资料．从投资增长与基础设施建设、经济增长与发展水平、产业结构变动等几个方面，研究了1997—2003年三峡库区区域经济发展的状况、特征和问题。研究表明．三峡库区进入二期移民阶段后，投资增长迅还．基础设施有明显改善，经济增长率略高于西部和重庆．但投资结构不合理．经济增长对投资的依赖程度较高。近几年三峡库区人均GDP与重庆市的相对差异有所缩小，但绝对差异在扩大．库区仍然是一个落后的欠发达地区。库区产业结构变动迅速，结构变动主要表现为第一产业比重下降很快，建筑业、第三产业上升很快，而工业发展缓慢．在国民经济中的地位下降。研究还揭示出三峡库区区县发展水平差异很大。并且呈继续扩大之势．真正发展困难的是库区的腹心地带。最后。针对三峡库区经济持续增长和发展中存在的问题．提出了国家应加强对库区产业的扶持、重点支持库区腹心地带的经济发展、重视培育库区腹心地带的增长极以及积极改善投资环境等几点对策建议。     

Characterizing cumulative impacts using a brook trout population dynamics model

An individuals-based modelling framework is used to characterize the nature of exploitation and toxaphene stressors acting simultaneously on a population of brook trout (Salvelinus fontinalis) in terms of age 0 + and adult abundance, survivorship and population size-structure. A no-stressor control case was estimated against which exploitation-only, toxaphene-only and cumulative exploitation and toxaphene stressor cases were compared to determine the extent and significance of impacts. Single stressor case results were used to predict cumulative impacts by assuming additivity and predictions compared to modelled cumulative stressor results. Comparisons indicated the inadequacy of assuming additivity in predicting cumulative impacts. A factorial experimental design was used to estimate the size and significance of interactive effects. Effects are substantial and underscore the necessity of interpreting probable impacts of increases in a single stressor in conjunction with knowledge of other stressors acting on a population. A positive functional relationship between variability in population abundance and stress was estimated and is suggested as a potentially useful means of characterizing risks posed to populations by increases in, or additions to, population stressors. Multiple stressors were also demonstrated to effectively eliminate the significance of density-dependent mortality processes in determining age 0 + and adult abundance. Taken together, results indicate the inappropriateness of attempting to predict additional perturbation impacts without considering the sum of population stressors and their associated interactions.     

台湾的人口,震害与防震减灾问题

众所周知,台湾是西太平洋弧形列岛中的一环,是我国也是全球地震的高发地带。对于地震,同其它自然灾害一样,应重在预防。增加生产和减灾防灾是社会经济建设问题的两个方面,二者相辅相成,缺一不可.因此,本文结合台湾现今的人口密度、经济发展等情况,讨论了台湾的减轻地震灾害问题,希望能引起台湾方面的重视。     

三峡库区农村移民城镇安置刍论

移民安置尤其农村移民安置是大型水利和水电工程普遍遇到一个复杂的大问题，关系工程成败命运。三峡工程移民数量巨大，安置任务繁重艰巨。农村移民城镇安置，具有可靠性大和稳定度高特点，应是三工程移民安置的重要途径。经库区城镇发展程度和农村移民素质适合城镇非农就业数量状况双重分析结果，三峡库区农村移民的城镇安置比重至少可达４５－５０％，可望争取达到６０－７０％。     

Effects of urbanization on heavy metal accumulation in surface soils, Beijing

Urbanization processes affect the accumulation of heavy metals in urban soils. Effects of urbanization on heavy metal accumulation in soils were studied using Beijing as an example. It has been suggested that the ecological function of vegetation covers shifting from natural to agricultural settings and then to urban greenbelts could increase the zinc(Zn) concentrations of soils successively. The Zn concentration of urban soils was significantly correlated to the percentage of the impervious land surface at the500 m × 500 m spatial scale. For urban parks, the age or years since the development accounted for 80% of the variances of cadmium(Cd) and Zn in soils. The population density,however, did not affect the heavy metal distributions in urban soils. To conclude, the urban age turned out to be a notable factor in quantifying heavy metal accumulation in urban soils.     

中国自然灾害转移、安置的财政补助机制

简要分析了转移、安置在应急管理与救灾实践中的重要意义。在分析转移、安置要素的基础上，结合灾害脆弱性分析提出了转移、安置规模和程度模型，讨论了人为决策影响因素对模型的影响，较好地体现了自然因素和人为因素的综合作用。根据对转移、安置的发生进程的分析，提出了转移、安置分级的概念并进行了简单的分级，阐述了转移、安置中的资源需求。在这些工作的基础上，进一步分析了我国当前转移、安置财政补助机制的优缺点，提出了基于上述模型和分级标准的改进建议。     

Northern New England's threatened soft-shell clam populations

Commercial exhaustion of soft-shell clam,Mya arenaria, had become the fate of many potentially productive clamming areas along the coasts of Massachusetts, New Hampshire, and southern Maine. Investigations of a particularly severe case of soft-shell clam stock depletion in Hampton-Seabrook estuary, New Hampshire, indicated that by 1976 human diggers had removed approximately 87% of the adult clam resource that had existed in 1971. Meanwhile, circumstantial evidence strongly implicated the green crab,Carcinus maenas, as responsible for successive stock recruitment failures, these crabs having consumed most of the young seed clams before they could grow to harvestable size. In 1976, this apparent population imbalance may have been at least partly redressed by a prodigious spatfall, resulting in a massive and widespread reseeding of many flats along the northern New England coast. Spat, or seed clam, densities of up to 1,700 individuals per square foot, over areas of several acres, have been observed. Those clamming areas where aggressive predator control programs had been instituted exhibited the most favorable response in terms of seed clam survival and growth. Evidence also indicated that crowding in thickly seeded portions of the clam flats inhibited shell growth.     

Population growth, economic growth, technology changes in relation to environmental changes──A theoretical modelling analysis of environmental changes

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