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.     

矿区周边土壤重金属污染治理的优势植物筛选——以关中西部某铅锌冶炼区为例

通过对关中西部某铅锌冶炼区周边实地调查、采样和室内样品分析,采用原子吸收分光光度计测定铅锌冶炼区周边地区长势良好的13种优势植物对Pb、Zn、Cd、Cr、Cu、Ni的吸收与富集能力及其富集特征。结果表明,矿区土壤均受到Pb、Zn、Cd 3种重金属的污染,13种植物体内的Pb、Zn、Cd的含量比正常植物的含量高出数倍,白蒿、蒲公英、播娘蒿、牛舌草和秃疮花这5种植物对于Pb、Zn、Cd这3种重金属的转移系数均大于1,从植物体内重金属含量、转运系数和富集系数3个指标来看,白蒿和蒲公英可作为首选的2种先锋植物。此结果为利用本土植物治理铅锌矿区土壤重金属污染提供一定的参考依据。     

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。     

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.     

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

Ｐｏｐｕｌａｔｉｏｎｇｒｏｗｔｈ，ｅｃｏｎｏｍｉｃｇｒｏｗｔｈ，ｔｅｃｈｎｏｌｏｇｙｃｈａｎｇｅｓｉｎｒｅｌａｔｉｏｎｔｏｅｎｖｉｒｏｎｍｅｎｔａｌｃｈａｎｇｅｓ──Ａｔｈｅｏｒｅｔｉｃａｌｍｏｄｅｌｌｉｎｇａｎａｌｙｓｉｓｏｆｅｎｖｉｒｏｎｍｅｎｔ...     

A cost-benefit analysis of a population screening programme for neural tube defects

Population screening for neural tube defects is possible by measuring maternal serum alpha-fetoprotein levels with appropriate follow-up as required. British Columbia has approximately 39 000 births annually and the incidence of neural tube defects is 1–55 per 1000 births (0–94 per 1000 livebirths). Results from a cost-benefit analysis suggest that the outlined screening programme would be cost-beneficial for British Columbia. Other important factors essential to consider before instituting a population screening programme are discussed.