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751.
752.
Ruff CP Schindler DE Armstrong JB Bentley KT Brooks GT Holtgrieve GW McGlauflin MT Torgersen CE Seeb JE 《Ecology》2011,92(11):2073-2084
Habitat heterogeneity can generate intraspecific diversity through local adaptation of populations. While it is becoming increasingly clear that population diversity can increase stability in species abundance, less is known about how population diversity can benefit consumers that can integrate across population diversity in their prey. Here we demonstrate cascading effects of thermal heterogeneity on trout-salmon interactions in streams where rainbow trout rely heavily on the seasonal availability of anadromous salmon eggs. Water temperature in an Alaskan stream varied spatially from 5 degrees C to 17.5 degrees C, and spawning sockeye salmon showed population differentiation associated with this thermal heterogeneity. Individuals that spawned early in cool regions of the 5 km long stream were genetically differentiated from those spawning in warmer regions later in the season. Sockeye salmon spawning generates a pulsed resource subsidy that supports the majority of seasonal growth in stream-dwelling rainbow trout. The spatial and temporal structuring of sockeye salmon spawn timing in our focal stream extended the duration of the pulsed subsidy compared to a thermally homogeneous stream with a single population of salmon. Further, rainbow trout adopted movement strategies that exploited the multiple pulses of egg subsidies in the thermally heterogeneous stream. Fish that moved to track the resource pulse grew at rates about 2.5 times higher than those that remained stationary or trout in the reference stream with a single seasonal pulse of eggs. Our results demonstrate that habitat heterogeneity can have important effects on the population diversity of dominant species, and in turn, influence their value to species that prey upon them. Therefore, habitat homogenization may have farther-reaching ecological effects than previously considered. 相似文献
753.
Demographic heterogeneity--variation among individuals in survival and reproduction--is ubiquitous in natural populations. Structured population models address heterogeneity due to age, size, or major developmental stages. However, other important sources of demographic heterogeneity, such as genetic variation, spatial heterogeneity in the environment, maternal effects, and differential exposure to stressors, are often not easily measured and hence are modeled as stochasticity. Recent research has elucidated the role of demographic heterogeneity in changing the magnitude of demographic stochasticity in small populations. Here we demonstrate a previously unrecognized effect: heterogeneous survival in long-lived species can increase the long-term growth rate in populations of any size. We illustrate this result using simple models in which each individual's annual survival rate is independent of age but survival may differ among individuals within a cohort. Similar models, but with nonoverlapping generations, have been extensively studied by demographers, who showed that, because the more "frail" individuals are more likely to die at a young age, the average survival rate of the cohort increases with age. Within ecology and evolution, this phenomenon of "cohort selection" is increasingly appreciated as a confounding factor in studies of senescence. We show that, when placed in a population model with overlapping generations, this heterogeneity also causes the asymptotic population growth rate lambda to increase, relative to a homogeneous population with the same mean survival rate at birth. The increase occurs because, even integrating over all the cohorts in the population, the population becomes increasingly dominated by the more robust individuals. The growth rate increases monotonically with the variance in survival rates, and the effect can be substantial, easily doubling the growth rate of slow-growing populations. Correlations between parent and offspring phenotype change the magnitude of the increase in lambda, but the increase occurs even for negative parent-offspring correlations. The effect of heterogeneity in reproductive rate on lambda is quite different: growth rate increases with reproductive heterogeneity for positive parent-offspring correlation but decreases for negative parent-offspring correlation. These effects of demographic heterogeneity on lambda have important implications for population dynamics, population viability analysis, and evolution. 相似文献
754.
755.
重点考察了不同外阻(10、150和1 000Ω)对污泥微生物燃料电池(sludge microbial fuel cell,SMFC)产电性能及有机物去除速率的影响。结果表明,外阻对电池产电和有机物降解有显著影响,低电阻有利于电流产生及有机物消耗。当外阻为10Ω时,输出电流最高(4.2 mA),且污泥溶解性化学需氧量(SCOD)去除速率最快(53 mg.d-1)。DGGE图谱显示,不同外阻导致阳极微生物菌落结构有明显差异;CV扫描发现外阻对生物膜氧化还原能力有显著影响,低电阻下运行的阳极生物膜氧化还原活性较强。本研究为理解外阻与阳极生物膜间的关系提供一条有益线索,也为MFC性能提高提供一条可操作性的途径。 相似文献
756.
为研究黄海漂浮铜藻的来源以及藻体特征,在北黄海、南黄海和青岛近岸采集漂浮铜藻,并对长岛海域定生铜藻开展调查研究。结果表明,漂浮和定生铜藻的植株形态呈现不同的季节性变化,11月两者的叶片和气囊形态差别不大,4-6月形态分化明显,表现为定生铜藻的叶片和气囊继续生长,而漂浮铜藻呈衰败趋势;漂浮铜藻的生殖托数量远低于定生铜藻,且较细短。同时,本文利用核基因(ITS2)和线粒体基因片段(cox3、rnl-atp9、rpl5-rps3和cob-cox2)研究铜藻样本的遗传多样性,结果显示,ITS2序列共发现2个多态性位点、5种基因型,线粒体基因片段共发现9个多态性位点、5个单倍型;不同地理群体间以及漂浮和定生群体间的遗传距离与群体内遗传距离差异不显著,表明该海域漂浮和定生铜藻可能来自相同的遗传群体。 相似文献
757.
Alyasi Haya Mackey Hamish R. McKay Gordon 《Journal of Polymers and the Environment》2022,30(7):2727-2738
Journal of Polymers and the Environment - Industrial effluents and stormwater runoff pose a significant threat to the environment and public health. Consequently, the water quality guidelines set... 相似文献
758.
基于碳减排目标与排放标准约束情景的火电大气污染物减排潜力 总被引:6,自引:6,他引:0
从我国"十四五"及2035年远景目标经济发展预测出发,结合碳减排战略目标下的既有与强化政策情景,基于弹性系数法预测电力需求,测算在不同污染物排放标准约束情景下火电大气污染物排放情况及减排潜力,结果表明,在不同的政策和排放标准约束情景下,我国火电行业烟尘、SO2和NOx排放水平变化呈现出不同的趋势,到2035年,在2016年水平上的减排潜力分别在45.97%~85.37%、52.61%~84.90%和33.80%~71.08%之间,来自碳减排目标下政策因素带来的减排潜力,较不同污染物排放标准约束条件带来的减排潜力更为明显,在强化政策情景下,采取保持模式标准约束的污染物减排潜力已与超低模式基本相当,甚至超过或接近既有政策下采取收严模式标准约束的效果,通过强化实施能源和电力优化政策,加快实现火电发电量达峰,合理引导高污染排放水平火电机组优先退出生产,同样可使火电大气污染物排放得到有效控制,还可避免环保改造投资的浪费和损失. 相似文献
759.
760.
Keke Xiao Zecong Yu Kangyue Pei Mei Sun Yuwei Zhu Sha Liang Huijie Hou Bingchuan Liu Jingping Hu Jiakuan Yang 《Frontiers of Environmental Science & Engineering》2022,16(2):23