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51.
Which populations are replenished primarily by immigrants (open) and which by local production (closed) remains an important question for management with implications for response to exploitation, protection, and disturbance. However, we lack methods for predicting population openness. Here, we develop a model for openness and show that considering habitat isolation explains the existence of surprisingly closed populations in high-dispersal species, including many marine organisms. Relatively closed populations are expected when patch spacing is more than twice the standard deviation of a species'. dispersal kernel. In addition, natural scales of habitat patchiness on coral reefs are sufficient to create both largely open and largely closed populations. Contrary to some previous interpretations, largely closed marine populations do not require mean dispersal distances that are unusually short, even for species with relatively long pelagic larval durations. We predict that habitat patchiness has strong control over population openness for many marine and terrestrial species with a highly dispersive life stage and relatively sedentary adults. This information can be used to make initial predictions about where populations will be more or less resilient to local exploitation and disturbance. 相似文献
52.
Hobbs WO Hobbs JM LaFran?ois T Zimmer KD Theissen KM Edlund MB Michelutti N Butler MG Hanson MA Carlson TJ 《Ecological applications》2012,22(5):1483-1496
Multiple stressors to a shallow lake ecosystem have the ability to control the relative stability of alternative states (clear, macrophyte-dominated or turbid, algal-dominated). As a consequence, the use of remedial biomanipulations to induce trophic cascades and shift a turbid lake to a clear state is often only a temporary solution. Here we show the instability of short-term manipulations in the shallow Lake Christina (Minnesota, USA) is governed by the long-term state following a regime shift in the lake. During the modern, managed period of the lake, three top-down manipulations (fish kills) were undertaken inducing temporary (5-10 years) unstable clear-water states. Paleoecological remains of diatoms, along with proxies of primary production (total chlorophyll a and total organic carbon accumulation rate) and trophic state (total P) from sediment records clearly show a single regime shift in the lake during the early 1950s; following this shift, the functioning of the lake ecosystem is dominated by a persistent turbid state. We find that multiple stressors contributed to the regime shift. First, the lake began to eutrophy (from agricultural land use and/or increased waterfowl populations), leading to a dramatic increase in primary production. Soon after, the construction of a dam in 1936 effectively doubled the depth of the lake, compounded by increases in regional humidity; this resulted in an increase in planktivorous and benthivorous fish reducing phytoplankton grazers. These factors further conspired to increase the stability of a turbid regime during the modern managed period, such that switches to a clear-water state were inherently unstable and the lake consistently returned to a turbid state. We conclude that while top-down manipulations have had measurable impacts on the lake state, they have not been effective in providing a return to an ecosystem similar to the stable historical period. Our work offers an example of a well-studied ecosystem forced by multiple stressors into a new long-term managed period, where manipulated clear-water states are temporary, managed features. 相似文献
53.
Mercury in sediments and vegetation in a moderately contaminated salt marsh
(Tagus Estuary, Portugal) 总被引:1,自引:1,他引:0
Jo?ao Can′ario Carlos Vale Laurier Poissant Marta Nogueir Martin Pilote Vasco Branco 《环境科学学报(英文版)》2010,22(8):1151-1157
Depth variations of total mercury (Hg) and methylmercury (MeHg) concentrations were studied in cores from non-colonized
sediments, sediments colonized by Halimione portulacoides, Sarcocornia fruticosa and Spartina maritima and belowground biomass,
in a moderately contaminated salt marsh (Tagus Estuary, Portugal). Concentrations in belowground biomass exceeded up to 3 (Hg) and
15 (MeHg) times the levels in sediments, and up to 198 (Hg) and 308 (MeHg) times those found in aboveground parts. Methylmercury
in colonized sediments reached 3% of the total Hg, 50 times above the maximum values found in non-colonized sediments. The absence
of correlations between total Hg concentrations in sediments and the corresponding MeHg levels suggested that methylation was only
dependent on the environmental and microbiological factors. The analysis of belowground biomass at high-depth resolution (2 cm)
provided evidence that Hg and MeHg were actively absorbed from sediments, with higher enrichment factors at layers where higher
microbial activity was probably occurring. The results obtained in this study indicated that the biotransformation of Hg to the toxic
MeHg could increase the toxicity of plant-colonized sediments. 相似文献
54.
M.González-Casta?o C.Morales J.C.Navarro de Miguel J.H.Boelte O.Klepel J.I.Flege H.Arellano-García 《绿色能源与环境(英文)》2023,(3):744-756
Among challenges implicit in the transition to the post±fossil fuel energetic model, the finite amount of resources available for the technological implementation of CO2 revalorizing processes arises as a central issue. The development of fully renewable catalytic systems with easier metal recovery strategies would promote the viability and sustainability of synthetic natural gas production circular routes. Taking Ni and NiFe catalysts supported over γ-Al2O3 oxid... 相似文献
55.
邻苯二甲酸酯在长江重庆段水体的概率风险分析 总被引:1,自引:0,他引:1
以长江重庆段水体12个采样断面4种邻苯二甲酸酯(PAEs)的监测结果及水生生物的生态毒性参数无观察效应浓度(NOEC)为基础资料,采用安全阈值和概率曲线分布两种概率风险评价方法分析了邻苯二甲酸酯的相对生态风险。研究结果表明:邻苯二甲酸二甲酯(DMP)、邻苯二甲酸二乙酯(DEP)、邻苯二甲酸正丁酯(DBP)、邻苯二甲酸双(2 乙基己基)酯(DEHP)的安全阈值分别为4 31079、2171、147、199,对水生生物无风险。以5%水生生物物种受影响作为可接受的效应水平终点(HC5),采用概率曲线分布进行分析,DBP、DEHP的浓度超过毒性值的风险概率分别为106×10-2、235×10-4,4种邻苯二甲酸酯风险大小依次为:DBP>DEHP>DEP>DMP,与安全阈值法结果一致。两种概率风险方法从不同的角度反映了污染物的生态风险。 相似文献
56.
次级河流回水区叶绿素a与影响因子的多元分析——以临江河为例 总被引:4,自引:0,他引:4
为了对次级河流回水区富营养化进行深入研究,把长江次级河流之一的临江河回水区为研究对象,根据2007年10月至2008年9月临江河回水区中游叶绿素a含量及其水质理化指标的监测数据,分析了临其叶绿素a浓度的时间分布,对叶绿素a浓度及影响因子进行相关分析,找出与叶绿素a显著相关的环境因子并建立多元逐步回归模型。结果表明:临江河回水区叶绿素a浓度峰值主要集中在5月上旬至9月下旬,变化范围为227~661 mg/m3。临江河回水区叶绿素a浓度变化受多个环境因子共同影响,与水温、流速、透明度、COD、总磷之间显著相关,而与总氮相关性不显著。经过叶绿素a及其影响因子的相关分析,建立了以水温、流速和总磷为自变量,叶绿素a浓度为应变量的逐步线性回归模型,模型初步验证结果表明:多元逐步回归模型可以用来描述临江河回水区叶绿素a浓度的变化。通过对临江河回水区叶绿素a及其影响因子的分析,控制临江河回水区水体中磷含量应是其富营养化防治工作的重点,防治工作应主要在春末和整个夏季,尤其是在5、6月份。 相似文献
57.
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59.
Experiments were carried out to characterize the transformation of lipids in activated sludge under aerobic conditions. Results showed that the overall lipid content in the effluent could not be reduced to values below 300 mg/L from an initial content of 2, 000 mg/L. However, the contents of individual fatty acids underwent drastic decreases and increases during all microbial growth phases. These changes in contents of individual fatty acids showed that fatty acids were used as substrates by microorganisms as well as released into the wastewater as by-products. We have therefore suggested a novel model of transformation of lipids in activated sludge, showing that utilization of microbial activity for complete removal of lipids from wastewater is limited. 相似文献
60.
The architectural complexity of ecosystems can greatly influence their capacity to support biodiversity and deliver ecosystem services. Understanding the components underlying this complexity can aid the development of effective strategies for ecosystem conservation. Caribbean coral reefs support and protect millions of livelihoods, but recent anthropogenic change is shifting communities toward reefs dominated by stress-resistant coral species, which are often less architecturally complex. With the regionwide decline in reef fish abundance, it is becoming increasingly important to understand changes in coral reef community structure and function. We quantify the influence of coral composition, diversity, and morpho-functional traits on the architectural complexity of reefs across 91 sites at Cozumel, Mexico. Although reef architectural complexity increases with coral cover and species richness, it is highest on sites that are low in taxonomic evenness and dominated by morpho-functionally important, reef-building coral genera, particularly Montastraea. Sites with similar coral community composition also tend to occur on reefs with very similar architectural complexity, suggesting that reef structure tends to be determined by the same key species across sites. Our findings provide support for prioritizing and protecting particular reef types, especially those dominated by key reef-building corals, in order to enhance reef complexity. 相似文献