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51.
Jenkins RA Ilgner RH Tomkins BA Peters DW 《Journal of the Air & Waste Management Association (1995)》2004,54(2):229-241
Protocols have been developed and applied for the generation of aerosols that are likely to be comparable to those encountered in field settings for the calibration of easily transportable/portable real-time particle monitors. Aerosols generated were simulated environmental tobacco smoke, cedar wood smoke, cooking oil fumes, and propane stove particles. The time-integrated responses of three nephelometers and a monitor for particle-bound polynuclear aromatic hydrocarbons (PAH) were compared with gravimetric respirable suspended particulate matter (RSP) in a controlled-atmosphere chamber. In general, the monitor responses increased linearly with increasing mass concentration. However, the two monitors that reported mass per volume concentrations tended to overreport the actual RSP concentrations by factors up to 4.4. The real-time PAH monitor did not respond to cooking oil fumes, indicative of little PAH being present in the aerosol. One of the monitors that has been used in a variety of studies reported in the literature (DustTrak) was collocated with gravimetric RSP samplers in several hospitality venues in the Louisville, KY, area. Field studies indicated that the units overreported actual RSP concentrations by factors of 2.6-3.1, depending on whether the sampling was conducted in the nonsmoking or smoking sections of the facilities. 相似文献
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The invasibility of marine algal assemblages: role of functional diversity and identity 总被引:6,自引:0,他引:6
The emergence of the biodiversity-ecosystem functioning debate in the last decade has renewed interest in understanding why some communities are more easily invaded than others and how the impact of invasion on recipient communities and ecosystems varies. To date most of the research on invasibility has focused on taxonomic diversity, i.e., species richness. However, functional diversity of the communities should be more relevant for the resistance of the community to invasions, as the extent of functional differences among the species in an assemblage is a major determinant of ecosystem processes. Although coastal marine habitats are among the most heavily invaded ecosystems, studies on community invasibility and vulnerability in these habitats are scarce. We carried out a manipulative field experiment in tide pools of the rocky intertidal to test the hypothesis that increasing functional richness reduces the susceptibility of macroalgal communities to invasion. We selected a priori four functional groups on the basis of previous knowledge of local species characteristics: encrusting, turf, subcanopy, and canopy species. Synthetic assemblages containing one, two, three, or four different functional groups of seaweeds were created, and invasion by native species was monitored over an eight-month period. Cover and resource availability in the assemblages with only one functional group showed different patterns in the use of space and light, confirming true functional differences among our groups. Experimental results showed that the identity of functional groups was more important than functional richness in determining the ability of macroalgal communities to resist invasion and that resistance to invasion was resource-mediated. 相似文献
55.
Jenkins DG 《Ecology》2006,87(6):1523-1531
Alternative models of community assembly emphasize regional, stochastic, dispersal-based processes or local, deterministic, niche-based processes. Community ecology's historical focus on local processes implicitly assumes that local processes surpass regional processes over time or across space to derive nonrandom metacommunity structure (i.e., a quorum effect). Quorum effects are expected late in succession among nearby sites, whereas quorum effects are not expected early in succession among distant sites. I conducted a meta-analysis of zooplankton data sets encompassing time scales of one to thousands of years and spatial scales of <1 m to thousands of kilometers. Species co-occurrence analyses statistically evaluated presence/absence patterns relative to random patterns obtained with Monte Carlo null models. A series of weighted analyses was conducted and alternative randomization algorithms and null models were evaluated. Most zooplankton metacommunities were randomly structured in unweighted analyses, and the distribution of significant structure did not follow quorum effect predictions. Weighted analyses (e.g., by habitat area) revealed significant, nonrandom structure in most zooplankton metacommunities, but the distribution of significant structure still did not adhere well to quorum effect predictions. Finally, additional weighting for study scale (number of sites) nullified most significant area-weighted structure, and again, the distribution of significant structure did not follow quorum effect predictions. Overall, a quorum effect was not supported, perhaps related to zooplankton life histories and energetics and/or the quorum effect itself. Results at the presence/absence level of resolution indicated that local processes did not generally override regional processes over time or across space to drive community structure. A full integration of dispersal- and niche-based concepts in metacommunity dynamics will be most fruitful for unraveling community assembly. Species co-occurrence analyses were scale dependent (habitat area and study size). Future analyses should use weights for important factors (e.g., habitat area), and meta-analyses should include study scale as an additional factor contributing to apparent patterns. 相似文献
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Ned?A.?DochtermannEmail author Stephen?H.?Jenkins 《Behavioral ecology and sociobiology》2011,65(1):37-45
Researchers in behavioral ecology are increasingly turning to research methods that allow the simultaneous evaluation of hypotheses.
This approach has great potential to increase our scientific understanding, but researchers interested in the approach should
be aware of its long and somewhat contentious history. Also, prior to implementing multiple hypothesis evaluation, researchers
should be aware of the importance of clearly specifying a priori hypotheses. This is one of the more difficult aspects of
research based on multiple hypothesis evaluation, and we outline and provide examples of three approaches for doing so. Finally,
multiple hypothesis evaluation has some limitations important to behavioral ecologists; we discuss two practical issues behavioral
ecologists are likely to face. 相似文献
58.
Cascio C Raab A Jenkins RO Feldmann J Meharg AA Haris PI 《Journal of environmental monitoring : JEM》2011,13(2):257-265
Rice is elevated in arsenic (As) compared to other staple grains. The Bangladeshi community living in the United Kingdom (UK) has a ca. 30-fold higher consumption of rice than white Caucasians. In order to assess the impact of this difference in rice consumption, urinary arsenicals of 49 volunteers in the UK (Bangladeshi n = 37; white Caucasians n = 12) were monitored along with dietary habits. Total urinary arsenic (As(t)) and speciation analysis for dimethylarsinic acid (DMA), monomethylarsonic acid (MA) and inorganic arsenic (iAs) was conducted. Although no significant difference was found for As(t) (median: Bangladeshis 28.4 μg L(-1)) and white Caucasians (20.6 μg L(-1)), the sum of medians of DMA, MA and iAs for the Bangladeshi group was found to be over 3-fold higher (17.9 μg L(-1)) than for the Caucasians (3.50 μg L(-1)). Urinary DMA was significantly higher (p < 0.001) in the UK Bangladeshis (median: 16.9 μg DMA L(-1)) than in the white Caucasians (3.16 μg DMA L(-1)) as well as iAs (p < 0.001) with a median of 0.630 μg iAs L(-1) for Bangladeshi and 0.250 μg iAs L(-1) for Caucasians. Cationic compounds were significantly lower in the Bangladeshis (2.93 μg L(-1)) than in Caucasians (14.9 μg L(-1)). The higher DMA and iAs levels in the Bangladeshis are mainly the result of higher rice consumption: arsenic is speciated in rice as both iAs and DMA, and iAs can be metabolized, through MA, to DMA by humans. This study shows that a higher dietary intake of DMA alters the DMA/MA ratio in urine. Consequently, DMA/MA ratio as an indication of methylation capacity in populations consuming large quantities of rice should be applied with caution since variation in the quantity and type of rice eaten may alter this ratio. 相似文献
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Diel swimming behaviors of juvenile anchovies (Anchoa spp.) were observed using stationary hydroacoustics and synoptic physicochemical and zooplankton profiles during four unique
water quality scenarios in the Neuse River Estuary, NC, USA. Vertical distribution of fish was restricted to waters with DO
greater than 2.5 mg O2 l−1, except when greater than 70% of the water column was hypoxic and a subset of fish were occupying water with 1 mg O2 l−1. We made the prediction that an individual fish would select a swim speed that would maximize net energy gain given the abundance
and availability of prey in the normoxic waters. During the day, fish adopted swim speeds between 7 and 8.8 bl s−1 that were near the theoretical optimum speeds between 7.0 and 8.0 bl s−1. An exception was found during severe hypoxia, when fish were swimming at 60% above the optimum speed (observed speed = 10.6 bl s−1, expected = 6.4 bl s−1). The anchovy is a visual planktivore; therefore, we expected a diel activity pattern characteristic of a diurnal species,
with quiescence at night to minimize energetic costs. Under stratified and hypoxic conditions with high fish density coupled
with limited prey availability, anchovies sustained high swimming speeds at night. The sustained nighttime activity resulted
in estimated daily energy expenditure over 20% greater than fish that adopted a diurnal activity pattern. We provide evidence
that the sustained nighttime activity patterns are a result of foraging at night due to a lower ration achieved during the
day. During severe hypoxic events, we also observed individual fish making brief forays into the hypoxic hypolimnion. These
bottom waters generally contained higher prey (copepod) concentrations than the surface waters. The bay anchovy, a facultative
particle forager, adopts a range of behaviors to compensate for the effects of increased conspecific density and reduced prey
availability in the presence of stratification-induced hypoxia. 相似文献
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