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191.
F. Badalamenti C. J. Sweeting N. V. C. Polunin J. Pinnegar G. D’Anna C. Pipitone 《Marine Biology》2008,154(5):765-773
Trawling has a significant effect on the structure of marine communities, yet the ubiquity of trawling impacts makes testing
such effects difficult. This study examines trawling impacts on trophodynamics of three fishes among the Gulfs of Castellammare
and Termini Imerese (northern Sicily), the first of which has been subject to a trawling ban since 1990 that initially resulted
in an eightfold increase in total fish biomass. The Gulf of Termini Imerese remains heavily fished and was treated as a control
site. Nitrogen and carbon stable isotope data were used to assess fishing induced changes in trophic levels or source of production
supporting three demersal fish species; Mullus barbatus,
Merluccius merluccius and Lophius budegassa following a control-impact approach. The exclusion of trawling resulted in only small alteration of δ15N in two of the three-three species. There were no systematic changes in the δ13C of any species sampled. Thus, a large influence of trawling on the trophodynamics of the studied species at sampled size
was discounted. Although stable isotopes do not have spatial or temporal resolution to identify detailed shifts in diet composition,
their integrative nature highlights that the trophic role these species play is robust to fishing impacts at scales over which
the fishery operates. This is despite a significant increase in the abundance of these species and of total fish biomass within
the protected area.
相似文献
C. J. SweetingEmail: |
192.
M. Eugenia D’Amato Gordon W. Harkins Tulio de Oliveira Peter R. Teske Mark J. Gibbons 《Marine Biology》2008,155(2):243-247
The genus Nyctiphanes (Malacostraca, Euphausiacea) comprises four neritic species that display antitropical geographic distribution in the Pacific
(N. simplex and N. australis) and Atlantic (N. couchii and N. capensis) Oceans. We studied the origin of this distribution applying methods for phylogenetic reconstruction and molecular dating
of nodes using a Bayesian MCMC analysis and the DNA sequence information contained in mtDNA 16S rDNA and cytochrome oxidase
(COI). We tested hypotheses of vicariance by contrasting the time estimates of cladogenesis with the onset of the major barriers
to ocean circulation. It was estimated that Nyctiphanes originated in the Pacific Ocean during the Miocene, with a lower limit of 18 miilion years ago (Mya). An Atlantic–Pacific
cladogenic event (95% HPD 3.2–9.6) took place after the closure of the Tethyan Sea, suggesting that dispersal occurred from
the Indo-Pacific, most likely via southern Africa. Similarly, the antitropical distribution pattern observed in the eastern
Atlantic Ocean likely resulted from recent Pliocene–Pleistocene (95% HPD 1.0–4.97) northward dispersal from the southern hemisphere.
Our results imply that dispersal appears to have had a significant role to play in the evolution of this group.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
193.
There is growing evidence that the sex ratios of wild vertebrate populations are determined by mechanisms that are directly
influenced by environmental characteristics. The Trivers–Willard (TWH) and extrinsic modification (EMH) hypotheses postulate
differing determinants of mammalian offspring sex ratios. TWH states that mothers allocate resources according to their current
condition and sex-specific offspring costs. EMH states that environmental forces that affect maternal condition determine
offspring sex ratios, independently of maternal tactics of sex-biased allocation. We statistically assessed support for each
of these hypotheses using long-term life histories of the allied rock-wallaby, Petrogale assimilis; a continuously breeding, polygynous, weakly dimorphic marsupial. We showed that birth sex ratios were equal and independent
of maternal and environmental conditions. However, secondary sex ratios were male-biased under good environmental conditions
and for high quality mothers or mothers in good condition. Sex differences in offspring survival contributed to these biases:
(1) environmental conditions strongly influenced survival to pouch emergence (in support of EMH) and (2) maternal quality
affected survival to the end of maternal care (in support of TWH). Environmental effects on survival were more important than
maternal factors over the entire period of maternal care and contributed most to male-biased sex ratios at pouch emergence.
In contrast, maternal mass was the best predictor of sex ratios at the end of maternal care—the life history stage where offspring
body mass differed between the sexes. 相似文献
194.
Anna Gagliardo Maria Savini Angelo De Santis Giacomo Dell’Omo Paolo Ioalè 《Behavioral ecology and sociobiology》2009,64(2):289-296
Some authors have proposed that homing pigeons are able to correct the error in orientation following a phase-shift treatment
by using the magnetic compass reference. They reported that clock-shifted pigeons bearing magnets display a greater deflection
compared to magnetically unmanipulated clock-shifted birds. However, this hypothesis tested by recording pigeons’ vanishing
bearings has led to contradictory results. The present study reports pigeons’ tracks recorded with a GPS and shows that clock-shifted
pigeons bearing magnets displayed a greater deviation through the whole route compared to the magnetically unmanipulated shifted
pigeons. Moreover, the analysis of the tracks shows that the birds belonging to both experimental groups stop in coincidence
with their subjective night. When re-starting their journey, the birds corrected the clock-shift induced error in orientation,
but the magnetically manipulated pigeons were less efficient in doing so. Our results are consistent with the hypothesis that
homing pigeons released from unfamiliar location re-orient after clock shift by using the magnetic compass. 相似文献
195.
Ocean acidification (OA) and the biological consequences of altered seawater chemistry have emerged as a significant environmental
threat to healthy marine ecosystems. Because a more acidic ocean interferes with fixation of calcium carbonate to form shells
or calcified skeletons, future ocean chemistry may significantly alter the physiology of calcifying marine organisms. These
alterations may manifest themselves directly in the calcification process, or have synergistic effects with other environmental
factors such as elevated temperatures. New tools permit us to explore subtle changes in gene expression patterns in response
to environmental conditions. We raised sea urchins (Strongylocentrotus franciscanus) under conditions simulating future atmospheric CO2 levels of 540 and 970 ppm. When larvae raised under elevated CO2 conditions were subjected to 1-h acute temperature stress, their ability to mount a physiological response (as measured by
expression of the molecular chaperone hsp70) was reduced relative to those raised under ambient CO2 conditions. These results represent the first use of gene expression assays to study the effects of OA on sea urchin development.
They highlight the importance of looking at multiple environmental factors simultaneously as this approach may reveal previously
unsuspected biological impacts of atmospheric changes. 相似文献
196.
M. Rubino C. Lubritto A. D’Onofrio F. Terrasi C. Kramer G. Gleixner M. F. Cotrufo 《Environmental Chemistry Letters》2009,7(1):85-95
We show the potentiality of coupling together different compound-specific isotopic analyses in a laboratory experiment, where 13C-depleted leaf litter was incubated on a 13C-enriched soil. The aim of our study was to identify the soil compounds where the C derived from three different litter species is retained. Three 13C-depleted leaf litter (Liquidambar styraciflua L., Cercis canadensis L. and Pinus taeda L., δ13CvsPDB ≈ ?43‰), differing in their degradability, were incubated on a C4 soil (δ13CvsPDB ≈ ?18‰) under laboratory-controlled conditions for 8 months. At harvest, compound-specific isotope analyses were performed on different classes of soil compounds [i.e. phospholipids fatty acids (PLFAs), n-alkanes and soil pyrolysis products]. Linoleic acid (PLFA 18:2ω6,9) was found to be very depleted in 13C (δ13CvsPDB ≈ from ?38 to ?42‰) compared to all other PLFAs (δ13CvsPDB ≈ from ?14 to ?35‰). Because of this, fungi were identified as the first among microbes to use the litter as source of C. Among n-alkanes, long-chain (C27–C31) n-alkanes were the only to have a depleted δ13C. This is an indication that not all of the C derived from litter in the soil was transformed by microbes. The depletion in 13C was also found in different classes of pyrolysis products, suggesting that the litter-derived C is incorporated in less or more chemically stable compounds, even only after 8 months decomposition. 相似文献
197.
采用真空式土壤溶液采样器收集了宜昌、巫山松树林中天然土壤溶液,采用高效液相色谱法Al-Lumogallion柱后荧光检测,分析测试了土壤溶液中可溶性铝的形态,研究了由于土壤酸化引起天然土壤溶液中不同形态铝的迁移转化结果表明,天然土壤溶液中含有不同形态的铝,主要是有机铝、 AISO4+、AIF2+、Al(OH)2+、Al3+等.宜昌、巫山地区土壤溶液中活性铝(Al3+、AlOH2+F)的含量比较低.土壤的酸化使得天然土壤溶液中总铝含量增加、铝形态的优势态发生变化,即土壤的酸化使得天然土壤溶液中活性铝-Al3+、AlOHF2+含量和比例增加.土壤酸化还降低了大然土壤溶液中的BC/Al比值,这些变化的结果都增加了对森林潜在的危害. 相似文献
198.
Richard J. Horwitz Thomas E. Johnson Paul F. Overbeck T. Kevin O’Donnell W. Cully Hession Bernard W. Sweeney 《Journal of the American Water Resources Association》2008,44(3):724-741
Abstract: The joint influences of riparian vegetation and urbanization on fish assemblages were analyzed by depletion sampling in paired forested and nonforested reaches of 25 small streams along an urbanization gradient. Nonforested reaches were narrower than their forested counterparts, so densities based on surface area differ from linear densities (based on reach length). Linear densities (based on number or biomass of fish) of American eel, white sucker and tesselated darter, and the proportion of biomass of benthic invertivores were significantly higher in nonforested reaches, while linear densities of margined madtom and the number of pool species were significantly higher in forested reaches. Observed riparian effects may reflect differences in habitat and algal productivity between forested and nonforested reaches. These results suggest that relatively small‐scale riparian restoration projects can affect local geomorphology and the abundance of fish. Dense vegetative cover in riparian zones and similar or analogous habitats in both forested and nonforested reaches, the relatively small scale of the nonforested reaches, and the low statistical power to detect differences in abundance of rare species may have limited the observed differences between forested and nonforested reaches. There was a strong urbanization gradient, with reductions of intolerant species and increases of tolerant species and omnivores with increasing urbanization. Interactions between riparian vegetation type and urbanization were found for blacknose dace, creek chub, tesselated darter, and the proportion of biomass of lithophilic spawners. The study did not provide consistent support for the hypotheses that responses of fish to riparian vegetation would be overwhelmed by urban degradation or insignificant at low urbanization. 相似文献
199.
The oxidation of gas phase elemental mercury (Hg0) by atmospheric pressure non-thermal plasma has been investigated at room temperature, employing both dielectric barrier discharge (DBD) of the gas mixture of Hg0 and injection of ozone (O3) into the gas mixture of Hg0. Results have shown that the oxidative efficiencies of Hg0 by DBD and the injection of O3 are 59% and 93%, respectively, with energy consumption of 23.7 J L(-1). This combined approach has indicated that O3 plays a decisive role in the oxidation of gas phase Hg0. Also the oxidation of Hg0 by injecting O3 into the gas mixture of Hg0 proceeds with better efficiency than DBD of the gas mixture of Hg0. These results have been explained by the incorporation of the competitive reaction pathways between the formation of HgO by O3 and the decomposition of HgO back to Hg0 in the plasma environment. 相似文献
200.
Seasonal and particle size-dependent variations in gas/particle partitioning of PCDD/Fs 总被引:1,自引:0,他引:1
Lee SJ Ale D Chang YS Oh JE Shin SK 《Environmental pollution (Barking, Essex : 1987)》2008,153(1):215-222
This study monitored particle size-dependent variations in atmospheric polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Two gas/particle partitioning models, the subcooled liquid vapor pressure (P(L)(0)) and the octanol-air partition coefficient (K(OA)) model, were applied to each particle sizes. The regression coefficients of each fraction against the gas/particle partition coefficient (K(P)) were similar for separated particles within the same sample set but differed for particles collected during different periods. Gas/particle partitioning calculated from the integral of fractions was similar to that of size-segregated particles and previously measured bulk values. Despite the different behaviors and production mechanisms of atmospheric particles of different sizes, PCDD/F partitioning of each size range was controlled by meteorological conditions such as atmospheric temperature, O(3) and UV, which reflects no source related with certain particle size ranges but mixed urban sources within this city. Our observations emphasize that when assessing environmental and health effects, the movement of PCDD/Fs in air should be considered in conjunction with particle size in addition to the bulk aerosol. 相似文献