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841.
Response of balanced network models to large-scale perturbation: Implications for evaluating the role of small pelagics in the Gulf of Maine 总被引:1,自引:0,他引:1
Jason Link Laurel Col Vincent Guida David Dow John O’Reilly Jack Green William Overholtz Debra Palka Chris Legault Joseph Vitaliano Carolyn Griswold Michael Fogarty Kevin Friedland 《Ecological modelling》2009
Exploring the response of an ecosystem, and subsequent tradeoffs among its biological community, to human perturbations remains a key challenge for the implementation of an ecosystem approaches to fisheries (EAF). To address this and related issues, we developed two network (or energy budget) models, Ecopath and Econetwrk, for the Gulf of Maine ecosystem. These models included 31 network “nodes” or biomass state variables across a broad range of trophic levels, with the present emphasis to particularly elucidate the role of small pelagics. After initial network balancing, various perturbation scenarios were evaluated to explore how potential changes to different fish, fisheries and lower trophic levels can affect model outputs. Categorically across all scenarios and interpretations thereof, there was minimal change at the second trophic levels and most of the “rebalancing” after a perturbation occurred via alteration of the diet matrix. Yet the model results from perturbations to a balanced energy budget fall into one of three categories. First, some model results were intuitive and in obvious agreement with established ecological and fishing theory. Second, some model results were counter-intuitive upon initial observation, seemingly contradictory to known ecological and fishing theory; but upon further examination the results were explainable given the constraints of an equilibrium energy budget. Finally, some results were counter-intuitive and difficult to reconcile with theory or further examination of equilibrium constraints. A detailed accounting of biomass flows for example scenarios explores some of the non-intuitive results more rigorously. Collectively these results imply a need to carefully track biomass flows and results of any given perturbation and to critically evaluate the conditions under which a new equilibrium is obtained for these types of models, which has implications for dynamic simulations based off of them. Given these caveats, the role of small pelagics as a prominent component of this ecosystem remains a robust conclusion. We discuss how one might use this approach in the context of further developing an EAF, recognizing that a more holistic, integrated perspective will be required as we continue to evaluate tradeoffs among marine biological communities. 相似文献
842.
Network structure and parasite transmission in a group living lizard,the gidgee skink, <Emphasis Type="Italic">Egernia stokesii</Emphasis> 总被引:1,自引:1,他引:0
Stephanie S. Godfrey C. Michael Bull Richard James Kris Murray 《Behavioral ecology and sociobiology》2009,63(7):1045-1056
Gidgee skinks (Egernia stokesii) form large social aggregations in rocky outcrops across the Flinders Ranges in South Australia. Group members share refuges
(rock crevices), which may promote parasite transmission. We measured connectivity of individuals in networks constructed
from patterns of common crevice use and observed patterns of parasitism by three blood parasites (Hemolivia, Schellackia and Plasmodium) and an ectoparasitic tick (Amblyomma vikirri). Data came from a 1-year mark-recapture study of four populations. Transmission networks were constructed to represent possible
transmission pathways among lizards. Two lizards that used the same refuge within an estimated transmission period were considered
connected in the transmission network. An edge was placed between them, directed towards the individual that occupied the
crevice last. Social networks, a sub-set of same-day only associations, were small and highly fragmented compared with transmission
networks, suggesting that non-synchronous crevice use leads to more transmission opportunities than direct social association.
In transmission networks, lizards infested by ticks were connected to more other tick-infested lizards than uninfected lizards.
Lizards infected by ticks and carrying multiple blood parasite infections were in more connected positions in the network
than lizards without ticks or with one or no blood parasites. Our findings suggest higher levels of network connectivity may
increase the risk of becoming infected or that parasites influence lizard behaviour and consequently their position in the
network.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
This contribution is part of the special issue “Social Networks: new perspectives” (Guest Editors: J. Krause, D. Lusseau and
R. James). 相似文献
843.
Erin H. Gillam Gary F. McCracken John K. Westbrook Ya-Fu Lee Michael L. Jensen Ben B. Balsley 《Behavioral ecology and sociobiology》2009,64(1):69-79
Bats alter their echolocation in response to changes in ecological and behavioral conditions, but little is known about how
they adjust call structure in response to changes in altitude. We examined altitudinal variation in the echolocation of Brazilian
free-tailed bats, Tadarida brasiliensis, a species known to fly to altitudes of 3,000 m above the ground. From 50.2 h of recordings, we analyzed 113 high-quality
echolocation call sequences recorded from 0 to 862 m above ground level. Bats flying near the ground used shorter, higher-frequency,
broader-bandwidth calls compared to bats at higher altitudes, an effect likely due to the greater levels of echo-producing
clutter (i.e., vegetation, buildings) found near the ground. When ground-level recordings are excluded, bats continue to shift
towards the use of longer-duration, lower-frequency, narrower-bandwidth calls with increasing altitude. We propose that the
observed high-altitude changes in call structure are a response to changing acoustic attenuation rates and/or decreasing insect
densities at higher altitudes. 相似文献
844.
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
845.
At specific locations within the Baltic Sea, thermoclines and haloclines can create rapid spatial and temporal changes in
temperature (T) and salinity (S) exceeding 10°C and 9 psu with seasonal ranges in temperature exceeding 20°C. These wide ranges in abiotic factors affect
the distribution and abundance of Baltic Sea copepods via species-specific, physiological-based impacts on vital rates. In
this laboratory study, we characterized the influence of T and S on aspects of reproductive success and naupliar survival of a southwestern Baltic population of Temora longicornis (Copepoda: Calanoida). First, using ad libitum feeding conditions, we measured egg production (EP, no. of eggs female−1 day−1) at 12 different temperatures between 2.5 and 24°C, observing the highest mean EP at 16.9°C (12 eggs female−1 day−1). Next, the effect of S on EP and hatching success (HS, %) was quantified at 12°C for cohorts that had been acclimated to either 8, 14, 20 or 26 psu
and tested at each of five salinities (8, 14, 20, 26 and 32 psu). The mean EP was highest for (and maximum EP similar among)
14, 20 and 26 psu cohorts when tested at their acclimation salinity whereas EP was lower at other salinities. For adults reared
at 8 psu, a commonly encountered salinity in Baltic surface waters, EP was relatively low at all test salinities—a pattern
indicative of osmotic stress. When incubated at 12°C and 15 different salinities between 0 and 34 psu, HS increased asymptotically
with increasing S and was maximal (82.6–84.3%) between 24 and 26 psu. However, HS did depend upon the adult acclimation salinity. Finally,
the 48-h survival of nauplii hatched and reared at 14 psu at one of six different temperatures (10, 12, 14, 16, 18 and 20°C)
was measured after exposure to a novel salinity (either 7 or 20 psu). Upon exposure to 7 psu, 48-h naupliar mortality increased
with increasing temperature, ranging from 26.7% at 10°C to 63.2% at 20°C. In contrast, after exposure to 20 psu, mortality
was relatively low at all temperatures (1.7% at 10°C and ≤26.7% for all other temperatures). An intra-specific comparison
of EP for three different T. longicornis populations revealed markedly different temperature optima and clearly demonstrated the negative impact of brackish (Baltic)
salinities. Our results provide estimates of reproductive success and early survival of T. longicornis to the wide ranges of temperatures and salinities that will aid ongoing biophysical modeling examining climate impacts on
this species within the Baltic Sea. 相似文献
846.
847.
The disposal of sewage sludge from municipal waste water treatment plants is suffering from raising costs.The gasification is an alternative way of treatment, which can reduce the amount of solid residues that must be disposed from a water treatment plant. The produced gas can be used very flexible to produce electrical energy, to burn it very cleanly or to use it for upgrading.The gasification in the fluidised bed and the gas cleaning with the granular bed filter has shown successful operation. A demonstration plant in Balingen was set up in 2002 and rebuilt to a larger throughput in 2010. As a next step a demonstration plant was built in Mannheim and is now at the end of the commissioning phase. Nowadays the product gas is blended with biogas from sludge fermentation and utilized in a gas engine or combustion chamber to produce heat. In the future the process control for a maximized efficiency and the removal of organic and inorganic impurities in the gas will be further improved. 相似文献
848.
A comprehensive laboratory investigation was performed on municipal solid waste (MSW) from a landfill located in northern California using a large-scale triaxial (TX) apparatus. An improved, standardized waste specimen preparation method was developed and used to prepare 27 large-scale TX specimens (d=300mm, h=600-630mm). The effects of waste composition, confining stress, unit weight, loading rate, and stress path on the drained stress-strain response of MSW were investigated. Waste composition has a significant effect on its stress-strain response. The commonly observed upward curvature of the stress-strain response of specimens composed of larger-sized waste materials results from the fibrous constituents (primarily paper, plastic and wood) reinforcing the waste matrix. This effect is greatest when the MSW specimen is sheared across the long axis of the fibrous particles. Due to this significant strain hardening effect and waste's in situ stress state, a limiting strain failure criterion of 5% axial strain from the K(o) field consolidation state is judged to be most appropriate. Results from this test program and data from the literature indicate that the TX compression secant friction angle of MSW varies from 34° to 44°, with 39° as a best estimate, at a confining stress of one atmosphere (assuming c=0). The friction angle decreases as confining stress increases. The friction angles measured in this testing program are representative of failure surfaces that are oriented at an angle to the predominant orientation of the long axis of the fibrous waste particles. These friction angles are higher than those obtained in direct shear tests where shearing typically occurs parallel to the orientation of the fibrous waste particles. 相似文献
849.
850.
Analysis of the relationship between ambient levels of O3, NO2 and NO as a function of NOx in the UK
Monitoring data from the UK Automatic Urban and Rural Network are used to investigate the relationships between ambient levels of ozone (O3), nitric oxide (NO) and nitrogen dioxide (NO2) as a function of NOx, for levels ranging from those typical of UK rural sites to those observed at polluted urban kerbside sites. Particular emphasis is placed on establishing how the level of ‘oxidant’, OX (taken to be the sum of O3 and NO2) varies with the level of NOx, and therefore to gain some insight into the atmospheric sources of OX, particularly at polluted urban locations. The analyses indicate that the level of OX at a given location is made up of NOx-independent and NOx-dependent contributions. The former is effectively a regional contribution which equates to the regional background O3 level, whereas the latter is effectively a local contribution which correlates with the level of primary pollution. The local oxidant source has probable contributions from (i) direct NO2 emissions, (ii) the thermal reaction of NO with O2 at high NOx, and (iii) common-source emission of species which promote NO to NO2 conversion. The final category may include nitrous acid (HONO), which appears to be emitted directly in vehicle exhaust, and is potentially photolysed to generate HOx radicals on a short timescale throughout the year at southern UK latitudes. The analyses also show that the local oxidant source has significant site-to-site variations, and possible reasons for these variations are discussed. Relationships between OX and NOx, based on annual mean data, and fitted functions describing the relative contributions to OX made by NO2 and O3, are used to define expressions which describe the likely variation of annual mean NO2 as a function of NOx at 14 urban and suburban sites, and which can take account of possible changes in the regional background of O3. 相似文献