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1.
Non-native brook trout have become widely established in North European streams. We combined evidence from an artificial-stream experiment and drainage-scale field surveys to examine whether brook trout suppressed the growth of the native brown trout (age 0 to age 2). Our experimental results demonstrated that brown trout were unaffected by the presence of brook trout but that brook trout showed reduced growth in the presence of brown trout. However, the growth reduction only appeared in the experimental setting, indicating that the reduced spatial constraint of the experimental system may have forced the fish to unnaturally intense interactions. Indeed, in the field, no effect of either species on the growth of the putative competitor was detected. These results caution against uncritical acceptance of findings from small-scale experiments because they rarely scale up to more complex field situations. This and earlier work suggest that the establishment of brook trout in North European streams has taken place mainly because of the availability of unoccupied (or underutilized) niche space, rather than as a result of species trait combinations or interspecific competition per se. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

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Six behavioural experiments were carried out to investigate the magnetic field effects on the nest-exiting flight directions of the honeybee Schwarziana quadripunctata (Meliponini). No significant differences resulted during six experiment days under varying geomagnetic field and the applied static inhomogeneous field (about ten times the geomagnetic field) conditions. A surprising statistically significant response was obtained on a unique magnetic storm day. The magnetic nanoparticles in these bees, revealed by ferromagnetic resonance, could be involved in the observed effect of the geomagnetic storm.  相似文献   

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Bacteria thriving in underground systems, such as karsts, adapt to use a variety of nutrients. Most of these nutrients derive from superficial processes. This study shows that bacteria are able to differentially induce carbonate precipitation or dissolution depending on the availability of nutrients for growth. Different bacterial strains isolated from caves, representing the most common components of these microbial communities, were cultured with different carbon and nitrogen sources (e.g., acetate, glucose, peptone, humic acids) and induced changes in pH were measured during growth. Carbonate can either precipitate or dissolve during bacterial growth. The induction of carbonate precipitates or their dissolution as a function of consumption of specific carbon sources revealed the existence of an active nutrient cycling process in karsts and links nutrients and environmental conditions to the existence of a highly significant carbon sink in subterraneous environments.  相似文献   

5.
Since the appearance of porcine reproductive and respiratory syndrome virus (PRRSV) in the late 1980s, the virus has become endemic throughout the world, with only the countries of Sweden, Switzerland, Finland, Norway, Australia, and New Zealand historically free of PRRS virus. Biosecurity is maintained largely through restrictions on the importation of pigs and semen. The risk for a PRRSV outbreak via the legal importation of fresh/chilled/frozen pork from PRRSV-positive countries remains controversial. However, examination of the historical record shows that countries retained a PRRSV-negative status during the importation of more than 500,000 tons of fresh/chilled/frozen pork from PRRSV-positive trading partners. This review describes some of the unique properties of PRRSV, including the poor stability of the virus in the environment, the low probability for airborne transmission, and the inability to sustain infections in feral swine, which make PRRSV a poor candidate for disease introduction through the legal importation of pork.  相似文献   

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In recent years, the notion of a nexus involving water, energy, and food has been gaining attention in the scholarly literature and popular press, due partly to the impetus provided by an international conference on the nexus in 2011, and partly to the increasing interest among researchers and public officials in determining the investments and policies needed to achieve and sustain water, energy, and food security. While the notion of such a nexus is compelling to some observers, interactions involving water, energy, and food have been known and studied for many years by scientists and policy analysts. The need for greater integration of research and policy discourse across sectors and regions has been expressed in international meetings since the late 1940s. In addition, the conceptual basis for including water, energy, and food in the “nexus,” to the exclusion of other resources and inputs is not evident. In many cases, the information excluded from studies claiming to implement a nexus approach might be of greater importance to science and policy than the information included in the analysis. In this paper, I review some of the experience gained in earlier attempts to enhance integration and policy coherence, and to promote systems analysis. The challenges observed in implementing programs of integrated natural resources management (INRM) and integrated water resources management (IWRM), in particular, suggest that efforts to implement a water-energy-food nexus approach will not enhance the policy process in all settings. In sum, it is not clear that the increasing attention given to studies claiming to implement a nexus approach is warranted.  相似文献   

8.
Animals assess the fighting ability of conspecifics either by engaging in aggressive interactions or observing contests between others. However, whether individuals assess physical prowess outside the context of aggressive interactions remains unknown. We examined whether male green swordtails (Xiphophorus helleri) extract information about the fighting ability of solitary individuals via observation and whether acquiring such information elicits behavioral modifications. Contests preceded by mutual visual assessment were significantly shorter than fights where only one or neither of the two individuals was informed in advance. Focal animals initiated aggressive behavior more often against larger opponents only after previewing their adversary, indicating that swordtails can extract information about relative body size from watching solitary conspecifics. When a fighting disadvantage is perceived, observers adopt tactics that increase their probability of winning the contest.  相似文献   

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Mitigation and Adaptation Strategies for Global Change - Indonesia and Peru harbor some of the largest lowland tropical peatland areas. Indonesian peatlands are subject to much greater...  相似文献   

11.
Toxic effect of Zn(Ⅱ) on a green alga (Chlorella pyrenoidasa) in the presence of sepiolite and kaolinite was investigated.The Zn-free clays were found to have a negative impact on the growth of C.pyrenoidosa in comparison with control samples (without adding any clay or Zn(Ⅱ)).When Zn(Ⅱ) was added,the algae in the presence of clays could be better survived than the control samples,which was actually caused by a decrease in Zn(Ⅱ) concentration in the solution owing to the adsorption of Zn(Ⅱ) on the clays.When the solution system was diluted,the growth of algae could be further inhibited as compared to that in a system which had the same initial Zn(Ⅱ) concentration as in the diluted system.This in fact resulted from desorption of Zn(Ⅱ) from the zinc-contaminated clays,although the effect varied according to the different desorption capabilities of sepiolite and kaolinite.Therefore the adsorption and desorption processes of Zn(Ⅱ) played an important part in its toxicity,and adsorption and desorption of pollutants on soils/sediments should be well considered in natural eco-environmental systems before their risk of toxicity to aquatic organisms was assessed objectively.  相似文献   

12.
In species with more than one male reproductive morph, there typically exists a larger morph with exaggerated secondary sexual characters, and a smaller morph with reduced secondary sexual characters. These exaggerated and reduced morphologies are commonly thought to represent specializations to alternative behavioral reproductive tactics—large body size and exaggerated secondary sexual characters should both facilitate territoriality, courtship, and pair-spawning; while small body size and reduced secondary sexual characters should facilitate sneaky cuckoldry. Given this postulated relationship between morphology and behavior, we examined the relationship between the morphology of exaggerated males and cuckoldry. In a field and aquarium study of the midshipman fish, a fish with both exaggerated and reduced morphs, we demonstrated cuckoldry in some males of the exaggerated morph. Since the reduced morphology is thought to be an adaptation towards sneaky cuckoldry, we predicted that, of males with the exaggerated morph, less-exaggerated (smaller) males would be better able to gain proximity to the spawning pair during cuckoldry. In contrast to that prediction, access to the spawning pair during cuckoldry increased with the body size of the cuckolding exaggerated-morph males. This may be related to our observation that exaggerated males often cuckolded aggressively. Thus the exaggerated morphology need not preclude adaptive plasticity to cuckoldry, and may even aid it.  相似文献   

13.
In this research, for the first time, a series of Co(Ⅱ) doped copper terephthalate(Co X-Cu BDC,where X is doping percentage) were successfully synthesized via solvothermal method and were tested for dye removal application. The physical properties of Co X-CuBDC were studied by several techniques including X-ray diffraction(XRD), field emission scanning electron microscopy(FESEM), energy-dispersive spectroscopy(EDS), thermogravimetric analysis(TGA)and Brunauer–Emmett–Teller(BET) surface area analysis. The incorporation of Co(Ⅱ) dopant leads to isomorphic substitution of Cu(II) in the CuBDC framework with the maximum doping percentage of 22. Doping and parent MOFs which are non-porous were used for removal of Methylene Blue(MB) from aqueous solution. Adsorption capacity of Co22-CuBDC and CuBDC are 52 and 58 mg/g, respectively, both of which are higher than the adsorption capacity recorded from several high porosity MOFs. Adsorption kinetic studies indicate that adsorption process follows pseudo-second order model while the adsorption mechanism is dominated by electrostatic attraction. Overall, even though these materials show non-porous characteristic,it can be used effectively in wastewater treatment application.  相似文献   

14.
IntroductionEnvironmentalprotectionexpertsinmanycountriespayhighattentiontothedisposalofthewastewaterwithdyeorwithdeepchroma.Thoughatpresentbiodegradationisusedinthedisposalofthewastewater,theconcentrationandchromainthedisposedwaterarestillveryhighand…  相似文献   

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Sustainable use of the planet will require a more robust regulatory and management framework for marine areas as advances in offshore technology and changes in market conditions lead to an increase in coastal populations and marine recreation and tourism. Although each area of the world presents unique problems, many principles of stewardship, which can appropriately modified, will serve well anywhere on the planet. The purpose of this brief synopsis is to share these principles ot stewardship with colleagues in China. This volume (Striking a balance: improving stewardship of marine areas) notes:" In addition to the governance problems created by multiple nonmarket uses of marine resources and maintaining access to them, existing systems have two fundamental problems first, fragmentation among federal and local agencies and second, not enough participation and coordination of interests at the local level"( p. 4 ). Although this book focuses on marine ecosystems associated with the United States coastline( such as the Gulf of maine/Massachusetts Bay, the Florida Keys National Marine Sanctuary/Florida Bay ecosystem, and the Southern California coast), the issues, the problems, and strategies should be, with minor adjustments, fully applicable anywhere in the world. The following general elements of the framework for improved governance and management of marine areas are given as recommendations(p. 5)[Comments given in brackets are those of the author].  相似文献   

17.
The North Frisian Wadden Sea represents one of the best researched natural regions in the world. Since the end of the 1980s, scientific research has been carried out to scientifically study, analyse and assess this intertidal coastal zone under the conceptual umbrella of ecosystem research. The outcome of this assessment materialised in the establishment of the Nationalpark Schleswig-Holsteinisches Wattenmeer. Its implementation caused considerable conflicts between coastal inhabitants, national park authorities and government officials. Arguments in these disputes revolved around the validity and relevance of scientific knowledge generated to assess and legitimately protect the tidelands and areas of the Waddensea. In summary, the whole implementation process was locally perceived as a politically endorsed top-down enforcement strategy only allowing scientific knowledge for decision-making purposes while local concerns and ‘knowledges’ were not included. To learn from these developments and past mistakes, we compare concepts of co-management, boundary work and boundary objects (BO) to theoretically and methodologically explore their potentials to generate shared meanings and instigate communication in the context of future managing purposes. Against this theoretical background, we propose the empirical show-case example of the German concept of ‘Heimat’ as a BO to assess its applicability to study place-based meanings and to illustrate it as a practice-oriented point of entry to initiate productive science-stakeholder interaction (SSI) in managing the North Frisian Wadden Sea.  相似文献   

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The Caribbean is highly vulnerable to coastal hazards. Based on their short recurrence intervals over the intra-American seas, high-category tropical cyclones and their associated effects of elevated storm surge, heavy wave impacts, mudslides and floods represent the most serious threat. Given the abundance of historical accounts and trigger mechanisms (strike-slip motion and oblique collision at the northern and southern Caribbean plate boundaries, submarine and coastal landslides, volcanism), tsunamis must be considered as well. This paper presents interdisciplinary multi-proxy investigations of sediment cores (grain size distribution, carbonate content, loss-on-ignition, magnetic susceptibility, microfauna, macrofauna) from Washington-Slagbaai National Park, NW Bonaire (Leeward Antilles). No historical tsunami is recorded for this island. However, an allochthonous marine layer found in all cores at Boka Bartol reveals several sedimentary criteria typically linked with tsunami deposits. Calibrated 14C data from these cores point to a palaeotsunami with a maximum age of 3,300 years. Alternative explanations for the creation of this layer, such as inland flooding during tropical cyclones, cannot entirely be ruled out, though in recent times even the strongest of these events on Bonaire did not deposit significant amounts of sediment onshore. The setting of Boka Bartol changed from an open mangrove-fringed embayment into a poly- to hyperhaline lagoon due to the establishment or closure of a barrier of coral rubble during or subsequent to the inferred event. The timing of the event is supported by further sedimentary evidence from other lagoonal and alluvial archives on Bonaire.  相似文献   

20.
El Niño is well known to affect marine fishery. The Southern Oscillation, however, may also have a strong effect on riverine fish production in floodplains via its effect on river discharge. In years with high river discharges larger parts of the floodplain are inundated, increasing the surface area of suitable nursery grounds for young fish stock. In this way high river discharges are thought to have a positive effect on fish production, while low discharges are thought to have a negative effect. The collapse of the sábalo fishery in the Pilcomayo River in Bolivia, for instance, can be attributed to the 1990–1995 El Niño event and subsequent overexploitation of the fish stocks.  相似文献   

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