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551.
John M. Logan Enrique Rodríguez-Marín Nicolas Goñi Santiago Barreiro Haritz Arrizabalaga Walter Golet Molly Lutcavage 《Marine Biology》2011,158(1):73-85
Atlantic bluefin tuna (Thunnus thynnus) are highly migratory predators whose abundance, distribution, and somatic condition have changed over the past decades.
Prey community composition and abundance have also varied in several foraging grounds. To better understand underlying food
webs and regional energy sources, we performed stomach content and stable isotope analyses on mainly juvenile (60–150 cm curved
fork length) bluefin tuna captured in foraging grounds in the western (Mid-Atlantic Bight) and eastern (Bay of Biscay) Atlantic
Ocean. In the Mid-Atlantic Bight, bluefin tuna diet was mainly sand lance (Ammodytes spp., 29% prey weight), consistent with historic findings. In the Bay of Biscay, krill (Meganyctiphanes norvegica) and anchovy (Engraulis encrasicolus) made up 39% prey weight, with relative consumption of each reflecting annual changes in prey abundance. Consumption of anchovies
apparently declined after the local collapse of this prey resource. In both regions, stable isotope analysis results showed
that juvenile bluefin tuna fed at a lower trophic position than indicated by stomach content analysis. In the Mid-Atlantic
Bight, stable isotope analyses suggested that >30% of the diet was prey from lower trophic levels that composed <10% of the
prey weights based upon traditional stomach content analyses. Trophic position was similar to juvenile fish sampled in the
NW Atlantic but lower than juveniles sampled in the Mediterranean Sea in previous studies. Our findings indicate that juvenile
bluefin tuna targeted a relatively small range of prey species and regional foraging patterns remained consistent over time
in the Mid-Atlantic Bight but changed in relation to local prey availability in the Bay of Biscay. 相似文献
552.
Dirivultid copepods are among the most successful organisms at deep-sea hydrothermal vents, as this family includes 50 morphologically
described species. We studied COI diversity of some species in various geographical areas and vent fluid regimes, in order
to gain a better understanding of true species diversity, dispersal strategies, and evolution. DNA taxonomy revealed the same
entities as described with morphological characters. No cryptic species were detected. With the help of COI analyses, it was
possible to identify a new species and match the dimorphic sexes of another species. The geographical distance between vents,
as well as the extreme physico-chemical environment, are thought to affect the gene flow of fauna. We could not detect any
sequence differences within species among different geographical scales (up to 2,000 km) or different vent fluid regimes.
We suggest that Dirivultidae have relatively high gene flow between vents and are able to disperse relatively easy along ridges.
Further, they have a broad physiological tolerance and thus might not have undergone speciation in response to heterogeneity
caused by vent fluids. 相似文献
553.
Cynthia A. Ursino María C. De Mársico Mariela Sued Andrés Farall Juan C. Reboreda 《Behavioral ecology and sociobiology》2011,65(12):2279-2286
Obligate avian brood parasites lay their eggs in nests of other species (hosts), which raise parasitic young. Parasitic nestlings
are likely to influence host’s parental behaviours as they typically beg for food more vigorously than young host for a given
hunger level. However, few studies have tested this idea, with conflicting results. These prior studies were largely limited
to biparental hosts, but little is known about the effect of brood parasitism on parental behaviours in hosts that breed cooperatively.
We followed a multimodel approach to examine the effect of brood parasitism on nest provisioning and helper recruitment in
the baywing (Agelaioides badius), a cooperative breeder parasitised by screaming (Molothrus rufoaxillaris) and shiny (Molothrus bonariensis) cowbirds. Multimodel inference results indicated that feeding visits increased with nestling age, cooperative group size
and number of cowbird nestlings in the brood. Brood size had little influence on feeding visits, which further suggests that
baywings adjusted their provisioning effort in response to cowbird parasitism. In addition, nests parasitised artificially
with shiny cowbird eggs or hatchlings recruited more helpers than unmanipulated nests having only host or screaming cowbird
young. Our results provide novel evidence that brood parasitism and cooperative breeding interact in determining the levels
of nest provisioning. 相似文献
554.
Understanding the conditions that force the implementation of management actions and their efficiency is crucial for conservation of endangered species. Wildlife managers are widely and increasingly using food supplementation for such species because the potentially immediate benefits may translate into rapid conservation improvements. Supplementary feeding can also pose risks eventually promoting undesired, unexpected, subtle, or indirect, and often unnoticed, effects that are generally poorly understood. For two decades, intensive food supplementation has been used in attempting to improve the breeding productivity of the Spanish Imperial Eagle, Aquila adalberti, one of the most endangered birds of prey in the world. Here, we examined the impact of this intensive management action on nestling health, including contamination, immunodepression, and acquisition of disease agents derived from supplementation techniques and provisioned food. Contrary to management expectations, we found that fed individuals were often inadvertently "medicated" with pharmaceuticals (antibiotics and antiparasitics) contained in supplementary food (domestic rabbits). Individuals fed with medicated rabbits showed a depressed immune system and a high prevalence and richness of pathogens compared with those with no or safe supplementary feeding using non-medicated wild rabbits. A higher presence of antibiotics (fluoroquinolones) was found in sick as opposed to healthy individuals among eaglets with supplementary feeding, which points directly toward a causal effect of these drugs in disease and other health impairments. This study represents a telling example of well-meaning management strategies not based on sound scientific evidence becoming a "contraindicated" action with detrimental repercussions undermining possible beneficial effects by increasing the impact of stochastic factors on extinction risk of endangered wildlife. 相似文献
555.
Age effect on the antioxidant activity of Daphnia magna (Anomopoda: Daphniidae): does younger mean more sensitivity? 总被引:1,自引:0,他引:1
Alberto AC Rocío OB Fernando MJ 《Journal of environmental biology / Academy of Environmental Biology, India》2011,32(4):481-487
It has been accepted that for most species newborns and senescent organisms are more sensitive than other ages to environmental stressors. Nevertheless, it must be considered that there are several biochemical and physiological compensatory processes which are not expressed with the same magnitude during the whole life cycle. With this aim, Daphnia magna individuals of different age were exposed to hexavalent chromium, Cr (VI), at two different sublethal concentrations (0.032 and 0.0064 mg l(-1)), and the activity of some antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR) and glutathione peroxidase (GPx) were evaluated during most of the life cycle of this cladoceran. The antioxidant enzymatic activity showed an inverse relationship with respect to age. The activity of CAT, GR and GPx were increased in the two treated groups, at all life stages tested. On the other hand, the activity of SOD decreased in the same groups. Both, increase and decrease in the antioxidant enzymatic activities, showed significant differences with respect to the control group, being higher for the 0.032 mg l(-1) group. The Cr (VI) LC50 was also estimated for these age groups, finding statistical differences among them. Even though adults exhibited higher responses, these enzymatic activity changes should not be interpreted as higher sensitivity, since the daphnids acute chromium toxicity followed a different pattern, with increasing LC50 values according to age. 相似文献
556.
Fernandes C Fontaínhas-Fernandes A Cabral D Salgado MA 《Environmental monitoring and assessment》2008,136(1-3):267-275
Esmoriz–Paramos lagoon is an ecosystem of great ecological importance that is located on the northwest coast of Portugal and
has been degraded as a result of industrial and anthropogenic activities. Concentrations of heavy metals (Cr, Cu, Pb and Zn)
were measured in water, sediment and in tissues (liver and muscle) of Liza saliens, which is the dominant fish from the lagoon. Comparisons between metal concentrations in water and sediments were made with
those in tissues of fish caught at the lagoon. Metals in water were quantified predominantly bound to particulate and equalled
or exceeded the limit of chronic reference values. Metal concentrations in sediments varied among sampled sites. The relative
order of concentrations was “Zn > Cu ∼ Pb > Cr” the same pattern observed for metals in water. Metals in fish tissues showed
higher concentrations in liver (262 mg Cu·Kg−1 and 89 mg Zn·Kg−1) than in muscle (<3 mg Cu·Kg−1 and 26 mg Zn·Kg−1), while Pb and Cr were not detected. These results suggest that Cu and Zn are the metals of major concern in the lagoon.
Mullet detritivorous feeding habits, bioaccumulation pattern and the high sediment metals concentrations relative to the water
suggest that sediments can be the most important source of contamination in this ecosystem. The positive relationship found
between Cu in liver and fish length demonstrates that time of exposure is a crucial factor in bioaccumulation. Condition indices
(K and HSI) in mullets from the lagoon were higher compared to mullets from sea, suggesting abnormal condition in the lagoon
population. We conclude that metals chronic exposure in the lagoon can impose considerable fish stress. The results also show
that the lagoon is an area of environmental concern. 相似文献
557.
The degree at which tropical forests are exposed to human pressure is spatially dependent. Population density, proximity to
roads, terrain slope, logging activities and land distribution projects are well known factors inducing deforestation and
forest degradation in Latin America. Using expert knowledge to weight these threat factors and a Geographical Information
System for spatial modeling, a multi-criteria analysis procedure is presented, that allows stratifying a study region in categories
of deforestation threat. The procedure was implemented in the Central Volcanic Mountain Range Conservation Area (CVMRCA) in
Costa Rica with the purpose of finding areas with a combination of physical and socioeconomic characteristics that is particularly
predisposing to a high probability of deforestation. To validate the map, the CVMRCA was stratified in categories of deforestation
risk, and the result was superposed to historical deforestation data of the period 1986–1996. The good correlation between
risk category and historical deforestation (r = 0.91, p < 0.001) indicates that the map can be used as a decision support tool for defining priority areas for conservation action. 相似文献
558.
López-Antón MA Díaz-Somoano M Cuesta AF Riesco AR Martínez-Tarazona MR 《Journal of environmental monitoring : JEM》2008,10(6):778-781
This study evaluates the behaviour of total Cr and Cr (VI) during coal combustion in two Spanish power stations. The content and distribution of Cr in the feed coal and combustion wastes was determined and the Cr contents were normalized using enrichment factor indexes. The speciation of Cr in the fly ash fractions from the different hoppers of the electrostatic precipitators was established and the possibility that the Cr (VI) might lixiviate when ashes are disposed of at landfill sites was assessed. Differences in the distribution and behavior of Cr in the two power stations were observed. According to European directive 1999/31/CEE, soluble Cr(VI) in the fly ashes studied would be unlikely to pose an environmental or health risk when the ash is disposed of. 相似文献
559.
Paisio CE Talano MA González PS Busto VD Talou JR Agostini E 《Environmental science and pollution research international》2012,19(8):3430-3439
Introduction
Wastewater derived from leather production may contain phenols, which are highly toxic, and their degradation could be possible through bioremediation technologies.Materials, methods and results
In the present work, microbial degradation of phenol was studied using a tolerant bacterial strain, named CS1, isolated from tannery sediments. This strain was able to survive in the presence of phenol at concentrations of up to 1,000?mg/L. On the basis of morphological and biochemical properties, 16S rRNA gene sequencing, and phylogenetic analysis, the isolated strain was identified as Rhodococcus sp. Phenol removal was evaluated at a lab-scale in Erlenmeyer flasks and at a bioreactor scale in a stirred tank reactor. Rhodococcus sp. CS1 was able to completely remove phenol in a range of 200 to 1,000?mg/L in mineral medium at 30 ± 2?°C and pH 7 as optimal conditions. In the stirred tank bioreactor, we studied the effect of some parameters, such as agitation (200?C600 rpm) and aeration (1?C3?vvm), on growth and phenol removal efficiency. Faster phenol biodegradation was obtained in the bioreactor than in Erlenmeyer flasks, and maximum phenol removal was achieved at 400?rpm and 1 vvm in only 12?h. Furthermore, Rhodococcus sp. CS1 strain was able to grow and completely degrade phenols from tannery effluents after 9?h of incubation.Conclusion
Based on these results, Rhodococcus sp. CS1 could be an appropriate microorganism for bioremediation of tannery effluents or other phenol-containing wastewaters. 相似文献560.
Navarro-Ortega A Acuña V Batalla RJ Blasco J Conde C Elorza FJ Elosegi A Francés F La-Roca F Muñoz I Petrovic M Picó Y Sabater S Sanchez-Vila X Schuhmacher M Barceló D 《Environmental science and pollution research international》2012,19(4):918-933