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991.
Babonneau Frédéric Biscaglia Stéphane Chotard David Haurie Alain Mairet Nicolas Lefillatre Thibaut 《Environmental Modeling and Assessment》2021,26(6):911-926
Environmental Modeling & Assessment - In this paper, we present a comprehensive, multi-timescale approach to evaluate energy transition policies aiming at fully renewable generation in power... 相似文献
992.
Lorien Pichegru Peter G. Ryan Robert J. M. Crawford Carl D. van der Lingen David Grémillet 《Marine Biology》2010,157(3):537-544
In variable environments, organisms are bound to track environmental changes if they are to survive. Most marine mammals and
seabirds are colonial, central-place foragers with long-term breeding-site fidelity. When confronted with environmental change,
such species are potentially constrained in their ability to respond to these changes. For example, if environmental conditions
deteriorate within their limited foraging range, long-lived species favour adult survival and abandon their current breeding
effort, which ultimately influences population dynamics. Should poor conditions persist over several seasons, breeding-site
fidelity may force animals to continue breeding in low-quality habitats instead of emigrating towards more profitable grounds.
We assessed the behavioural response of a site-faithful central-place forager, the Cape gannet Morus capensis, endemic to the Benguela upwelling system, to a rapid shift in the distribution and abundance of its preferred prey, small
pelagic shoaling fish. We studied the distribution and the abundance of prey species, and the diet, foraging distribution,
foraging effort, energy requirements, and breeding success of gannets at Malgas Island (South Africa) over four consecutive
breeding seasons. Facing a rapid depletion of preferred food within their foraging range, Cape gannets initially increased
their foraging effort in search of their natural prey. However, as pelagic fish became progressively scarcer, breeding birds
resorted to scavenging readily available discards from a nearby demersal fishery. Their chicks cannot survive on such a diet,
and during our 4-year study, numbers of breeding birds at the colony decreased by 40% and breeding success of the remaining
birds was very low. Such behavioural inflexibility caused numbers of Cape gannets breeding in Namibia to crash by 95% following
over-fishing of pelagic fish in the 1970s. In the context of rapid environmental changes, breeding-site fidelity of long-lived
species may increase the risk of local or even global extinction, rendering these species particularly vulnerable to global
change. 相似文献
993.
Quantitative polymerase chain reaction (qPCR) for the identification and quantification of microbes has become a common tool
for the study of harmful algal blooms (HABs). We developed a qPCR method for the diatom genus Pseudo-nitzschia. Several species of this genus form toxic blooms through the production of the neurotoxin domoic acid (DA). Outbreaks of
toxicity attributed to DA along the US west coast have caused sickness and death of marine mammals and seabirds through food
web contamination. The method developed here quantifies Pseudo-nitzschia spp. at low abundances in natural samples, thereby, providing a method to improve our understanding of the environmental
conditions leading to blooms of these species. This has been accomplished previously by techniques for identification and
quantification that are slow and laborious compared to qPCR. The approach was successfully tested and validated using eight
species of Pseudo-nitzschia and 33 non-target organisms and employed to follow local bloom dynamics. 相似文献
994.
Sea lions are generally considered opportunistic feeders. However, studies from different areas suggest their diet consists
mostly of four to five types of prey. Previous studies in Galapagos sea lions have identified at least three feeding strategies
for this species, suggesting diversification of their diet. Diet diversification is favored in organisms with relatively high
trophic position and subject to high intra-specific and low inter-specific competition. Zalophus wollebaeki meet these criteria as the only pinniped on San Cristobal Island, where three sea lion rookeries are located within 11 km:
a distance considerably shorter than their 41 km foraging range. To measure the degree of diet diversification, we used scats
and stable isotope analyses. A total of 270 scat samples from lactating females and 142 fur samples from sea lion pups were
collected during the breeding season 2006. The scat analysis identified distinct diets among rookeries, with minimal trophic
overlap (Cλ = 0.19), a trophic level TL = 4.5 (secondary–tertiary carnivore), and trophic breadth of a specialist predator (B
i
= 0.37). The mean δ15N and δ13C values were 13.07 ± 0.52 and −16.34 ± 0.37, respectively. No significant difference was found in the δ15N values from the sea lion rookeries, but differences were found inter- and intra-population in δ13C values for pups from different groups (ANOVA P < 0.05). Our results indicate that diet diversification is present in the Galapagos sea lion and may play important role
to the survival of the species in a habitat where pinniped populations are limited. 相似文献
995.
Patterns of connectivity are important in understanding the geographic scale of local adaptation in marine populations. While natural selection can lead to local adaptation, high connectivity can diminish the potential for such adaptation to occur. Connectivity, defined as the exchange of individuals among subpopulations, is presumed to be significant in most marine species due to life histories that include widely dispersive stages. However, evidence of local adaptation in marine species, such the Atlantic silverside, Menidia menidia, raises questions concerning the degree of connectivity. We examined geochemical signatures in the otoliths, or ear bones, of adult Atlantic silversides collected in 11 locations along the northeastern coast of the United States from New Jersey to Maine in 2004 and eight locations in 2005 using laser ablation inductively coupled plasma mass spectrometry (ICP-MS) and isotope ratio monitoring mass spectrometry (irm-MS). These signatures were then compared to baseline signatures of juvenile fish of known origin to determine natal origin of these adult fish. We then estimated migration distances and the degree of mixing from these data. In both years, fish generally had the highest probability of originating from the same location in which they were captured (0.01-0.80), but evidence of mixing throughout the sample area was present. Furthermore, adult M. menidia exhibit highly dispersive behavior with some fish migrating over 700 km. The probability of adult fish returning to natal areas differed between years, with the probability being, on average, 0.2 higher in the second year. These findings demonstrate that marine species with largely open populations are capable of local adaptation despite apparently high gene flow. 相似文献
996.
Many species of marine fish are typified by large population sizes, strong migratory behavior, high fecundity, and pelagic
eggs and larvae that are passively transported by ocean currents, all features that tend to increase gene flow, and hence
reduce genetic partitioning, among localized populations. The plaice, Pleuronectes platessa, is a commercially important demersal species that exhibits all of these characteristics. We analyzed genetic variation at
eight microsatellite loci in samples of spawning adults (N = 348) from the coasts of Ireland, Iceland, and, for the first time, from the Baltic Sea. Significant differentiation was
observed between Iceland and Irish and Baltic Sea samples. However, there were no genetic differences between Irish and Baltic
Sea samples, which contrast with the significant differentiation reported between Baltic Sea and North Sea/Atlantic populations
of other flatfish species. To increase the data set, we carried out a cross-calibration exercise, allowing us to perform a
joint analysis of data with an earlier study on adult and juvenile plaice (N = 480) collected over a broad geographic range, using six microsatellite loci in common to the two studies. Significant differentiation
was observed between fish collected at the northern (Iceland, Faeroes, Norway) and southern (Bay of Biscay) parts of the species
range. In contrast, the results showed little evidence of genetic structuring over much of the continental shelf of Europe.
We believe that bathymetric and hydrographic barriers are the major factors shaping genetic structure, while lack of structure
over much of the European continental shelf may be explained by a combination of past historical events, population structure,
and dynamics of the species. 相似文献
997.
Prolonged dormancy is a life-history stage in which mature plants fail to resprout for one or more growing seasons and instead remain alive belowground. Prolonged dormancy is relatively common, but the proximate causes and consequences of this intriguing strategy have remained elusive. In this study we tested whether stored resources are associated with remaining belowground, and investigated the resource costs of remaining belowground during the growing season. We measured stored resources at the beginning and end of the growing season in Astragalus scaphoides, an herbaceous perennial in southwest Montana, USA. At the beginning of the growing season, dormant plants had lower concentrations of stored mobile carbon (nonstructural carbohydrates, NSC) than did emergent plants. Surprisingly, during the growing season, dormant plants gained as much NSC as photosynthetically active plants, an increase most likely due to remobilization of structural carbon. Thus, low levels of stored NSC were associated with remaining belowground, and remobilization of structural carbon may allow for dormant plants to emerge in later seasons. The dynamics of NSC in relation to dormancy highlights the ability of plants to change their own resource status somewhat independently of resource assimilation, as well as the importance of considering stored resources in understanding plant responses to the environment. 相似文献
998.
We formulate a two-sex model of temperature-dependent sex determination (TSD) for a freshwater turtle (C. picta) population. The aim is to understand how environmental temperature variations and nest heat conduction properties affect the long term dynamics of the population. This is a key to understanding how global temperature changes may affect their survival. With stochastic inputs of ambient temperature and solar radiation, the model uses the heat equation to determine the temperature in the egg layer in the nest; in turn, this determines the sex ratio in the egg clutch using a variable degree-day model. Finally, a nonlinear Leslie type, stage-based, two-sex model, is used to determine the long term male and female populations. A two-sex model is required because of different development rates for males and females. The model is flexible enough to enable other researchers to examine the effects of temperature variation variations on other species with TSD, e.g., crocodilians, reptilians, as well as other turtle species. It can be adapted to study effects of nest location, soil type, rain events, different incubation periods, and density effects, for example, the dependence of the mating function on the ratio of males to females and each’s contribution to the sex of hatchlings. Modifications can be easily made to fit a specific life history traits. The model is a beginning step in understanding the long term, high fitness shown by many reptile species with TSD, and it may suggest to experimentalists what data may be relevant to these issues; it can also be useful to wildlife managers in developing strategies for intervention if needed. Among the principal findings are that temperature variability and detailed nest heat conduction properties may buffer projected negative effects on a population. 相似文献
999.
An understanding of the causal mechanisms and processes that shape macroinvertebrate communities at a local scale has important implications for the management and conservation of freshwater biodiversity. Here we compare the performance of linear and non-linear statistics to explore diversity-environment relationships using data from 76 temporary and fluctuating ponds in two regions of southern England. We focus on aquatic beetle assemblages, which have been shown to be excellent surrogates of wider freshwater macroinvertebrate diversity. Ponds in the region contained a rich coleopteran fauna, totaling 68 species, which provided an excellent model system with which to compare the performance of two non-linear procedures (artificial neural networks—ANNs and generalised additive models—GAMs) and one more traditional linear approach (Multiple linear regression—MLR) to modelling diversity-environment relationships. Of all approaches employed, the best fit was obtained using an ANN model with only four input variables (conductivity, turbidity, magnesium concentration and depth). This model accounted for 82% of the observed variability in Shannon diversity index across ponds. In contrast, the best GAM and MLR models only explained 50% and 14% of this variation, respectively. Contribution profile analysis of conductivity, turbidity, magnesium concentration and depth, obtained from the best fit ANN through a hierarchical cluster analysis, allowed the identification of direct and proxy effects in relation to the environmental variables measured in this study. In each case, distinct clusters of ponds were identified in contribution profile analysis, suggesting that ponds across the two regions fall into a number of discrete groups, whose beetle faunas respond in subtly yet significantly different ways to key environmental variables. Aquatic coleopteran diversity in ponds in the two regions appears to be driven at a local scale by changes in relatively few physicochemical gradients, which are related to diversity in a clearly non-linear manner. 相似文献
1000.
Youneng Tang Michal Ziv-El Chen Zhou Jung Hun Shin Chang Hoon Ahn Kerry Meyer Daniel Candelaria David Friese Ryan Overstreet Rick Scott Bruce E. Rittmann 《Frontiers of Environmental Science & Engineering》2010,4(3):280-285
A long-term pilot-scale H2-based membrane biofilm reactor (MBfR) was tested for removal of nitrate from actual groundwater. A key feature of this second-generation pilot MBfR is that it employed lower cost polyester hollow fibers and still achieved high loading rate. The steady-state maximum nitrate surface loading at which the effluent nitrate and nitrite concentrations were below the Maximum Contaminant Level (MCL) was at least 5.9 g·N·(m2·d)?1, which corresponds to a maximum volumetric loading of at least 7.7 kg·N·(m3·d) ?1. The steady-state maximum nitrate surface area loading was higher than the highest nitrate surface loading reported in the first-generation MBfRs using composite fibers (2.6 g·N·(m2·d)?1). This work also evaluated the H2-utilization efficiency in MBfR. The measured H2 supply rate was only slightly higher than the stoichiometric H2-utilization rate. Thus, H2 utilization was controlled by diffusion and was close to 100% efficiency, as long as biofilm accumulated on the polyester-fiber surface and the fibers had no leaks. 相似文献