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991.
Craig E. Hebert D. V. Chip Weseloh Lewis T. Gauthier Michael T. Arts Robert J. Letcher 《Oecologia》2009,160(1):15-23
Food web structure regulates the pathways and flow rates of energy, nutrients, and contaminants to top predators. Ecologically
and physiologically meaningful biochemical tracers provide a means to characterize and quantify these transfers within food
webs. In this study, changes in the ratios of stable N isotopes (e.g., δ15N), fatty acids (FA), and persistent contaminants were used to trace food web pathways utilized by herring gulls (Larus argentatus) breeding along the shores of the St Lawrence River, Canada. Egg δ15N values varied significantly among years and were used as an indicator of gull trophic position. Temporal trends in egg δ15N values were related to egg FA profiles. In years when egg δ15N values were greater, egg FA patterns reflected the consumption of more aquatic prey. Egg δ15N values were also correlated with annual estimates of prey fish abundance. These results indicated that temporal changes
in aquatic prey availability were reflected in the gull diet (as inferred from ecological tracer profiles in gull eggs). Analysis
of individual eggs within years confirmed that birds consuming more aquatic prey occupied higher trophic positions. Furthermore,
increases in trophic position were associated with increased concentrations of most persistent organic contaminants in eggs.
However, levels of highly brominated polybrominated diphenyl ether congeners, e.g, 2,2′,3,3′,4,4′,5,5′,6,6′-decabromoDE (BDE-209),
showed a negative relationship with trophic position. These contrasting findings reflected differences among contaminant groups/homologs
in terms of their predominant routes of transfer, i.e., aquatic versus terrestrial food webs. High trophic level omnivores,
e.g., herring gulls, are common in food webs. By characterizing ecological tracer profiles in such species we can better understand
spatial, temporal, and individual differences in pathways of contaminant, energy, and nutrient flow. 相似文献
992.
Chose the arid interior district Shiyang River basin four issues of Landsat/TM images from 1986 to 2006 to visually interpret, and analyze the natural succession of ecological environment and the landscape pattern characteristic under the human activity interference. The results showed that in past 20 years, the number of landscape patch has increased, but the average patch size was decreasing, which explained that the landscape fragmentation degree was increasing, the landscape integrity was declining. The edge density of landscape remained invariable basically, which explained its stability maintained good. The diversity and evenness index continually enhanced, the diversity increased from 0.73 in 1986 to 0.84 in 2006. The mean core patch area of study area reduced from134.47 hm2 in 1994 to 127.67 hm2 in 2006, which indicated that the landscape core area was decreasing. On the one hand, it accelerated circulatory speed of species and reduced resistance of the energy flux. On the other hand it destroyed the integrity of the original landscape, easily caused the core area reducing continually, and led to vicious circle of the landscape separation. Seen from the whole study area, The utilization of landscape developed to the heterogeneous direction, indicated the proportional difference between various landscapes types was increasing, this kind of change has reflected the human activity’s influence to the whole landscape to a certain extent. It is believed that there are a series of landscape ecological problems such as low landscape ecological connectivity, simplified landscape structure and the more oasis fragmentation. In order to solve these problems, according to the principle that the movements of flow, energy and material in a landscape are related to some factors such as distance, time, impedance, etc., this study adopts the minimum accumulative resistance surface (MARS), the minimum cost resistance (MCR) model, and uses the surface diffusion technology to analyze compactness of landscape structure and the spatial difference of ecological function in Shiyang River basin. Then constructs some landscape components such as source, corridor and ecological node to strengthen the spatial connection of ecological network, and further discusses the landscape pattern optimization proposal. 相似文献
993.
The Guadiana River basin’s freshwater fish species richness, endemicity and threatened status (92% of native species are threatened)
highlight the need for a large-scale study to identify priority areas for their conservation. One of the most common problems
in conservation planning is the assessment of a site’s relative value for the conservation of regional biodiversity. Here
we used a two-tiered approach, which integrates an assessment of biodiversity loss and the evaluation of conservation value
through site-specific measures. These measures based on the reference condition approach introduce the ability to make objective
comparisons throughout the Guadiana River basin, thus avoiding a priori target areas. We identified a set of biodiversity
priority areas of special conservation significance—which contain rare taxa as well as intact fish communities—because of
their outstanding contribution to the basin’s biodiversity. The inclusion of complete sub-basins in these priority areas might
guarantee an optimal solution in terms of spatial aggregation and connectivity. However, the high spatial fragmentation to
which the Guadiana River basin is submitted due to river regulation highlights the necessity of a systematic approach to evaluate
the capability of the identified priority areas to maintain the Guadiana’s freshwater fish biodiversity.
Handling editor: R. H. Norris 相似文献
994.
It is essential to know the nutrient limitation status of biofilms to understand how they may buffer uptake and export of
nutrients from polluted watersheds. We tested the effects of nutrient additions on biofilm biomass (chlorophyll a, ash free dry mass (AFDM), and autotrophic index (AI, AFDM/chl a)) and metabolism via nutrient-diffusing substrate bioassays (control, nitrogen (N), phosphorus (P), and N + P treatments)
at 11 sites in the Upper Snake River basin (southeast Idaho, USA) that differed in the magnitude and extent of human-caused
impacts. Water temperature, turbidity, and dissolved inorganic N concentrations all changed seasonally at the study sites,
while turbidity and dissolved inorganic N and P also varied with impact level. Chl a and AI on control treatments suggested that the most heavily impacted sites supported more autotrophic biofilms than less-impacted
sites, and that across all sites biofilms were more heterotrophic in autumn than in summer. Nutrient stimulation or suppression
of biofilm biomass was observed for chl a in 59% of the experiments and for AFDM in 33%, and the most frequent response noted across all study sites was N limitation.
P suppression of chl a was observed only at the most-impacted sites, while AFDM was never suppressed by nutrients. When nutrient additions did have
significant effects on metabolism, they were driven by differences in biomass rather than by changes in metabolic rates. Our
study demonstrated that biofilms in southeast Idaho rivers were primarily limited by N, but nutrient limitation was more frequent
at sites with good water quality than at those with poor water quality. Additionally, heterotrophic and autotrophic biofilm
components may respond differently to nutrient enrichment, and nutrient limitation of biofilm biomass should not be considered
a surrogate for metabolism in these rivers.
Handling editor: D. Ryder 相似文献
995.
996.
M. G. Bennett J. Heath Howell B. R. Kuhajda R. M. Wood 《Journal of fish biology》2009,75(9):2363-2372
The mitochondrial cytochrome b gene was sequenced for six individuals of the pygmy madtom, Noturus stanauli, a globally imperilled catfish, from both known localities in Tennessee (U.S.A.) separated by over 1055 river km. Phylogenetic and population genetic analyses revealed little divergence between these populations for this locus. 相似文献
997.
Influence of Consumption of Cadmium-Polluted Rice or Jinzu River Water on Occurrence of Renal Tubular Dysfunction and/or Itai-itai Disease 总被引:4,自引:0,他引:4
Kobayashi E Suwazono Y Dochi M Honda R Kido T 《Biological trace element research》2009,127(3):257-268
The aim of this study was to clarify whether consumption of cadmium (Cd)-polluted rice or Jinzu River water exerted any influence
on the occurrence of renal tubular dysfunction and/or Itai-itai disease. From the participants of health examinations conducted
in 1967 and 1968, 3,078 subjects who had resided for >30 years in the present hamlet and were aged >50 years were selected
as the target population and were divided according to their residence in 55 hamlets. In a multiple regression analysis, the
regression coefficients between rice-Cd concentration and prevalence of abnormal urinary findings (proteinuria, glucosuria,
or proteinuria with glucosuria) or patients with Itai-itai disease were statistically significant between both sexes. The
correlation between the prevalence of users of Jinzu River water and the occurrence of glucosuria in men as well as abnormal
urinary findings in women was not statistically significant. We surmise that eating Cd-polluted rice and drinking and/or cooking
with Jinzu River water influenced the occurrence of Itai-itai disease. The occurrence of renal tubular dysfunction is likely
to have also been influenced by both factors, with eating Cd-polluted rice having a greater impact on the occurrence of renal
tubular dysfunction as compared to drinking and/or cooking with Jinzu River water. 相似文献
998.
甘肃白龙江中上游流域的黏菌 总被引:1,自引:1,他引:0
本文报道了采自甘肃白龙江中上游流域的黏菌52种,其中紫高杯菌Craterium paraguayenese、山地双皮菌Diderma montanum和双被绒泡菌Physarum bitectum为中国新记录种,另有34种为甘肃新记录种。 相似文献
999.
Phosphorus is an essential and oftenlimiting nutrientin both marine andfreshwater ecosystems,yetits oversup-plyis of concern in many environments due to its role ineutrophication[1].Phosphorus enters rivers from diffusecatchment sources(particularly agriculture)and point(effluent)sources.However,river systems have an im-portant internal capacity to remove or release phosphorusfrom/to the water column and to trans-form phosphorusbetween organic,inorganic,particulate and dissolvedforms.River bed… 相似文献
1000.
VIOLAINE NICOLAS BERTIN AKPATOU WIM WENDELEN JULIAN KERBIS PETERHANS AYODEJI OLAYEMI JAN DECHER ALAIN‐DIDIER MISSOUP CHRISTIANE DENYS PATRICK BARRIERE CORINNE CRUAUD MARC COLYN 《Zoological Journal of the Linnean Society》2010,160(2):397-419
The rodent genus Praomys is widely distributed in the African tropics. The species are cryptic, rendering the species taxonomy unclear. There are differences of opinion concerning the specific status of Praomys misonnei and Praomys tullbergi, and their geographical distribution. We sequenced the cytochrome b and/or the 16S gene of 221 specimens from 12 countries in order to evaluate the genetic variability within these two species, and to precisely determine their geographical distribution. Morphological and morphometrical analyses on the sequenced specimens were also performed to find criteria useful for the identification of museum specimens. Our results confirm that P. misonnei and P. tullbergi are two valid species that can be separated by molecular data. However, no single discrete morphological character or simple metric measurement can be used to discriminate them. The percentage of misclassified individuals in multivariate discriminant analysis is relatively high (10%). The two species have allopatric distributions: P. tullbergi occurs in West Africa, from eastern Guinea to western Ghana, and P. misonnei is widely distributed from eastern Ghana to western Kenya. Within P. misonnei we identified three or four major geographical clades: a West Central African clade, an East African clade, a Nigerian clade, and a possible West African clade. Within P. misonnei, high geographical morphometrical variability was also identified. The role of both rivers and Pleistocene forest refugia in promoting speciation within the genus Praomys is discussed. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 397–419. 相似文献