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1.
We used stable carbon (δ13 C) and nitrogen (δ15 N) isotopes to assess the importance of benthic algae for the zooplankton individual growth in winter in a shallow, clear subarctic lake. The δ13 C values of calanoid ( Eudiaptomus graciloides ) and cyclopoid ( Cyclops scutifer ) zooplankton in autumn suggest a food resource of pelagic origin during the ice-free period. The zooplankton δ13 C values were high in spring compared to autumn. E. graciloides did not grow over winter and the change in δ13 C was attributed to a decrease in lipid content during the winter. In contrast, the increase in δ13 C values of C. scutifer over the winter was explained by their growth on organic carbon generated by benthic algae. The δ15 N of the C. scutifer food resource during winter was low compared to δ15 N of the benthic community, suggesting that organic matter generated by benthic algae was mainly channelled to zooplankton via 15 N-depleted heterotrophic bacteria. The results demonstrate that benthic algae can sustain zooplankton metabolic demands and growth during long winters, which, in turn, may promote zooplankton growth on pelagic resources during the summer. Such multi-chain omnivory challenges the view of zooplankton as mainly dependent on internal primary production and stresses the importance of benthic resources for the productivity of plankton food webs in shallow lakes. 相似文献
2.
R. L. FRANCE 《Freshwater Biology》1996,36(1):1-6
1. Although marine research has indicated that metabolic fractionations of 13 C due to differences in organismal trophic position and proximal composition can complicate the isotopic interpretation of energy flow pathways, such potentially confounding problems have never been examined in freshwater benthic food webs.
2. The δ13 C values of animals comprising a littoral benthic food web composited from four Canadian Shield lakes showed no relationship with either individual trophic position (δ15 N) or lipid content (C/N ratios).
3. Differences in the relative incorporation of autochthonous and allochthonous energy sources by freshwater benthic organisms will alter their δ13 C and δ15 N values, thereby masking any possibility of observing 13 C trophic enrichment.
4. Removal of the possibly confounding influences of lipids through either empirical correction or by analytical extraction may be unnecessary in studies of freshwater benthic food webs. Likewise, a priori adjustments in δ13 C for freshwater benthic organisms in order to accommodate trophic fractionations which are presumed to occur, based on data from marine offshore food webs, may also be inappropriate. 相似文献
2. The δ
3. Differences in the relative incorporation of autochthonous and allochthonous energy sources by freshwater benthic organisms will alter their δ
4. Removal of the possibly confounding influences of lipids through either empirical correction or by analytical extraction may be unnecessary in studies of freshwater benthic food webs. Likewise, a priori adjustments in δ
3.
1. Although marine research has indicated that metabolic fractionations of 13 C due to differences in organismal trophic position and proximal composition can complicate the isotopic interpretation of energy flow pathways, such potentially confounding problems have never been examined in freshwater benthic food webs.
2. The δ13 C values of animals comprising a littoral benthic food web composited from four Canadian Shield lakes showed no relationship with either individual trophic position (δ15 N) or lipid content (C/N ratios).
3. Differences in the relative incorporation of autochthonous and allochthonous energy sources by freshwater benthic organisms will alter their δ13 C and δ15 N values, thereby masking any possibility of observing 13 C trophic enrichment.
4. Removal of the possibly confounding influences of lipids through either empirical correction or by analytical extraction may be unnecessary in studies of freshwater benthic food webs. Likewise, a priori adjustments in δ13 C for freshwater benthic organisms in order to accommodate trophic fractionations which are presumed to occur, based on data from marine offshore food webs, may also be inappropriate. 相似文献
2. The δ
3. Differences in the relative incorporation of autochthonous and allochthonous energy sources by freshwater benthic organisms will alter their δ
4. Removal of the possibly confounding influences of lipids through either empirical correction or by analytical extraction may be unnecessary in studies of freshwater benthic food webs. Likewise, a priori adjustments in δ
4.
1. Changes of δ13 C and its relation to leaf development, biochemical content and water stress were monitored over a 2 year period in two co-occurring Mediterranean oak species: the deciduous Quercus pubescens and the evergreen Quercus ilex .
2. The time course of leaf δ13 C showed different patterns in the two species. Young Q. pubescens leaves had a high δ13 C and a marked decrease occurred during leaf growth. In contrast, leaves at budburst and maturity did not differ significantly in the case of Q. ilex . We suggest that the difference between δ13 C of young leaves was linked to differential use of reserves of carbon compounds in the two species.
3. δ13 C values of mature leaves were negatively correlated with minimum seasonal values of predawn water potential, suggesting that a functional adjustment to water resources occurred.
4. There was a significant correlation between individual δ13 C values for two successive years. This interannual dependence showed that δ13 C rankings between trees were constant through time. 相似文献
2. The time course of leaf δ
3. δ
4. There was a significant correlation between individual δ
5.
Stable isotope analysis of macroinvertebrates and their food sources in a glacier stream 总被引:5,自引:0,他引:5
Rainer Zah Peter Burgherr Stefano M. Bernasconi & Urs Uehlinger 《Freshwater Biology》2001,46(7):871-882
1. Food sources and trophic structure of the macroinvertebrate community along a longitudinal gradient were examined in a glacier stream of the Swiss Alps (Val Roseg). Analysis of multiple stable isotopes (δ13 C and δ15 N) and measurement of C : N ratios were used to differentiate between allochthonous and autochthonous organic matter.
2. Although isotopic signatures of algae varied widely among sites and dates, it was possible to discriminate between allochthonous and autochthonous food sources using a site-specific approach.
3. Dominant food sources of herbivorous invertebrates in all main channel sites were epilithic diatoms and the filamentous gold alga Hydrurus foetidus . Allochthonous organic matter was of some importance only in a groundwater-fed stream close to the floodplain margin.
4. Seasonal changes in the δ13 C signature of the macroinvertebrates corresponded with seasonal changes in δ13 C of the gold alga H. foetidus . This indicated that the energy base remains autochthonous throughout the year.
5. Because of limited food sources, feeding plasticity of the invertebrate community was high. Both grazers and shredders fed predominantly on algae, whereas gatherer-collectors seemed to be omnivorous.
6. The overall enrichment of δ15 N was 2.25‰ ( r 2 =0.99) per trophic level. On a gradient from the glacier site to a downstream forested site trophic enrichment was constant but variation in δ15 N within trophic levels decreased. 相似文献
2. Although isotopic signatures of algae varied widely among sites and dates, it was possible to discriminate between allochthonous and autochthonous food sources using a site-specific approach.
3. Dominant food sources of herbivorous invertebrates in all main channel sites were epilithic diatoms and the filamentous gold alga Hydrurus foetidus . Allochthonous organic matter was of some importance only in a groundwater-fed stream close to the floodplain margin.
4. Seasonal changes in the δ
5. Because of limited food sources, feeding plasticity of the invertebrate community was high. Both grazers and shredders fed predominantly on algae, whereas gatherer-collectors seemed to be omnivorous.
6. The overall enrichment of δ
6.
Seasonal Variation of δ^13C of Four Tree Species: A Biological Integrator of Environmental Variables 总被引:2,自引:0,他引:2
Hai-Tao LI Jun XIA Le XIANG Tao LIANG Qi-Jing LIU 《植物学报(英文版)》2005,47(12):1459-1469
Foliar δ^13C values, an indicator of long-term intercellular carbon dioxide concentration and, thus, of long-term water use efficiency (WUE) in plants, were measured for Pinus massoniana Lamb., P. elliottii Engelm., Cunninghamia laceolata (Lamb.) Hook., and Schima superba Gardn. et Champ. in a restored forest ecosystem in the Jiazhu River Basin. Seasonal variation and the relationship between the foliar δ^13C values of the four species and environmental factors (monthly total precipitation, monthly average air temperature, relative humidity, atmospheric pressure, and monthly total solar radiation and evaporation) were investigated. The monthly δ^13C values and WUE of the four species increased with increasing precipitation, air temperature, solar radiation, and evaporation, whereas δ^13C values of the four species decreased with increasing relative humidity and atmospheric pressure. Despite significant differences in δ^13C seasonal means for the four species, our results demonstrate a significant convergence in the responses of δ^13C values and WUE to seasonal variations in environmental factors among the species investigated and that the δ^13C signature for each species gives a strong indication of environmental variables. 相似文献
7.
R. L. France 《Freshwater Biology》1999,41(1):101-105
1. Littoral biota in boreal lakes are known to assimilate epilithon. Being able to predict the stable isotopic composition of these alga will help to identify those systems in which δ13 C and δ15 N analysis can be used in foodweb investigations of allochthony and biomagnification.
2. In a survey of 15 boreal lakes, the concentration of dissolved organic carbon (DOC) explained 76% of the variation in epilithon δ13 C, and 86% of the variation in epilithon δ15 N.
3. Because both δ13 C and δ15 N values were depressed and similar to terrestrial values in humic (high DOC) lakes, it will be more difficult to successfully employ stable isotopic techniques for estimating allochthony in such systems. Lower δ15 N values in humic lakes also indicate that trophic positions estimated by stable isotopes are not directly comparable to those of similar biota inhabiting clearwater lakes, unless autochthonous baseline corrections are made. 相似文献
2. In a survey of 15 boreal lakes, the concentration of dissolved organic carbon (DOC) explained 76% of the variation in epilithon δ
3. Because both δ
8.
Isotopic analysis of the sources of organic carbon for zooplankton in shallow subarctic and arctic waters 总被引:1,自引:0,他引:1
Shallow high-latitude lakes and ponds are usually characterized by an oligotrophic water column overlying a biomass-rich, highly productive benthos. Their pelagic food webs often contain abundant zooplankton but the importance of benthic organic carbon versus seston as their food sources has been little explored. Our objectives were to measure the δ13 C and δ15 N isotopic signatures of pelagic and benthic particulate organic matter (POM) in shallow water bodies in northern Canada and to determine the relative transfer of this material to zooplankton and other aquatic invertebrates. Fluorescence analysis of colored dissolved organic matter (CDOM) indicated a relatively strong terrestrial carbon influence in five subarctic waterbodies whereas the CDOM in five arctic water columns contained mostly organic carbon of autochthonous origin. The isotopic signatures of planktonic POM and cohesive benthic microbial mats were distinctly different at all study sites, while non-cohesive microbial mats often overlapped in their δ13 C signals with the planktonic POM. Zooplankton isotopic signatures indicated a potential trophic link with different fractions of planktonic POM and the non-cohesive mats whereas the cohesive mats did not appear to be used as a major carbon source. The zooplankton signals differed among species, indicating selective use of resources and niche partitioning. Most zooplankton had δ13 C values that were intermediate between the values of putative food sources and that likely reflected selective feeding on components of the pelagic or benthic POM. The results emphasize the likely importance of benthic-pelagic coupling in tundra ecosystems, including for species that are traditionally considered pelagic and previously thought to be dependent only on phytoplankton as their food source. 相似文献
9.
Correlations Between Foliar Stable Carbon Isotope Composition and Environmental Factors in Desert Plant Reaumuria soongorica (Pall.) Maxim. 总被引:2,自引:0,他引:2
Jian-Ying MA Tuo CHEN Wei-Ya QIANG Gang WANG 《植物学报(英文版)》2005,47(9):1065-1073
Leaves of 407 individuals of Reaumuria soongorica (Pall.) Maxim. collected from the major distribution areas were measured to investigate the distribution characteristics of the stable carbon isotope in this desert plant, as well as correlations between δ^13C values and environmental factors. Results showed that δ^13C values in R. soongorica ranged from -22.77‰ to -29.85‰ and that the mean δ^13C value (-26.52‰) was higher than a previously reported δ^13C value for a different desert ecosystem. This indicates that R. soongorica belongs to the C3 photosynthetic pathway and has higher water use efficiency than other species. The correlations between δ^13C values and environmental factors demonstrated that the foliar δ^13C values in R. soongorica increased significantly with decreasing mean annual precipitation and mean relative humidity, and decreased with decreasing duration of sunshine and evaporation. The spatial distribution trend of δ^13C values in R. soongorica was not obvious and there was no significant correlation between the δ^13C values and mean annual temperature. We conclude that different distribution trends in δ^13C values for R. soongorica were likely caused by stomatal limitation rather than by nutrient-related changes in photosynthetic efficiency and that precipitation played an important role in the wide distribution range of R. soongorica. This pattern of δ^13C values for R. soongorica reinforced that it is a super-xerophil in terms of its adaptive strategies to a desert environment. 相似文献
10.
Tracing carbon and oxygen isotope signals from newly assimilated sugars in the leaves to the tree-ring archive 总被引:1,自引:0,他引:1
ARTHUR GESSLER ELKE BRANDES NINA BUCHMANN GERHARD HELLE HEINZ RENNENBERG & ROMAIN L. BARNARD 《Plant, cell & environment》2009,32(7):780-795
The analysis of δ 13 C and δ 18 O in tree-ring archives offers retrospective insights into environmental conditions and ecophysiological processes. While photosynthetic carbon isotope discrimination and evaporative oxygen isotope enrichment are well understood, we lack information on how the isotope signal is altered by downstream metabolic processes.
In Pinus sylvestris , we traced the isotopic signals from their origin in the leaf water ( δ18 O) or the newly assimilated carbon ( δ 13 C), via phloem sugars to the tree-ring, over a time-scale that ranges from hours to a growing season.
Seasonally, variable13 C enrichment of sugars related to phloem loading and transport did lead to uncoupling between δ 13 C in the tree-ring, and the c i / c a ratio at the leaf level. In contrast, the oxygen isotope signal was transferred from the leaf water to the tree-ring with an expected enrichment of 27‰, with time-lags of approximately 2 weeks and with a 40% exchange between organic oxygen and xylem water oxygen during cellulose synthesis.
This integrated overview of the fate of carbon and oxygen isotope signals within the model tree species P. sylvestris provides a novel physiological basis for the interpretation of δ13 C and δ 18 O in tree-ring ecology. 相似文献
In Pinus sylvestris , we traced the isotopic signals from their origin in the leaf water ( δ
Seasonally, variable
This integrated overview of the fate of carbon and oxygen isotope signals within the model tree species P. sylvestris provides a novel physiological basis for the interpretation of δ
11.
We evaluated diurnal and seasonal patterns of carbon isotope composition of leaf dark-respired CO2 ( δ 13 Cl ) in the C3 perennial shrub velvet mesquite ( Prosopis velutina ) across flood plain and upland savanna ecosystems in the south-western USA. δ 13 Cl of darkened leaves increased to maximum values late during daytime periods and declined gradually over night-time periods to minimum values at pre-dawn. The magnitude of the diurnal shift in δ 13 Cl was strongly influenced by seasonal and habitat-related differences in soil water availability and leaf surface vapour pressure deficit. δ 13 Cl and the cumulative flux-weighted δ 13 C value of photosynthates were positively correlated, suggesting that progressive 13 C enrichment of the CO2 evolved by darkened leaves during the daytime mainly resulted from short-term changes in photosynthetic 13 C discrimination and associated shifts in the δ 13 C signature of primary respiratory substrates. The 13 C enrichment of dark-respired CO2 relative to photosynthates across habitats and seasons was 4 to 6‰ at the end of the daytime period (1800 h), but progressively declined to 0‰ by pre-dawn (0300 h). The origin of night-time and daytime variations in δ 13 Cl is discussed in terms of the carbon source(s) feeding respiration and the drought-induced changes in carbon metabolism. 相似文献
12.
The sloughed skin from three captive manatees at Lowry Park Zoological Garden (Tampa, Florida) was examined over a period of one year to determine its stable carbon isotopic composition (δ13 C). The food consumed by these manatees in a controlled diet was also sampled and its δ13 C values determined. The sloughed skin δ13 C values from the captive manatees were enriched by an average of +4.1%0 relative to lettuce (generally >98% of the diet) the animals consumed. δ13 C values of the skin were shown to be related to changes in δ13 C values of the lettuce.
The stable carbon isotopic composition of internal tissues (liver, kidney, and blubber) and skin from dead, stranded manatees was also determined. These values were compared to values of vegetation that manatees are known to eat in the wild. The δ13 C values of the internal tissues and skin of wild manatees were consistent with the range of δ13 C values of their expected diet. 相似文献
The stable carbon isotopic composition of internal tissues (liver, kidney, and blubber) and skin from dead, stranded manatees was also determined. These values were compared to values of vegetation that manatees are known to eat in the wild. The δ
13.
Minghua Song Deyu Duan Hui Chen Qiwu Hu Feng Zhang Xingliang Xu Yuqiang Tian Hua Ouyang Changhui Peng 《Ecography》2008,31(4):499-508
Leaf δ13 C is an indicator of water-use efficiency and provides useful information on the carbon and water balance of plants over longer periods. Variation in leaf δ13 C between or within species is determined by plant physiological characteristics and environmental factors. We hypothesized that variation in leaf δ13 C values among dominant species reflected ecosystem patterns controlled by large-scale environmental gradients, and that within-species variation indicates plant adaptability to environmental conditions. To test these hypotheses, we collected leaves of dominant species from six ecosystems across a horizontal vegetation transect on the Tibetan Plateau, as well as leaves of Kobresia pygmaea (herbaceous) throughout its distribution and leaves of two coniferous tree species ( Picea crassifolia, Abies fabri ) along an elevation gradient throughout their distribution in the Qilian Mountains and Gongga Mountains, respectively. Leaf δ13 C of dominant species in the six ecosystems differed significantly, with values for evergreen coniferous13 C values of the dominant species and of K. pygmaea were negatively correlated with annual precipitation along a water gradient, but leaf δ13 C of A. fabri was not significantly correlated with precipitation in habitats without water-stress. This confirms that variation of δ13 C between or within species reflects plant responses to environmental conditions. Leaf δ13 C of the dominant species also reflected water patterns on the Tibetan Plateau, providing evidence that precipitation plays a primary role in controlling ecosystem changes from southeast to northwest on the Tibetan Plateau. 相似文献
14.
1. The δ13 C and δ15 N signatures of zooplankton vary with dissolved organic carbon (DOC), but inconsistent and limited taxonomic resolution of previous studies have masked differences that may exist among orders, genera or species and are attributable to dietary and/or habitat differences. Here we investigate differences among the isotopic signatures of five zooplankton taxa ( Daphnia , Holopedium , large Calanoida, small Calanoida and Cyclopoida) in Precambrian shield lakes with a sixfold range of DOC concentration.
2. δ13 C signatures of Daphnia , small calanoids and large calanoids became more depleted with increasing lake DOC, whereas Holopedium and cyclopoid δ13 C became enriched with increasing DOC concentration.
3. The variability of δ13 C and δ15 N isotopic signatures among zooplankton groups was reduced in high-DOC, compared to low-DOC lakes, especially for δ13 C. Differences in δ13 C and POM-corrected δ15 N accounted for up to 33.7% and 19.5% of the variance, respectively, among lakes of varying DOC concentration.
4. The narrow range of signatures found in higher DOC lakes suggests that different taxa have similar food sources and/or habitats. In contrast, the wide range of signatures in low-DOC lakes suggests that different taxa are exploiting different food sources and/or habitats. Together with the variable trends in zooplankton isotopic signatures along our DOC gradient, these results suggest that food web dynamics within the zooplankton community of temperate lakes will change as climate and lake DOC concentrations change. 相似文献
2. δ
3. The variability of δ
4. The narrow range of signatures found in higher DOC lakes suggests that different taxa have similar food sources and/or habitats. In contrast, the wide range of signatures in low-DOC lakes suggests that different taxa are exploiting different food sources and/or habitats. Together with the variable trends in zooplankton isotopic signatures along our DOC gradient, these results suggest that food web dynamics within the zooplankton community of temperate lakes will change as climate and lake DOC concentrations change. 相似文献
15.
1. Applying Keeling plot techniques to derive δ13 C of respiratory input in a closed non-equilibrated chamber can lead to large errors because steady-state diffusion rules are violated in a non-steady-state environment. To avoid these errors, respiratory δ13 C can be derived using equilibrated closed chambers.
2. We introduce a new method to obtain stem respired CO2 δ13 C (δst - r ) with closed equilibrated stem chambers (E-SC). We present a theoretical model describing the equilibration process, test the model against field data and find excellent agreement. The method is further tested by comparing it with closed non-equilibrated stem chambers (NE-SC); we found no difference between these methods.
3. Our theoretical model to describe CO2 diffusion from the respiratory pool into the chamber and the equation to derive the δ13 C of the efflux are general. They could be applied to other ecosystem components (e.g. soils).
4. Our method is easy to implement, cost effective, minimizes sources of error and allows for rigorous leak detection. One major limitation is its inability to detect rapid change; the equilibration process requires 15 ± 2 h. A second limitation is that it cannot be used for species that produce abundant pitch at sites of stem wounding (e.g. Pseudotsuga menziesii ).
5. Investigating δ13 C of CO2 respired by different ecosystem components is necessary to interpret δ13 C of ecosystem respiration. This parameter has major implications with respect to global carbon cycle science. 相似文献
2. We introduce a new method to obtain stem respired CO
3. Our theoretical model to describe CO
4. Our method is easy to implement, cost effective, minimizes sources of error and allows for rigorous leak detection. One major limitation is its inability to detect rapid change; the equilibration process requires 15 ± 2 h. A second limitation is that it cannot be used for species that produce abundant pitch at sites of stem wounding (e.g. Pseudotsuga menziesii ).
5. Investigating δ
16.
Changes in feeding niche widths of perch and roach following biomanipulation, revealed by stable isotope analysis 总被引:1,自引:0,他引:1
1. We made an empirical test of a recent proposal that feeding niche widths might be determined as variance of stable isotope values. We determined δ 13 C and δ 15 N values of perch ( Perca fluviatilis ), roach ( Rutilus rutilus ) and their prey from a biomanipulated lake, when the mass removal of fish led to reduced inter- and intra-specific competition and increases in zooplankton abundance and body size.
2. After the first fish removals, both perch and roach mean δ13 C values decreased and mean δ 15 N values increased, indicating a greater diet contribution from pelagic sources.
3. Variances of both δ13 C and δ 15 N values first increased in both fish populations, indicating a wider food spectrum and expanded feeding niche width following reduced fish abundances. Observed changes were greater for the perch population than for roach.
4. In 2006, the perch population abruptly changed its diet so that most individuals were primarily consuming the abundant young-of-the-year fish, and this was reflected in significantly reduced variances of both δ13 C and δ 15 N values.
5. We conclude that isotopic variance can indeed reflect changes in feeding niche width and offers a promising way to study such general ecological concepts. 相似文献
2. After the first fish removals, both perch and roach mean δ
3. Variances of both δ
4. In 2006, the perch population abruptly changed its diet so that most individuals were primarily consuming the abundant young-of-the-year fish, and this was reflected in significantly reduced variances of both δ
5. We conclude that isotopic variance can indeed reflect changes in feeding niche width and offers a promising way to study such general ecological concepts. 相似文献
17.
Effects of water stress and nocturnal temperature on carbon allocation in the perennial grass, Leymus chinensis 总被引:3,自引:0,他引:3
Water deficit and high temperature often occur simultaneously, but their effects on plants are usually investigated separately. The aim of this study was to test how interactions between water stress and nocturnal warming affect carbon allocation in the perennial grass, Leymus chinensis . Plant biomass, dry mass allocation, 14 C partitioning and carbon isotope composition (δ13 C) were measured. Severe and extreme water stress during nocturnal warming decreased the allocation of dry mass and 14 C partitioning below ground to the roots, but moderate water stress significantly increased the below-ground allocation of dry mass and 14 C, especially at the lower night temperature. The δ13 C values were more positive at day/night temperatures of 30/20°C than at 30/25°C, and greater in the roots than in the leaves. By plotting the δ13 C values of the leaves against the δ13 C values of the roots, the slopes of regressions were steeper at low than at high night temperature, also indicating that nocturnal warming reduces carbon allocation below ground to the roots. The results suggest that nocturnal warming may weaken acclimation during water stress in this species by regulating carbon allocation between source and sink organs. 相似文献
18.
Sulphur stable isotopes can distinguish trophic dependence on sediments and plankton in boreal lakes
1. Stable isotopes of carbon are useful for differentiating between freshwater food chains based on planktonic algae or benthic algae, but are reported to be of limited use for identifying food chains based on sedimentary detritus. Because data from marine systems suggest that stable isotopes of sulphur (δ34 S values) have potential in this regard, we tested their utility in freshwater lakes.
2. We found that sulphate in the water column of four boreal lakes was enriched in34 S compared to the sulphur in bulk sediments from these lakes. Furthermore, within a given lake, insects known to feed on sediment (directly or via predation) had δ34 S values similar to those of sediment, whereas planktonic and benthic invertebrates known to feed on suspended particles had δ34 S values similar to those of sulphate in the water column.
3. Using the stable S isotope values of invertebrates that obtain their S from either the sediment or the water column as end members in a two-source mixing model, we show that two fish species obtain their food from both planktonic and sedimentary sources. Furthermore, model results suggest that, as expected, the more benthic-feeding fish species obtains more of its S from the sediment compartment than does the species that feeds in the water-column.
4. Our results suggest that measurements of stable sulphur isotopes provide a means of distinguishing between members of food chains that are based in the water column from those based on sedimentary detritus. As such, they would be a useful complement to stable C isotopes that are used to distinguish between food chains based on planktonic or benthic algae. 相似文献
2. We found that sulphate in the water column of four boreal lakes was enriched in
3. Using the stable S isotope values of invertebrates that obtain their S from either the sediment or the water column as end members in a two-source mixing model, we show that two fish species obtain their food from both planktonic and sedimentary sources. Furthermore, model results suggest that, as expected, the more benthic-feeding fish species obtains more of its S from the sediment compartment than does the species that feeds in the water-column.
4. Our results suggest that measurements of stable sulphur isotopes provide a means of distinguishing between members of food chains that are based in the water column from those based on sedimentary detritus. As such, they would be a useful complement to stable C isotopes that are used to distinguish between food chains based on planktonic or benthic algae. 相似文献
19.
1. Stable isotope analysis, coupled with dietary data from the literature, was used to investigate trophic patterns of freshwater fauna in a tropical stream food web (Guadeloupe, French West Indies).
2. Primary producers (biofilm, algae and plant detritus of terrestrial origin) showed distinct δ13 C signatures, which allowed for a powerful discrimination of carbon sources. Both autochthonous (13 C-enriched signatures) and allochthonous (13 C-depleted signatures) resources enter the food web. The migrating behaviour of fishes and shrimps between marine and freshwater during their life cycles can be followed by carbon isotopes. Here, shrimp δ13 C signatures were shown to shift from −16‰ (for juveniles under marine influence) to −24.7‰ (for adults in freshwater habitats). For resident species, δ13 C values partly reflected the species' habitat preferences along the river continuum : species living in river mouths were 13 C-enriched in comparison with those collected upstream.
3. Nitrogen isotopic ratios were also discriminating and defined three main trophic guilds among consumers. The δ15 N values of herbivores/detritivores were 5.0–8.4‰, omnivores 8.8–10.2‰ and carnivores 11–12.7‰.
4. Mixing model equations were employed to calculate the possible range of contribution made by respective food sources to the diet of each species. The results revealed the importance of omnivorous species and the dependence of riverine biota on terrestrial subsidies, such as leaf detritus and fruits. Finally, the abundance of shrimps and their feeding habits placed in relief their key role in tropical freshwater food webs. Isotopic analysis provides a useful tool for assessing animal feeding patterns. 相似文献
2. Primary producers (biofilm, algae and plant detritus of terrestrial origin) showed distinct δ
3. Nitrogen isotopic ratios were also discriminating and defined three main trophic guilds among consumers. The δ
4. Mixing model equations were employed to calculate the possible range of contribution made by respective food sources to the diet of each species. The results revealed the importance of omnivorous species and the dependence of riverine biota on terrestrial subsidies, such as leaf detritus and fruits. Finally, the abundance of shrimps and their feeding habits placed in relief their key role in tropical freshwater food webs. Isotopic analysis provides a useful tool for assessing animal feeding patterns. 相似文献
20.
Nitrogen and carbon isotope ratios in termites: an indicator of trophic habit along the gradient from wood-feeding to soil-feeding 总被引:5,自引:0,他引:5
1. Nitrogen and carbon stable-isotope ratios (δ15 N and δ13 C) of body tissues, mound/nest materials and dietary substrates were determined in termite species with differing trophic habits, sampled from the Mbalmayo Forest Reserve, southern Cameroon.
2. δ15 N of termite tissues was enriched gradually along a spectrum of species representing a trophic gradient from wood- to soil-feeding. Species that could be identified from their general biology and from gut content analysis as feeding on well-rotted wood or as wood/soil interface feeders showed δ15 N intermediate between sound-wood-feeders and soil-feeders. It is proposed that δ15 N is therefore a possible indicator of the functional position of species in the humification process. Differences in δ13 C were also observed between wood-feeding and soil-feeding forms.
3. High values of δ15 N in soil-feeding termites suggest that nitrogen fixation is of little importance in these species.
4. A wide range of isotope effects (the difference in isotope ratios between termites and their diet) was observed for both nitrogen (Δδ15 N = –1.6 to + 8.8‰) and carbon (Δδ13 C = –2.2 to + 3.0‰), which suggests a diversity of nutrient acquisition mechanisms within termites and diverse relationships between termites and their intestinal micro-organisms. 相似文献
2. δ
3. High values of δ
4. A wide range of isotope effects (the difference in isotope ratios between termites and their diet) was observed for both nitrogen (Δδ