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1. It is increasingly realised that aquatic and terrestrial systems are closely linked. We investigated stable isotope variations in Odonata species, putative prey and basal resources of aquatic and terrestrial systems of northern Mongolia during summer. 2. In permanent ponds, δ13C values of Odonata larvae were distinctly lower than those of putative prey, suggesting that body tissue comprised largely of carbon originating from isotopically light carbon sources. Presumably, prey consumed during autumn and winter when carbon is internally recycled and/or methanotrophic bacteria form an important basal resource of the food web. In contrast, in a temporary pond, δ13C values of Odonata larvae were similar to those of putative prey, indicating that their body carbon originated mainly from prey species present. 3. Changes in δ15N and δ13C values between larvae and adults were species specific and reflected differential replacement of the larval isotopic signature by the terrestrial diet of adult Odonata. The replacement was more pronounced in Odonata species of permanent ponds than in those of the temporary pond, where larvae hatched later in the year. Replacement of larval carbon varied between tissues, with wings representing the larval isotopic signature whereas thoracic muscles and eggs reflected the δ15N and δ13C values of the terrestrial diet of adults. 4. The results suggest that because of their long larval development, Odonata species of permanent ponds carry the larval signature, which is partly replaced during their terrestrial life. Terrestrial prey forms the basis for egg production and thus the next generation of aquatic larvae. In temporary ponds, in contrast, Odonata species rely on prey from a single season, engage in a prolonged aquatic phase and hatch later, leaving less time to acquire terrestrial prey resources for offspring production. Stable isotope analysis provided important insights into the food webs of the waterbodies and their relationship to the terrestrial system. 相似文献
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Allochthonous and autochthonous particulate organic matter in floodplains of the River Danube: the importance of hydrological connectivity 总被引:3,自引:0,他引:3
Thomas Hein Christian Baranyi Gerhard J. Herndl Wolfgang Wanek Fritz Schiemer 《Freshwater Biology》2003,48(2):220-232
SUMMARY 1. The elemental composition, the proportion of living organic carbon and the carbon stable isotope signatures of particulate organic matter (POM) were determined in a large river floodplain system in order to elucidate the major carbon sources in relation to the hydrological conditions over a 13‐month period. 2. Two floodplain segments and the main channel of the River Danube downstream of Vienna (Austria), were compared on the basis of discharge and water age estimations. The more dynamic floodplain was connected to the main channel for 46% of the study period and drained up to 12% of total discharge at high water. 3. The mean C : N ratio and δ13C signature of the POM increased from the floodplain site that was more isolated from the river (6.6; ?33‰) to the main channel (8.4; ?25‰). At the dynamic floodplain site, the C : N ratio and the δ13C signature of the POM increased with hydrological connectivity (expressed as water age). 4. Only during flood events (4% frequency of occurrence), a considerable input of riverine POM was observed. This input was indicated by a C : N ratio of the POM pool of more than 10, the amount of detrital carbon (>80% of the total POM pool) and a δ13C signature of POM of more than ?25‰ in the dynamic floodplain. 5. Plankton derived carbon, indicated by C : N ratios less than eight and δ13C values lower than ?25‰, dominated the particulate organic carbon (POC) pool at both floodplain sites, emphasising the importance of local (autochthonous) production. Phytoplankton was the major plankton compartment at the dynamic site, with highest biomasses at medium water ages. 6. At the dynamic floodplain site, the Danube Restoration Project has enhanced the duration of upstream surface connection with the main channel from 4 to 46% frequency of occurrence. Therefore, the export of living POC to the main channel is now established during phases of maximum phytoplankton production and doubled the estimated total export of non‐refractory POM compared with prerestoration conditions. 相似文献
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Bobby J. Nakamoto Marilyn L. Fogel Carson A. Jeffres Joshua H. Viers 《Freshwater Biology》2020,65(9):1569-1584
- We sampled freshwater suspended particulate organic matter (POM) to determine its carbon and nitrogen stable isotope composition and collected co-located water chemistry data in California's Sacramento—San Joaquin Delta from sites on the Mokelumne and Cosumnes rivers. A 10-km2 area was sampled across 12 sites and divided among three habitat types (i.e. riverine, slackwater/slough, and off-channel), 34 times between November 2016 and July 2017. Here, we describe the variability in water quality and POM variables, and assess factors associated with that variability using dimensional reduction and linear modelling within the context of our habitat types.
- The stable isotope composition of freshwater POM and water chemistry variables differed significantly across small areas (<10 km) and short time frames (weekly). Hydrological connectivity amongst sites was found to be an important factor in the isotopic and elemental composition of POM.
- During periods of low hydrological connectivity, in situ dynamics were strongly associated with differentiation of POM in different habitats. Discharge (16–433 m3/s) and water temperature (8–30°C) were the variables most associated with variations in the composition of POM. Slackwater sites showed the greatest variability in POM composition, which may be symptomatic of longer water residence times, increased cycling rates of nutrients and organic matter, or a combination of the two.
- Variability in POM stable isotope composition demonstrates that caution should be exercised when interpreting analyses that assume a static POM stable isotope composition based on two-end member mixing. Unconstrained variability in space or time could confound interpretations of models and data. Moving forward, conceptual and numerical models for river ecosystems that emphasise temporally heterogeneous lateral exchange amongst habitat patches should be prioritised when considering restoration efforts and monitoring outcomes.
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Adam D. P. Cross Jonas Hentati‐Sundberg Henrik Österblom Rona A. R. McGill Robert W. Furness 《Ibis》2014,156(3):676-681
The presence of one of the largest colonies of House Martins in Europe on the small island of Stora Karlsö, Sweden, led us to investigate the source of their food by analysis of stable isotopes of carbon and nitrogen. Carbon isotopic values of House Martin nestlings were the same as those of Common Guillemot Uria aalge nestlings fed on marine fish, but differed from local Collared Flycatcher Ficedula albicollis nestlings fed on woodland insects. We infer that these House Martins fed their chicks almost exclusively on insects that had used nutrients derived from seabirds, indicating a dependence on the presence of a large seabird colony. We suggest by extension that some populations of island passerines of high conservation importance may also be dependent on nutrient subsidies from seabird colonies. 相似文献
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1. Stable isotopes of nitrogen are useful for quantifying the trophic structure of food webs, but only if the variation in trophic enrichment (ΔN), which is the difference in δ15N between a consumer and its food, is small relative to the value of ΔN itself. 2. We examined the sources of variation in zooplankton ΔN by measuring the trophic enrichment (ΔN) of seven species of freshwater cladocerans, and by testing for an effect of age and temperature on the ΔN of Daphnia pulicaria. 3. We found that ΔN was similar among Cladocera and was not correlated with body size. Overall, the ΔN for D. pulicaria was 1.4‰ (SE = 0.69, n = 57), as was expected for the detritus diet that we used in our experiments. We found no effect of temperature (15–25 °C) on ΔN, but found that ΔN of D. pulicaria increased with increasing age (10–30 days). 4. We developed a new method to test for trophic‐level variation in a group of consumers that explicitly accounts for the uncertainty in ΔN. Using this approach, we confirmed that natural assemblages of zooplankton feed at several trophic levels in lake food webs. 相似文献
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RICHARD J. HUNT TIMOTHY D. JARDINE STEPHEN K. HAMILTON STUART E. BUNN TROPICAL RIVERS COASTAL KNOWLEDGE RESEARCH HUB 《Freshwater Biology》2012,57(3):435-450
1. High light availability and stable base flow during the dry season promote primary production in perennial rivers of the wet–dry tropics, in contrast to production during the wet season which is often limited by turbidity and scouring. The Mitchell River of northern Queensland (Australia) was studied to understand controls on aquatic production and respiration in the dry season in relation to spatial and temporal gradients of light and temperature. 2. At three sites along the river, whole‐ecosystem gross primary production (GPP) and respiration (ER) were measured from diel changes of dissolved oxygen using the open‐channel single station method. Using stable carbon and nitrogen isotope analysis, aquatic consumers and their potential basal food resources were also assessed to determine food web relationships at the beginning and end of the dry season. 3. Nutrient limitation of aquatic net primary production was implied from the oligotrophic conditions and high algal C:N ratios. Rates of GPP were comparable with other tropical and temperate rivers and were regulated by light availability. 4. Respiration rates were high and similar to other tropical and subtropical rivers. Up to 52% of temporal variation of ER was explained by temperature, while P/R was lowest at the downstream site. 5. Benthic algae were the major carbon source for primary and secondary benthic consumers (insects) in the dry season but not for higher consumers (fish and crustaceans). Despite high rates of ER, which were probably supported by decaying terrestrial C3 plant material, this carbon source was not identified as contributing to animal consumer biomass. 6. While benthic algal production in the dry season sustained benthic invertebrates, the importance of external subsidies of carbon along the river, probably from the floodplain, was emphasised for fish and large invertebrates, which evidently were feeding on carbon sources not present in channel waterholes during the dry season. 相似文献
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1. We investigated the spatial (longitudinal position and reach geomorphology) and seasonal (spring and autumn) influences on the variation of δ13C among organic matter sources and consumers in a forested Piedmont river, South Carolina, U.S.A. 2. Six sites were sampled along a continuum and varied in basin area from approximately 30 to 300 km2. Sites fell into two geomorphic categories (i) high‐gradient, rock bed (‘rock’) or (ii) low‐gradient, sand bed (‘sand’) sites. 3. Variation in δ13C was more strongly related to reach geomorphology than longitudinal position. δ13C of biofilm and consumers was consistently enriched at rock sites. Leaf litter (i.e. coarse particulate organic matter, CPOM) δ13C did not vary with bed type. There was significant δ13C enrichment at rock sites for biofilm, seston, fine benthic organic matter (FBOM), and eight of nine consumer trophic guilds (e.g. grazing invertebrates, insectivorous fishes). δ13C of biofilm and four trophic guilds was also positively correlated with drainage area, but the magnitude of enrichment was less than between bed types. 4. δ13C was generally enriched in spring, but this varied among organic matter types, consumers, and by bed type. CPOM and seston were enriched in spring, FBOM was enriched in autumn, and biofilm showed no trend. Five consumer guilds were enriched in spring, and only one fish guild, generalised carnivores, showed enrichment of muscle tissue in autumn. 5. Consumer δ13C enrichment at rock sites suggests greater reliance on algal carbon than for consumers at sand sites, but we also found δ13C enrichment of biofilm at rock sites. Thus, differences in consumer δ13C between bed types could be related to (i) increased consumption of biofilm at rock compared with sand sites, or (ii) consumption of biofilm at rock sites that is enriched relative to biofilm at sand sites or (iii) both mechanisms. 6. δ13C signatures in local food webs appear to respond to processes operating at multiple spatial scales. Overall downstream enrichment of biofilm and consumers was disrupted by strong local effects related to bed morphology. These results suggest that human alteration of channel habitat will have corresponding effects on stream food webs, as assessed by changes in δ13C. 相似文献
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1. Trophic fractionation was studied in short‐term laboratory feeding experiments with larvae of the deposit‐feeding midge Chironomus riparius. Larvae were fed food of terrestrial (oats, peat) and aquatic origin (Spirulina, Tetraphyll®). 2. By analysing both whole larvae and isolated gut contents we were able to distinguish between the isotopic signature of recently ingested food and that of assimilated carbon and nitrogen in body tissue. Additionally we studied the effects of microbial conditioning, i.e. the colonisation and growth on food particles of microbes, on the isotopic signal of food resources. 3. Nitrogen fractionation for the different food types ranged from 0.67‰ to 2.68‰ between consumer and diet and showed that isotopic fractionation can be much lower than the value of 3.4‰ that is commonly assumed. 4. Microbial degradation of food particles resulted in an approximate doubling of the δ15N in 8 days, from 6.24 ± 0.05‰ to 11.36 ± 0.56‰. Values for δ13C increased only marginally, from ?20.66 ± 0.11‰ to ?20.34 ± 0.12‰. These results show that microbial conditioning of food may affect dietary isotope signatures (in particular N) and, unless accounted for, could introduce an error in measures of trophic fractionation. Microbial conditioning could well account for some of the variation in fractionation reported in the literature. 相似文献
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Isotope variability of particulate organic matter at the PN section in the East China Sea 总被引:18,自引:0,他引:18
The source of particulate organic matter at the PN section in the East China Sea has been evaluated using stable carbon and nitrogen isotopes. The results showed that the 13C and 15N compositions varied from –19 to –31 and 0.7–9.5 respectively, and the isotope compositions were statistically distinct, enabling, by use of a simple components mixing equations, assessment of the ability of each tracer to estimate the terrestrial, Kuroshio Water, marine and remineralized sources' contributions. The dominance of terrestrial inputs of the Changjiang could be observed 250 km far from the river mouth in the East China Sea. In the shelf water column, the remineralization of biogenic organic matter becomes an important source except for the terrigenous and marine sources. The estimation of sources recorded by 13C data was partly confirmed by equivalent 15N and C/N compositions that reflected greater control by organic matter diagenesis and biological processing. However, the lighter contribution of 13C data of the Kuroshio samples also indicates the alteration of the isotope values by microbial or other processes. The net export flux of POC in the PN section is estimated to be 4.1 kmol C/s and the annual export is 129 Gmol C/yr, which is account for 20% of the East China Sea. 相似文献
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Robert Serrouya Melanie Dickie Clayton Lamb Harry van Oort Allicia P. Kelly Craig DeMars Philip D. McLoughlin Nicholas C. Larter Dave Hervieux Adam T. Ford Stan Boutin 《Proceedings. Biological sciences / The Royal Society》2021,288(1943)
Changes in primary productivity have the potential to substantially alter food webs, with positive outcomes for some species and negative outcomes for others. Understanding the environmental context and species traits that give rise to these divergent outcomes is a major challenge to the generality of both theoretical and applied ecology. In aquatic systems, nutrient-mediated eutrophication has led to major declines in species diversity, motivating us to seek terrestrial analogues using a large-mammal system across 598 000 km2 of the Canadian boreal forest. These forests are undergoing some of the most rapid rates of land-use change on Earth and are home to declining caribou (Rangifer tarandus caribou) populations. Using satellite-derived estimates of primary productivity, coupled with estimates of moose (Alces alces) and wolf (Canis lupus) abundance, we used path analyses to discriminate among hypotheses explaining how habitat alteration can affect caribou population growth. Hypotheses included food limitation, resource dominance by moose over caribou, and apparent competition with predators shared between moose and caribou. Results support apparent competition and yield estimates of wolf densities (1.8 individuals 1000 km−2) above which caribou populations decline. Our multi-trophic analysis provides insight into the cascading effects of habitat alteration from forest cutting that destabilize terrestrial predator–prey dynamics. Finally, the path analysis highlights why conservation actions directed at the proximate cause of caribou decline have been more successful in the near term than those directed further along the trophic chain. 相似文献
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GUY WOODWARD JOHN B. DYBKJÆR JÓN S. ÓLAFSSON GÍSLI M. GÍSLASON ELÍSABET R. HANNESDÓTTIR NIKOLAI FRIBERG 《Global Change Biology》2010,16(7):1979-1991
The Earth is experiencing historically unprecedented rates of warming, with surface temperatures projected to increase by 3–5 °C globally, and up to 7.5 °C in high latitudes, within the next century. Knowledge of how this will affect biological systems is still largely restricted to the lower levels of organization (e.g. species range shifts), rather than at the community, food web or ecosystem level, where responses cannot be predicted from studying single species in isolation. Further, many correlational studies are confounded with time and/or space, whereas experiments have been mostly confined to laboratory microcosms that cannot capture the true complexity of natural ecosystems. We used a ‘natural experiment’ in an attempt to circumvent these shortcomings, by characterizing community structure and trophic interactions in 15 geothermal Icelandic streams ranging in temperature from 5 °C to 45 °C. Even modest temperature increases had dramatic effects across multiple levels of organization, from changes in the mean body size of the top predators, to unimodal responses of species populations, turnover in community composition, and lengthening of food chains. Our results reveal that the rates of warming predicted for the next century have serious implications for the structure and functioning of these fragile ‘sentinel’ ecosystems across multiple levels of organization. 相似文献
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Longitudinal patterns of organic matter transport and turnover along a New Zealand grassland river 总被引:1,自引:0,他引:1
1. We determined the longitudinal pattern of organic matter concentration, quality, size composition and spiralling length along a 310-km grassland river system (Taieri River, New Zealand). 2. Organic seston concentration (0.24–4.05 mg ash-free dry mass (AFDM) l–1) and dissolved organic carbon (DOC) concentration (2.3–5.7 mg C l–1) showed no obvious longitudinal patterns. In contrast, there was a significant downstream increase in inorganic seston concentration (0.13–13.73 mg ash l–1), presumably because of a downstream increase in the proportion of the catchment developed for agriculture. 3. Although there was a trend toward increasing particle size in the first 25 km of the river continuum, organic seston was primarily composed of ultrafine particles (0.6–30 μm) at all study sites. The ratio of coarse (> 250 μm) to ultrafine organic seston decreased logarithmically down the continuum. Organic content generally decreased with particle size. Ultrafine particles, however, had significantly higher organic fractions than fine (60–100 μm) and very fine (30–60 μm) particles. 4. Daily organic carbon turnover length ranged from 10 to 98 km and increased downstream. This is consistent with other studies along river continua and suggests that organic carbon turnover length is largely controlled by the relationship between channel dimensions and discharge, rather than the presence of specific retention devices. 5. Concentrations and nutritional quality of organic seston and concentrations of DOC were highest in an unconstrained floodplain reach in the upper river. These data suggest that new material enters the river channel in this reach, potentially providing an important energy source for the river community downstream. The effect of this reach on the longitudinal pattern of organic matter concentration and quality emphasizes how changes in channel form can alter river ecosystem structure and function. 相似文献
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CHRISTOPHER M. HARDY EVELYN S. KRULL DIANA M. HARTLEY RODERICK L. OLIVER 《Molecular ecology》2010,19(1):197-212
Determining the source and flow of carbon, energy and nutrients through food webs is essential for understanding ecological connectivity and thus determining the impact of management practices on biodiversity. We combined DNA sequencing, microarrays and stable isotope analyses to test whether this approach would allow us to resolve the carbon flows through food webs in a weir pool on the lower Murray River, a highly impacted, complex and regulated ecosystem in southern Australia. We demonstrate that small fish in the Murray River consume a wide range of food items, but that a significant component of carbon and nitrogen entering the food web during dry periods in summer, but not spring, is derived from nonconventional sources other than in-channel primary producers. This study also showed that isotopic analyses alone cannot distinguish food sources and that a combined approach is better able to elucidate food-consumer dynamics. Our results highlight that a major river ecosystem, stressed by reduced environmental flows, can rapidly undergo significant and previously undetected changes that impact on the ecology of the system as a whole. 相似文献
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Sources of organic carbon supporting the food web of an arid zone floodplain river 总被引:12,自引:0,他引:12
SUMMARY 1. Many Australian inland rivers are characterised by vast floodplains with a network of anastomosing channels that interconnect only during unpredictable flooding. For much of the time, however, rivers are reduced to a string of disconnected and highly turbid waterholes. Given these features, we predicted that aquatic primary production would be light-limited and the riverine food web would be dependent on terrestrial carbon from floodplain exchanges and direct riparian inputs.
2. To test these predictions, we measured rates of benthic primary production and respiration and sampled primary sources of organic carbon and consumers for stable isotope analysis in several river waterholes at four locations in the Cooper Creek system in central Australia.
3. A conspicuous band of filamentous algae was observed along the shallow littoral zone of the larger waterholes. Despite the high turbidity, benthic gross primary production in this narrow zone was very high (1.7–3.6 g C m−2 day−1 ); about two orders of magnitude greater than that measured in the main channel.
4. Stable carbon isotope analysis confirmed that the band of algae was the major source of energy for aquatic consumers, ultimately supporting large populations of crustaceans and fish. Variation in the stable carbon and nitrogen isotope signatures of consumers suggested that zooplankton was the other likely major source.
5. Existing ecosystem models of large rivers often emphasise the importance of longitudinal or lateral inputs of terrestrial organic matter as a source of organic carbon for aquatic consumers. Our data suggest that, despite the presence of large amounts of terrestrial carbon, there was no evidence of it being a significant contributor to the aquatic food web in this floodplain river system. 相似文献
2. To test these predictions, we measured rates of benthic primary production and respiration and sampled primary sources of organic carbon and consumers for stable isotope analysis in several river waterholes at four locations in the Cooper Creek system in central Australia.
3. A conspicuous band of filamentous algae was observed along the shallow littoral zone of the larger waterholes. Despite the high turbidity, benthic gross primary production in this narrow zone was very high (1.7–3.6 g C m
4. Stable carbon isotope analysis confirmed that the band of algae was the major source of energy for aquatic consumers, ultimately supporting large populations of crustaceans and fish. Variation in the stable carbon and nitrogen isotope signatures of consumers suggested that zooplankton was the other likely major source.
5. Existing ecosystem models of large rivers often emphasise the importance of longitudinal or lateral inputs of terrestrial organic matter as a source of organic carbon for aquatic consumers. Our data suggest that, despite the presence of large amounts of terrestrial carbon, there was no evidence of it being a significant contributor to the aquatic food web in this floodplain river system. 相似文献
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应用稳定碳(δ13C)、氮(δ15N)同位素探讨了三峡库区一级支流小江库湾枯水期(2010.7)和丰水期间(2010.12)鱼类食物网结构。研究结果显示:初级生产者颗粒有机物(POM)和固着藻类δ13C、δ15N值范围分别为-23.33‰~-21.05‰、-25.13‰~-24.54‰,3.99‰~6.25‰、4.64‰~4.79‰。POM和固着藻类构成了小江库湾食物网能量的主要来源,其中丰水期间陆生营养物质输入是其食物网能量来源的一种重要补充途径。小江库湾常见鱼类食性可分为杂食偏植物食性、杂食偏动物食性及动物食性3种营养类群。在不同时期(枯水期和丰水期)小江库湾鱼类食物网营养级长度均有三级并且存在4种主要营养路径,表明了在三峡工程运行初期小江库湾已经形成了相对稳定的食物网结构。研究为小江库湾鱼类资源管理及生态系统恢复提供了一定的指导意义。 相似文献
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Michelle Evans-White Walter K. Dodds Lawrence J. Gray Ken M. Fritz 《Hydrobiologia》2001,462(1-3):131-144
Omnivorous fish, such as the central stoneroller minnow (Campostoma anomalum(Rafinesque)), and crayfish often play important roles in the trophic dynamics of streams. The trophic role of these two omnivores has not been compared within a system even though they both consume algae, detritus and invertebrates and often co-occur in streams in the Midwestern United States. Natural abundance of 15N and 13C isotopes and a whole stream 15N-labeled ammonium chloride release were used to compare the trophic ecology of the central stoneroller minnow (Campostoma anomalum (Rafinesque)) and two species of crayfish (Orconectes neglectus (Faxon) and Orconectes nais (Faxon)) in a tallgrass prairie stream. The 15N and 13C values of Orconectes spp. were more similar to coarse benthic organic matter (CBOM) and filamentous green algae than to invertebrates, fine benthic organic matter (FBOM), and periphyton. Values for 15N and 13C in C. anomalum were more similar to grazer and collector invertebrates and filamentous green algae than to FBOM and periphyton. Results from a 15N tracer release also indicated a portion of algae and/or invertebrates were a component of nitrogen assimilated in Orconectes spp. and C. anomalum diets. Gut contents of C. anomalum were also analyzed. In contrast to stable isotope data, amorphous detritus was a significant component of C. anomalum guts, followed by diatoms and filamentous green algae. A significant percentage of invertebrate material was found in C. anomalum guts sampled in the spring. Experiments were conducted in artificial streams to determine if Orconectes spp. and C. anomalum could reduce epilithic algal biomass in small streams. Algal biomass on clay tile substrata was decreased relative to controls in artificial stream channels containing O. neglectus (3.4 fold, p=0.0002), C. anomalum (2.1 fold, p=0.0012), and both species combined (3.0 fold, p=0.0003). Results indicate that Orconectes spp. are functioning more as algal and detrital processors than as predators in Kings Creek. Isotope and gut content data show that C. anomalum includes invertebrates as well as algae and detritus in its diet. Both species have the potential to affect algal biomass and are important omnivores in the stream food web. 相似文献