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1.
Stable carbon isotopes (δ 13C) were determined for autotrophic producers and animals from Lake Baikal (eastern Siberia), the deepest, the oldest and largest body of fresh water in the world. The extensive survey shows that the mean carbon isotope compositions of planktonic and benthic autotrophs differ in Lake Baikal by 21.5 ‰ the largest difference ever observed for lakes, thus giving an easy means to distinguish between pelagic and inshore carbon flows. Furthermore, our data give evidence that inshore macrofauna, which contributes greatly to the diversity within Baikalian animals, is supported by less abundant but highly diversified benthic flora, rather than by phytoplankton or terrigenous organic matter that dominate in the global carbon cycle of the lake. 相似文献
2.
Stable isotopes of carbon (δ 13C) and nitrogen (δ 15N) often have unique values among lake habitats (e.g. benthic, littoral, pelagic), providing a widely used tool for measuring
the structure and energy flow in aquatic food webs. However, there has been little recognition of the spatial and temporal
variabilities of these isotopes within habitats of aquatic ecosystems. To address this, δ 13C and δ 15N were measured in seston, zebra mussels ( Dreissena polymorpha) and young-of-year (YOY) yellow ( Perca flavescens), and white perch ( Morone americana) collected from four sites across the offshore habitat of the western basin of Lake Erie during June–September 2009. Values
of δ 13C and δ 15N showed significant spatial and temporal variations, with month accounting for >50% of the variation, for both stable isotopes
and all the species except seston. Such variation in isotope values has the potential to significantly influence or confound
interpretation of stable isotopes in measures, such as trophic position (TP) which use lower trophic level organisms as their
baseline. For example, TP was found to vary up to 0.7 for yellow and white perch (TP = δ 15N fish − δ 15N zebra mussel/diet-tissue fractionation factor) depending on the zebra mussel data used (e.g., from a different location or a different
collection month). As the use of stable isotopes continues to move from qualitative to more quantitative measures of trophic
structure, food web research must recognize the importance of stable isotopes' variability in lower trophic level organisms,
especially in large lake systems. 相似文献
3.
We used multiple analytical methods to demonstrate resource partitioning in five species of coexisting endemic gastropods
in the family Baicaliidae and the genus Megalovalvata (Valvatidae) in rocky walls of the underwater canyons in Lake Baikal. We tested whether filter-feeding baicaliids and valvatids
consume and assimilate different food using data from gut contents, stable δ 13C and δ 15N isotopes and radular morphology, with subsequent combined analyses. Our results showed that the four baicaliid species assimilate
microalgae, diatoms and bacteria, whereas the single Megalovalvata species mostly assimilates plant detritus. The δ 15N variations in the baicaliids reflect differences in their digestion of seston components, whereas the δ 13C similarity illustrates consumption of food particles derived from similar primary producers. Gut contents in the baicaliids
were dominated by a single species of planktonic diatom, although more than 30 species of microalgae were recorded in all
seasons. However, the composition and quantity of additional food particles varied by species. Our results showed that baicaliids
have significant fine scale differences in radular tooth morphology, which may allow partitioning of food resources. 相似文献
4.
Since 2006, the known distribution of Hemimysis anomala has greatly expanded in the Great Lakes ecosystem, with, to date, 45 sites of occurrence among 91 monitored sites, located
in four of the Great Lakes and the upper St. Lawrence River. By means of carbon and nitrogen stable isotopes, a first assessment
of the feeding ecology of Hemimysis was completed. The δ 13C values of 18 individuals collected in Lake Erie (Port Mainland) on a single date (Sept. 23, 2008) ranged from −30.2 to −24.5‰,
indicating that Hemimysis could feed on multiple carbon sources including pelagic and littoral autochthonous and terrestrial carbon. In Lake Erie,
variation in δ 13C was related to δ 15N, indicating the importance of food source for determining the trophic position of Hemimysis. The δ 15N signatures of individuals were strongly related to their C/N ratios, suggesting that variations in the nutritional value
of Hemimysis may depend on trophic position. Isotopic variation among individuals in Lake Erie was complemented by temporal variation
in Lake Ontario. Monthly changes (from June to December 2008) in carbon isotope signatures were observed and related to changes
in water temperature, highlighting the variations in the baseline prey signatures that fuel Hemimysis diets. The observed variation in stable isotope signatures occurring among individuals within a localized Hemimysis assemblage and temporally should be considered as a key design feature in further studies attempting to identify the possible
effects of Hemimysis on nearshore food webs in the Great Lakes. 相似文献
5.
Potential body size-trophic position relationships of the Darkbarbel catfish Pelteobagrus vachelli (Richardson 1846) were examined using stable isotope analysis. Pelteobagrus vachelli is a benthic feeding fish from Lake Poyang, the largest freshwater lake in China. Two-source mixing model with mussel ( Corbicula fluminea) and snail ( Bellamya aeruginosa) as baseline primary consumers of planktonic and benthic food webs, respectively, was used to estimate contribution of carbon
derived from planktonic vs. benthic food web. Results showed that as an indicator of trophic position, δ 15N was negatively correlated with the body length and weight of the fish; on the other hand, as an indicator of the end-member
food sources, δ 13C was not correlated with fish size. The mixing model results showed that the averaged trophic position of our sampled 3.3–12.7 cm
Pelteobagrus vachelli was 3.1 ± 0.2 and derived 68 ± 27% of their food from the benthic food web, confirming that the feeding behavior of the catfish
favors benthic food sources. 相似文献
6.
We explored the use of carbon and nitrogen isotope ratios (δ 13C, δ 15N) in sediment organic matter as proxy indicators of historical changes in the trophic state of Lake Taihu, the third largest
freshwater lake in China. Stable isotope signatures in four sediment cores spanning the 20th century were compared with instrumental
records of lake-water trophic state. The comparative study shows that, between ∼
∼1950 and 1990 AD, the δ 13C and δ 15N of sediment organic matter throughout Lake Taihu increased along the trophic gradient from oligotrophy to eutrophy due to
biological isotopic fractionation. However, in the 1990s, the trophic state of Lake Taihu diverged into two different trophic
systems, a hypereutrophic western Lake Taihu dominated by blue-green algae and a mesoeutrophic eastern Lake Taihu dominated
by vascular aquatic plants. During the post-1990 AD shift from mesoeutrophic to hypereutrophic state in western Lake Taihu,
organic matter δ 13C and δ 15N decreased sharply in response to pronounced shifts in the aquatic ecosystem. The results indicate that 13C-depleted phytoplankton replaced macrophytes in western Lake Taihu. δ 15N values in western Lake Taihu also decreased because of N 2 fixation by cyanobacteria in this highly productive ecosystem. By contrast, in eastern Lake Taihu, organic matter δ 13C and δ 15N values show a post-1990 AD trend towards slightly lower values, but they remain higher than the long-term average. This
recent 13C–enrichment of organic matter indicates that periods of high productivity in the restricted eastern sub-basin of Lake Taihu
limited aqueous CO 2 availability, causing a decrease in isotopic discrimination during photosynthesis. After ∼
∼1990 AD, organic matter δ 15N values for eastern Lake Taihu only dropped slightly, suggesting that the contribution of phytoplankton to the sediment organic
matter increased slightly. Taken together, the results indicate that nitrogen-fixing cyanobacteria probably played a much
smaller role in primary productivity in this part of eastern Lake Taihu, compared with western Lake Taihu. Despite the complexity
of carbon and nitrogen cycles in lakes, the agreement between the stable isotope signatures and instrumental records for Lake
Taihu suggests that δ 13C and δ 15N in sediment organic matter are capable of recording important shifts in the spatial and temporal evolution of lake-water
trophic state. 相似文献
7.
Change in the abundance of benthic macroinvertebrates and the stable isotope composition (C, N) of benthic invertebrates and
zooplankton in Lake Vaeng, Denmark, was investigated over an 18-year period following biomanipulation (removal of cyprinids).
During the first nine years after biomanipulation, the lake was clear and submerged macrophytes were abundant; after this
period, a shift occurred to low plant abundance and high turbidity. Two years after the biomanipulation, total density of
benthic macroinvertebrates reached a maximum of 17042 (±2335 SE) individuals m −2 and the density was overall higher when the lake was in a clear state. Redundancy analysis (RDA) suggested macrophyte abundance
and total nitrogen (TN) concentration were the dominant structuring forces on the benthic macroinvertebrate assemblage. Stable
isotope analysis revealed that δ 13C of macroinvertebrates and zooplankton was markedly higher in years with high submerged macrophyte abundance than in years
without macrophytes, most likely reflecting elevated δ 13C of phytoplankton and periphyton mediated by a macrophyte-induced lowering of lake water CO 2 concentrations. We conclude that the strong relationship between macrophyte coverage and δ 13C of macroinvertebrates and cladocerans may be useful in paleoecological studies of past changes in the dynamics of shallow
lakes, as change in macrophyte abundance may be tracked by the δ 13C of invertebrate remains in the sediment. 相似文献
8.
Summary Four autotrophic compartments were recognised in Lake Kitiesh, King George Island (Southern Shetland) at the beginning of the summer in 1987: snow microalgae, ice bubble communities, phytoplankton in the water column and benthic communities of moss with epiphytes. Chlorophyll a concentration and pigment absorption spectra were obtained in these four compartments before and/or after the thawing of the ice cover. During the ice free period, carbon fixation and biomass was measured in the phytoplankton and in the benthic moss Campyliadelphus polygamus. From these measurements we conclude that the benthic moss is the most significant autotrophic component in this lake in terms of biomass, chlorophyll a content and primary productivity. The integral assimilation number (The ratio of carbon fixation per unit area to biomass per unit area) values were similar for both phytoplankton and the moss, ranging from 3.6 to 5.4 mg C (mg Chl a) –1h –1in phytoplankton and from 4.0 to 6.4 mgC (mg Chl a) –1h –1 in the benthic moss. This approach allows comparisons of carbon fixation efficiency of the chlorophyll a under a unit area between compartments in their different light environments. 相似文献
9.
A pilot study was conducted to assess the potential for stable isotope analyses to reveal the fate of waste pelleted food material from fish farms in freshwater food webs. Esthwaite Water (Cumbria, UK) was selected as the study site, as it hosts an established salmonid farm, and a wealth of complementary limnological data exists. Salmonid pellet feed consists of primarily marine-derived material and thus exhibits carbon and nitrogen stable isotopic compositions distinct to most freshwater organic material. Comparison of the isotopic ratios of organisms at the cage site with an unaffected control site, supports incorporation of pellet-derived material to the diet of planktonic and benthic communities. Moreover, after allowing for a number of trophic transfers, stable isotope analyses revealed the predatory cladoceran Leptodora kindti also utilised pellet material, while roach were probably short-circuiting the food chain by directly consuming particulate pellet material, as well as via ingestion of their zooplankton prey. Isotope data substituted into a simple two-source mixing model suggested that approximately 65% of Daphnia, and >80% of roach body carbon may be derived from pellet material in the plankton, and that chironomid larvae may incorporate >50% in the sediment environs. However, contributions calculated from both
13C and
15N values were inconsistent, which may simply be due to the constraints of the model and parameters used, but may also reflect different routing of isotopes from the original pellet source, via soluble or particulate routes. 相似文献
10.
Stable isotope signatures of freshwater snails and mussels have been established as a convenient baseline measurement at the
primary consumer level for food-web coupling studies. We measured δ 15N and δ 13C of primary consumers, including mussels ( Anodonta woodiana, Cristaria plicata, and Unio douglasiae), snails ( Bellamya aeruginosa and Hippeutis sp.), and zooplankton from the same habitat within a shallow eutrophic lake. Primary consumers showed positive relationship
between δ 15N and δ 13C, indicating a linkage between planktonic and benthic habitats in this system. The variation in isotope ratios was higher
in short-lived primary consumers (zooplankton) compared with the long-lived primary consumers (mussels and snails), suggesting
limited availability of short-lived primary consumers as isotopic baselines in aquatic food-web assessment. Significant differences
in isotope ratios were also found among three species of mussels, and when using these mussels separately as pelagic baselines
to calculate trophic position and contribution of planktonic and benthic sources of fishes, bias and even misestimates were
observed. This finding suggests that caution is needed when multiple primary consumers coexist in the same habitat, and it
is important to assess potential effects of different baselines used. 相似文献
11.
Studies were performed of the carbon and nitrogen stable isotope (δ 13C and δ 15N) composition (δ 13C and δ 15N) of the corals Porites cylindrica and P. lutea (5 years after damaging the colonies by the bleaching events) and of epilithic algae settled onto damaged areas of coral
colonies. Coral polyps and three epilithic algal communities (‘red algal turf, green algal turf and red calcified crusts’)
were sampled along the boundary between communities of coral polyps and algal colonizers from differently illuminated habitats
from 2 to 90% of incident surface photosynthetically active radiation (PAR 0). It was found that communities with a predominance of red algae significantly differed from communities with a predominance
of green algae in δ 13C but not in δ 15N values. An influence of habitat irradiance was found only for communities of coral polyps for δ 13C and δ 15N values: under bright light (70–90% PAR 0) polyp tissues of both coral species were significantly enriched in heavy carbon isotopes and insignificantly in nitrogen
isotopes (δ 13C values difference ~4‰) relative to tissues of corals under lower light 15–50% PAR 0. On the basis of these results we assumed that differences in light intensities in the habitat ranging from 15 to 90% PAR 0 do not influence on accessibility of the main carbon and nitrogen sources for corals and algae, and exchange by these elements
between organisms. We also assumed that the relative enrichment in the heavy carbon isotopes of coral tissues in high light
is a result of decreased isotope fractionation (or the absence of fractionation in photosynthesis of their zooxanthellae). 相似文献
12.
Trophic patterns of omnivorous freshwater shrimps, Exopalaemon modestus and Macrobrachium nipponensis, were investigated in two shallow eutrophic lakes by using stable isotope analysis. δ 15N and δ 13C of M. nipponensis and E. modestus increased with increasing body weight, which might be attributed to larger individuals ingesting organisms that feed higher
up the food chain and/or increased assimilation of benthic food items with enriched isotopic signatures. Of the freshwater
shrimps occurring in the studied lakes, those from Lake Taihu had significantly elevated δ 15N and δ 13C values (4.3‰ and 1.8‰, respectively) compared with those from the less eutrophic Lake Chaohu, indicating that the isotopic
signature might partially reflect the trophic states of their habitats. Mixing model results suggested that the benthic food
web provides the primary carbon source for both shrimp species, and that E. modestus assimilated relatively more pelagic food sources than M. nipponensis in these lakes.
Handling editor: S. Wellekens 相似文献
13.
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 (δ 34S 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 in 34S 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 δ 34S values similar to those of sediment, whereas planktonic and benthic invertebrates known to feed on suspended particles had δ 34S 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
14.
Trophic polymorphism was recently reported in introduced bluegill ( Lepomis macrochirus) in Lake Biwa, Japan, where three morphs are specialized in benthic invertebrates (benthivorous type), submerged aquatic
plants (herbivorous type), and zooplankton (planktivorous type). We evaluated the long-term effects of food resource utilization
by these trophic morphs using stable isotope ratios, δ 15N and δ 13C. A significant difference in δ 15N was found between the benthivorous and planktivorous types. The planktivorous type had the higher δ 15N value, which corresponded with the value expected from its prey, zooplankton. The lower δ 15N value of the benthivorous type would be derived from the lower δ 15N values of benthic prey organisms compared to zooplankton. These results support previous findings that the benthivorous
and planktivorous types have different food resource utilization. In contrast, the δ 15N and δ 13C values of the herbivorous type were distinctly different from the expected values, indicating that this type was unlikely
to utilize aquatic plants substantially, contradicting the results of the dietary analysis. 相似文献
15.
When using stable isotopes as dietary tracers it is essential to consider effects of nutritional state on isotopic fractionation.
While starvation is known to induce enrichment of 15N in body tissues, effects of moderate food restriction on isotope signatures have rarely been tested. We conducted two experiments
to investigate effects of a 50–55% reduction in food intake on δ 15N and δ 13C values in blood cells and whole blood of tufted puffin chicks, a species that exhibits a variety of adaptive responses to
nutritional deficits. We found that blood from puffin chicks fed ad libitum became enriched in 15N and 13C compared to food-restricted chicks. Our results show that 15N enrichment is not always associated with food deprivation and argue effects of growth on diet–tissue fractionation of nitrogen
stable isotopes (Δ 15N) need to be considered in stable isotope studies. The decrease in δ 13C of whole blood and blood cells in restricted birds is likely due to incorporation of carbon from 13C-depleted lipids into proteins. Effects of nutritional restriction on δ 15N and δ 13C values were relatively small in both experiments (δ 15N: 0.77 and 0.41‰, δ 13C: 0.20 and 0.25‰) compared to effects of ecological processes, indicating physiological effects do not preclude the use of
carbon and nitrogen stable isotopes in studies of seabird ecology. Nevertheless, our results demonstrate that physiological
processes affect nitrogen and carbon stable isotopes in growing birds and we caution isotope ecologists to consider these
effects to avoid drawing spurious conclusions. 相似文献
16.
The biostratigraphy (larger foraminifers, dasycladaleans), microfacies, sedimentology, and geochemistry ( δ
13C, strontium-isotope stratigraphy) of a continuous, 148-m-thick section of shallow-water platform carbonates that contain
the Cretaceous/Paleogene (K/P) boundary were analyzed. The boundary is constrained within a 7-m-thick interval, between the
last occurrence of Maastrichtian larger benthic foraminifers and the first occurrence of Danian benthic foraminifers. Although
this interval is intensively dolomitized, there is no sedimentological evidence of a major hiatus at the K/P boundary. The
correlation of bulk rock δ
13C values with stable isotope data from DSDP Site 384 (NW Atlantic Ocean) supports this interpretation and indicates a Selandian
age for the top of the section. The Qalhat section is a unique example of a carbonate platform that has recorded persisting
open marine environmental conditions across the K/P boundary (Maastrichtian–Selandian), as indicated by the abundance of rudists,
larger benthic foraminifers (Maastrichtian), calcareous algae and scleractinian corals. 相似文献
17.
It is widely accepted that stable isotope ratios in inert tissues such as feather keratin reflect the dietary isotopic signature
at the time of the tissue synthesis. However, some elements such as stable nitrogen isotopes can be affected by individual
physiological state and nutritional stress. Using malaria infection experiment protocols, we estimated the possible effect
of malaria parasite infections on feather carbon (δ 13C) and nitrogen (δ 15N) isotope signatures in juvenile common crossbills Loxia curvirostra. The birds were experimentally infected with Plasmodium relictum (lineage SGS1) and P. ashfordi (GRW2), two widespread parasites of passerines. Experimental birds developed heavy parasitemia of both parasites and maintained
high levels throughout the experiment (33 days). We found no significant difference between experimental and control birds
in both δ 13C and δ 15N values of feathers re-grown. The study shows that even heavy primary infections of malaria parasites do not affect feather
δ 13C and δ 15N isotopic signatures. The results of this experiment demonstrate that feather isotope values of wild-caught birds accurately
reflect the dietary isotopic sources at the time of tissue synthesis even when the animal’s immune system might be challenged
due to parasitic infection. 相似文献
18.
δ 13C and δ 15N measurements are still poorly conducted in benthic invertebrate larvae. To assess the δ 13C and δ 15N changes occurring after a dietary shift, experiments were conducted on veliger larvae of Crepidula fornicata fed with two cultured microalgae ( Isochrysis galbana and Pavlova lutheri) of known isotopic composition, 13C-enriched and 15N-depleted compared to the initial values of the larvae. Rapid changes in larval δ 13C and δ 15N were observed after the dietary shift, with an increase in δ 13C and a decrease in δ 15N. After 19 days of feeding, isotopic equilibrium was still not reached, a period which is close to the duration of the pelagic life of the larvae. This implies that the isotopic composition measured in field-collected larvae might only partly reflect actual larval feeding but also the parental isotopic signature, especially during the early developmental stages. Isotopic measurements in marine invertebrate larvae should thus be interpreted cautiously. In planktonic food web investigations, the study of field-collected larvae of different size/developmental stage may reduce potential misinterpretations. 相似文献
19.
Non-indigenous freshwater bivalves negatively affect invaded ecosystems through different mechanisms, including inter-specific competition for trophic resources. Here, we investigated in Lake Trasimeno (Central Italy) the diet of the invasive Dreissena polymorpha and the native Anodonta anatina. δ15N and δ13C stable isotopes were measured in winter and summer in bivalves, phytoplankton, and sedimentary organic matter (SOM); the relative dietary contributions of the two resources were determined using Bayesian mixing models. To elucidate the different carbon and nitrogen pools characterizing the study site, isotopic analyses were extended to zooplankton and to representatives of the benthic flora and macroinvertebrate fauna. Independently from the season, the two bivalves showed a limited trophic overlap, as mixing models indicated for D. polymorpha a diet based primarily on phytoplankton, while A. anatina relied mainly on SOM. Dietary differences were less marked in summer, when comparable isotopic values characterized phytoplankton and SOM. In winter, conversely, the trophic differentiation between the two species was more evident, and corresponded with a significant enrichment in SOM δ13C values, likely due to a substantial contribution of carbon deriving from decaying macrophytes. Whether differences in ecological and behavioral traits alone can explain the observed trophic segregation between the two species, or if they have actively shifted their diet to reduce competition for food is discussed. We conclude emphasizing the need of an advanced resolution of the influence of non-indigenous species on the flux of energy and matter in invaded lentic systems, including Lake Trasimeno. 相似文献
20.
Carbon and nitrogen stable isotopes are frequently used to study energy sources and food web structure in ecosystems, and
more recently, to study the effects of anthropogenic stress on aquatic ecosystems. We investigated the effect of nutrient
enrichment on δ 13C and δ 15N in fine (FPOM), coarse (CPOM) particulate organic matter, periphyton, invertebrates and fish in nine boreal streams in south-central
Sweden. In addition, we analysed the diet of benthic consumers using stable isotope data. Increases in δ 15N of periphyton ( R
2 = 0.88), CPOM (0.78), invertebrates (0.92) and fish (0.89) were related to nutrient enrichment. In contrast, δ 13C signatures did not change along the nutrient gradient. Our results show that δ 15N has potential as a sensitive indicator of nutrient enrichment in boreal streams. Carbon and nitrogen isotopes failed to
elucidate putative diets of selected aquatic consumers. Indeed, comparison of low- and high-impact sites showed that δ 13C of many consumers were found outside the ranges of basal resource δ 13C. Moreover, ranges of basal resource δ 13C and δ 15N overlapped at both low and high sites, making discrimination between the importance of allochthonous and autochthonous production
difficult. Our findings show that a fractionation rate of 3.4‰ is not always be appropriate to assess trophic interactions,
suggesting that more studies are needed on fractionation rates along gradients of impairment.
Handling editor: M. Power 相似文献
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