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1.
Aurore Aubail Jonas Teilmann Rune Dietz Frank Rig��t Tero Harkonen Olle Karlsson Aqqalu Rosing-Asvid Florence Caurant 《Polar Biology》2011,34(9):1411-1420
Recent studies have shown that the complementary analysis of mercury (Hg) concentrations and stable isotopic ratios of nitrogen
(δ15N) and carbon (δ13C) can be useful for investigating the trophic influence on the Hg exposure and accumulation in marine top predators. In this
study, we propose to evaluate the interspecies variability of Hg concentrations in phocids from polar areas and to compare
Hg bioaccumulation between both hemispheres. Mercury concentrations, δ15N and δ13C were measured in fur from 85 individuals representing 7 phocidae species, a Ross seal (Ommatophoca rossii), Weddell seals (Leptonychotes weddellii), crabeater seals (Lobodon carcinophagus), harbour seals (Phoca vitulina), grey seals (Halichoerus grypus), ringed seals (Pusa hispida) and a bearded seal (Erignathus barbatus), from Greenland, Denmark and Antarctica. Our results showed a positive correlation between Hg concentrations and δ15N values among all individuals. Seals from the Northern ecosystems displayed greater Hg concentrations, δ15N and δ13C values than those from the Southern waters. Those geographical differences in Hg and stable isotopes values were likely
due to higher environmental Hg concentrations and somewhat greater number of steps in Arctic food webs. Moreover, dissimilarities
in feeding habits among species were shown through δ15N and δ13C analysis, resulting in an important interspecific variation in fur Hg concentrations. A trophic segregation was observed
between crabeater seals and the other species, resulting from the very specific diet of krill of this species and leading
to the lowest observed Hg concentrations. 相似文献
2.
Sean B. Menke Andy V. Suarez Chadwick V. Tillberg Cheng T. Chou David A. Holway 《Oecologia》2010,164(3):763-771
Studies of food webs often employ stable isotopic approaches to infer trophic position and interaction strength without consideration
of spatio-temporal variation in resource assimilation by constituent species. Using results from laboratory diet manipulations
and monthly sampling of field populations, we illustrate how nitrogen isotopes may be used to quantify spatio-temporal variation
in resource assimilation in ants. First, we determined nitrogen enrichment using a controlled laboratory experiment with the
invasive Argentine ant (Linepithema humile). After 12 weeks, worker δ15N values from colonies fed an animal-based diet had δ15N values that were 5.51% greater compared to colonies fed a plant-based diet. The shift in δ15N values in response to the experimental diet occurred within 10 weeks. We next reared Argentine ant colonies with or without
access to honeydew-producing aphids and found that after 8 weeks workers from colonies without access to aphids had δ15N values that were 6.31% larger compared to colonies with access to honeydew. Second, we sampled field populations over a
1-year period to quantify spatio-temporal variability in isotopic ratios of L. humile and those of a common native ant (Solenopsis xyloni). Samples from free-living colonies revealed that fluctuations in δ15N were 1.6–2.4‰ for L. humile and 1.8–2.9‰ for S. xyloni. Variation was also detected among L. humile castes: time averaged means of δ15N varied from 1.2 to 2.5‰ depending on the site, with δ15N values for queens ≥ workers > brood. The estimated trophic positions of L. humile and S. xyloni were similar within a site; however, trophic position for each species differed significantly at larger spatial scales. While
stable isotopes are clearly useful for examining the trophic ecology of arthropod communities, our results suggest that caution
is warranted when making ecological interpretations when stable isotope collections come from single time periods or life
stages. 相似文献
3.
Disentangling effects of growth and nutritional status on seabird stable isotope ratios 总被引:1,自引:0,他引:1
A growing number of studies suggest that an individual’s physiology affects its carbon and nitrogen stable isotope signatures,
obscuring a signal often assumed to be only a reflection of diet and foraging location. We examined effects of growth and
moderate food restriction on red blood cell (RBC) and feather δ15N and δ13C in rhinoceros auklet chicks (Cerorhinca monocerata), a piscivorous seabird. Chicks were reared in captivity and fed either control (75 g/day; n = 7) or ~40% restricted (40 g/day; n = 6) amounts of high quality forage fish. We quantified effects of growth on isotopic fractionation by comparing δ15N and δ13C in control chicks to those of captive, non-growing subadult auklets (n = 11) fed the same diet. To estimate natural levels of isotopic variation, we also collected blood from a random sample of
free-living rhinoceros auklet adults and chicks in the Gulf of Alaska (n = 15 for each), as well as adult feather samples (n = 13). In the captive experiment, moderate food restriction caused significant depletion in δ15N of both RBCs and feathers in treatment chicks compared to control chicks. Growth also induced depletion in RBC δ15N, with chicks exhibiting lower δ15N when they were growing the fastest. As growth slowed, δ15N increased, resulting in an overall pattern of enrichment over the course of the nestling period. Combined effects of growth
and restriction depleted δ15N in chick RBCs by 0.92‰. We propose that increased nitrogen-use efficiency is responsible for 15N depletion in both growing and food-restricted chicks. δ15N values in RBCs of free-ranging auklets fell within a range of only 1.03‰, while feather δ15N varied widely. Together, our captive and field results suggest that both growth and moderate food restriction can affect
stable isotope ratios in an ecologically meaningful way in RBCs although not feathers due to greater natural variability in
this tissue. 相似文献
4.
Seasonal oscillations in the carbon (δ13C) and nitrogen (δ15N) isotope signatures of aquatic algae can cause seasonal enrichment–depletion cycles in the isotopic composition of planktonic
invertebrates (e.g., copepods). Yet, there is growing evidence that seasonal enrichment–depletion cycles also occur in the
isotope signatures of larger invertebrate consumers, taxa used to define reference points in isotope-based trophic models
(e.g., trophic baselines). To evaluate the general assumption of temporal stability in non-zooplankton aquatic invertebrates,
δ13C and δ15N time series data from the literature were analyzed for seasonality and the influence of biotic (feeding group) and abiotic
(trophic state, climate regime) factors on isotope temporal patterns. The amplitude of δ13C and δ15N enrichment–depletion cycles was negatively related to body size, although all size-classes of invertebrates displayed a
winter-to-summer enrichment in δ13C and depletion in δ15N. Among feeding groups, periphytic grazers were more variable and displayed larger temporal changes in δ13C than detritivores. For nitrogen, temporal variability and magnitude of directional change of δ15N was most strongly related to ecosystem trophic state (eutrophic > mesotrophic, oligotrophic). This study provides evidence
of seasonality in the isotopic composition of aquatic invertebrates across very broad geographical and ecological gradients
as well as identifying factors that are likely to modulate the strength and variability of seasonality. These results emphasize
the need for researchers to recognize the likelihood of temporal changes in non-zooplankton aquatic invertebrate consumers
at time scales relevant to seasonal studies and, if present, to account for temporal dynamics in isotope trophic models. 相似文献
5.
Todd W. Miller 《Environmental Biology of Fishes》2006,76(2-4):177-189
The objective of this study was to measure the tissue-specific response of isotope δ15N to changes in isotopic signature of diet in an adult Pacific herring, Clupea pallasi, and to examine the importance of growth and metabolism in this shift. This was accomplished by placing wild adult Pacific herring in captivity and monitoring isotopic shift in tissues with a corresponding isotopic shift in diet, and the application of a metabolism/growth mixing model. Tissues examined were blood, eye, heart, liver, and white muscle. One group of herring was given a δ15N diet depleted by approximately 5.4‰, and another given a 15N-enriched diet labeled with 98 atom% l-phenylalanine. This study showed that (i) isotopic response of individual tissues following an isotopic shift in diet varied in both rate of change and fractionation level, (ii) most of this isotopic shift is due to growth, and (iii) white muscle and liver tissue appeared the most responsive to isotopic shift in diet, reaching isotopic equilibrium with diet in a matter of months (not years). For trophic studies using δ15N, these results indicate that field measurement of Pacific herring should be done after much of summer growth has occurred. 相似文献
6.
Regional food web studies that fail to account for small-scale isotopic variability can lead to a mismatch between an organism’s
inferred and true trophic position. Misinterpretation of trophic status may result, substantially limiting spatial and temporal
comparability of food web studies. We sampled several carbon sources and consumers in a nested design to assess the variability
of food web members across small spatial scales (100 s of m to several km) in regions around the Windmill Islands and Vestfold
Hills in East Antarctica. For carbon sources, δ13C in sea ice POM was particularly variable between locations (km apart) and between sites (100 s of m apart) with replicate
samples varying by up to 16‰. Macroalgae δ13C was less variable (replicate samples ranging up to 6.9‰ for the red alga Iridaea cordata), yet still differed between locations. Sediment POM and pelagic POM were the least variable, displaying minimal differences
between locations or sites for δ13C and δ15N. Three out of eight consumers were significantly different between locations for δ13C, and five out of eight for δ15N, with the fish Trematomus bernacchii the most variable for both δ13C and δ15N. At smaller scales, the amphipod Paramorea walkeri showed significant variation between sites in δ13C but not in δ15N. We attribute small-scale variability to the dynamic physical environment for carbon sources in coastal systems and a close
coupling of diet to habitat for consumers. We highlight the need to account for small-scale spatial variation in sampling
designs for regional food web studies. 相似文献
7.
A basic understanding of current food web dynamics and baseline data from which to measure future change is necessary to understand
species re-distribution and altered competition for food with climate change. We use mercury (Hg) and carbon (δ13C) and nitrogen (δ15N) stable isotope ratios as biomarkers to understand species diet differences and age class differences among ringed (Phoca hispida), bearded (Erignathus barbatus), and harbour (P. vitulina) seals in a subarctic marine ecosystem. Adult bearded seals had significantly lower δ15N and muscle Hg than bearded seal pups, whereas the opposite was observed in ringed seals where pups had lower δ15N than adults, suggesting age specific foraging differences in trophic food level for both species. For harbour seals, δ15N did not differ significantly among ages while Hg and δ13C did. The δ13C in muscle supports that bearded seals in this study are benthic feeders and are part of a separate food web from ringed
seals and harbour seals. Harbour seals had the highest levels of mercury and δ15N, indicating they feed at a higher trophic level relative to the other two seal species. Carbon and nitrogen isotopic ratios
and Hg levels illustrate how resources are partitioned among three seal species and offer evidence for separation based on
life stages within species. 相似文献
8.
Stable isotope signatures of primary producers display high inter- and intraspecific variation. This is assigned to species-specific
differences in isotope fractionation and variable abiotic conditions, e.g., temperature, and nutrient and light availability.
As consumers reflect the isotopic signature of their food source, such variations have direct impacts on the ecological interpretation
of stable isotope data. To elucidate the variability of isotope fractionation at the primary producer level and the transfer
of the signal through food webs, we used a standardised marine tri-trophic system in which the primary producers were manipulated
while the two consumer levels were kept constant. These manipulations were (1) different algal species grown under identical
conditions to address interspecific variability and (2) a single algal species cultivated under different nutrient regimes
to address nutrient-dependent variability. Our experiments resulted in strong interspecific variation between different algal
species (Thalassiosira weissflogii, Dunaliella salina, and Rhodomonas salina) and nutrient-dependent shifts in stable isotope signatures in response to nutrient limitation of R. salina. The trophic enrichment in 15N and 13C of primary and secondary consumers (nauplii of Acartia tonsa and larval herring) showed strong deviations from the postulated degree of 1.0‰ enrichment in δ13C and 3.4‰ enrichment in δ15N. Surprisingly, nauplii of A. tonsa tended to keep “isotopic homeostasis” in terms of δ15N, a pattern not described in the literature so far. Our results suggest that the diets’ nutritional composition and food
quality as well as the stoichiometric needs of consumers significantly affect the degree of trophic enrichment and that these
mechanisms must be considered in ecological studies, especially when lower trophic levels, where variability is highest, are
concerned. 相似文献
9.
The use of stable isotopes to investigate animal diets, habitat use, and trophic level requires understanding the rate at
which animals incorporate the 13C and 15N from their diets and the factors that determine the magnitude of the difference in isotopic composition between the animal’s
diet and that of its tissues. We determined the contribution of growth and catabolic turnover to the rate of 13C and 15N incorporation into several tissues that can be sampled non-invasively (skin, scute, whole blood, red blood cells, and plasma
solutes) in two age classes of a rapidly growing ectotherm (loggerhead turtles, Caretta caretta). We found significant differences in C and N incorporation rates and isotopic discrimination factors (Δ13C = δ13Ctissues − δ13Cdiet and Δ15N = δ15Ntissues − δ15Ndiet) among tissues and between age classes. Growth explained from 26 to 100% of the total rate of incorporation in hatchling
turtles and from 15 to 52% of the total rate of incorporation in juvenile turtles. Because growth contributed significantly
to the rate of isotopic incorporation, variation in rates among tissues was lower than reported in previous studies. The contribution
of growth can homogenize the rate of isotopic incorporation and limit the application of stable isotopes to identify dietary
changes at contrasting time scales and to determine the timing of diet shifts. The isotopic discrimination factor of nitrogen
ranged from −0.64 to 1.77‰ in the turtles’ tissues. These values are lower than the commonly assumed average 3.4‰ discrimination
factors reported for whole body and muscle isotopic analyses. The increasing reliance on non-invasive and non-destructive
sampling in animal isotopic ecology requires that we recognize and understand why different tissues differ in isotopic discrimination
factors. 相似文献
10.
Do stable isotopes reflect nutritional stress? Results from a laboratory experiment on song sparrows
Kempster B Zanette L Longstaffe FJ MacDougall-Shackleton SA Wingfield JC Clinchy M 《Oecologia》2007,151(3):365-371
Stable isotope analysis is an increasingly valuable tool in ecological studies and shows promise as a measure of nutritional
stress in wild animals. Thus far, however, the only studies on endotherms that have conclusively shown changes in δ15N and δ13C values in response to nutritional stress were conducted on fasting animals and animals growing under extreme levels of food
restriction. We conducted a laboratory experiment to test whether δ15N and δ13C values provide a general index of nutritional stress. We compared the isotopic composition of whole blood, liver, muscle
and feathers between two groups of juvenile song sparrows (Melospiza melodia) hand-reared in captivity under identical conditions except for feeding regime. To verify that our experimental treatment
induced a biologically meaningful level of nutritional stress, we simultaneously measured the effects on physiology, growth
and development at multiple scales. While food-restricted birds were physiologically stressed, physically smaller, and showed
poorer growth and brain development compared to ad libitum-fed birds, there was no effect of feeding regime on either δ15N or δ13C values in any tissue. Instead of a continuum where the level of change in 15N or 13C contents corresponds to the level of nutritional stress, we suggest there may be a threshold level of nutritional stress
below which such isotopic changes are likely to be negligible. 相似文献
11.
Investigations into trophic ecology and aquatic food web resolution are increasingly accomplished through stable isotope analysis.
The incorporation of dietary and metabolic changes over time results in variations in isotope signatures and turnover rates
of producers and consumers at tissue, individual, population and species levels. Consequently, the elucidation of trophic
relationships in aquatic systems depends on establishing standard isotope values and tissue turnover rates for the level in
question. This study investigated the effect of diet and food quality on isotopic signatures of four mussel tissues: adductor
muscle, gonad, gill and mantle tissue from the brown mussel Perna perna. In the laboratory, mussels were fed one of the two isotopically distinct diets for 3 months. Although not all results were
significant, overall δ13C ratios in adductor, mantle and gill tissues gradually approached food source signatures in both diets. PERMANOVA analyses
revealed significant changes over time in tissue δ13C (mantle and gill) with both diets and in δ15N (all tissues) and C:N ratios (mantle and gill) for one diet only. The percentage of replaced carbon isotopes were calculated
for the 3 month period and differed among tissues and between diets. The tissue with the highest and lowest amount of replaced
isotopes over 81 days were mantle tissue on the kelp diet (33.89%) and adductor tissue on the fish food diet (4.14%), respectively.
Percentages could not be calculated for any tissue in either diet for δ15N due to the lack of significant change in tissue nitrogen. Fractionation patterns in tissues for both diets can be linked
to nutritional stress, suggesting that consumer isotopic signatures are strongly dependent on food quality, which can significantly
affect the degree of isotopic enrichment within a trophic level. 相似文献
12.
Stable isotopes and trophic positions of littoral fishes from a Mediterranean marine protected area 总被引:1,自引:0,他引:1
Stable isotope analyses were employed to explore feeding and foraging habitats and trophic levels of littoral fishes in a
western Mediterranean Marine Protected Area (Egadi Islands, Sicily, Italy). Carbon and nitrogen stable isotope ratios were
measured in primary producers, invertebrates and fishes collected in December 2001 and January 2002. Fishes of the littoral
region of the Egadi Islands had isotopic signatures that fell into a wider range for δ
13C (about 6‰) than for δ
15N (about 3‰). Carbon isotope ratios were consistent with a food web based on mixed sources and two trophic pathways leading
to different fish species. Differences in the isotopic composition between islands were higher for benthivorous than for planktivorous
fishes. The overall picture gained from this study is of a isotopic distinction between planktivorous and benthivorous fishes,
resource partitioning facilitating the coexistence of similar species within the same ecosystem, and spatial variability in
the isotopic signatures and trophic level of fishes. Asymmetrical analysis of variance showed that estimated trophic levels
were lower in the area with the highest level of protection (Zone A) for only two out of the nine fishes analysed. As a consequence,
overall spatial differences do not seem to be a consequence of protection, since in most cases trophic levels did not change
significantly between zone A and zones C where professional fishing (trawling apart) is permitted, but of natural sources
of variation (e.g. variability in food availability and site-specific food preferences of fishes). However, the results of
this study suggest a different response at the species compared to the community level. 相似文献
13.
Trophic patterns of omnivorous freshwater shrimps, Exopalaemon modestus and Macrobrachium nipponensis, were investigated in two shallow eutrophic lakes by using stable isotope analysis. δ15N and δ13C 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 δ15N and δ13C 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
14.
Researchers will be able to use stable isotope analysis to study community structure in an efficient way, without a need for extensive calibrations, if isotopic enrichment values are consistent, or if variation in enrichment values can be predicted. In this study, we generated an experimental data set of δ15N and δ13C enrichment means for 22 terrestrial herbivorous arthropods feeding on 18 different host plants. Mean enrichments observed across a single trophic transfer (plants to herbivores) were −0.53±0.26‰ for δ13C (range: −3.47‰ to 1.89‰) and 1.88±0.37‰ for δ15N (range: −0.20‰ to 6.59‰). The mean δ13C enrichment was significantly lower than that reported in recent literature surveys, whereas the mean δ15N enrichment was not significantly different. The experimental data set provided no support for recent hypotheses advanced to explain variation in enrichment values, including the proposed roles for consumer feeding mode, development type, and diet C:N ratio. A larger data set, formed by combining our experimental data with data from the literature, did suggest possible roles for feeding mode, nitrogen recycling, herbivore life stage, and host plant type. Our results indicate that species enrichment values are variable even in this relatively narrow defined group of organisms and that our ability to predict enrichment values of terrestrial herbivorous arthropods based on physiological, ecological, or taxonomic traits is low. The primary implications are that (1) mean enrichment may have to be measured empirically for each trophic link of interest, rather than relying on estimates from a broad survey of animal taxa and (2) the advantage of using stable isotope analysis to probe animal communities that are recalcitrant to other modes of study will be somewhat diminished as a consequence.Electronic Supplementary Material Supplementary material is available for this article at 相似文献
15.
Food web structure of a shallow eutrophic lake (Lake Taihu,China) assessed by stable isotope analysis 总被引:1,自引:0,他引:1
Lake Taihu is a large, shallow, and eutrophic lake in China. It has provided local communities with valuable fisheries for
centuries, but little is known of the trophodynamics, or of its faunal communities. Carbon and nitrogen isotopic composition
was used to assess its trophic pathways and the food web structure [food sources and trophic levels (TL)]. Basal food sources
were distinguishable based on their δ13C values, ranging from −27.2 to −15.2‰. Consumers were also well separated in δ13C (−26.9 to −17.9‰ for invertebrates and −25.7 to −18.1‰ for fishes), which allowed for an effective discrimination of carbon
sources between these fauna. An average trophic enrichment factor of 3.4‰ was used to calculate the TLs based on δ15N of zooplankton, with results indicating a food web having four TLs. Although δ15N values overlap and cover a large range within trophic compartments, the isotopic signatures of the species assessed revealed
a general trend of 15N enrichment with increasing TL. Stable isotope signatures were also used to establish a general food web scheme in which
five main trophic pathways were analyzed. 相似文献
16.
Determining diet and trophic position of species with stable isotopes requires appropriate trophic enrichment estimates between an animal and its potential foods. These estimates are particularly important for cryptic foragers where there is little comparative dietary information. Nonetheless, many trophic enrichment estimates are based on related taxa, without confirmation of accuracy using laboratory trials. We used stable isotope analysis to investigate diet and to resolve trophic relationships in a large endemic insect, the Auckland tree weta (Hemideina thoracica White). Comparisons of isotopes in plant foods fed to captive wetas with isotope ratios in their frass provided variable results, so frass isotope values had limited usefulness as a proxy indicator of trophic level. Isotopic values varied between different tissues, with trophic depletion of 15N highest in body fat and testes. Tissue fractionation was consistent in captive and wild caught wetas, and isotopic values were not significantly different between the two groups, suggesting that this weta species is primarily herbivorous. Whole-body values in captive wetas demonstrated trophic depletion (Δδ) for δ15N of about −0.77‰ and trophic enrichment of 4.28‰ for δ13C. These values differ from commonly estimated trophic enrichments for both insects and herbivores and indicate the importance of laboratory trials to determine trophic enrichment. Isotopic values for femur muscles from a number of local wild weta populations did not vary consistently with body weight or size, suggesting that juveniles eat the same foods as adults. Considerable variation among individuals within and between populations suggests that isotopic values are strongly influenced by food availability and individual foraging traits. 相似文献
17.
Organic Matter Stable Isotope (δ13C, δ15N) Response to Historical Eutrophication of Lake Taihu, China 总被引:1,自引:0,他引:1
We explored the use of carbon and nitrogen isotope ratios (δ13C, δ15N) 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 δ13C and δ15N 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 δ13C and δ15N decreased sharply in response to pronounced shifts in the aquatic ecosystem. The results indicate that 13C-depleted phytoplankton replaced macrophytes in western Lake Taihu. δ15N values in western Lake Taihu also decreased because of N2 fixation by cyanobacteria in this highly productive ecosystem. By contrast, in eastern Lake Taihu, organic matter δ13C and δ15N 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 CO2 availability, causing a decrease in isotopic discrimination during photosynthesis. After ∼
∼1990 AD, organic matter δ15N 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 δ13C and δ15N 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
18.
The species composition, abundance, and isotopic signature of millipedes (Myriapoda, Diplopoda) were investigated in seven
biotopes of Kaluzhskie Zaseki State Nature Reserve. Nine Diplopoda species were found in total, and the local species diversity
(within a sampling plot) reached seven species. The Diplopoda tissues were similar to the plant litter in the isotopic composition
of nitrogen (δ15N was by 0.4‰ higher, on average), but were strongly enriched in heavy carbon (δ13C was by 4‰ higher, on average). Removal of mineral carbon from the cuticle reduced δ13C of Diplopoda by about 1.4‰ on average. Differences in the δ15N and δ13C values between the species did not exceed 2.5‰. Differences in the isotopic compositions of the considered species were
small, and, it is impossible to distinguish particular trophic guilds in the Diplopoda community. Analysis of the published
data confirmed that isotopic differentiation of millipedes was much less pronounced than in other investigated groups of soil
animals. Hence, millipedes of the deciduous forest form a uniform trophic group. 相似文献
19.
Stable carbon and nitrogen isotope ratio profiling of sperm whale teeth reveals ontogenetic movements and trophic ecology 总被引:1,自引:0,他引:1
Teeth from male sperm whales (Physeter macrocephalus) stranded in the North-eastern Atlantic were used to determine whether chronological profiles of stable isotope ratios of
C (δ13C) and N (δ15N) across dentine growth layers could be used to detect known ontogenetic benchmarks in movements and trophic ecology. Profiles
showed a general decrease in δ13C (median = 1.91‰) and an increase in δ15N (median = 2.42‰) with age. A marked decline in δ13C occurred for all 11 teeth around 9–10 years and again for six individuals around 20 years. After the early twenties the
δ13C continued to decline with age for all teeth. These results are consistent with males segregating from natal groups in low
latitudes with the onset of puberty between 4 and 15 years and gradually dispersing pole-ward into 13C-depleted temperate waters. Penetration into further depleted, productive high latitudes after the age of 20 might facilitate
the spurt of accelerated growth rate observed around this age. Breeding migrations back to lower latitudes were not reflected
in the δ13C profiles possibly due to being short compared to the time spent feeding in high latitudes. The timings of marked isotopic
change in the δ15N profiles reflect those of the δ13C profiles, suggesting a link between dietary changes and movements. The observed increase in δ15N with age is likely to be caused by a trophic level increase as males grow in size, probably feeding on larger prey. An additional
explanation could be that, in the higher latitudes of the North Atlantic, the main prey source is the high trophic level squid
Gonatus fabricii. Also, the lower latitudes from where males disperse are depleted in basal 15N. Profiles of δ13C and δ15N in sperm whale teeth gathered from different regions, sexes, and periods in time, could provide a unique way to understand
the ecology of this species across different oceans. 相似文献
20.
Size-related diet shifts are important characteristics of fish trophodynamics. Here, body size–related changes in muscle δ15N and δ13C of four coral reef fishes, Acanthurus nigrofuscus (herbivore), Chaetodon lunulatus (corallivore), Chromis xanthura (planktivore) and Plectropomus leopardus (piscivore) were investigated at two locations in the Solomon Islands. All four species occupied distinct isotopic niches
and the concurrent δ13C′ values of C. xanthura and P. leopardus suggested a common planktonic production source. Size-related shifts in δ15N, and thus trophic level, were observed in C. xanthura, C. lunulatus and P. leopardus, and these trends varied between location, indicating spatial differences in trophic ecology. A literature review of tropical
fishes revealed that positive δ15N-size trends are common while negative δ15N-size trends are rare. Size-δ15N trends fall into approximately equal groups representing size-based feeding within a food chain, and that associated with
a basal resource shift and occurs in conjunction with changes in production source, indicated by δ13C. The review also revealed large scale differences in isotope-size trends and this, combined with small scale location differences
noted earlier, highlights a high degree of plasticity in the reef fishes studied. This suggests that trophic size analysis
of reef fishes would provide a productive avenue to identify species potentially vulnerable to reef impacts as a result of
constrained trophic behaviour. 相似文献