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1.
Significance of instream autotrophs in trophic dynamics of the Upper Mississippi River 总被引:1,自引:0,他引:1
Trophic dynamics of large river–floodplain ecosystems are still not well understood despite development of several conceptual
models over the last 25 years. To help resolve questions about the relative contribution of algal and detrital organic matter
to food webs in the Upper Mississippi River, we (1) separated living and detrital components of ultrafine and fine transported
organic matter (UTOM and FTOM, respectively) by colloidal silica centrifugation; (2) identified stable isotope signatures
(δ13C and δ15N) for these two portions of transported organic matter and other potential organic matter sources; and (3) employed a multiple
source, dual-isotope mixing model to determine the relative contribution of major energy sources to primary consumers and
the potential contribution of basal sources to the biomass of secondary consumers. The δ13C and δ15N of living and detrital fractions of UTOM and FTOM were distinct, indicating clear differences in isotopic composition of
the algal and detrital fractions of transported organic matter. Living and detrital transported organic matter also differed
from other potential organic matter sources by either δ13C or δ15N. A six-source mixing model using both δ13C and δ15N indicated that algal transported organic matter was the major resource assimilated by primary consumers. The contribution
of detrital transported organic matter was small in most cases, but there were a small number of taxa for which it could potentially
contribute to more than half the assimilated diet. Colloidal dissolved organic matter, which includes heterotrophic bacteria,
accounted for only a small fraction of the organic matter assimilated by most primary consumers, indicating that coupling
between microbial processes and metazoan production is minimal. Terrestrial C3 litter from the floodplain forest floor and aquatic macrophytes were also relatively unimportant to the assimilated diet
of primary consumers. Application of the mixing model to compare basal source isotopic ratios to secondary consumers revealed
that most organic matter moving from primary to secondary consumers originated from algal TOM. Our findings indicate that
autochthonous organic matter is the major energy source supporting metazoan production in the main channel of this large river,
at least during the summer. This study joins a number of other investigations performed globally that indicate organic matter
originating from instream production of sestonic and benthic microalgae is a major driver in the trophic dynamics of large
river ecosystems. 相似文献
2.
Ayato Kohzu Ichiro Tayasu Chikage Yoshimizu Atsushi Maruyama Yukihiro Kohmatsu Fujio Hyodo Yukio Onoda Akitake Igeta Kiyoshi Matsui Takanori Nakano Eitaro Wada Toshi Nagata Yasuhiro Takemon 《Ecological Research》2009,24(1):127-136
We examined how nitrogen-stable isotopic signatures of food web components (basal resources, primary and lower consumers,
and omnivores) in rivers change with increasing levels of human population density (HPD) in their watersheds. Samples were
collected from 22 rivers flowing in the Lake Biwa basin, Japan. Among three potential resources at the base of food webs (epilithon,
benthic and suspended particulate organic matter), the mean isotopic values (δ15N) of the epilithon (4.5–7.8%) were consistently higher than those of other items (1.9–4.2%) and displayed the most pronounced
elevation (by 3.3%) with increasing HPD. The mean δ15N values of the individual taxa of lower consumers (bivalve, snail and caddisfly) tended to increase with increasing HPD,
although the pattern and the extent of the elevation were highly variable among the taxa. These results suggest a taxon-specific
feature in the N source (or sources) of lower consumers. Our data suggested that human activities (e.g. nutrient loading)
potentially induce changes in the N baselines of river food webs. The major N source of bivalves appeared to be shifted from
suspended particulate organic matter to other items with increasing HPD. Trophic levels of goby fish (Rhinogobius sp. OR) and shrimp (Palaemon paucidens), being estimated to be at 2.4–3.8 and 2.1–3.4, respectively, did not differ significantly among rivers with different HPD
levels.
An erratum to this article can be found at 相似文献
3.
North American beavers (Castor canadensis) were introduced to Tierra del Fuego Island in 1946 for their fur, and have since spread across the archipelago and onto
the South American mainland. We assessed the impact of invasive beavers on streams of these forested watersheds by quantifying
the trophic basis of production (TBP) and consumptive organic matter flows of benthic macroinvertebrate assemblages. TBP was
determined in two streams: clear- and black-water. Stable isotopes were used across four streams to further elucidate food
web structure and dominant pathways. TBP and stable isotopes showed that terrestrially derived organic matter (amorphous detritus,
leaves, and wood) supported a majority of secondary production in the benthic food webs at all sites (forested reaches, beaver
ponds, and sections downstream of ponds with foraged riparian zones). The magnitude of these flows was enhanced in beaver-modified
sites compared with forested habitats (4.0–5.3× increase g AFDM m−2 year−1 in pond habitats, 1.1–2.1× increase in downstream habitats). Diatoms were the only autochthonous resource identified in macroinvertebrate
guts, but their contribution to secondary production was small. Consumptive flows mirrored trends in TBP (i.e., dominance
of terrestrial sources and greater magnitude in beaver ponds). Collector–gatherer consumption of amorphous detrital material
dominated food web flows in all habitats, but was higher in beaver ponds relative to other habitats. Food web structure was
simplified in beaver ponds; only two of the five possible functional groups contributed >1% of total organic matter flow in
ponds (collector–gatherers and predators). Consumptive flows to predators increased in ponds, and stable isotopes of nitrogen
and carbon (δ15N and δ13C) corroborated a relatively greater importance of predators (greater trophic distance), as well as less diversity of basal
resources (less variation in δ13C) in ponds. Our findings indicate that invasive beaver’s engineering activities resulted in greater flows of terrestrial
organic matter subsidies to in-stream food webs, which had a relatively greater change in the clear-water than in the black-water
stream. Owing to the fact that these streams were naturally dependent on allochthonous resources for a majority of production
and material flows, changes wrought by beavers to streams in forested environments are probably less than in watersheds with
inherently greater dependence on autochthonous production such as the adjacent steppe biome. 相似文献
4.
Duncan P. Gray Jon S. Harding Bo Elberling Travis Horton Tim J. Clough Mike J. Winterbourn 《Ecosystems》2011,14(4):583-597
Natural braided river floodplains typically possess high groundwater–surface water exchange, which is vital to the overall
function and structure of these complex ecosystems. Spring-fed streams on the floodplain are also hotspots of benthic invertebrate
diversity and productivity. The sources of carbon that drive these productive spring-fed systems are not well-known. We conducted
field assessments and a manipulation, modeling, and a laboratory experiment to address this issue. Initially δ13C values of both dissolved inorganic carbon (DIC) and food-web components of five springs were used to assess the sources
of carbon to spring food webs. Partial pressures of CO2 in upwelling water ranged from 2 to 7 times atmospheric pressure, but rapidly approached equilibrium with the atmosphere
downstream commensurate with 13C enrichment of DIC. Speciation modeling and a laboratory out-gassing experiment suggested that downstream changes in pH could
be explained solely by CO2 out-gassing. However, field results indicated that both out-gassing and photosynthetic drawdown by aquatic plants controlled
the net flux of CO2. A whole stream manipulation indicated out-gassing was the primary effect at the spring source, which was confirmed by invariant
diel pH. At 1296 m downstream from the spring source a large diel shift in pH indicated a plant effect on CO2 concentration which would contribute to the overall downstream gradient in δ13C DIC. Within the first 1296 m the gradient in δ13 DIC was transmitted through three trophic levels of the spring food web. These findings indicate dependency on groundwater
inorganic carbon by spring stream food webs and strong hydrologically mediated linkages connecting terrestrial, subsurface,
and aquatic components of the floodplain. 相似文献
5.
Craig E. Hebert D. V. Chip Weseloh Lewis T. Gauthier Michael T. Arts Robert J. Letcher 《Oecologia》2009,160(1):15-23
Food web structure regulates the pathways and flow rates of energy, nutrients, and contaminants to top predators. Ecologically
and physiologically meaningful biochemical tracers provide a means to characterize and quantify these transfers within food
webs. In this study, changes in the ratios of stable N isotopes (e.g., δ15N), fatty acids (FA), and persistent contaminants were used to trace food web pathways utilized by herring gulls (Larus argentatus) breeding along the shores of the St Lawrence River, Canada. Egg δ15N values varied significantly among years and were used as an indicator of gull trophic position. Temporal trends in egg δ15N values were related to egg FA profiles. In years when egg δ15N values were greater, egg FA patterns reflected the consumption of more aquatic prey. Egg δ15N values were also correlated with annual estimates of prey fish abundance. These results indicated that temporal changes
in aquatic prey availability were reflected in the gull diet (as inferred from ecological tracer profiles in gull eggs). Analysis
of individual eggs within years confirmed that birds consuming more aquatic prey occupied higher trophic positions. Furthermore,
increases in trophic position were associated with increased concentrations of most persistent organic contaminants in eggs.
However, levels of highly brominated polybrominated diphenyl ether congeners, e.g, 2,2′,3,3′,4,4′,5,5′,6,6′-decabromoDE (BDE-209),
showed a negative relationship with trophic position. These contrasting findings reflected differences among contaminant groups/homologs
in terms of their predominant routes of transfer, i.e., aquatic versus terrestrial food webs. High trophic level omnivores,
e.g., herring gulls, are common in food webs. By characterizing ecological tracer profiles in such species we can better understand
spatial, temporal, and individual differences in pathways of contaminant, energy, and nutrient flow. 相似文献
6.
Currently, the impact of declining seasonal sea ice extent in the Arctic on polar food webs remains uncertain. Previously,
a range of proxy techniques has been employed to determine links between sea ice or phytoplankton primary production and the
Arctic marine food web, although it is accepted that such approaches have their limitations. Here, we propose a novel approach
to tracing sea ice primary production through Arctic food webs using the sea ice diatom biomarker, IP25. Various benthic macrofaunal specimens were collected between March and May 2008 from Franklin Bay in the Amundsen Gulf,
Arctic Canada, as part of the International Polar Year–Circumpolar Flaw Lead system study. Each specimen was analysed for
the presence of the sea ice diatom biomarker IP25 in order to provide evidence for feeding by benthic organisms on sea ice algae. IP25 was found in nineteen out of the twenty-one specimens analysed, often as the most abundant of the highly branched isoprenoid
biomarkers detected. The stable isotope composition of IP25 (δ13C = −17.1 ± 0.5‰) in the sea urchin (Strongylocentrotus sp.) specimens was similar to that reported previously for this biomarker in Arctic sea ice, sedimenting particles and sediments.
It is concluded that detection of IP25 in Arctic benthic macrofauna represents a novel approach to providing convincing evidence for feeding on sea ice algae. It
is also proposed that analysis of IP25 may be used to trace trophic transfer of sea ice algal-derived organic matter through Arctic food webs in the future. 相似文献
7.
Diverse populations of invertebrates constitute the food web in detritus layers of a forest floor. Heterogeneity in trophic
interactions within such a species-rich community food web may affect the dynamic properties of biological communities such
as stability. To examine the vertical heterogeneity in trophic interactions among invertebrates in litter and humus layers,
we studied differences in species composition and variations in carbon and nitrogen stable-isotope ratios (δ13C and δ15N) using community-wide metrics of the forest floors of temperate broadleaf forests in Japan. The species composition differed
between the two layers, and the invertebrates in the litter layer were generally larger than those in the humus layer, suggesting
that these layers harbored separate food webs based on different basal resources. However, the δ13C of invertebrates, an indicator of differences in the basal resources of community food webs, did not provide evidence for
separate food webs between layers even though plant-derived organic matter showed differences in stable-isotope ratios according
to decomposition state. The minimum δ15N of invertebrates also did not differ between layers, suggesting sharing of food by detritivores from the two layers at lower
trophic levels. The maximum and range of δ15N were greater in the humus layer, suggesting more trophic transfers (probably involving microorganisms) than in the litter
layer and providing circumstantial evidence for weak trophic interactions between layers at higher trophic levels. Thus, the
invertebrate community food web was not clearly compartmentalized between the detrital layers but still showed a conspicuous
spatial (vertical) heterogeneity in trophic interactions. 相似文献
8.
Hideyuki Doi Elena I. Zuykova Eisuke Kikuchi Shuichi Shikano Keiichi Kanou Natalia Yurlova Elena Yadrenkina 《Hydrobiologia》2006,571(1):395-400
We investigated spatial changes in the isotope ratios of the plankton food web in Lake Chany, Siberia, Russia, especially
at an estuarine transition zone of the lake. The δ13C values of particulate organic matter (POM) varied among the sampling sites, and increased with increasing pH of the lake
water. This may reflect a shift by phytoplankton from using CO2 to using bicarbonate for photosynthesis with increasing pH. The δ13C values of zooplankton community also changed at each site along with those of the POM. This was indicative of carbon isotope
changes of plankton food webs between the stations along an environmental gradient. 相似文献
9.
Gianluca Sarà Maurizio De Pirro Mario Sprovieri Paola Rumolo Halldór Pálmar Halldórsson Jörundur Svavarsson 《Helgoland Marine Research》2009,63(4):309-315
Stable isotopes (δ13C and δ15N) were used to examine the origin of organic matter for the most representative demersal species of the SW Icelandic fishery,
accounting for over 70% of landings of those species in the North Atlantic. Samples were collected during a 2-week period
in early September 2004 from landings and directly during fishing cruises. Stable isotopes showed that particulate organic
matter and sedimentary organic matter were at the base of the food web and appeared to fill two different compartments: the
pelagic and the benthic. The pelagic realm was composed of only capelin and sandeel; krill and redfish occupied an intermediate
position between pelagic and benthic realms; while anglerfish, haddock, cod and ling resulted as the true demersal species
while tusk, rays and plaice were strongly linked to the benthic habitat. 相似文献
10.
Stream food web function is often assessed using carbon stable isotope assessments of the relative contribution of autochthonous
and allochthonous sources of organic matter to consumer diets. As a result, variability in source signatures can strongly
influence the assessment of carbon flows. To examine the implications of temporal source variability on food web interpretations,
benthic algal δ13C signatures were measured over 8 weeks in five streams in subtropical Queensland, Australia. All food webs were largely driven
by benthic algal carbon; however, substantial week-to-week variation in benthic algal δ13C signatures modified the calculated contributions of algae to consumer diets, with differences in autochthonous contributions
of up to 11% between weeks. In addition, variable algal signatures led to many occasions in which the δ13C signatures of some consumers was beyond the range of available sources, meaning the mixing model analyses did not have a
valid solution. Together, these findings suggest that temporal variability in algal δ13C signatures can strongly influence the interpretation of carbon flows in stream food webs. Future food web studies should
assess the temporal variability of sources prior to sampling consumers, in order to characterise end member signatures and
their relevance to consumers at the time of collection. 相似文献
11.
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
12.
13.
Contributions of stable-isotope data to elucidating food webs of Mediterranean rocky littoral fishes 总被引:18,自引:0,他引:18
The food webs of rocky infra-littoral ecosystems in the Mediterranean have been little studied. In this investigation stable
isotopes and dietary data were compared in an attempt to describe features of the food webs concerned. δ13C and δ15N were determined for plants, invertebrates and fishes from the Bay of Calvi, Corsica. Dietary data were derived from the
literature. δ13C of plants ranged from –8.59‰ to –33.74‰, of benthic invertebrates from –17.0‰ to –20.52‰, of planktonic invertebrates from
–20.08‰ to –22.34‰ and of fishes from –16.27‰ to –19.59‰. δ15N was generally greater at higher trophic levels. δ15N of plants was 0.95–2.92‰, of benthic invertebrates 1.69–6.54‰, of planktonic invertebrates 3.51–6.82‰ and of fishes 4.63–9.77‰.
13C enrichment tended to be associated with benthic food chains and 13C depletion with planktonic chains. Stable-isotope data suggested more varied diets for many species than implied by gut-contents
data. Omnivory and trophic plasticity were widespread, and many consumers fed lower down the food chain than previous studies
had suggested. Both stable-isotope and gut-contents analysis resolved differences between fishes feeding on planktonic and
benthic prey and indicated that the herbivorous fish Sarpa salpa fed on a diet substantially different from that of other fishes. Zooplankton were important in the diets of several consumers
(both primary and secondary), as was plankton derived detritus. One species of fish previously identified as planktivorous
was shown to feed largely on benthic organisms, whilst several species of benthic invertebrates may feed on plankton-derived
detritus. Although herbivores seemed to obtain most of their C from macroalgae, δ15N data suggested that many of these animals supplemented their intake of N, although gut-contents analysis did not provide
evidence for such uptake. The isotopic data have elucidated several features of the food web which we would not otherwise
have detected.
Received: 26 April 1999 / Accepted: 24 September 1999 相似文献
14.
Origin and cycling of riverine inorganic carbon in the Sava River watershed (Slovenia) inferred from major solutes and stable carbon isotopes 总被引:1,自引:0,他引:1
The Sava River and its tributaries in Slovenia represent waters strongly influenced by chemical weathering of limestone and
dolomite. The carbon isotopic compositions of dissolved inorganic carbon (DIC) and suspended organic carbon (POC) fractions
as well as major solute concentrations yielded insights into the origin and fluxes of carbon in the upper Sava River system.
The major solute composition was dominated by carbonic acid dissolution of calcite and dolomite. Waters were generally supersaturated
with respect to calcite, and dissolved CO2 was about fivefold supersaturated relative to the atmosphere. The δ13C of DIC ranged from −13.5 to −3.3‰. Mass balances for riverine inorganic carbon suggest that carbonate dissolution contributes
up to 26%, degradation of organic matter ∼17% and exchange with atmospheric CO2 up to 5%. The concentration and stable isotope diffusion models indicated that atmospheric exchange of CO2 predominates in streams draining impermeable shales and clays while in the carbonate-dominated watersheds dissolution of
the Mesozoic carbonates predominates. 相似文献
15.
Stable isotopic structure of aquatic ecosystems 总被引:1,自引:0,他引:1
Isotopic, biogeochemical and ecological structure can provide a new dimension for understanding material flows, and the simultaneous
function and structure of an ecosystem. Distributions ofδ
13C andδ
15N for biogenic substances in the Nanakita river estuary involving Gamo lagoon in Japan were investigated to construct isotope
biogeochemical and ecological structure for assessing fate and transfer of organic matter, and food web structure. The isotopic
framework of the ecosystem was successfully described in aδ
15N–δ
13C map. In this estuary the variations of isotope ratios of biogenic substances were clearly explained by the mixing of land-derived
organic matter, and marine-derived organic matter.
A trophic-level effect of15N enrichment was clearly observed. Organisms were classified into three groups depending upon the contribution of land-derived
organic matter in a food chain. Almost all biota except mollusca in the lagoon depend on organic matter of marine origin.
The contributions of both land and marine organic matter were comparable for mollusca in the lagoon. 相似文献
16.
Tracing biogeochemical subsidies from glacier runoff into Alaska's coastal marine food webs 总被引:1,自引:0,他引:1 下载免费PDF全文
Mayumi L. Arimitsu Keith A. Hobson D'Arcy N. Webber John F. Piatt Eran W. Hood Jason B. Fellman 《Global Change Biology》2018,24(1):387-398
Nearly half of the freshwater discharge into the Gulf of Alaska originates from landscapes draining glacier runoff, but the influence of the influx of riverine organic matter on the trophodynamics of coastal marine food webs is not well understood. We quantified the ecological impact of riverine organic matter subsidies to glacier‐marine habitats by developing a multi‐trophic level Bayesian three‐isotope mixing model. We utilized large gradients in stable (δ13C, δ15N, δ2H) and radiogenic (Δ14C) isotopes that trace riverine and marine organic matter sources as they are passed from lower to higher trophic levels in glacial‐marine habitats. We also compared isotope ratios between glacial‐marine and more oceanic habitats. Based on isotopic measurements of potential baseline sources, ambient water and tissues of marine consumers, estimates of the riverine organic matter source contribution to upper trophic‐level species including fish and seabirds ranged from 12% to 44%. Variability in resource use among similar taxa corresponded to variation in species distribution and life histories. For example, riverine organic matter assimilation by the glacier‐nesting seabirds Kittlitz's murrelet (Brachyramphus brevirostris) was greater than that of the forest‐nesting marbled murrelet (B. marmoratus). The particulate and dissolved organic carbon in glacial runoff and near surface coastal waters was aged (12100–1500 years BP 14C‐age) but dissolved inorganic carbon and biota in coastal waters were young (530 years BP 14C‐age to modern). Thus terrestrial‐derived subsidies in marine food webs were primarily composed of young organic matter sources released from glacier ecosystems and their surrounding watersheds. Stable isotope compositions also revealed a divergence in food web structure between glacial‐marine and oceanic sites. This work demonstrates linkages between terrestrial and marine ecosystems, and facilitates a greater understanding of how climate‐driven changes in freshwater runoff have the potential to alter food web dynamics within coastal marine ecosystems in Alaska. 相似文献
17.
The Effect of Forest Type on Benthic Macroinvertebrate Structure and Ecological Function in a Pine Plantation in the North Carolina Piedmont 总被引:1,自引:1,他引:0
We examined the impact of small-scale commercial forestry on the structure and function of 6 headwater streams in the North
Carolina Piedmont. During 2001–2003 terrestrial organic matter inputs, temperature, macroinvertebrate community composition
and tolerance, leaf breakdown rate, and food web structure were quantified for 2 streams draining mature stands of managed
loblolly pine, 2 streams draining mature hardwood forests, and 2 streams draining 3-year-old clear cuts, which had been replanted
with loblolly pine. Streams in the clear-cuts and pine plantations were bordered by a 15 m hardwood buffer. Despite differences
in watershed land-use, there were no significant differences in the organic matter supply or temperature between streams draining
different forest types. However, algal biomass was significantly higher in clear-cut sites than forested sites, and was also
higher in hardwood sites than pine sites. Streams draining the clear-cut sites contained lower macroinvertebrate richness
and diversity, and fewer intolerant species, than streams draining pine and hardwood stands. Despite the differences in macroinvertebrates
community composition, there was no difference among forest types in leaf-pack breakdown rates. Analysis of δ15N and δ13C natural abundance of functional feeding group indicated that the shredders and predators collected from streams draining
clear-cuts had a δ15N value that was enriched relative to the macroinvertebrates of streams draining pine and hardwood forests. This difference
in δ15N signature appears to be the result of the incorporation of riparian grass species in the clear-cuts, which have a higher
δ15N, into the diet of shredders. Pine sites had similar food webs to natural hardwood sites. Our results suggest that clear-cutting
changes both the trophic dynamics and macroinvertebrate composition of low-order Piedmont streams in North Carolina despite
the presence of hardwood buffers. However, large differences were not found between older pine and hardwood stands, indicating
rapid recovery following re-growth of forest vegetation, when hardwood buffer strips were present. 相似文献
18.
Particulate organic matter transported from rivers to estuaries (POMR) varies quantitatively and qualitatively across estuaries; however, a lack of comparative studies poses a challenge in general
understanding of responses of estuarine food webs to POMR input. We studied 20 estuarine tidal flats of the Pacific Northwest coast of North America, with watershed areas ranging
from 7 to 8000 km2. We used carbon-stable isotope (δ13C) to test the hypothesis that the nutritional contribution of POMR to macrobenthos is proportional to relative abundances of POMR in tidal flat sediments. The predominant origin of total POM (TPOM) in tidal flat sediments generally shifted from marine-origin
POM (POMM) to POMR as watershed area increased; however, terrestrial-origin POMR with high C/N predominated sediment TPOM even in estuaries with small watershed areas. Some macrobenthos species assimilated
POM sources in proportion to sediment TPOM composition, and incorporated POMR in POMR-predominant sediments. These species were considered to have low food selectivity; however, the relative nutritional contribution
of POMR to these macrobenthos was still lower than the fraction of POMR in sediment TPOM. Other species disproportionately utilized POMM and/or benthic microalgae regardless of the relative abundance of POMR, indicating their high food selectivity. The species-specific, low- or high-food selectivity was likely linked with deposit-feeding
and filter-feeding, respectively. Hence, our hypothesis was supported conditionally. Our findings indicate that watershed
area, relative abundance of POMR in an estuary, and food selectivity of estuarine species are key factors controlling the tightness of linkage between watersheds
and estuarine food webs. 相似文献
19.
20.
Decreased trophic position as a function of increasing body size of a benthic omnivorous fish from the largest freshwater lake in China 总被引:1,自引:0,他引:1
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, δ15N 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, δ13C 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