共查询到20条相似文献,搜索用时 31 毫秒
1.
Most nutrient enrichment studies in aquatic systems have focused on autotrophic food webs in systems where primary producers
dominate the resource base. We tested the heterotrophic response to long-term nutrient enrichment in a forested, headwater
stream. Our study design consisted of 2 years of pretreatment data in a reference and treatment stream and 2 years of continuous
nitrogen (N) + phosphorus addition to the treatment stream. Studies were conducted with two leaf species that differed in
initial C:N, Rhododendron maximum (rhododendron) and Acer rubrum (red maple). We determined the effects of nutrient addition on detrital resources (leaf breakdown rates, litter C:N and microbial
activity) and tested whether nutrient enrichment affected macroinvertebrate consumers via increased biomass. Leaf breakdown
rates were ca. 1.5 and 3× faster during the first and second years of enrichment, respectively, in the treatment stream for
both leaf types. Microbial respiration rates of both leaf types were 3× higher with enrichment, and macroinvertebrate biomass
associated with leaves increased ca. 2–3× with enrichment. The mass of N in macroinvertebrate biomass relative to leaves tended
to increase with enrichment up to 6× for red maple and up to 44× for rhododendron leaves. Lower quality (higher C:N) rhododendron
leaves exhibited greater changes in leaf nutrient content and macroinvertebrate response to nutrient enrichment than red maple
leaves, suggesting a unique response by different leaf species to nutrient enrichment. Nutrient concentrations used in this
study were moderate and equivalent to those in streams draining watersheds with altered land use. Thus, our results suggest
that similarly moderate levels of enrichment may affect detrital resource quality and subsequently lead to altered energy
and nutrient flow in detrital food webs.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
2.
Springs are important freshwater habitats that provide refuge for many rare species. In this study, the fauna and abiotic
parameters of 20 perennial springs in north-western Switzerland were investigated. Correlation of abiotic and macrozoobenthos
data showed that physicochemical parameters had little impact on macrozoobenthic composition, whereas specific substrate parameters
strongly influenced the composition of the macrofauna. Surprisingly, nonmetric multidimensional scaling did not reveal a grouping
of springs with similar substrate composition or macrozoobenthic assemblages. However, discharge was identified as the factor
significantly determining substrate and the composition of macroinvertebrate assemblages. This justifies the hypothesis that,
variation in discharge is the disturbance factor governing the macrofaunal composition temporally and spatially within and
between patches.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. 相似文献
3.
Species invasions are of global significance, but predicting their impacts can be difficult. Introduced ecosystem engineers,
however, provide an opportunity to test the underlying mechanisms that may be common to all invasive engineers and link relationships
between changes in diversity and ecosystem function, thereby providing explanatory power for observed ecological patterns.
Here we test specific predictions for an invasive ecosystem engineer by quantifying the impacts of habitat and resource modifications
caused by North American beavers (Castor canadensis) on aquatic macroinvertebrate community structure and stream ecosystem function in the Cape Horn Biosphere Reserve, Chile.
We compared responses to beavers in three habitat types: (1) forested (unimpacted) stream reaches, (2) beaver ponds, and (3)
sites immediately downstream of beaver dams in four streams. We found that beaver engineering in ponds created taxonomically
simplified, but more productive, benthic macroinvertebrate assemblages. Specifically, macroinvertebrate richness, diversity
and number of functional feeding groups were reduced by half, while abundance, biomass and secondary production increased
three- to fivefold in beaver ponds compared to forested sites. Reaches downstream of beaver ponds were very similar to natural
forested sections. Beaver invasion effects on both community and ecosystem parameters occurred predominantly via increased
retention of fine particulate organic matter, which was associated with reduced macroinvertebrate richness and diversity (via
homogenization of benthic microhabitat) and increased macroinvertebrate biomass and production (via greater food availability).
Beaver modifications to macroinvertebrate community structure were largely confined to ponds, but increased benthic production
in beaver-modified habitats adds to energy retention and flow for the entire stream ecosystem. Furthermore, the effects of
beavers on taxa richness (negative) and measures of macroinvertebrate biomass (positive) were inversely related. Thus, while
a generally positive relationship between diversity and ecosystem function has been found in a variety of systems, this work
shows how they can be decoupled by responding to alterative mechanisms.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
4.
Food web of macroinvertebrate community in a Yangtze shallow lake: trophic basis and pathways 总被引:1,自引:0,他引:1
No detailed food web research on macroinvertebrate community of lacustrine ecosystem was reported in China. The present study
is the first attempt on the subject in Lake Biandantang, a macrophytic lake in Hubei Province. Food webs of the macroinvertebrate
community were compiled bimonthly from March, 2002 to March, 2003. Dietary information was obtained from gut analysis. Linkage
strength was quantified by combining estimates of energy flow (secondary production) with data of gut analysis. The macroinvertebrate
community of Lake Biandantang was based heavily on detritus. Quantitative food webs showed the total ingestion ranged from
6930 to 36,340 mg dry mass m−2 bimonthly. The ingestion of macroinvertebrate community was higher in the months with optimum temperature than that in other
periods with higher or lower temperature. Through comparison, many patterns in benthic food web of Lake Biandantang are consistent
with other detritus-based webs, such as stream webs, but different greatly from those based on autochthonous primary production
(e.g. pelagic systems). It suggests that the trophic basis of the web is essential in shaping food web structure.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. 相似文献
5.
The macroinvertebrate fauna of five karst (limestone) springbrook systems with contrasting physical habitat and discharge patterns were investigated to examine the role of flow permanence and habitat structure on macroinvertebrate community composition. Clear physical differences were identified between perennial and intermittent springs and individual sampling stations. However, flow permanence, water temperature and the input of leaf litter exerted a greater influence on the aquatic invertebrate community than habitat structure. Perennial sites were characterised by a greater abundance of macroinvertebrates and greater Ephemeroptera, Plecoptera and Trichoptera (EPT) richness than intermittent sites. The fauna of all of the springbrook systems examined were dominated by relatively common and ubiquitous taxa (e.g. Gammarus pulex) although a number of taxa displaying life cycle adaptations to ephemeral aquatic habitats (e.g. Limnephilus auricula and Stenophylax permistus) were recorded at intermittent sites. 相似文献
6.
Mark P. Gustafson 《Hydrobiologia》2008,605(1):235-246
The variation in thermal regime and elevation among streams in the Sawtooth Mountains of Idaho, USA was used to test hypotheses
about forces structuring larval mayfly assemblages. Sites above and below lakes were included to maximize variation in thermal
regime. Forty-five sites were sampled for mayfly larvae and their summer thermal regime was measured. Ordination methods were
used to analyze variation in the mayfly assemblages. Principal components analysis showed that mayfly assemblages were strongly
and consistently affected by lakes within the stream system, apparently through the effects of lakes on stream temperature.
Redundancy analysis explained 51% of the variation in assemblages and identified maximum water temperature and elevation as
strong predictors of mayfly assemblages. Elevation influenced assemblage structure independently of summer maximum water temperature,
suggesting that air temperature or some other elevation-dependent feature is also important. As predicted by the River Continuum
Concept, mayfly diversity increased with increasing maximum daily range in temperature.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Handling editor: R. Bailey 相似文献
7.
Tree leaf litter inputs to freshwater systems are a major resource and primary drivers of ecosystem processes and structure. Spatial variation in tree species distributions and forest composition control litter inputs across landscapes, but inputs to individual lentic habitat patches are determined by adjacent plant communities. In small, ephemeral, fishless ponds, resource quality and abundance can be the most important factor affecting habitat selection preferences of colonizing animals. We used a landscape of experimental mesocosms to assess how natural populations of aquatic beetles respond over time to variation in tree leaf litter composition (pine or hardwood). Patches with faster-decomposing hardwood leaf litter were initially colonized at higher rates than slower-decomposing pine pools by most species of Hydrophilidae, but this pattern reversed later in the experiment with higher colonization of pine pools by hydrophilids. Colonization did not differ between pine and hardwood for dytiscids and the small hydrophilid Paracymus, but there were distinct beetle assemblages between pine and hardwood patches both early and late in the experiment. Our data support the importance of patch quality and habitat selection as determinants of species abundances, richness, and community structure in freshwater aquatic systems, not only when new habitat patches are formed and initial conditions set, but as patches change due to interactions of processes such as decomposition with time. 相似文献
8.
At the time of this study Fossil Creek was being considered as a site for the restoration of a native fish assemblage, however
there was concern amongst fisheries managers about the stream being food limited due to calcium carbonate (travertine) deposition.
To evaluate the effects of travertine deposition on the aquatic food base we used leaf litterbags to compare decomposition
rates and nutrient diffusing artificial substrates to compare algal accrual rates and nutrient limitation between two distinct
reaches in Fossil creek: a travertine dam forming reach and a reach without travertine dam formation (riffle-pool reach).
Decomposition was significantly faster in the travertine dam forming reach than in the riffle-pool reach. Macroinvertebrates
in the leaf packs were more diverse in the travertine reach but more abundant in the riffle-pool reach. Algae accrued more
quickly in the travertine reach than in the riffle-pool reach and only responded to nutrient enrichment in the travertine
reach. This study was conducted prior to a hydroelectric dam decommissioning project in Fossil Creek where full flows were
reintroduced back into the stream after a century of diversion. Our results suggest concurrent increases in algal productivity,
decomposition, and macroinvertebrate diversity in the next decade as travertine dams rebuild, providing a richer food base
for fish and other aquatic organisms.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users.
Handling editor: K. Martens 相似文献
9.
Microbial succession during leaf breakdown was investigated in a small forested stream in west-central Georgia, USA, using multiple culture-independent techniques. Red maple (Acer rubrum) and water oak (Quercus nigra) leaf litter were incubated in situ for 128 days, and litter breakdown was quantified by ash-free dry mass (AFDM) method and microbial assemblage composition using phospholipid fatty acid analysis (PLFA), ribosomal intergenic spacer analysis (RISA), denaturing gradient gel electrophoresis (DGGE), and bar-coded next-generation sequencing of 16S rRNA gene amplicons. Leaf breakdown was faster for red maple than water oak. PLFA revealed a significant time effect on microbial lipid profiles for both leaf species. Microbial assemblages on maple contained a higher relative abundance of bacterial lipids than oak, and oak microbial assemblages contained higher relative abundance of fungal lipids than maple. RISA showed that incubation time was more important in structuring bacterial assemblages than leaf physicochemistry. DGGE profiles revealed high variability in bacterial assemblages over time, and sequencing of DGGE-resolved amplicons indicated several taxa present on degrading litter. Next-generation sequencing revealed temporal shifts in dominant taxa within the phylum Proteobacteria, whereas γ-Proteobacteria dominated pre-immersion and α- and β-Proteobacteria dominated after 1 month of instream incubation; the latter groups contain taxa that are predicted to be capable of using organic material to fuel further breakdown. Our results suggest that incubation time is more important than leaf species physicochemistry in influencing leaf litter microbial assemblage composition, and indicate the need for investigation into seasonal and temporal dynamics of leaf litter microbial assemblage succession. 相似文献
10.
Spatial and temporal distributions of epiphytic diatoms growing on Thalassia testudinum Banks ex König: relationships to water quality 总被引:1,自引:1,他引:0
The spatial and temporal distributions of the epiphytic diatom flora on Thalassia testudinum was described within the Florida Bay estuary and at one Atlantic site east of the Florida Keys over a 1-year period. Species
of the genus Mastogloia dominated the epiphytic diatom flora (82 out of 332 total species). Nonmetric Multidimensional Scaling (NMDS) and Analysis
of Similarity (ANOSIM) revealed four distinct spatial assemblages and two temporal assemblages. Eastern and western Florida
Bay assemblages were identified within the estuary. The eastern diatom assemblage was characterized by high relative abundances
of Brachysira aponina and Nitzschia liebetruthii, while the western assemblage was characterized by the abundance of Reimerothrix floridensis, particularly during summer. Two diverse and distinct marine assemblages, one located in the Gulf of Mexico along the western
edge of Florida Bay and the other behind the Florida reef tract in the Atlantic Ocean, were also identified. Analysis of the
spatial distribution of diatoms and water quality characteristics within Florida Bay suggest that these assemblages may be
structured by salinity and nutrient availability, particularly P. The Gulf of Mexico and the western Florida Bay assemblages
were associated with higher water column salinities and TP concentrations and lower DIN concentrations and TN:TP ratios relative
to the eastern Florida Bay assemblage. The temporal variation in diatom assemblages was associated with water temperature,
though temporal indicator species were few relative to the number of spatial indicators.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. 相似文献
11.
Short-term responses of decomposers to flow restoration in Fossil Creek,Arizona, USA 总被引:1,自引:1,他引:0
Jeffrey D. Muehlbauer Carri J. LeRoy Jacqueline M. Lovett Kathleen K. Flaccus Julie K. Vlieg Jane C. Marks 《Hydrobiologia》2009,618(1):35-45
Dam decommissioning projects, although numerous, rarely include complete sets of data before and after restoration for evaluating
the ecological consequences of such projects. In this study, we used a before-after control-impact (BACI) design to assess
changes in leaf litter decomposition and associated macroinvertebrate and fungal decomposers following dam decommissioning
in Fossil Creek, Arizona, USA. Leaf litterbags were deployed in a relatively pristine site above the dam and a highly disturbed
site below the dam where over 95% of the flow was previously diverted for hydropower generation. Leaf litter decomposition
was significantly slower below the dam both measurement years (pre- and post-restoration) with no site-year interaction, indicating
that decomposition in this stream section was not affected by increased flow. In contrast, both macroinvertebrates and fungi
differed significantly above and below the dam prior to restoration but were similar post-restoration, supporting the concept
that decomposer communities can quickly rebound following reintroduction of full flow. Our results indicate that some aquatic
ecosystem variables can return to a more natural state following ecological restoration activities such as water flow restoration.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Handling editor: S. Stendera 相似文献
12.
Across-reach consistency in macroinvertebrate distributions among litter patch types in Japanese headwater streams 总被引:2,自引:0,他引:2
Different types of litter patches with contrasting macroinvertebrate assemblages have been observed within a stream reach. This study examined whether distributions of macroinvertebrates among three litter patch types (riffle, middle, edge) were consistent between reaches with different channel characteristics in headwater streams in central Japan. Mass of leaves per unit area was significantly higher in riffle and edge patches than in middle patches, which was consistent between reaches, while no consistent pattern was evident between reaches for mass of either woody material or small litter fragments. Distribution among the patch types was consistent between reaches for 11 out of 13 dominant macroinvertebrate taxa; density was highest in riffle patches for 5 taxa and in middle patches for 5 taxa. Although we previously related densities of some taxa to mass of woody material or small litter fragments, hydraulic characteristics (water depth, current velocity), which were consistent between reaches, may be more important determinants of macroinvertebrate distributions among the patch types, even within pools (i.e. middle and edge patches) where current is uniformly low. The results of this study indicate that a reach-scale macroinvertebrate community structure associated with litter is likely to vary according to litter patch type composition, which would be affected by channel characteristics of the reaches. 相似文献
13.
Jeffrey H. Braatne S. Maeika P. Sullivan Erin Chamberlain 《International Review of Hydrobiology》2007,92(6):656-665
Japanese knotweed (Fallopia japonica Houtt. Ronse Decrane ) is a highly invasive exotic plant that forms monocultures in riparian areas, effectively reducing plant diversity. This change in riparian plant composition alters the allocthonous input of leaf litter into adjacent streams. A field experiment was completed to understand how leaf decomposition and macroinvertebrate colonisation associated with the incorporation of exotic leaf litter. Leaf packs of Japanese knotweed, native alder (Alnus incana L.), native cottonwood (Populus trichocarpa Torr . and Gray ), and two additional mixed pack types (alder and cottonwood; alder, cottonwood, and Japanese knotweed) were placed into a 50 m stream reach in Clear Creek, Idaho, and removed over a three‐month period. Leaf decomposition and macroinvertebrate assemblages were similar between leaf types, despite differences in nitrogen and phosphorus content. The diversity of leaf types within a given leaf pack also had no effect on leaf decomposition or macroinvertebrate dynamics. These findings suggest that allochthonous inputs of Japanese knotweed fulfill a detrital function similar to that of native leaf litter. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
14.
Macroinvertebrate assemblages were related to environmental factors that were quantified at the sample scale in streams subjected
to a gradient of cattle grazing. Environmental factors and macroinvertebrates were concurrently collected so assemblage structure
could be directly related to environmental factors and the relative importance of stressors associated with cattle grazing
in structuring assemblages could be assessed. Based on multivariate and inferential statistics, measures of physical habitat
(% fines and substrate homogeneity) had the strongest relationships with macroinvertebrate assemblage structure. Detrital
food variables (coarse benthic and fine benthic organic matter) were also associated with assemblage structure, but the relationships
were never as strong as those with physical habitat measures, while autochthonous food variables (chlorophyll a and epilithic biomass) appeared to have no association with assemblage structure. The amount of variation explained in taxa
composition and macroinvertebrate metrics is within values reported from studies that have examined macroinvertebrate metric–sediment
relationships. The % Coleoptera and % crawlers had consistent relationships with % fines during this study, which suggests
they may be useful metrics when sediment is a suspected stressor to macroinvertebrate assemblages in Blue Ridge streams. Findings
from this study also demonstrate the importance of quantitative sampling through time when research goals are to identify
relationships between macroinvertebrates and environmental factors. 相似文献
15.
16.
C. Dang X. de Montaudouin J. Bald F. Jude N. Raymond L. Lanceleur I. Paul-Pont N. Caill-Milly 《Hydrobiologia》2009,630(1):139-148
Knowledge of temporal variation in nearshore Laurentian Great Lakes fish assemblages is important for understanding species–habitat
associations, how abiotic and biotic influences vary temporally, and when sampling should occur. Using spring and fall seining
data from Lake Erie beaches, we compared day and night fish assemblages and tested for differences among sampling periods.
Beaches were utilized by a diverse collection of Lake Erie basin fishes (one-third of known species). During all sampling
periods, catches were dominated by cyprinid species (53–91%), and by invertivores and planktivorous fishes. Diel differences
were detected in abundance, species richness and assemblage structure. Multivariate analyses (canonical analysis of principal
coordinates) indicated that season had a larger influence on fish assemblage structure than diel period. Given observed temporal
variation in assemblage structure, studies of Laurentian Great Lakes beach fishes should be restricted to a single time period
(e.g. day-time spring sampling), or adopt sampling designs that permit diel period and season to be included as factors in
analyses. Second, the large seasonal variation in assemblage composition combined with higher night species richness indicates
that night sampling during both spring and fall would be the most efficient and comprehensive approach for beach fish inventory.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Handling editor: J. Trexler 相似文献
17.
The benthic macroinvertebrate community is an important component of stream diversity, because its members are fundamental
connectors among the different trophic levels of running waters. In this study, we assessed alpha and beta diversities of
benthic macroinvertebrates in three stream sites and four microhabitats: (i) moss in the air-water interface; (ii) submerged
roots of terrestrial plants; (iii) leaf litter deposited in pools; (iv) stones in riffles. We constructed rarefaction curves
and compared species richness among microhabitats for each stream site. Additionally, we evaluated which factor, stream site,
or microhabitat, was most important in determining variation in assemblage structure, i.e., beta diversity. There was no significant
difference among microhabitats in terms of taxa richness evaluated by rarefaction curves. Using partial Constrained Correspondence
Analysis (pCCA), we found that microhabitat was most important in determining community composition, accounting for 42.02%
of the total variation. Stream sites accounted for 22.27%. In accordance with the pCCA, exploratory multivariate methods (ordination
and classification) revealed four distinct groups, corresponding to the four microhabitats, independent of stream sites. Our
results indicated that differences among environmental conditions are much more important in the determination of stream assemblage
structure than are differences in spatial location. Accordingly, adjacent microhabitats in a single stream site harbor macroinvertebrate
assemblages more dissimilar than those found in a single microhabitat at different stream sites.
Handling editor: D. Dudgeon 相似文献
18.
19.
We investigated the linkages between leaf litter quality and decomposability in a savanna plant community dominated by palatable-spinescent
tree species. We measured: (1) leaf litter decomposability across five woody species that differ in leaf chemistry; (2) mass
decomposition, nitrogen (N); and carbon (C) dynamics in leaf litter of a staple browse species (Acacia nigrescens) as well as (3) variation in litter composition across six sites that experienced very different histories of attack from
large herbivores. All decomposition trials included litter bags filled with chopped straw to control for variation in site
effects. We found a positive relationship between litter quality and decomposability, but we also found that Acacia and straw litter mass remaining did not significantly vary between heavily and lightly browsed sites. This is despite the
fact that both the quality and composition of litter returned to the soil were significantly different across sites. We observed
greater N resorption from senescing Acacia leaves at heavily browsed sites, which in turn contributed to increase the C:N ratio of leaf litter and caused greater litter
N immobilization over time. This, together with the significantly lower tree- and herb-leaf litter mass beneath heavily browsed
trees, should negatively affect decomposition rates. However, estimated dung and urine N deposition from both browsers and
grazers was significantly greater at high- than at low-herbivory sites. We hypothesize that N inputs from dung and urine boost
litter N mineralization and decomposition (especially following seasonal rainfall events), and thereby offset the effects
of poor leaf litter quality at chronically browsed sites.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
20.
1. Decomposition of litter mixtures in both terrestrial and aquatic ecosystems often shows non‐additive diversity effects on decomposition rate, generally interpreted in streams as a result of the feeding activity of macroinvertebrates. The extent to which fungal assemblages on mixed litter may influence consumption by macroinvertebrates remains unknown. 2. We assessed the effect of litter mixing on all possible three‐species combinations drawn from four tree species (Alnus glutinosa, Betula pendula, Juglans regia and Quercus robur) on both fungal assemblages and the rate of litter consumption by a common shredder, Gammarus fossarum. After a 9‐week inoculation in a stream, batches of leaf discs were taken from all leaf species within litter mixture combinations. Ergosterol, an indicator of fungal biomass, and the composition of fungal assemblages, assessed from the conidia released, were determined, and incubated litter offered to G. fossarum in a laboratory‐feeding experiment. 3. Mixing leaf litter species enhanced both the Simpson’s index of the fungal assemblage and the consumption of litter by G. fossarum, but had no clear effect on mycelial biomass. Specifically, consumption rates of J. regia were consistently higher for mixed‐species litter packs than for single‐species litter. In contrast, the consumption rates of B. pendula were not affected by litter mixing, because of the occurrence of both positive and negative litter‐mixing effects in different litter species combinations that counteracted each other. 4. In some litter combinations, the greater development of some fungal species (e.g. Clavariopsis aquatica) as shown by higher sporulation rates coincided with increased leaf consumption, which may have resulted from feeding preferences by G. fossarum for these fungi. 5. Where litter mixture effects on decomposition rate are mediated via shredder feeding, this could be due to indirect effects of the fungal assemblage. 相似文献