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Eric Chauvet - One of the best experts on this subject based on the ideXlab platform.
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aquatic hyphomycetes and litter decomposition in tropical subtropical low order streams
Fungal Ecology, 2016Co-Authors: Manuel A S Graca, Eric ChauvetAbstract:Leaf litter decomposition is an important ecosystem function carried out by a diverse array of consumers, including aquatic hyphomycetes. Aquatic hyphomycetes are found in streams worldwide, but their diversity and abundance varies across systems. In general, species diversity is lower across tropical and subtropical systems when compared with temperate biomes. The low diversity in tropical and subtropical areas may be related to: (a) lower seasonality; (b) our inability to detect fungi by traditional techniques; (c) low turbulence of rivers where many studies were carried out; (d) low nutrient content in many studied tropical systems; (e) leaves highly defended against consumers; and (1) competition from other decomposers. In terms of function, fungal biomass, sporulation rates and litter decomposition by aquatic hyphomycetes in the tropics was reported to be equivalent to or much lower than observed in temperate zones. The feeding ecology of Shredder invertebrates is strongly related to the presence of microbial decomposers in the environment. The lack of Shredders reported for some tropical rivers may be related to a low microbial biomass, well defended tropical leaves and frequent hydrological events which remove leaves before they can be used by Shredders. Seasonal variations in rain fall in tropical and subtropical systems are likely to affect litter fall, the identity and quality of litter, the reproduction of aquatic hyphomycetes (due to turbulence effects) and therefore the community composition of aquatic hyphomycetes throughout the year. Future research on aquatic hyphomycetes and litter decomposition in the tropics and sub-tropics should address the diversity/identity gap, altitudinal gradient changes and the contribution of aquatic hyphomycetes to the trophic ecology of Shredders. (C) 2015 Elsevier Ltd and The British Mycological Society. All rights reserved.
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Relative influence of Shredders and fungi on leaf litter decomposition along a river altitudinal gradient
Hydrobiologia, 2014Co-Authors: Barry R. Taylor, Eric ChauvetAbstract:We compared autumn decomposition rates of European alder leaves at four sites along the Lasset–Hers River system, southern France, to test whether changes in litter decomposition rates from upstream (1,300 m elevation) to downstream (690 m) could be attributed to temperature-driven differences in microbial growth, Shredder activity, or composition of the Shredder community. Alder leaves lost 75–87% of original mass in 57 days, of which 46–67% could be attributed to microbial metabolism and 8–29% to Shredder activity, with no trend along the river. Mass loss rates in both fine-mesh (excluding Shredders) and coarse-mesh (including Shredders) bags were faster at warm, downstream sites (mean daily temperature 7–8°C) than upstream (mean 1–2°C), but the differ- ence disappeared when rates were expressed in heat units to remove the temperature effect. Mycelial biomass did not correlate with mass loss rates. Faster mass loss rates upstream, after temperature correction, evidently arise from more efficient shredding by Nemourid stoneflies than by the Leuctra-dominated assemblage downstream. The influence of water temperature on decomposition rate is therefore expressed both directly, through microbial metabolism, and indirectly, through the structure of Shredder commu- nities. These influences are evident even in cold water where temperature variation is small.
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early stages of leaf decomposition are mediated by aquatic fungi in the hyporheic zone of woodland streams
Freshwater Biology, 2010Co-Authors: Eric Chauvet, Pierre Marmonier, Julien Cornut, Arnaud Elger, Didier LambrigotAbstract:SUMMARY 1. Leaf litter constitutes the major source of organic matter and energy in woodland stream ecosystems. A substantial part of leaf litter entering running waters may be buried in the streambed as a consequence of flooding and sediment movement. While decomposition of leaf litter in surface waters is relatively well understood, its fate when incorporated into river sediments, as well as the involvement of invertebrate and fungal decomposers in such conditions, remain poorly documented. 2. We tested experimentally the hypotheses that the small interstices of the sediment restrict the access of the largest Shredders to buried organic matter without compromising that of aquatic hyphomycetes and that fungal decomposers in the hyporheic zone, at least partly, compensate for the role of invertebrate detritivores in the benthic zone. 3. Alder leaves were introduced in a stream either buried in the sediment (hyporheic), buried after 2 weeks of exposure at the sediment surface (benthic-hyporheic), or exposed at the sediment surface for the entire experiment (benthic). Leaf decomposition was markedly faster on the streambed surface than in the two other treatments (2.1- and 2.8-fold faster than in the benthic-hyporheic and hyporheic treatments, respectively). 4. Fungal assemblages were generally less diverse in the hyporheic habitat with a few species tending to be relatively favoured by such conditions. Both fungal biomass and sporulation rates were reduced in the hyporheic treatment, with the leaves subject to the benthic-hyporheic treatment exhibiting an intermediate pattern. The initial 2-week stage in the benthic habitat shaped the fungal assemblages, even for leaves later subjected to the hyporheic conditions. 5. The abundance and biomass of Shredders drastically decreased with burial, except for Leuctra spp., which increased and was by far the most common leaf-associated taxon in the hyporheic zone. Leuctra spp. was one of the rare Shredder taxa displaying morphological characteristics that increased performance within the limited space of sediment interstices. 6. The carbon budgets indicated that the relative contributions of the two main decomposers, Shredders and fungi, varied considerably depending on the location within the streambed. While the Shredder biomass represented almost 50% of the initial carbon transformed after 80 days in the benthic treatment, its contribution was <0.3% in the hyporheic one and 2.0% in the combined benthic-hyporheic treatment. In contrast,
Florian Altermatt - One of the best experts on this subject based on the ideXlab platform.
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species turnover and invasion of dominant freshwater invertebrates alter biodiversity ecosystem function relationship
Ecological Monographs, 2018Co-Authors: Chelsea J Little, Florian AltermattAbstract:Freshwater ecosystems rely on allochthonous resources. Integration of these subsidies depends on diversity of both terrestrial resources and aquatic Shredder and decomposer communities, but the diversity effects on leaf litter breakdown and decomposition are less clear in aquatic than terrestrial ecosystems. We need a better understanding of this relationship because aquatic communities are rapidly changing with species invasions and anthropogenic impacts. Here, we experimentally disentangled the effects of leaf and Shredder richness on leaf litter breakdown by macroinvertebrates in mesocosm experiments using three species of amphipods, a dominant guild of crustaceans in European freshwater ecosystems. Increased leaf richness led to lower-than-predicted leaf consumption by native Shredders, with mixed evidence of resource-switching or prioritization of preferred food items within a leaf mix. Higher Shredder species richness never promoted leaf consumption rates compared to predictions from relevant single-species experiments, and instead sometimes substantially decreased leaf consumption. We then conducted a meta-analysis of leaf litter consumption rates by seven widely distributed amphipod species (the three used in the experiments and four additional species). As expected based on our own experiments, nonnative amphipod species generally had lower biomass- adjusted leaf litter consumption rates, although their larger body size led to higher per-individual leaf consumption rates. Contamination of the water by metals, pesticides, and other chemicals additionally significantly decreased leaf litter consumption by multiple native and nonnative species compared to unpolluted systems. While the meta-analysis suggested that litter consumption, and thus breakdown, would decline if native Shredders are replaced by nonnative heterospecifics, complete species replacement is not the only outcome following immigration in a meta-community context. Our experiments suggest that breakdown rates could remain reasonably high where native species coexist with nonnative arrivals. Experiments that neglect the ecological realism of species coexistence will necessarily mischaracterize effects on ecosystem functioning.
Chelsea J Little - One of the best experts on this subject based on the ideXlab platform.
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species turnover and invasion of dominant freshwater invertebrates alter biodiversity ecosystem function relationship
Ecological Monographs, 2018Co-Authors: Chelsea J Little, Florian AltermattAbstract:Freshwater ecosystems rely on allochthonous resources. Integration of these subsidies depends on diversity of both terrestrial resources and aquatic Shredder and decomposer communities, but the diversity effects on leaf litter breakdown and decomposition are less clear in aquatic than terrestrial ecosystems. We need a better understanding of this relationship because aquatic communities are rapidly changing with species invasions and anthropogenic impacts. Here, we experimentally disentangled the effects of leaf and Shredder richness on leaf litter breakdown by macroinvertebrates in mesocosm experiments using three species of amphipods, a dominant guild of crustaceans in European freshwater ecosystems. Increased leaf richness led to lower-than-predicted leaf consumption by native Shredders, with mixed evidence of resource-switching or prioritization of preferred food items within a leaf mix. Higher Shredder species richness never promoted leaf consumption rates compared to predictions from relevant single-species experiments, and instead sometimes substantially decreased leaf consumption. We then conducted a meta-analysis of leaf litter consumption rates by seven widely distributed amphipod species (the three used in the experiments and four additional species). As expected based on our own experiments, nonnative amphipod species generally had lower biomass- adjusted leaf litter consumption rates, although their larger body size led to higher per-individual leaf consumption rates. Contamination of the water by metals, pesticides, and other chemicals additionally significantly decreased leaf litter consumption by multiple native and nonnative species compared to unpolluted systems. While the meta-analysis suggested that litter consumption, and thus breakdown, would decline if native Shredders are replaced by nonnative heterospecifics, complete species replacement is not the only outcome following immigration in a meta-community context. Our experiments suggest that breakdown rates could remain reasonably high where native species coexist with nonnative arrivals. Experiments that neglect the ecological realism of species coexistence will necessarily mischaracterize effects on ecosystem functioning.
Luz Boyero - One of the best experts on this subject based on the ideXlab platform.
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stream ecosystem integrity is impaired by logging and shifting agriculture in a global megadiversity center sarawak borneo
Science of The Total Environment, 2012Co-Authors: Tajang Jinggut, Catherine M Yule, Luz BoyeroAbstract:In common with most of Borneo, the Bakun region of Sarawak is currently subject to heavy deforestation mainly due to logging and, to a lesser extent, traditional slash-and-bum farming practices. This has the potential to affect stream ecosystems, which are integrators of environmental change in the surrounding terrestrial landscape. This study evaluated the effects of both types of deforestation by using functional and structural indicators (leaf litter decomposition rates and associated detritivores or 'Shredders', respectively) to compare a fundamental ecosystem process, leaf litter decomposition, within logged, farmed and pristine streams. Slash-and-bum agricultural practices increased the overall rate of decomposition despite a decrease in Shredder species richness (but not Shredder abundance) due to increased microbial decomposition. In contrast, decomposition by microbes and invertebrates was slowed down in the logged streams, where Shredders were less abundant and less species rich. This study suggests that Shredder communities are less affected by traditional agricultural farming practices, while modem mechanized deforestation has an adverse effect on both Shredder communities and leaf breakdown.
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effects of diversity loss on ecosystem function across trophic levels and ecosystems a test in a detritus based tropical food web
Austral Ecology, 2008Co-Authors: Mikis Bastian, Richard G Pearson, Luz BoyeroAbstract:We investigated the effects of biodiversity loss across trophic levels and across ecosystems (terrestrial to aquatic) on ecosystem function, in a detritus-based tropical food web. Diversities of consumers (stream Shredders) and resources (leaf litter) were experimentally manipulated by varying the number of species from 3 to 1, using different species combinations, and the effects on leaf breakdown rates were examined. In single-species Shredder treatments, leaf diversity loss affected breakdown rates, but the effect depended on the identity of the leaves remaining in the system: they increased when the most preferred leaf species remained, but decreased when this species was lost (leaf preferences were the same for all Shredders). In multi-species Shredder assemblages, breakdown rates were lower than expected from single-species treatments, suggesting an important role of interspecific competition. This pattern was also evident when oneleaf species was available but not with higher leaf diversity, suggesting that lowered leaf diversity promotes competitive interactions among Shredders. The influence of diversity and identity of species across trophic levels and ecosystems on stream functioning points to complex interactions that may well be reflected in other types of ecosystem.
Neusa Hamada - One of the best experts on this subject based on the ideXlab platform.
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effects of increasing temperature and co2 on quality of litter Shredders and microorganisms in amazonian aquatic systems
PLOS ONE, 2017Co-Authors: Renato Tavares Martins, Renan De Souza Rezende, Jose Francisco Goncalves, Aline Lopes, Maria Teresa Fernandez Piedade, Heloide De Lima Cavalcante, Neusa HamadaAbstract:Climate change may affect the chemical composition of riparian leaf litter and, aquatic organisms and, consequently, leaf breakdown. We evaluated the effects of different scenarios combining increased temperature and carbon dioxide (CO2) on leaf detritus of Hevea spruceana (Benth) Mull. and decomposers (insect Shredders and microorganisms). We hypothesized that simulated climate change (warming and elevated CO2) would: i) decrease leaf-litter quality, ii) decrease survival and leaf breakdown by Shredders, and iii) increase microbial leaf breakdown and fungal biomass. We performed the experiment in four microcosm chambers that simulated air temperature and CO2 changes in relation to a real-time control tracking current conditions in Manaus, Amazonas, Brazil. The experiment lasted seven days. During the experiment mean air temperature and CO2 concentration ranged from 26.96 ± 0.98oC and 537.86 ± 18.36 ppmv in the control to 31.75 ± 0.50oC and 1636.96 ± 17.99 ppmv in the extreme chamber, respectively. However, phosphorus concentration in the leaf litter decreased with warming and elevated CO2. Leaf quality (percentage of carbon, nitrogen, phosphorus, cellulose and lignin) was not influenced by soil flooding. Fungal biomass and microbial leaf breakdown were positively influenced by temperature and CO2 increase and reached their highest values in the intermediate condition. Both total and Shredder leaf breakdown, and Shredder survival rate were similar among all climatic conditions. Thus, low leaf-litter quality due to climate change and higher leaf breakdown under intermediate conditions may indicate an increase of riparian metabolism due to temperature and CO2 increase, highlighting the risk (e.g., decreased productivity) of global warming for tropical streams.
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Effects of climate change on leaf breakdown by microorganisms and the Shredder Phylloicus elektoros (Trichoptera: Calamoceratidae)
Hydrobiologia, 2017Co-Authors: Renato T. Martins, Adriano S. Melo, José F. Gonçalves, Claudimir M. Campos, Neusa HamadaAbstract:Climate change may affect species diversity and, consequently, ecological processes such as leaf decomposition. We evaluated the effects of increased temperature and carbon dioxide (CO_2) on fungal biomass, leaf breakdown, and on survival and growth of the Shredder Phylloicus elektoros . We hypothesized that climatic changes would result in lower survival and growth of Shredders and lower leaf consumption by these organisms. On the other hand, we predicted an increase in fungal biomass in response to climatic changes. We conducted an experiment in Manaus, Brazil, using four microcosms that simulate real-time air temperature and CO_2 (control chamber), as well as three other chambers subjected to fixed increases in temperature and CO_2 as compared to the control chamber. The “extreme” condition represented an increase of ~4.5°C in temperature and ~870 ppm in CO_2 in relation to the control chamber. Total and Shredder leaf-breakdown rates, fungal biomass, and Shredder survival rates were significantly lower in warmer and CO_2 concentrated atmospheres. Shredder growth rate and leaf breakdown by microorganisms were similar among all climatic conditions. With climatic changes, we found an increase in the relative importance of microorganisms on leaf-breakdown rates as compared to Shredders. Thus, lower leaf breakdown and a change in the main decomposer due to future climatic conditions may result in major changes in the pathways of organic matter processing and, consequently, in aquatic food webs.
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responses of aquatic invertebrate assemblages and leaf breakdown to macroconsumer exclusion in amazonian terra firme streams
Fundamental and Applied Limnology, 2008Co-Authors: Victor Lemes Landeiro, Neusa Hamada, Adriano S. MeloAbstract:Many authors have reported a lack of insect Shredders in tropical streams and some have suggested that macroconsumers, such as fish and shrimp, are potential substitutes for insect Shredders. We experimentally excluded macroconsumers (fish and shrimp) from leaf packs to examine their role in determining the rate of leaf breakdown and their effects on the associated invertebrate community. The experiment was designed in blocks and replicated in two reaches of four streams. Temperature of all stream reaches studied was 24 °C (without variation), and water conductivity was low, varying from 8.8 to 10.8 μs/cm. Fish were never observed near the leaf packs and therefore the effects of the macroconsumer treatment were attributed to shrimps. We found a significant effect on leaf breakdown, with greater leaf breakdown (i.e., less mass remaining after 17 days) in the control (65 % leaf mass remaining) compared to the macroconsumer exclusion (70 % leaf mass remaining). However, the mechanism for this effect was not clear. Considerable variation in leaf decomposition occurred among blocked stream sites, suggesting that some factors differing among these sites, perhaps macroinvertebrate Shredder abundance, was contributing to decomposition. Leaves were visually inspected at the conclusion of the experiment and there was no sign of shrimp directly feeding on the leaves. There was no difference in insect Shredder abundance between treatments. There was, however, a significantly greater amount of non-mining chironomids in the absence of macroconsumers. This is probably due to the release from predation by shrimp.
