103 research outputs found
Effects of riparian plant diversity loss on aquatic microbial decomposers become more pronounced at longer times
We examined the potential long-term impacts of riparian plant diversity loss on diversity and activity of aquatic microbial decomposers. Microbial assemblages were obtained
in a mixed-forest stream by immersion of mesh bags contain-ing three leaf species (alder, oak and eucalyptus), commonly
found in riparian corridors of Iberian streams. Simulation of
species loss was done in microcosms by including a set of all
leaf species, retrieved from the stream, and non-colonized
leaves of three, two or one leaf species. Leaves were renewed
every month throughout six months, and microbial inoculum
was ensured by a set of colonized leaves from the previous
month. Microbial diversity, leaf mass loss and fungal biomass
were assessed at the second and sixth months after plant
species loss. Molecular diversity of fungi and bacteria, as the
total number of operational taxonomic units per leaf diversity
treatment, decreased with leaf diversity loss. Fungal biomass
tended to decrease linearly with leaf species loss on oak and
eucalyptus, suggesting more pronounced effects of leaf diver-sity on lower quality leaves. Decomposition of alder and
eucalyptus leaves was affected by leaf species identity, mainly
after longer times following diversity loss. Leaf decomposi-tion of alder decreased when mixed with eucalyptus, while
decomposition of eucalyptus decreased in mixtures with oak.
Results suggest that the effects of leaf diversity on microbial
decomposers depended on leaf species number and also on
which species were lost from the system, especially after
longer times. This may have implications for the management
of riparian forests to maintain stream ecosystem functioning.FEDER-POFC-COMPETE and the Portuguese
Foundation for Science and Technology supported this study (PEst-C/
BIA/UI4050/2011, PTDC/AAC-AMB/113746/2009 and PTDC/AAC-AMB/117068/2010), S. Duarte (SFRH/BPD/47574/2008) and I.
Fernandes (SFRH/BD/42215/2007)
The role of the freshwater shrimp atyaephyra desmarestii in leaf litter breakdown in streams
This version does not correspond to the published one. To access the final version go to: http://www.springerlink.com/content/a31518u452m03286/In aquatic ecosystems, microorganisms and invertebrates provide critical links between plant detritus and higher trophic levels. Atyaephyra desmarestii is an omnivorous decapod that inhabits freshwaters and exhibits high tolerance to temperature oscillations and high ability to colonize new habitats. Although A. desmarestii is able to ingest a variety of foods, few studies have been conducted to elucidate the role of this freshwater shrimp on detritus breakdown in streams. In this study, A. desmarestii was allowed to feed on conditioned or unconditioned alder and eucalyptus leaves in microcosms with or without access to its fecal pellets. At the end of the experiment, total body length of the animals was measured, and the remaining leaves and fecal pellets were used for dry mass quantification and assessment of bacterial and fungal diversity by denaturing gradient gel electrophoresis (DGGE). Cluster analyses of DGGE fingerprints indicated that the major differences in microbial communities on leaves were between leaf types, while on fecal pellets were between conditioned and unconditioned leaves. However, the consumption rate by the shrimp did not differ between leaf types, and was significantly higher on leaves conditioned by microorganisms and in treatments without access to feces. In treatments without access to feces, the production of feces and fine particulate organic matter was also significantly higher for conditioned leaves. Overall, our results support the feeding plasticity of A. desmarestii and its potential role in plant litter breakdown in streams. This might have implications for maintaining stream ecosystem functioning, particularly if more vulnerable shredders decline.The Portuguese Foundation for the
Science and Technology supported S. Duarte (SFRH/BPD/47574/2008
Relative influence of shredders and fungi on leaf litter decomposition along a river altitudinal gradient
We compared autumn decomposition rates of European alder leaves at four sites along the LassetâHers 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 75â87% of original mass in 57 days, of which 46â67% could be attributed to microbial metabolism and 8â29% 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 7â8°C) than upstream (mean 1â2°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
The trophic importance of epiphytic algae in a freshwater macrophyte system (Potamogeton perfoliatus L.): stable isotope and fatty acid analyses
Stable isotope and fatty acid analyses were used to study carbon sources for animals in a submerged plant bed. Epiphytes growing on Potamogeton perfoliatus, sand microflora, and alder leaves were the most important carbon sources. The most abundant macrophyte, P. perfoliatus was unimportant as a food source. Modelling (IsoSource) showed that epiphytes were the most important food source for the most abundant benthic invertebrates, the isopod Asellus aquaticus (annual mean contribution 64%), the amphipod Gammarus pulex (66%), and the gastropod Potamopyrgus antipodarum (83%). The mean annual contributions of sand microflora were, respectively, 21, 19, and 9%; and of alder leaves, 15, 15, and 8% for these three species. The relative importance of carbon sources varied seasonally. The relative contribution of epiphytes was lowest for all three grazer species in July: A. aquaticus 38%, G. pulex 43%, and P. antipodarum 42%. A decline in epiphyte biomass in summer may have caused this switch to less attractive food sources. P. perfoliatus provided habitat and shelter for consumers, but food was mainly supplied indirectly by providing space for attached epiphytes, which are fast-growing and provide a highly nutritious food source
Effect of habitat heterogeneity in the composition and distribution of Chironomidae (Diptera) assemblage in different microhabitats of preserved streams in the Brazilian Atlantic Forest
Impact of anti-inflammatories, beta-blockers and antibiotics on leaf litter breakdown in freshwaters
Pharmaceuticals are now recognised as important pollutants in freshwater systems but a shortcoming of effects studies is that they have focused on structural endpoints and impacts on ecosystem functioning are poorly understood. The decomposition of organic matter is an important functional process in aquatic systems and it is known that this can be impacted by the presence of pollutants. Previous studies on leaf litter breakdown have only considered the effects of antibiotics and not other groups of drugs though. The current study investigated the effects of anti-inflammatories, a beta-blocker and an antibiotic on microbially mediated breakdown of leaf litter in the laboratory, colonisation of leaf packs by benthic macroinvertebrates when placed in a stream and shredding of leaf litter by these organisms. Furthermore, the effects of single compounds relative to their mixture were assessed. It was found that exposure of leaf litter to the study compounds did not influence its breakdown by microbes in the laboratory or macroinvertebrates in a stream. Exposure of leaf litter to pharmaceuticals also had no effect on its colonisation by macroinvertebrates in this study. Many unknowns remain, however, and further studies of the effects of pharmaceuticals on structural and functional endpoints are needed to aid aquatic conservation
Experimental assessment of temperature increase and presence of predator carcass changing the response of invertebrate shredders
Comunicação entre a equipe de saĂșde e a famĂlia da criança com asfixia perinatal grave
Antibiotic mixture effects on growth of the leaf-shredding stream detritivore Gammarus fossarum
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