Microbial decomposition is highly sensitive to leaf litter emersion in a permanent temperate stream (original) (raw)
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Hydrobiologia, 2017
The present study aims to understand how microbial decomposition of leaf litter from two riparian tree species differing in their quality varies among streams covering a gradient of nutrient concentrations. We incubated leaf litter from alder (Alnus glutinosa) and sycamore (Platanus 9 hispanica) in 3 streams with low human pressure and 2 streams influenced by wastewater treatment plant effluents. We quantified leaf litter decomposition rates (k) and examined the temporal changes in the leaf litter concentrations of carbon (C) and nitrogen (N) throughout the incubation period. We measured the extracellular enzyme activities involved in degradation of C (i.e., cellobiohydrolase) and organic phosphorus (i.e., phosphatase). Results showed that alder k decreased with increasing nutrient concentrations, while sycamore decomposed similarly among streams. For both species, leaf litter N concentrations were positively related to in-stream dissolved N concentrations. However, we found different temporal patterns of leaf litter N concentrations between species. Finally, we found relevant differences in the enzymatic activities associated to each leaf litter species across the nutrient gradient. These results suggest that the intrinsic characteristics of the leaf litter resources may play a relevant role on the microbially driven leaf litter decomposition and mediate its response to dissolved nutrient concentrations across streams.
Tdx, 2014
ADVERTIMENT. L'accés als continguts d'aquesta tesi doctoral i la seva utilització ha de respectar els drets de la persona autora. Pot ser utilitzada per a consulta o estudi personal, així com en activitats o materials d'investigació i docència en els termes establerts a l'art. 32 del Text Refós de la Llei de Propietat Intel•lectual (RDL 1/1996). Per altres utilitzacions es requereix l'autorització prèvia i expressa de la persona autora. En qualsevol cas, en la utilització dels seus continguts caldrà indicar de forma clara el nom i cognoms de la persona autora i el títol de la tesi doctoral. No s'autoritza la seva reproducció o altres formes d'explotació efectuades amb finalitats de lucre ni la seva comunicació pública des d'un lloc aliè al servei TDX. Tampoc s'autoritza la presentació del seu contingut en una finestra o marc aliè a TDX (framing). Aquesta reserva de drets afecta tant als continguts de la tesi com als seus resums i índexs. CONTENTS Summary/Resumen/Resum General Introduction Materials and Methods CHAPTER I. Factors controlling seasonality in leaf litter breakdown for a Mediterranean stream CHAPTER II. Dynamic microbial assemblages and enzyme activities throughout leaf litter decomposition in a Mediterranean stream CHAPTER III. Summer drought affects autumn leaf decomposition in streams CHAPTER IV. Emersion affects leaf litter microbial processing in a pristine temperate stream CHAPTER V. Eutrophication alters responses of stream-dwelling microbial decomposers to drought General Discussion General Conclusions References
Applied and Environmental Microbiology, 2013
into open-land streams, whereas tree litter is predominant in forested streams. We set out to elucidate whether the activity and structure of microbial communities on decomposing leaves are determined by litter quality (i.e., grass or tree leaves colonized) or whether changes during riparian succession affecting litter standing stocks on the stream bed play an overriding role. We used 15 outdoor experimental streams to simulate changes in litter supplies reflecting five stages of riparian succession: (i) a biofilm stage with no litter, (ii) an open-land stage characterized by grass litter inputs, (iii) a transitional stage with a mix of grass and tree litter, (iv) an early forested stage with tree litter, and (v) an advanced forested stage with 2.5 times the amount of tree litter. Microbial activities on tree (Betula pendula) and grass (Calamagrostis epigejos) litter were unaffected by either the quantity or type of litter supplied to the experimental streams (i.e., litter standing stock) but differed between the two litter types. This was in stark contrast with bacterial and fungal community structure, which markedly differed on grass and tree litter and, to a lesser extent, also among streams receiving different litter inputs. These patterns reveal distinct responses of microbial community structure and activity to the bulk litter available in streams but consistent responses to the litter type colonized.
Fungal and Bacterial Colonization of Submerged Leaf Litter in a Mediterranean Stream
International Review of Hydrobiology, 2011
Microbial colonization dynamics of fungi and bacteria were analyzed in an intermittent Mediterranean forested stream using two different leaf substrata (Platanus acerifolia and Populus nigra). Results showed that fungal and bacterial biomass accumulation was stimulated on both leaves due to a flooding episode that increased dissolved inorganic nitrogen (DIN) and dissolved oxygen (DO) availability in the stream water. Leaf mass loss coincided with the parallel increase in microbial biomass and extracellular enzymatic activities after the flood event. Differences in litter quality favoured bacterial biomass accumulation and β-glucosidase and cellobiohydrolase enzymatic activities in the soft Populus species. Microbial heterotrophs colonization of submerged leaf litter and organic matter use in Mediterraneantype streams are modulated by environmental conditions, especially the hydrological variability.
2016
Riparian areas are fundamental to aquatic ecosystems by regulating temperature and light regimes, and providing allochthonous subsidies critical to the survival of aquatic and terrestrial species. On a global scale, increased rates of anthropogenic disturbance from agricultural activities and urbanization have caused the degradation of aquatic habitats. As a result, billions of dollars have been spent on stream restoration projects to protect aquatic resources; however, fundamental ecosystem processes like litter decomposition are rarely addressed. We conducted a litterbag experiment in a degraded high desert stream proposed for large-scale restoration to test the effects of reach location, canopy cover, and temperature on the rates of leaf litter breakdown attributed to microbial activity and macroinvertebrate shredders. Results from coarse mesh litterbags indicated that total leaf breakdown rates per degree-day were significantly faster in upstream, less degraded reaches, associat...
Microbiological research, 2010
Although a number of studies have indicated that microbes are key players in nutrient cycling, limitations on how to accurately assess their diversity have constrained further knowledge on the role of microbial diversity in organic matter decomposition in streams. Microbial diversity on leaf litter of Alnus glutinosa was assessed by microscopic analysis of bacterial cells and released fungal conidia, and by the number of operational taxonomic units (OTUs) from denaturing gradient gel electrophoresis using two different primer pairs targeting the rDNA of fungi (ITS2 and 5′ end of the 18S region) and bacteria (V3 region and V6–V8 regions). Fingerprints of fungal and bacterial DNA showed a higher diverse microbial community on decomposing leaves than that assessed by microscopy-based techniques. Higher number of OTUs was obtained with primers targeting the ITS2 region of fungi, but the selected primers for bacteria showed similar number of OTUs. A succession of fungal or bacterial taxa throughout leaf decomposition was found, regardless of the chosen primer. These microbial communities ensured a rapid decomposition of submerged leaf litter (k=−0.045 day−1). Fungal biomass (up to 58 mg g−1 AFDM) contributed with more than 98% to the total microbial biomass, supporting a greater role of fungi than bacteria in leaf-litter decomposition in streams.
Limnetica, 2015
Microbial colonisation and litter decomposition in a Cerrado stream are limited by low dissolved nutrient concentra- tions Litter decomposition in the streams of the Brazilian Cerrado (Savannah) is generally slow. In this study, we tested the hypothesis that leaf litter decomposition is limited by low dissolved nutrient availability. We measured the decomposition of the litter of the riparian species Protium heptaphyllum in a local stream under nutrient enrichment promoted by nutrient- diffusing substrates (nutrient-enriched treatment; N and P), and under control conditions (no added nutrients). Leaves were enclosed in fine (0.5 mm) mesh bags and immersed in the stream. Replicate samples were retrieved periodically over 56 days. At the end of the experiment, leaf mass loss, associated microbial biomass (ATP and ergosterol) and fungal sporulation rates were significantly higher in nutrient-enriched bags than in control bags. These results suggest that litter decomposition in certain ...
2016
Microbial colonisation and litter decomposition in a Cerrado stream are limited by low dissolved nutrient concentrations Litter decomposition in the streams of the Brazilian Cerrado (Savannah) is generally slow. In this study, we tested the hypothesis that leaf litter decomposition is limited by low dissolved nutrient availability. We measured the decomposition of the litter of the riparian species Protium heptaphyllum in a local stream under nutrient enrichment promoted by nutrientdiffusing substrates (nutrient-enriched treatment; N and P), and under control conditions (no added nutrients). Leaves were enclosed in fine (0.5 mm) mesh bags and immersed in the stream. Replicate samples were retrieved periodically over 56 days. At the end of the experiment, leaf mass loss, associated microbial biomass (ATP and ergosterol) and fungal sporulation rates were significantly higher in nutrient-enriched bags than in control bags. These results suggest that litter decomposition in certain Cerr...
International Review of Hydrobiology, 2009
We conducted a transplant experiment between two streams in NW Portugal impacted by agricultural runoff, mainly differing in phosphate concentration, to determine whether fungi on decomposing leaves would adapt to the new environment or would be replaced by fungi of the recipient stream. The most nutrient enriched stream had lower fungal diversity but faster leaf decomposition. Leaf transplantation did not alter fungal activity or species dominance. Multidimensional scaling ordination of fungal communities, from DNA fingerprint or conidial production, revealed that transplanted communities resembled more those of the original stream than the recipient stream. Results suggest that early fungal colonizers will determine the development and activity of fungal communities on decomposing leaves in streams impacted by agricultural practices. * Corresponding author 400 K. R. SRIDHAR et al.
Microbial Ecology, 2016
Ongoing climate change is expected to affect the diversity and activity of aquatic microbes, which play a key role in plant litter decomposition in forest streams. We used a before-after control-impact (BACI) design to study the effects of warming on a forest stream reach. The stream reach was divided by a longitudinal barrier, and during 1 year (ambient year) both stream halves were at ambient temperature, while in the second year (warmed year) the temperature in one stream half was increased by ca. 3°C above ambient temperature (experimental half). Fine-mesh bags containing oak (Quercus robur L.) leaves were immersed in both stream halves for up to 60 days in spring and autumn of the ambient and warmed years. We assessed leaf-associated microbial diversity by denaturing gradient gel electrophoresis and identification of fungal conidial morphotypes and microbial activity by quantifying leaf mass loss and productivity of fungi and bacteria. In the ambient year, no differences were found in leaf decomposition rates and microbial productivities either between seasons or stream halves. In the warmed year, phosphorus concentration in the stream water, leaf decomposition rates, and productivity of bacteria were higher in spring than in autumn. They did not differ between stream halves, except for leaf decomposition, which was higher in the experimental half in spring. Fungal and bacterial communities differed between seasons in both years. Seasonal changes in stream water variables had a greater impact on the activity and diversity of microbial decomposers than a warming regime simulating a predicted global warming scenario.