Graphical abstract (Martínez et al. 2013 FEMS-ME) (original) (raw)
Related papers
Fungal Ecology, 2013
We examine the relative importance of substrate quality and temperature in the establishment of aquatic hyphomycete assemblages and in their ability to decompose leaves. We used leaves of alder (Alnus glutinosa) and oak (Quercus robur) and we tested four temperatures (5 , 10 , 15 and 20 C). Differences in decomposition rates and fungal assemblages were higher substrata than across temperatures. In both species, decomposition efficiency measured as the ratio of decay rate to fungal biomass, was greater at higher temperatures. Oak leaves were colonized by fewer aquatic hyphomycete species than was alder. Decomposition rates of oak increased with temperature but that of alder was not affected. We conclude that the substratum is a key driver of aquatic hyphomycete assemblages and can attenuate the effects of temperature differences on litter decomposition.
Fungal diversity during initial stages of leaf decomposition in a stream
Mycological Research, 2005
Maple, linden and oak leaves were immersed in a stream for 1-21 d. Cumulative mass loss, ergosterol content, and species richness of released aquatic hyphomycete conidia increased with time. Numbers and richness of attached conidia were highest on days 1 and 2. Denaturing gradient gel electrophoresis revealed up to seven fungal phylotypes on the leaves before their immersion in the stream and after one day of stream exposure. After 5 d of immersion the contribution of these terrestrial fungi decreased and that of aquatic hyphomycetes increased. The dominant phylotypes belonged to Anguillispora filiformis, Articulospora tetracladia and Flagellospora curvula, which also dominated the community of released spores. The molecular diversity was highest on day 2 and 3 on all substrates. This may be due to a few species of terrestrial fungi, later outcompeted by aquatic hyphomycetes, and to many different conidia of aquatic hyphomycetes, some of which may germinate but are unable to establish themselves and reproduce.
BREAKDOWN AND COLONIZATION OF ALDER IN REGULATED ITALIAN WATERCOURSES
2000
SUMMARY This paper summarises the results of studies carried out on three different Italian watercourses. We compared the breakdown rates and macroinvertebrate colonization of alder (Alnus glutinosa L.) leaves, incubated: 1) in spring and autumn in the Bidente (Appenines), and its tnbutary, the Bacine, both regulated; 2) in sumrner and winter along the Gardena (Alps), a regulated stream with some
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.
Q-RT-PCR for Assessing Archaea, Bacteria, and Fungi During Leaf Decomposition in a Stream
Microbial Ecology, 2008
Leaf disks of Tilia cordata were exposed for up to 5 weeks in a first-order stream in Nova Scotia, Canada. The exponential decay rate k was 0.008 day −1 . Ergosterol levels increased linearly to a maximum of 134 μg g −1 dry leaf mass. Release of conidia peaked at 700 day −1 mg −1 on leaves that had been exposed for 3 weeks; after 5 weeks, it declined to 15 mg −1 . In total, 23 taxa of aquatic hyphomycetes were distinguished. Anguillospora filiformis contributed over 76% of the conidia during weeks 1, 2, and 3, and 16.5% in week 5. Three sets of primers specific for Bacteria, Archaea, and Fungi were applied in quantitative real-time polymerase chain reaction (Q-RT-PCR) to estimate relative DNA amounts. Archaeal DNA was consistently present at low levels. Bacterial and fungal DNA peaked between weeks 2 and 3, and declined in week 5. With the exception of week 1, fungal DNA exceeded bacterial DNA by between 12 and 110%.
Microbial Ecology, 2014
We investigated how fungal decomposer (aquatic hyphomycetes) communities colonizing alder and eucalyptus leaf litter respond to changes in habitat characteristics (transplantation experiment). We examined the breakdown of leaf materials and the associated fungal communities at two contrasting sites, a headwater stream (H) and a midreach (M). Agroforestry increased from headwater to midreach. One month after the start of experiments at both sites, some leaf samples from the midreach site were transplanted to the headwater site (M-H treatment). Although both sites showed similar dissolved inorganic nutrient concentrations, eucalyptus leaves initially incubated at the midreach site (M, M-H) increased their breakdown rate compared to those incubated along the experiment at the headwater site (H). Alder breakdown rate was not enhanced, suggesting that their consumption was not limited by nutrient availability. Sporulation rates clearly differed between leaf types (alder > eucalyptus) and streams (H > M), but no transplantation effect was detected. When comparing conidial assemblages after transplantation, an inoculum effect (persistence of early colonizing species) was clear in both leaf species. Substrate preference and shifts in the relative importance of some fungal species along the process were also observed. Overall, our results support the determining role of the initial conditioning phase on the whole litter breakdown process, highlighting the importance of intrinsic leaf characteristics and those of the incubation habitat.
Freshwater …, 2010
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, Correspondence: Julien Cornut, Laboratoire d'écologie fonctionnelle, 2541 mycelial and conidial production in the permanently hyporheic environment accounted for 12% of leaf mass loss, i.e. 2-3 times more than in the two other conditions. These results suggest that the role of fungi is particularly important in the hyporheic zone. 7. Our findings indicate that burial within the substratum reduces the litter breakdown rate by limiting the access of both invertebrate and fungal decomposers to leaves. As a consequence, the hyporheic zone may be an important region of organic matter storage in woodland streams and serve as a fungal inoculum reservoir contributing to further dispersal. Through the temporary retention of litter by burial, the hyporheic zone must play a significant role in the carbon metabolism and overall functioning of headwater stream ecosystems.
Initial Colonization, Nutrient Supply, and Fungal Activity on Leaves Decaying in Streams
Applied and Environmental Microbiology, 2000
Aquatic hyphomycetes dominate leaf decomposition in streams, and their biomass is an important component in the diet of leaf-eating invertebrates. After 2 weeks of exposure in a first-order stream, maple leaf disks had low levels of fungal biomass and species diversity. Spore production by aquatic hyphomycetes also was low. Subsets of these disks were left in the stream for another 3 weeks or incubated in defined mineral solutions with one of three levels of nitrate and phosphate. Stream disks lost mass, increased ergosterol levels and spore production, and were colonized by additional fungal species. External N and P significantly stimulated mass loss, ergosterol accumulation, and spore production of laboratory disks. On disks incubated without added N and P, ergosterol levels declined while conidium production continued, suggesting conversion of existing hyphal biomass to propagules. In all other treatments, approximately equal amounts of newly synthesized biomass were invested in...