Shading and sediment structure effects on stream metabolism resistance and resilience to infrequent droughts

Zlatanović, Sanja; Fabian, Jenny; Premke, Katrin; Mutz, Michael

doi:10.1016/j.scitotenv.2017.10.105

Cited by 21 publications

(28 citation statements)

References 77 publications

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“…Before the drying experiment, sediment community respiration (CR) was measured under flowing conditions as dissolved oxygen (DO) consumption in 30 ml glass columns (FORTUNA OPTIMA, Poulten & Graf, GmbH, Wertheim, Germany). We perfused sediment with artificial river water ( Lehman, 1980 ; Zlatanović et al, 2017 ) enriched with 200 μg L –1 NH 4 -N and 10 μg L –1 PO 4 3– , mimicking concentrations in Spree river water (Landesamt für Umwelt, Cottbus Sandower Brücke, 2015). The artificial stream water was pumped through the columns filled with non-enriched or enriched Spree riverbed sediment ( n = 3) at a rate of 0.04 ml min –1 to generate a gentle interstitial flow, similar to that observed in shallow, sandy riverbed sediments in the region ( Angermann et al, 2012 ).…”

Section: Methodsmentioning

confidence: 99%

Attributes of Drying Define the Structure and Functioning of Microbial Communities in Temperate Riverbed Sediment

et al. 2021

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Combined effects of climate change and increasing anthropogenic water demand have increased and extended dry period occurrences in rivers worldwide. Riverbed drying can significantly affect sediment microorganisms, crucial drivers of biogeochemical processes in lotic systems. In this study, we evaluated how sediment bacterial and fungal community structure and composition (based on 16S rRNA gene and ITS metabarcoding) and microbial functions (community respiration and extracellular enzymatic activities) respond to different riverbed drying intensities over 90 days. Riverbed sediment collected in a flowing reach of the Spree river in northeastern Germany was dried under different rates in outdoor mesocosms during the summer months of 2018. Our results demonstrate that drying attributes (duration and intensity) and sediment organic matter (OM) content play a crucial role in sediment microbial community assembly and functioning throughout drying. Milder drying surprisingly triggered a more rapid and drastic change in the microbial community composition and diversity. After 90 days of drying, Bacilli (Firmicutes) became the dominant bacterial class in most treatments, except in sediments with low OM content under the most severe drying treatment. Fungal amplicon sequence variants (ASVs) from Dothideomycetes (Ascomycota) had by far the highest relative abundance in all our treatments at the end of the drying experiment, making up 65.1% to 94.0% of the fungal reads. CO2 fluxes, a proxy for sediment community respiration, were rapidly and strongly affected by drying in all treatments. Our results imply that even short riverbed drying periods are likely to have significant consequences for the biogeochemical dynamics in recently formed non-perennial temperate rivers.

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Section: Methodsmentioning

confidence: 99%

Attributes of Drying Define the Structure and Functioning of Microbial Communities in Temperate Riverbed Sediment

et al. 2021

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“…Consequently, our results support that the streambed structure influences the proportional utilization of leaf C within the microbial food web, but also demonstrate that streambed structure had only a marginal influence on the magnitude of leaf C respiration. One possible explanation for these contradictory results could be the significant contribution of algae to leaf C respiration in our approach ( Zlatanović et al, 2017 ). As previously mentioned, phototrophic and heterotrophic activities were not equally affected by our streambed treatments.…”

Section: Discussionmentioning

confidence: 84%

“…However, periodic desiccation of sediments has also been described to increase the bioavailability of leaf litter, thereby stimulating its microbial turnover ( Abril et al, 2016 ; Weise et al, 2016 ). Indeed, drought disturbed microbial activity as discussed in detail by Zlatanović et al (2017) , accompanied by a lower respiration rate of leaf C ( Figure 2 ). The decline in leaf C respiration accords well with previously reported adverse effects of drought on ecosystem function ( Datry et al, 2014 ) associated with the death of the microbial cells from osmotic stress and consequently a reduction in microbial biomass ( Birch, 1960 ; Rees et al, 2006 ).…”

Section: Discussionmentioning

confidence: 85%

“…Phototrophic activities were strongly related to light availability as primary production was significantly higher under ambient than under reduced light conditions (see Zlatanović et al, 2017 for detailed discussion). Accordingly, we hypothesized that the decomposition of leaf C increases with increasing light availability because of a previously postulated stimulating effect of phototrophic activities on microbial leaf breakdown ( Danger et al, 2013 ; Kuehn et al, 2014 ; Rier et al, 2014 ).…”

Section: Discussionmentioning

confidence: 99%

“…The stable isotope composition of the respired C pool and, consequently, the proportion of leaf C in the respired C pool, is the sum of heterotrophic and phototrophic activities ( Fry and Sherr, 1989 ). At the ecosystem level, the phototrophic activities did not differ between the two streambed treatments ( Zlatanović et al, 2017 ). Accordingly, the observed interactive effect of the streambed structure and the light availability on the composition of the respired C pool must underlie changes in the breakdown of leaf litter by heterotrophic activities.…”

Section: Discussionmentioning

confidence: 99%

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Environmental Control on Microbial Turnover of Leaf Carbon in Streams – Ecological Function of Phototrophic-Heterotrophic Interactions

et al. 2018

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In aquatic ecosystems, light availability can significantly influence microbial turnover of terrestrial organic matter through associated metabolic interactions between phototrophic and heterotrophic communities. However, particularly in streams, microbial functions vary significantly with the structure of the streambed, that is the distribution and spatial arrangement of sediment grains in the streambed. It is therefore essential to elucidate how environmental factors synergistically define the microbial turnover of terrestrial organic matter in order to better understand the ecological role of photo-heterotrophic interactions in stream ecosystem processes. In outdoor experimental streams, we examined how the structure of streambeds modifies the influence of light availability on microbial turnover of leaf carbon (C). Furthermore, we investigated whether the studied relationships of microbial leaf C turnover to environmental conditions are affected by flow intermittency commonly occurring in streams. We applied leaves enriched with a 13C-stable isotope tracer and combined quantitative and isotope analyses. We thereby elucidated whether treatment induced changes in C turnover were associated with altered use of leaf C within the microbial food web. Moreover, isotope analyses were combined with measurements of microbial community composition to determine whether changes in community function were associated with a change in community composition. In this study, we present evidence, that environmental factors interactively determine how phototrophs and heterotrophs contribute to leaf C turnover. Light availability promoted the utilization of leaf C within the microbial food web, which was likely associated with a promoted availability of highly bioavailable metabolites of phototrophic origin. However, our results additionally confirm that the structure of the streambed modifies light-related changes in microbial C turnover. From our observations, we conclude that the streambed structure influences the strength of photo-heterotrophic interactions by defining the spatial availability of algal metabolites in the streambed and the composition of microbial communities. Collectively, our multifactorial approach provides valuable insights into environmental controls on the functioning of stream ecosystems.

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Biofilm pigments in temporary streams indicate duration and severity of drying

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et al. 2021

Limnology & Oceanography

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Increased duration and frequency of droughts under global change may affect both temporary and formerly permanent watercourses. Streambed desiccation, cooccurring solar radiation, and high temperature all may affect the composition and metabolism of photoautotrophic organisms in benthic biofilms. To test these effects, we characterized the composition of pigments when biofilms were exposed to dry conditions, and compared this to pigments measured after flow resumed, as well as to others measured from permanent streams in the same region. This comparison revealed important differences in pigmentary composition based on flow conditions. Active chlorophylls decreased exponentially with the duration and severity of the nonflow period, while chlorophyll degradation products and protective carotenoids increased. Streams experiencing longer and more severe nonflow periods showed the highest dissimilarities in their biofilm pigmentary composition, and this pattern was maintained after flow resumed. Our results pointed to duration of nonflowing periods as the major driver of pigmentary composition, regardless of whether these were interrupted or not by short intervals of water flows. Multivariate changes in pigmentary composition between sampling periods highlighted the influence of the long‐term hydrological history on the relative abundance of different taxonomic groups and their associated pigments. Overall, pigmentary fingerprints are informative of the biofilm capacity to resist water flow interruption and of their ability to recover after water flow returns.

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Shading and sediment structure effects on stream metabolism resistance and resilience to infrequent droughts

Cited by 21 publications

References 77 publications

Attributes of Drying Define the Structure and Functioning of Microbial Communities in Temperate Riverbed Sediment

Attributes of Drying Define the Structure and Functioning of Microbial Communities in Temperate Riverbed Sediment

Environmental Control on Microbial Turnover of Leaf Carbon in Streams – Ecological Function of Phototrophic-Heterotrophic Interactions

Biofilm pigments in temporary streams indicate duration and severity of drying

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