Top‐down and bottom‐up control of litter decomposers in streams

Gonçalves, Ana Lúcia; Chauvet, Éric; Bärlocher, Feli×; Graça, Manuel A. S.; Canhoto, Cristina

doi:10.1111/fwb.12420

Cited by 43 publications

(27 citation statements)

References 48 publications

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“…This species was shown to be unpalatable/rejected by gammarids in previous ecological and ecotoxicological studies e.g. ( Gonçalves et al, 2014). As a consequence, it cannot be excluded that an avoidance mechanism was responsible for the decrease in Gammarus feeding rates on drought-stressed leaves at the end of the experiment.…”

Section: Drought and Tbz Stress Effects Along The Aquatic Detrital Fomentioning

confidence: 81%

Combined effects of drought and the fungicide tebuconazole on aquatic leaf litter decomposition

et al. 2016

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Highlights• The combined effects of drought and the fungicide tebuconazole on aquatic leaf litter decomposition (LLD) were assessed.• TBZ applied alone had no significant effect on LLD.• Drought strongly impacted the microbial LLD process and led to cascading effects on Gammarus feeding.• Structural and functional effects increased when drought and TBZ were applied simultaneously. AbstractLoss of biodiversity and altered ecosystem functioning are driven by the cumulative effects of multiple natural and anthropogenic stressors affecting both quantity and quality of water resources. Here we performed a 40-day laboratory microcosm experiment to assess the individual and combined effects of drought and the model fungicide tebuconazole (TBZ) on leaf litter decomposition (LLD), a fundamental biogeochemical process in freshwater ecosystems. Starting out from a worst-case scenario perspective, leaf-associated microbial communities were exposed to severe drought conditions (four 5-day drought periods alternated with 4-day immersion periods) and/or a chronic exposure to TBZ (nominal concentration of 20 µg L−1). We assessed the direct effects of drought and fungicide on the structure (biomass, diversity) and activity (extracellular enzymatic potential) of fungal and bacterial assemblages colonizing leaves. We also investigated indirect effects on the feeding rates of the amphipod Gammarus fossarum on leaves previously exposed to drought and/or TBZ contamination. Results indicate a stronger effect of drought stress than fungicide contamination under the experimental conditions applied. Indeed, the drought stress strongly impacted microbial community structure and activities, inhibiting the LLD process and leading to cascading effects on macroinvertebrate feeding. However, despite the lack of significant effect of TBZ applied alone, the effects of drought on microbial functions (i.e., decrease in LLD and in enzymatic activities) and on Gammarus feeding rates were more pronounced when drought and TBZ stresses were applied together. In a perspective of ecological risk assessment and ecosystem management for sustainability, these findings stress the need for deeper insight into how multiple stressors can affect the functioning of aquatic ecosystems and associated services.

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Section: Drought and Tbz Stress Effects Along The Aquatic Detrital Fomentioning

confidence: 81%

Combined effects of drought and the fungicide tebuconazole on aquatic leaf litter decomposition

et al. 2016

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“…Ferreira & Chauvet ; Gonçalves et al . ). This might explain the lack of enhanced decomposition at elevated N concentration for most plant species.…”

Section: Discussionmentioning

confidence: 97%

Stream nitrogen concentration, but not plant N‐fixing capacity, modulates litter diversity effects on decomposition

et al. 2017

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Summary We are facing major biodiversity loss and there is evidence that such loss can alter ecosystem functioning. However, the effects of plant diversity on decomposition – a key component of the global carbon cycle – are still unclear. A recent study suggested that a plant trait – their nitrogen (N)‐fixing capacity – could mediate effects of litter diversity on decomposition by means of a microbial transfer of N from N‐fixers to non‐fixers. We explored this possibility in a microcosm experiment in which we manipulated litter species richness (one, two or four species), N‐fixing capacity (N‐fixer or non‐fixer species), the presence of detritivores (Sericostoma pyrenaicum larvae present or absent) and water N concentration [natural stream water (0·366 mg L−1 of NO3‐N) or elevated N concentration (five times the natural concentration: 1·835 mg L−1)]. We show that litter diversity accelerated decomposition by micro‐organisms and detritivores (by 7% and 15% respectively), mostly through complementarity effects. However, enhanced decomposition did not result in higher detritivore growth, possibly because all litter combinations provided sufficient resources for their maximum growth. The plant N‐fixing capacity had no effect on decomposition, which varied among species most likely because of differences in a combination of litter traits. Detritivores maximized the consumption of their preferred resource in litter mixtures, but also exploited less preferred resources, and their C : N ratios increased during the experiment regardless of litter type or water N concentration. Microbial decomposition of litter with low N content was enhanced at elevated water N concentration, suggesting that micro‐organisms used nutrients from the water when those nutrients were limiting in leaf litter. In contrast, detritivore growth was impaired at elevated water N concentration, possibly because a stoichiometric imbalance entails metabolic costs. Our findings suggest that loss of plant diversity in riparian forests would mostly affect decomposition in streams of high nutrient status, where effects on microbial decomposition would be more evident and detritivore populations may be reduced. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12837/suppinfo is available for this article.

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“…This group of fungi has a key role in the enzymatically mediated degradation of recalcitrant carbon, enhancing the nutritional value of the leaves to the shredding invertebrates which also profit from the fungal biomass as a nitrogen and phosphate rich food source (Cummins & Klug, ; Graça, ; Aßmann et al ., ). The nutritional quality of the leaves for the invertebrates depends on the fungal biomass accrual but also on the composition of the fungal communities found on the leaves (Suberkropp, Arsuffi & Anderson, ; Graça, ; but see Gonçalves et al ., ). Most studies indicate that fungal growth and activity is stimulated by increases in water temperature (Dang et al ., ; Friberg et al ., ; Ferreira & Chauvet, ,b).…”

Section: Introductionmentioning

confidence: 99%

Effects of increased water temperature on leaf litter quality and detritivore performance: a whole‐reach manipulative experiment

et al. 2014

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Summary We compared leaf litter conditioning in two artificial stream channels that were connected to a second‐order stream (both in‐ and outflow). The water in one channel had the same temperature as the stream and in the other channel was warmed (3 °C above ambient stream water temperature). In addition to measuring leaf decomposition by microbes, we ran feeding trials in the artificial streams and the laboratory that addressed the feeding preferences, resource acquisition and performance of a dominant detritivore. Oak leaves were conditioned for three weeks in both channels and then offered during the following five weeks to Sericostoma vittatum larvae kept in cages in the same channels. Additionally, leaves conditioned in both conditions were simultaneously offered to the larvae in a feeding preference laboratory trial. Leaves conditioned in the channel with elevated temperature had reduced toughness, fewer phenols and lower carbon : nitrogen ratios. However, individuals did not prefer these leaves over those conditioned at ambient stream temperature. We observed lower carbon : nitrogen imbalances and increased consumption rates in the stream channel at warmer temperature but these were not translated into higher growth rates. Higher metabolic rates of the S. vittatum individuals and other temperature‐mediated factors such as changes in leaf quality could explain the increased consumption. We observed higher lipid storage and earlier pupation of S. vittatum at warmer temperatures, suggesting that individuals allocated resources to metamorphosis and reproduction, rather than to somatic growth. We argue that microbial and invertebrate‐mediated organic matter cycling will be faster in streams under future warming scenarios. However, these systems will likely become less efficient in carbon retention via effects on larval performance (growth and developmental time) and timing of prey availability to the stream and coupled riparian food webs.

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Top‐down and bottom‐up control of litter decomposers in streams

Cited by 43 publications

References 48 publications

Combined effects of drought and the fungicide tebuconazole on aquatic leaf litter decomposition

Combined effects of drought and the fungicide tebuconazole on aquatic leaf litter decomposition

Stream nitrogen concentration, but not plant N‐fixing capacity, modulates litter diversity effects on decomposition

Effects of increased water temperature on leaf litter quality and detritivore performance: a whole‐reach manipulative experiment

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