Combined Effects of Dissolved Nutrients and Oxygen on Plant Litter Decomposition and Associated Fungal Communities

Abstract

Aquatic ecosystems worldwide have been substantially altered by human activities, which often induce changes in multiple factors that can interact to produce complex effects. Here, we evaluated the combined effects of dissolved nutrients (nitrogen [N] and phosphorus [P]; three levels: concentration found in oligotrophic streams in the Cerrado biome, 10× and 100× enriched) and oxygen (O; three levels: hypoxic [4% O], depleted [55% O], and saturated [96% O]) on plant litter decomposition and associated fungal decomposers in laboratory microcosms simulating stream conditions under distinct scenarios of water quality deterioration. Senescent leaves of Maprounea guianensis were incubated for 10 days in an oligotrophic Cerrado stream to allow microbial colonization and subsequently incubated in microcosms for 21 days. Leaves lost 1.1-3.0% of their initial mass after 21 days, and this was not affected either by nutrients or oxygen levels. When considering simultaneous changes in nutrients and oxygen concentrations, simulating increased human pressure, fungal biomass accumulation, and sporulation rates were generally inhibited. Aquatic hyphomycete community structure was also affected by changes in nutrients and oxygen availability, with stronger effects found in hypoxic treatments than in depleted or saturated oxygen treatments. This study showed that the effects of simultaneous changes in the availability of dissolved nutrients and oxygen in aquatic environments can influence the activity and composition of fungal communities, although these effects were not translated into changes in litter decomposition rates.

An affordable and reliable assessment of aquatic decomposition: Tailoring the Tea Bag Index to surface waters

“…In aquatic environments, as opposed to the terrestrial ecosystem, moisture is not a determining factor, while oxygen plays a much more important role (Pascoal and C assio, 2004). As oxygen concentrations drop, microbial decomposition slows down substantially, albeit not coming to a full stop (Gomes et al 2018). Aquatic microbial communities frequently encounter low oxic conditions due to anthropogenic factors such as intensified agriculture resulting in higher nutrient concentrations in waters.…”

Mass loss and nutrient release during the decomposition of sixteen types of plant litter with contrasting quality under three precipitation regimes

“…This trend was not in agreement with the exponential function of mass loss, where the mass rate decreases with time of decomposition (Corrigan & Oelbermann, 2010; Wu, Li, & Wan, 2013). Previous studies have shown that Creosote bush ( Larrea tridentata ) fine litter mass loss over a 3‐month period accounted for approximately 20% of the original mass (Moorhead & Reynolds, 1989), and litter mass loss after 21 days of incubation in the laboratory was extremely low (<3%) (Gomes, Ferreira, Tonin, Adriana, & José, 2017). The results from Gomes, Medeiros, and Gonçalves (2016) showed 17.5% mass loss for Maprounea guianensis litter after 10 days of incubation in laboratory microcosms.…”

Testing the Tea Bag Index as a potential indicator for assessing litter decomposition in aquatic ecosystems

“…It is The copyright holder for this preprint this version posted April 27, 2021. ; https://doi.org/10.1101/2021.04.26.441560 doi: bioRxiv preprint Litter decomposition is an important process in aquatic systems (Graça et al, 2015), playing a major role in the global cycling of carbon and nutrients (Battin et al, 2009;Gessner et al, 1999;Graça et al, 2015). Three main factors control aquatic litter decomposition: litter quality (Jabiol et al, 2019;Neiff et al, 2006); environmental factors such as temperature, nutrient availability, salinity, acidity, and oxygen concentration (Almeida Júnior et al, 2020;Ferreira et al, 2015;Gomes et al, 2018;Griffiths and Tiegs, 2016;Woodward et al, 2012;Young et al, 2008); and decomposer community composition, including macroinvertebrates, fungi, and bacteria (Balibrea et al, 2020;Hieber and Gessner, 2002).…”