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Abstract. Heterotrophic microbes play key roles in regulating fluxes ofenergy and nutrients, which are increasingly affected by globally changingenvironmental conditions such as warming and nutrient enrichment. While theeffects of temperature and nutrients on microbial mineralization of carbonhave been studied in some detail, much less attention has been given to howthese factors are altering uptake rates of nutrients. We used laboratoryexperiments to simultaneously evaluate the temperature dependence of solublereactive phosphorus (SRP) uptake and respiration by leaf-litter-associatedmicrobial communities from temperate headwater streams. Additionally, weevaluated the influence of the initial concentration of SRP on thetemperature dependence of P uptake. Finally, we used simple simulationmodels to extrapolate our results and estimate the effect of warming and Pavailability on cumulative gross uptake. We found that the temperaturedependence of P uptake was lower than that of respiration (0.48 vs. 1.02 eV). Further, the temperature dependence of P uptake increased with theinitial concentration of SRP supplied, ranging from 0.12 to 0.48 eV over an11 to 212 µg L−1 gradient in initial SRP concentration.Finally, despite our laboratory experiments showing increases inmass-specific rates of gross P uptake with temperature, our simulationmodels predict declines in cumulative P uptake with warming, because theincreased rates of respiration at warmer temperatures more rapidly depletedbenthic carbon substrates and consequently reduced the biomass of thebenthic microbial community. Thus, even though mass-specific rates of P uptake were higher at the warmer temperatures, cumulative P uptake was lowerover the residence time of a pulsed input of organic carbon. Our resultshighlight the need to consider the combined effects of warming, nutrientavailability, and resource availability and/or magnitude on carbon processing asimportant controls of nutrient processing in heterotrophic ecosystems.
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This content will become publicly available on February 3, 2026
On the breakdown of woody debris across a groundwater gradient in Neotropical streams, Costa Rica
Forested headwater streams disproportionately rely on inputs of organic matter to fuel their food webs, and characterizing the breakdown of organic matter offers insights into ecosystem function. Organic matter breakdown rates can be influenced by the availability of limiting nutrients, and describing patterns of breakdown rates across nutrient gradients is increasingly relevant as inland waters undergo eutrophication. Here, we determined the breakdown rates of coarse woody debris (kwood) across 5 streams located at La Selva Biological Station, Costa Rica, that receive a gradient of interbasin modified groundwater inputs, creating a gradient in P concentration (6–134 lg/L soluble reactive P [SRP]). The fastest breakdown rate (kwood 50.77/y) occurred in the stream with the highest SRP, and kwood was positively correlated with SRP across the 5 streams. Further, we characterized the assemblage of macroinvertebrates from wood packs. Macroinvertebrate assemblages were different between the 5 streams, with more dense and diverse assemblages in streams with higher SRP and faster breakdown rates. Our results contribute to a growing field of study on the effect of nutrients on organic matter dynamics in inland waters by characterizing the effect of SRP on breakdown rates of wood in tropical streams.
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- Award ID(s):
- 2154228
- PAR ID:
- 10570958
- Publisher / Repository:
- Society for Freshwater Science
- Date Published:
- Journal Name:
- Freshwater Science
- ISSN:
- 2161-9549
- Page Range / eLocation ID:
- 000 to 000
- Subject(s) / Keyword(s):
- wood breakdown rate organic matter macroinvertebrates nutrients tropical streams
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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