Journal
FUNCTIONAL ECOLOGY
Volume 33, Issue 1, Pages 188-201Publisher
WILEY
DOI: 10.1111/1365-2435.13235
Keywords
bacteria; detritus; ecological stoichiometry; light; microbial heterotrophs; periphyton; priming effects; streams
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Funding
- United States National Science Foundation Division of Biological Infrastructure [0923063]
- National Institute of General Medical Sciences [P20GM103476]
- United States National Science Foundation Division of Environmental Biology [1457217]
- Lake Thoreau Environmental Center
- University of Southern Mississippi Honors College
- NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES [P20GM103476] Funding Source: NIH RePORTER
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Well-documented in terrestrial settings, priming effects describe stimulated heterotrophic microbial activity and decomposition of recalcitrant carbon by additions of labile carbon. In aquatic settings, algae produce labile exudates which may elicit priming during organic matter decomposition, yet the directions and mechanisms of aquatic priming effects remain poorly tested. We tested algal-induced priming during decomposition of two leaf species of contrasting recalcitrance, Liriodendron tulipifera and Quercus nigra, in experimental streams under light or dark conditions. We measured litter-associated algal, bacterial, and fungal biomass and activity, stoichiometry, and litter decomposition rates over 43 days. Light increased algal biomass and production rates, in turn increasing bacterial abundance 141%-733% and fungal production rates 20%-157%. Incubations with a photosynthesis inhibitor established that algal activity directly stimulated fungal production rates in the short term. Algal-stimulated fungal production rates on both leaf species were not coupled to long-term increases in fungal biomass accrual or litter decomposition rates, which were 154%-157% and 164%-455% greater in the dark, respectively. The similar patterns on fast- vs. slow-decomposing L. tulipifera and Q. nigra, respectively, indicated that substrate recalcitrance may not mediate priming strength or direction. In this example of negative priming, periphytic algae decoupled fungal activity from decomposition, likely by providing labile carbon invested towards greater fungal growth and reproduction instead of recalcitrant carbon degradation. If common, algal-induced negative priming could stimulate heterotrophy reliant on labile carbon yet suppress decomposition of recalcitrant carbon, modifying energy and nutrients available to upper trophic levels and enhancing organic carbon storage or export in well-lit aquatic habitats.
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