Life Sciences Commons^™

Algal-Mediated Priming Effects On The Ecological Stoichiometry Of Leaf Litter Decomposition: A Meta-Analysis, Halvor M. Halvorson, Steven N. Francoeur, Robert H. Findlay, Kevin A. Kuehn

Faculty Publications

In aquatic settings, periphytic algae exude labile carbon (C) that can significantly suppress or stimulate heterotrophic decomposition of recalcitrant C via priming effects. The magnitude and direction of priming effects may depend on the availability and stoichiometry of nutrients like nitrogen (N) and phosphorus (P), which can constrain algal and heterotrophic activity; in turn, priming may affect heterotrophic acquisition not only of recalcitrant C, but also N and P. In this study, we conducted a meta-analysis of algal-mediated priming across leaf litter decomposition experiments to investigate (1) bottom-up controls on priming intensity by dissolved N and P concentrations, and (2) …

Periphytic Algae Decouple Fungal Activity From Leaf Litter Decomposition Via Negative Priming, Halvor M. Halvorson, Jacob R. Barry, Matthew B. Lodato, Robert H. Findlay, Steven N. Francoeur, Kevin A. Kuehn

Faculty Publications

1. 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.

2. 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.

3. Light increased algal biomass and …

Detrital Nutrient Content And Leaf Species Differenitally Affect Growth And Nutritional Regulation Of Detritivores, Halvor M. Halvorson, Chris L. Fuller, Sally A. Entrekin, J. Thad Scott, Michelle A. Evans-White

Faculty Publications

© 2018 The Authors Resource nutrient content and identity are common bottom–up controls on organismal growth and nutritional regulation. One framework to study these factors, ecological stoichiometry theory, predicts that elevated resource nitrogen (N) and phosphorus (P) contents enhance organism growth by alleviating constraints on N and P acquisition. However, the regulatory mechanisms underlying this response – including whether responses depend on resource identity – remain poorly understood. In this study, we tested roles of detrital N and P contents and identity (leaf species) in constraining growth of aquatic invertebrate detritivores. We synthesized results from seven detritivore species fed wide …

Algal Regulation Of Extracellular Enzyme Activity In Stream Microbial Communities Associated With Inert Substrata And Detritus, Steven T. Rier, Kevin A. Kuehn, Steven N. Francoeur

Faculty Publications

We tested the hypothesis that algae influence the activities of extracellular enzymes involved in mineralization processes within microbial assemblages in streams. We tested the prediction that the factors that influence algal biomass and photosynthesis (i.e., diel fluctuations in photosynthetically active radiation [PAR], long-term variations in light regime, and community development stage) would have a corresponding effect on extracellular enzyme activities. We also tested the prediction that algae would influence enzyme activities on inorganic substrata and in detrital communities where they ultimately would influence plant litter decomposition rates. We allowed microbial communities to develop on inert substrata (glass-fiber filters) or on …