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1. Consumer‐Driven Nutrient Cycling Interacts With Light to Impact Stream Sediment Nutrient Dynamics

   https://doi.org/10.1111/fwb.70183  

   Lodato, Matthew B; Ledford, Taylor C; Lopez, Jonathan W; Atkinson, Carla L (February 2026, Freshwater Biology)

   ABSTRACT Consumers can strongly impact nutrient cycling in freshwater ecosystems. However, their effects are mediated by interactions between species traits and environmental conditions. While the direct effects of consumer‐driven nutrient dynamics (CND) on ecosystem function have been extensively investigated, their indirect effects have received less attention.In streams, dense and diverse freshwater mussel assemblages can create nutrient cycling hotspots. Here, we performed a series of in situ dark–light incubation experiments using benthic metabolic chambers, along with nutrient excretion and organic matter (OM) biodeposition assays, to examine how four mussel species (Amblema plicata,Fusconaia cerina,Lampsilis ornata, andPustulosa kieneriana) with contrasting traits—specifically, ammonium (NH₄⁺–N) and soluble reactive phosphorus (SRP) excretion and OM biodeposition rates—affect sediment NH₄⁺–N, SRP, and microbial N₂cycling.We hypothesized that: (H1) mussels directly enhance NH₄⁺–N and SRP fluxes through excretion, with the magnitude of their effect depending on species‐specific excretion rates; (H2) mussels indirectly stimulate microbially driven N₂fluxes via NH₄⁺–N excretion and OM biodeposition, with the extent of these influences varying by species‐specific rates of both processes; and (H3) light would modulate all nutrient fluxes by enhancing benthic photoautotrophic activity.We observed interspecific differences in mass‐specific NH₄⁺–N excretion and OM biodeposition rates, but not in mass‐specific SRP excretion rates. Our results support our first hypothesis (H1), as mussels directly influenced NH₄⁺–N and SRP fluxes through excretion, and species with greater biomass contributed more to these fluxes. Conversely, our second hypothesis (H2) was not supported, as mussels did not indirectly affect ambient or potential microbial N₂fluxes. We also found support for our third hypothesis (H3), as light significantly modulated all nutrient fluxes, likely by enhancing benthic photoautotrophic activity.Our findings demonstrate that mussel CND can influence stream nutrient cycling at the patch‐scale and that their direct and indirect effects are modulated by light availability. This study highlights the importance of integrating local environmental conditions into trait‐based research to fully understand the impact of CND on ecosystem function. 

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2. Tadpole aggregations create biogeochemical hotspots in wetland ecosystems

   https://doi.org/10.1111/1365-2656.14222  

   Corline, Nicholas J; Hotchkiss, Erin R; Badgely, Brian; Strahm, Brian D; Scott, Durelle T; McLaughlin, Daniel L (April 2025, Journal of Animal Ecology)

   Abstract Animal waste can contribute substantially to nutrient cycling and ecosystem productivity in many environments. However, little is known of the biogeochemical impact of animal excretion in wetland habitats.Here we investigate the effects of wood frog (Lithobates sylvaticus) tadpole aggregations on nutrient recycling, microbial metabolism and carbon cycling in geographically isolated wetlands.We used a paired mesocosm and field study approach that utilized measurements of tadpole excretion rates, microbial extracellular enzyme activities, and litter degradation.We found a strong relationship between tadpole development and nutrient excretion, demonstrating that ontological changes impact tadpole‐mediated nutrient cycling in wetland habitats. Further, the interplay between population‐level tadpole excretion and wetland hydrologic conditions increased ambient and concentrations by 56 and 14 times, respectively, compared to adjacent wetlands without tadpoles. Within our mesocosm study, microbes decreased extracellular enzyme production associated with nitrogen acquisition in response to the presence of tadpole‐derived nitrogen. In addition to microbial metabolic responses, tadpole presence enhanced litter breakdown in both mesocosms and wetlands by 7% and 12%, respectively, in comparison to reference conditions.These results provide evidence for the functional and biogeochemical role of tadpole aggregations in wetland habitats, with important implications for ecosystem processes, biodiversity conservation, and ecosystem management. 

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3. Stable isotope values of consumers, producers, and organic matter in the Shark River Slough and Taylor Slough, Everglades National Park (FCE LTER), Florida, USA, 2019 – ongoing

   https://doi.org/10.6073/pasta/da36c97eccd5461ba32eecce23a53892  

   Rezek, Ryan (January 2024, Environmental Data Initiative)

   {"Abstract":["Wetland food webs have often been characterized as detrital-based ‘brown’ energy pyramids, whereas the relative role of autotrophic (‘green’) vs. microbial (‘brown’) energy sources falls along a continuum set by physical drivers, as well as autochthonous and allochthonous inputs (Moore et al. 2004; Evans-White & Halvorson 2017) that change with ecosystem development (Schmitz et al. 2006). In the Florida Coastal Everglades (FCE), metabolic imbalances, including the collapse of calcareous periphyton mats, begin with a loss of foundation species primary production and legacy organic matter (Gaiser et al. 2006). This process likely enhances heterotrophic microbial productivity (Schulte 2016) and the supply of detrital energy to consumers by changing bioavailable and recalcitrant carbon supplies (Baggett et al. 2013). A shift from complex periphyton communities to transient planktonic communities under elevated P exposure reduces habitat structure and animal refuges but increases ‘green’ energy supplies and edibility (Trexler et al. 2015; Naja et al. 2017). Multiple sites (n=9) within the FCE were selected to document changes in coastal food webs as a result of eutrophication and increasing hydrologic variability. The project began in 2019 and is currently ongoing.\n \n References:\n Baggett, L. P., Heck, K. L., Frankovich, T. A., Armitage, A. R., & Fourqurean, J. W. (2013). Stoichiometry, growth, and fecundity responses to nutrient enrichment by invertebrate grazers in sub-tropical turtle grass (Thalassia testudinum) meadows. Marine biology, 160, 169-180.\n Evans-White, M. A., and H. M. Halvorson. 2017. Comparing the Ecological Stoichiometry in Green and Brown Food Webs – A Review and Meta-analysis of Freshwater Food Webs. Frontiers in Microbiology 8:1184. \n Gaiser, E. E., Childers, D. L., Jones, R. D., Richards, J. H., Scinto, L. J., & Trexler, J. C. (2006). Periphyton responses to eutrophication in the Florida Everglades: cross‐system patterns of structural and compositional change. Limnology and Oceanography, 51(1part2), 617-630.\n Moore, J. C., E. L. Berlow, D. C. Coleman, P. C. Ruiter, Q. Dong, A. Hastings, N. C. Johnson, K. S. McCann, K. Melville, P. J. Morin, K. Nadelhoffer, A. D. Rosemond, D. M. Post, J. L. Sabo, K. M. Scow, M. J. Vanni, and D. H. Wall. 2004. Detritus, trophic dynamics and biodiversity: Detritus, trophic dynamics and biodiversity. Ecology Letters 7:584–600. \n Naja, M., Childers, D. L., & Gaiser, E. E. (2017). Water quality implications of hydrologic restoration alternatives in the Florida Everglades, United States. Restoration Ecology, 25, S48-S58.\n Schmitz, O. J., Kalies, E. L., & Booth, M. G. (2006). Alternative dynamic regimes and trophic control of plant succession. Ecosystems, 9, 659-672.\n Schulte, Nicholas O., "Controls on Benthic Microbial Community Structure and Assembly in a Karstic Coastal Wetland" (2016). FIU Electronic Theses and Dissertations. 2447. 10.25148/etd.FIDC000233\n Trexler, J. C., Gaiser, E. E., Kominoski, J. S., & Sanchez, J. (2015). The role of periphyton mats in consumer community structure and function in calcareous wetlands: lessons from the Everglades. Microbiology of the everglades ecosystem, 155-179."]} 

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4. Evolutionary history drives aspects of stoichiometric niche variation and functional effects within a guild

   https://doi.org/10.1002/ecy.3100  

   Atkinson, Carla L.; van Ee, Brian C.; Pfeiffer, J. (January 2020, Ecology)

   Functional traits are characteristics of an organism that represent how it interacts with its environment and can influence the structure and function of ecosystems. Ecological stoichiometry provides a framework to understand ecosystem structure and function by modeling the coupled flow of elements (e.g. carbon [C], nitrogen [N], phosphorus [P]) between consumers and their environment. Animals tend to be homeostatic in their nutrient requirements and preferentially sequester the element in shortest supply relative to demand, and release relatively more of the element in excess. Tissue stoichiometry is an important functional trait that allows for predictions among the elemental composition of animals, their diet, and their waste products, with important effects on the cycling and availability of nutrients in ecosystems. Here we examined the tissue stoichiometric niches (C:N:P) and nutrient recycling stoichiometries (N:P) of several filter‐feeding freshwater mussels in the subfamily Ambleminae. Despite occupying the same functional‐feeding group and being restricted to a single subfamily‐level radiation, we found that species occupied distinct stoichiometric niches and that these niches varied, in part, as a function of their evolutionary history. The relationship between phylogenetic divergence and functional divergence suggests that evolutionary processes may be shaping niche complementarity and resource partitioning. Tissue and excretion stoichiometry were negatively correlated as predicted by stoichiometric theory. When scaled to the community, higher species richness and phylogenetic diversity resulted in greater functional evenness and reduced functional dispersion. Filter‐feeding bivalves are an ecologically important guild in freshwater ecosystems globally, and our study provides a more nuanced view of the stoichiometric niches and ecological functions performed by this phylogenetically and ecologically diverse assemblage. 

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5. Soil nutrients cause threefold increase in pathogen and herbivore impacts on grassland plant biomass

   https://doi.org/10.1111/1365-2745.14111  

   Zaret, Max; Kinkel, Linda; Borer, Elizabeth T.; Seabloom, Eric W. (August 2023, Journal of Ecology)

   Abstract A combination of theory and experiments predicts that increasing soil nutrients will modify herbivore and microbial impacts on ecosystem carbon cycling.However, few studies of herbivores and soil nutrients have measured both ecosystem carbon fluxes and carbon pools. Even more rare are studies manipulating microbes and nutrients that look at ecosystem carbon cycling responses.We added nutrients to a long‐term, experiment manipulating foliar fungi, soil fungi, mammalian herbivores and arthropods in a low fertility grassland. We measured gross primary production (GPP), ecosystem respiration (ER), net ecosystem exchange (NEE) and plant biomass throughout the growing season to determine how nutrients modify consumer impacts on ecosystem carbon cycling.Nutrient addition increased above‐ground biomass and GPP, but not ER, resulting in an increase in ecosystem carbon uptake rate. Reducing foliar fungi and arthropods increased plant biomass. Nutrients amplified consumer effects on plant biomass, such that arthropods and foliar fungi had a threefold larger impact on above‐ground biomass in fertilized plots.Synthesis. Our work demonstrates that throughout the growing season soil resources modify carbon uptake rates as well as animal and fungal impacts on plant biomass production. Taken together, ongoing nutrient pollution may increase ecosystem carbon uptake and drive fungi and herbivores to have larger impacts on plant biomass production. 

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