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1. Quantifying Nutrient Budgets for Sustainable Nutrient Management

   https://doi.org/10.1029/2018GB006060  

   Zhang, X.; Davidson, E. A.; Zou, T.; Lassaletta, L.; Quan, Z.; Li, T.; Zhang, W. (March 2020, Global Biogeochemical Cycles)
2. Stochastic nutrient-plankton models

   https://doi.org/10.1016/j.jde.2023.08.017  

   Hening, Alexandru; Hieu, Nguyen Trong; Nguyen, Dang Hai; Nguyen, Nhu Ngoc (December 2023, Journal of Differential Equations)
3. 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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4. Limited progress in nutrient pollution in the U.S. caused by spatially persistent nutrient sources

   https://doi.org/10.1371/journal.pone.0258952  

   Frei, Rebecca J.; Lawson, Gabriella M.; Norris, Adam J.; Cano, Gabriel; Vargas, Maria Camila; Kujanpää, Elizabeth; Hopkins, Austin; Brown, Brian; Sabo, Robert; Brahney, Janice; et al (November 2021, PLOS ONE)

   Toor, Gurpal S. (Ed.)

   Human agriculture, wastewater, and use of fossil fuels have saturated ecosystems with nitrogen and phosphorus, threatening biodiversity and human water security at a global scale. Despite efforts to reduce nutrient pollution, carbon and nutrient concentrations have increased or remained high in many regions. Here, we applied a new ecohydrological framework to ~12,000 water samples collected by the U.S. Environmental Protection Agency from streams and lakes across the contiguous U.S. to identify spatial and temporal patterns in nutrient concentrations and leverage (an indicator of flux). For the contiguous U.S. and within ecoregions, we quantified trends for sites sampled repeatedly from 2000 to 2019, the persistence of spatial patterns over that period, and the patch size of nutrient sources and sinks. While we observed various temporal trends across ecoregions, the spatial patterns of nutrient and carbon concentrations in streams were persistent across and within ecoregions, potentially because of historical nutrient legacies, consistent nutrient sources, and inherent differences in nutrient removal capacity for various ecosystems. Watersheds showed strong critical source area dynamics in that 2–8% of the land area accounted for 75% of the estimated flux. Variability in nutrient contribution was greatest in catchments smaller than 250 km 2 for most parameters. An ensemble of four machine learning models confirmed previously observed relationships between nutrient concentrations and a combination of land use and land cover, demonstrating how human activity and inherent nutrient removal capacity interactively determine nutrient balance. These findings suggest that targeted nutrient interventions in a small portion of the landscape could substantially improve water quality at continental scales. We recommend a dual approach of first prioritizing the reduction of nutrient inputs in catchments that exert disproportionate influence on downstream water chemistry, and second, enhancing nutrient removal capacity by restoring hydrological connectivity both laterally and vertically in stream networks. 

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5. Bryospheres in oligotrophic headwater streams provide nutrient-dense habitats and dominate stream nutrient cycling

   https://doi.org/10.1086/733067  

   Steele, Jessee_J B; Thellman, Audrey N; Vought, Olivia K; Rosi, Emma J; Wooster, Tammy; Solomon, Christopher T; Bernhardt, Emily S (December 2024, Freshwater Science)

   Stream bryophytes (mosses and liverworts) are widely recognized as important macroinvertebrate habitats, but their overall role in the stream ecosystem, particularly in nutrient cycling, remains understudied. Hubbard Brook Experimental Forest in New Hampshire, USA, contains some of the most extensively researched streams in the world, yet few studies mention their bryophytes. Perhaps this is because early estimates place bryophyte coverage in these streams at an insignificant 2%. However, data from 2019 show that contemporary coverage ranges from 4 to 40% among streams. To investigate how stream bryophyte cover may be changing over time and influencing stream nutrient stocks, we conducted field surveys, measured the mass of organic and inorganic bryophyte contents, and quantified nutrient uptake with bottle incubations of bryophyte mats. This study marks a novel attempt to map stream bryophyte coverage with estimates of C, P, and N stocks and fluxes. From our 2022 field surveys, we found that median bryophyte coverage varied across streams in the same catchment (0–41.4%) and shifted from just 3 y prior. We estimate that these bryophyte mats stored between 14 and 414 g of organic matter per m2 of stream in the form of live biomass and captured particulates. Within 12 h of light incubation, 35 out of 36 bryophyte clump samples sorbed peak historical water-column concentrations of PO43– as measured in the Hubbard Brook stream chemistry record. In Bear Brook, our scaled estimate of bryophyte mat NO3– uptake (2.3 g N/y) constitutes a substantial portion of previously estimated whole-stream NO3– uptake (12 g N/y). Cumulatively, our data demonstrate that bryophytes and their associated mineral substrates and biota—known as the bryosphere—are crucial in facilitating headwater stream nutrient cycling. These bryospheres may contribute significantly to interannual variability in stream nutrient concentrations within nutrient-poor streams, especially in climate-sensitive regions. 

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