Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Journal of Geophysical Research: Biogeosciences
Heterotrophic aquatic bacteria require carbon and nutrients to survive, and consequently, remove dissolved nutrients and organic matter from streams – acting as a form of water filter. While this process is well understood, it is less certain how the balance of nutrients and organic matter, as well as variation in organic matter composition, impacts the efficiency of nutrient removal by heterotrophic bacteria.
Peñarroya et al. [2024] investigate the ability of microbes to remove nitrate, a major component of fertilizers that may cause water quality issues*.* The study was conducted in a series of Mediterranean headwater streams representing a range of carbon and nutrient stream water concentrations. The researchers found that the ratio of dissolved organic carbon to nitrate, as well as the ratio of nitrate to soluble and more reactive forms of phosphate, are strong indicators of the rate of nitrate removal from streams, with soluble phosphate acting as major limiting factor of this process.
Carbon-Nutrient ratios (Carbon:Nitrogen:Phosphorous) of the samples were normalized to that of typical freshwater bacterial plankton bacteria to highlight possible deficiencies in nutrient availability, with results indicating a predominant nutrient limitation at most sites, supporting the hypothesis that nutrient removal rates are dependent on prevailing DOC:nutrient ratios and demand for certain nutrients by microbes. Credit:Peñarroya et al. [2024], Figure 8
The study results show that not only does the relative amount of dissolved organic matter affect nitrate removal, but the type of organic matter is important, with the increased presence of less complex and bio-available forms of organic matter encouraging nitrate uptake and removal by stream microbes. These findings further deepen our current understanding of nutrient interactions in aquatic ecosystems and their consequences for water quality, carbon and nutrient cycling, and ecosystem dynamics in a changing world.
Citation: Peñarroya, X., Catalán, N., Freixa, A., Lupon, A., Triadó-Margarit, X., Martí, E., et al. (2024). Organic matter composition and water stoichiometry are main drivers of heterotrophic nitrate uptake in Mediterranean headwater streams. Journal of Geophysical Research: Biogeosciences*, 129, e2024JG008346.*https://doi.org/10.1029/2024JG008346
—Kyle Boodoo, Early Career Editorial Fellow, JGR: Biogeosciences; and Suzanne Tank, Associate Editor, JGR: Biogeosciences
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