Biomodulation of Nitrogen Cycle in Suspended Sediment

Abstract

Biogeochemical experiments and modeling were coupled to investigate how nutrient leaching to aquatic ecosystems changes the dynamics of microbial community on suspended sediment and how these changes modulate the nitrogen cycle. Mineral suspensions amended with inorganic nitrogen (NH 4+ and NO 3−) and inoculated with native sedimentary microbial strains were tested in a settling column under continuous water quality measurements. Experiments were used to calibrate and validate a kinetic model that explicitly described the chemical adsorption on minerals, aqueous complexation, gas dissolution, microbial metabolism, necromass dynamics, and microbial competition for limiting substrates. Modeling revealed that the interactions between microbial functional groups were highly nonlinear and highly sensitive to changes in nutrient and dissolved oxygen concentrations, showing shifts in regimes where a functional group became prevalent over the others. Our results suggested that necromass dynamics played a major role in sustaining microbial growth in low nutrient conditions and had an important control over the N cycle. The reaction network and model structure presented in this study provide a tool to analyze and predict the long‐term nutrient dynamics of both natural and engineered aquatic ecosystems.

An Approach to Modeling Biofilm Growth During the Flocculation of Suspended Cohesive Sediments

“…Time variations of measured dissolved inorganic nitrogen (DIN) concentrations for suspended sediment concentrations (a) 0.1, (b) 0.2, and (c) 0.4 g/L, respectively (Tang & Maggi, ). For each suspended sediment concentration, seven kaolinite samples are prepared: (i) nutrient‐free and biomass‐free (NFBF) and (ii–vii) nutrient‐affected and biomass‐free (NABF) and nutrient‐affected and biomass‐affected (NABA) with initial nutrients 1.5, 3.0, and 6.0 mM, respectively.…”

“…We would like to thank the three anonymous reviewers for their valuable comments that greatly contributed to improving this manuscript. We also acknowledge the raw data on water quality in all experiments, which was published as supporting information in Tang and Maggi (, https://doi.org/10.1002/2017JG004165) and can be downloaded online (from https://agupubs.onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1002%2F2017JG004165&file=jgrg21007-sup-0003-supinfo.txt). This research was supported by the Open Research Fund of State Key Laboratory of Estuarine and Coastal Research of China (Grant SKLEC‐KF201811), the National Key R&D Program of China (Grant 2017YFC0405402), the National Natural Science Foundation of China (Grant 51339005), the Belt and Road Special Foundation of the State Key Laboratory of Hydrology‐Water Resources and Hydraulic Engineering of China (Grant 2018490911), and the Belgian Science Policy Office (BELSPO, Belgium) within the BRAIN.BE project INDI67 (Grant BR/143/A2/INDI67), and the JPI‐OCEANS Microplastics project WEATHER‐MIC (Grant BR/154/A1/WEATHER‐MIC).…”

“…Some predicted size classes are smaller than the median primary particle size, l p , especially the size of the first class under G = 96 s −1 . For NABF (Tang & Maggi, 2018). For each suspended sediment concentration, seven kaolinite samples are prepared: (i) nutrient-free and biomass-free (NFBF) and (ii-vii) nutrient-affected and biomass-free (NABF) and nutrient-affected and biomass-affected (NABA) with initial nutrients 1.5, 3.0, and 6.0 mM, respectively.…”

“…Recently, Tang and Maggi () have carried out a settling column experiment to determine the FSDs of nutrient and biomass‐affected kaolinite suspensions under shear dominant conditions. A biogeochemical model was later adopted by Tang and Maggi () to mimic the nitrogen cycle in suspended sediments. The purpose of our study is to predict the equilibrium or quasi‐equilibrium FSDs (rather than only the representative sizes of the FSDs) of cohesive sediments, including the processes of aggregation, breakage, and biomass growth, by using a quadrature‐based multiclass PBE and the observed FSDs and the measurements of time evolutions of nitrate and ammonia in Tang ()’s experiment.…”

Ammonia Emissions from Mudflats of River, Lake, and Sea

“…In lacustrine, riverine, and estuarine environments, both mineral and organic particulate matter and dissolved nutrients are deposited and accumulate to form mudflats . Nutrients can be adsorbed by the sediments and recycled through vegetation and microbial communities . Intensive studies have shown that successive flood/drain cycles, inherent to intertidal zones, can favor N 2 O release with the frequently changing aerobic/anaerobic status. ,− Recently, using a high-resolution map of NH 3 obtained from satellite observations, Van Damme et al also identified drying mudflats in the vicinity of Lake Natron in Tanzania as a previously unknown natural NH 3 source.…”