An article co-authored by Zahra Akbarzadeh, former ERG PhD student Taylor Maavara, Stephanie Slowinski and Philippe Van Cappellen, titled “Effects of Damming on River Nitrogen Fluxes: A Global Analysis” published in the journal Global Biogeochemical Cycles in 2019 was in the top 10 cited articles in Global Biogeochemical Cycles in the 2017-2021 5-year publication period.
The article evaluated the impact of dam reservoirs on riverine nitrogen (N) loads to coastal zones at the global-scale by implementing a reservoir nitrogen mass balance model into a global-scale, spatially explicit model of riverine N loads to the reservoirs and riverine N loads to coastal zones. N is an important (co-)limiting nutrient which controls algal growth, especially in coastal zones. Dam reservoirs modify both the hydrology and biogeochemical cycling of N in rivers by increasing the water residence time in that part of the river which promotes intensified biogeochemical cycling of N. The key findings of the study were: (1) riverine N loads were reduced by reservoirs because the loss of N via the combination of the denitrification and burial fluxes was higher than the addition of N to the reservoir via the N fixation flux; (2) the largest changes in the in-reservoir N fixation, N burial, and denitrification fluxes in the coming decades are predicted to happen in Asia; and (3) dam reservoirs increase riverine N loads more than riverine phosphorus (P) loads (i.e., increase riverine N:P ratios) due to in-reservoir N fixation, which reduces the degree of N limitation, making P the more important limiting nutrient for controlling algal growth, in downstream water bodies.
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