Simulated Global Coastal Ecosystem Responses to a Half-Century Increase in River Nitrogen Loads

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Journal Article

Coastal ecosystems are increasingly threatened by anthropogenic stressors such as harmful algal blooms and hypoxia through the combined effects of eutrophication and warming. As a major terrestrial nitrogen source to the ocean, rivers play a key role in shaping coastal nitrogen budgets and biogeochemical cycling. Combining an enhanced-resolution, global ocean biogeochemical model with temporally changing river inputs, we estimate that elevated river nitrogen loads alone resulted in a 5.8% increase (16.6 Tg) in the global coastal nitrogen inventory from 1961 to 2010, accompanied by increases in coastal net primary productivity (+4.6%) and benthic detrital flux (+7.3%). The ecosystems most sensitive to added nitrogen were those with long residence times and strong nitrogen limitation. While even enhanced-resolution global models remain limited in their capacity to resolve shelf-scale responses, these basic factors provide two relevant axes for frameworks assessing the comparative coastal ecosystem susceptibility to enhanced nitrogen loads, and the effectiveness of mitigation strategies.

Geophysical Research Letters
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Date Published
September 2021
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