Nutrient content and stoichiometry of pelagic Sargassum reflects increasing nitrogen availability in the Atlantic Basin

The pelagic brown macroalgae Sargassum spp. have grown for centuries in oligotrophic waters of the North Atlantic Ocean supported by natural nutrient sources, such as excretions from associated fishes and invertebrates, upwelling, and N(2) fixation. Using a unique historical baseline, we show that s...

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Bibliographic Details
Published in:Nature Communications
Main Authors: Lapointe, B. E., Brewton, R. A., Herren, L. W., Wang, M., Hu, C., McGillicuddy, D. J., Lindell, S., Hernandez, F. J., Morton, P. L.
Format: Text
Language:English
Published: Nature Publishing Group UK 2021
Subjects:
Article
North Atlantic
Online Access:http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8144625/
http://www.ncbi.nlm.nih.gov/pubmed/34031385
https://doi.org/10.1038/s41467-021-23135-7
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Summary:The pelagic brown macroalgae Sargassum spp. have grown for centuries in oligotrophic waters of the North Atlantic Ocean supported by natural nutrient sources, such as excretions from associated fishes and invertebrates, upwelling, and N(2) fixation. Using a unique historical baseline, we show that since the 1980s the tissue %N of Sargassum spp. has increased by 35%, while %P has decreased by 44%, resulting in a 111% increase in the N:P ratio (13:1 to 28:1) and increased P limitation. The highest %N and δ(15)N values occurred in coastal waters influenced by N-rich terrestrial runoff, while lower C:N and C:P ratios occurred in winter and spring during peak river discharges. These findings suggest that increased N availability is supporting blooms of Sargassum and turning a critical nursery habitat into harmful algal blooms with catastrophic impacts on coastal ecosystems, economies, and human health.

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