Silicic acid limitation drives bloom termination and potential carbon sequestration in an Arctic bloom

• Published in: Scientific Reports
• Main Authors: Krause, Jeffrey W., Schulz, Isabelle K., Rowe, Katherine A., Dobbins, William, Winding, Mie H.S., Sejr, Mikael K., Duarte, Carlos M., Agustí, Susana
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: Arctic; Arctic Ocean; Atlantic Arctic; Atlantic-Arctic; Subarctic
• Online Access: https://pure.au.dk/portal/da/publications/silicic-acid-limitation-drives-bloom-termination-and-potential-carbon-sequestration-in-an-arctic-bloom(297c69b3-e9bd-4fbf-b384-fec0b2151755).html; https://doi.org/10.1038/s41598-019-44587-4; http://www.scopus.com/inward/record.url?scp=85066463207&partnerID=8YFLogxK

The spring diatom bloom in the Arctic Ocean accounts for significant annual primary production leading to the most rapid annual drawdown of water-column pCO 2 . Late-winter waters in the Atlantic Arctic & Subarctic Provinces (AASP) have lower silicic acid concentrations than nitrate, which suggests diatom blooms may deplete Si before N. Here we test a facet of the hypothesis that silicic acid limitation terminates the spring diatom bloom in the AASP and the sinking of the senescent and dead diatoms helps drive carbon sequestration. During a 6-week study, diatoms bloomed and progressively consumed silicic acid to where it limited their growth. The onset of growth limitation was concurrent with the minimum pCO 2 in the surface waters and increases in both the proportion of dead diatoms and the diatom assemblage sedimentation rate. Data reanalysis within the AASP shows a highly significant and positive correlation between silicic acid and pCO 2 in the surface waters, but no significant relationship with nitrate and pCO 2 was observed unless data were smoothed. Therefore, understanding the future of the AASP spring diatom bloom requires models that explicitly consider changes in silicic acid supply as a driver of this process.