Sponge skeletons as an important sink of silicon in the global oceans

• Published in: Nature Geoscience
• Main Authors: Maldonado, Manuel, López-Acosta, María, Sitjà, Cèlia, García-Piug, Marta, Galobart, Cristina, Ercilla, Gemma, Leynaert, Aude
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2019
• Subjects: Biogeochemistry; Environmental sciences; Ocean sciences; Silicon; European Union; Horizon 2020; Deep-Sea Sponge Grounds Ecosystems of the North Atlantic: An integrated approach towards their preservation and sustainable exploitation; SponGES; Grant Agreement No 679849; Talberg; North Atlantic
• Online Access: https://zenodo.org/record/3381404; https://doi.org/10.1038/s41561-019-0430-7

Silicon (Si) is a pivotal element in the biogeochemical and ecological functioning of the ocean. The marine Si cycle is thought to be in internal equilibrium, but the recent discovery of Si entries through groundwater and glacial melting have increased the known Si inputs relative to the outputs in the global oceans. Known outputs are due to the burying of diatom skeletons or their conversion into authigenic clay by reverse weathering. Here we show that non-phototrophic organisms, such as sponges and radiolarians, also facilitate significant Si burial through their siliceous skeletons. Microscopic examination and diges- tion of sediments revealed that most burial occurs through sponge skeletons, which, being unusually resistant to dissolution, had passed unnoticed in the biogeochemical inventories of sediments. The preservation of sponge spicules in sediments was 45.2 ± 27.4%, but only 6.8 ± 10.1% for radiolarian testa and 8% for diatom frustules. Sponges lead to a global burial flux of 1.71 ± 1.61 TmolSi yr−1 and only 0.09 ± 0.05 TmolSi yr−1 occurs through radiolarians. Collectively, these two non-phototrophi- cally produced silicas increase the Si output of the ocean to 12.8 TmolSi yr−1, which accounts for a previously ignored sink that is necessary to adequately assess the global balance of the marine Si cycle. ACKNOWLEDGEMENTS: We thank the British Ocean Sediment Core Research Facility (BOSCORF-NOC) for providing access to cores 1, 12, 14 and 16. We also thank E. Kenchington, C. Campbell, K. Jarrett and J. Murillo (BIO) for making the data and sediment of cores 2 and 4 available. A. Ehrhold (IFREMER) is thanked for core 3, M. A. Mateo (CEAB) for core 7 and T. Whiteway (Australian Geosciences) for core 15. R. Ventosa and M. Abad are thanked for helping with the DSi autoanalyser determinations, B. Dursunkaya for helping with the digestion experiments and P. Talberg and L. Cross for providing strains of the Thalassiossira diatom. J. Krause is especially thanked for comments and insight on the manuscript. This ...