PT  - JOURNAL ARTICLE
AU  - María López-Acosta
AU  - Manuel Maldonado
AU  - Jacques Grall
AU  - Axel Ehrhold
AU  - Cèlia Sitjà
AU  - Cristina Galobart
AU  - Aude Leynaert
TI  - Sponge contribution to the silicon cycle of a diatom-rich shallow bay
AID  - 10.1101/2021.10.20.465147
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.10.20.465147
4099  - http://biorxiv.org/content/early/2021/10/21/2021.10.20.465147.short
4100  - http://biorxiv.org/content/early/2021/10/21/2021.10.20.465147.full
AB  - In coastal systems, planktonic and benthic silicifiers compete for the pool of dissolved silicon, a nutrient required to make their skeletons. The contribution of planktonic diatoms to the cycling of silicon in coastal systems is often well characterized, while that of benthic silicifiers such as sponges has rarely been quantified. Herein, silicon fluxes and stocks are quantified for the sponge fauna in the benthic communities of the Bay of Brest (France). A total of 45 siliceous sponge species living in the Bay account for a silicon standing stock of 1215 tons, while that of diatoms is only 27 tons. The silicon reservoir accumulated as sponge skeletons in the superficial sediments of the Bay rises to 1775 tons, while that of diatom skeletons is only 248 tons. These comparatively large stocks of sponge silicon were estimated to cycle two orders of magnitude slower than the diatom stocks. Sponge silicon stocks need years to decades to be renewed, while diatom turnover lasts only days. Although the sponge monitoring over the last 6 years indicates no major changes of the sponge stocks, our results do not allow to conclude if the silicon sponge budget of the Bay is at steady state, and potential scenarios are discussed. The findings buttress the idea that sponges and diatoms play contrasting roles in the marine silicon cycle. The budgets of these silicon major users need to be integrated and their connections revealed, if we aim to reach a full understanding of the silicon cycling in coastal ecosystems.Competing Interest StatementThe authors have declared no competing interest.