Tag Archive for: biogeochemistry

The TONGA mission

David Gonzalez Santana and Géraldine Sarthou from the Chibido team are on board the R/V Atalante in the South Pacific for the TONGA cruise (PIs Sophie Bonnet (MIO) and Cécile Guieu (LOV), + link on the CHIBIDO team website).

The objective of TONGA is to study the inputs of trace elements from shallow hydrothermal sources and their potential impact on biological productivity and the biological carbon pump.

Halfway through the cruise, they are on their way to the ultra-oligotrophic waters (their reference station) after having studied a shallow area (~ 200 m) particularly intense in terms of hydrothermal activity.

Then, the search of a second hydrothermal site is scheduled.

You can follow them on their Twitter account.

(C) Hubert Bataille/ IRD

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

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 digestion 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-phototrophically 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.


Maldonado, M., López-Acosta, M., Sitjà, C., García-Puig, M., Galobart, C., Ercilla, G., & Leynaert, A. (2019). Sponge skeletons as an important sink of silicon in the global oceans. Nature Geoscience. https://doi.org/10.1038/s41561-019-0430-7


Read the publication

Daniel Conley’s seminar (Lund University, Sweden) on April 29

On April 29th at 10am in room A215 (IUEM) we will welcome Daniel Conley from Lund University in Sweden who will present his work on the following theme:

Constraining variations in the global biogeochemical silica cycle through geologic time.

Summary of his presentation:

It is widely recognized that the emergence and expansion of silica biomineralization in the oceans has affected evolutionary competition for dissolved Si (DSi). This resulted in changes in the global biogeochemical cycles of silica, carbon (C) and other nutrients that regulate ocean productivity and ultimately climate. However, a series of very recent discoveries in geology and biology suggest that the first biological impacts on the global Si cycle were likely by prokaryotes during the Archean with further decreases in oceanic DSi with the evolution of widespread, large-scale skeletal biosilicification significantly earlier than the current paradigm. Our project interweaves geology and biology and will create new knowledge into the interactions between biosilicification in organisms and the environment and how these interactions have evolved through Earth’s history. Together, these geological and biological analyses will provide novel insights into the key events during periods of DSi drawdown, which reorganize the distribution of carbon and nutrients, changing energy flow and productivity in the biological communities of the ancient oceans.

Tag Archive for: biogeochemistry

Frédéric LE MOIGNE


Nicolas CASSAR

Tag Archive for: biogeochemistry