Transparent Exopolymeric Particles (TEP) Selectively Increase Biogenic Silica Dissolution From Fossil Diatoms as Compared to Fresh Diatoms

Toullec, Jordan; Moriceau, Brivaëla

doi:10.3389/fmars.2018.00102

Cited by 9 publications

(2 citation statements)

References 60 publications

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“…4.1.1). Diatoms secrete transparent exopolymeric particles (TEP), which act like glue to hold aggregates together, leading to faster sinking of marine particles and a more efficient biological pump (Chen & Thornton, 2015;Toullec & Moriceau, 2018). TEP production also increases the C:N ratio (Kim et al, 2021;Passow, 2002).…”

Section: Biological Effects On Quantifying the Bcpmentioning

confidence: 99%

The Changing Biological Carbon Pump of the South Atlantic Ocean

Delaigue,

Sulpis,

Reichart

et al. 2024

Preprint

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Global marine anthropogenic CO2 inventories have traditionally emphasized the North Atlantic’s role in the carbon cycle, while Southern hemisphere processes are less understood. The South Subtropical Convergence (SSTC) in the South Atlantic, a juncture of distinct nutrient-rich waters, offers a valuable study area for discerning the potential impacts of climate change on the ocean’s biological carbon pump (Csoft). Using discrete observations from GLODAPv2.2022 and BGC-Argo at 40°S in the Atlantic Ocean, an increase in dissolved inorganic carbon (DIC) of +1.44 ± 0.11 μmol kg-1 yr-1 in surface waters was observed. While anthropogenic CO2 played a role, variations in the contribution of Csoft were observed. Discrepancies emerged in assessing Csoft based on the tracers employed: when using AOU, Csoft(AOU) recorded an increase of +0.20 ± 0.03 μmol kg‑1 yr-1, whereas, using nitrate as the reference, Csoft(NO3) displayed an increase of +0.85 ± 0.07 μmol kg-1 yr-1. Nonetheless, our observations at 40°S indicate a significant intensification of Csoft, which, scaled to the entire ocean, represents an additional 23% to 35% of organic carbon degradation within the water column. Key processes such as water mass composition shifts, changes in oxygenation, remineralization in the Southern Ocean, and the challenges they pose in accurately representing the evolving Csoft are discussed. These findings highlight that while global studies primarily attribute DIC increase to anthropogenic CO2, observations at 40°S reveal an intensified biological carbon pump, showing that regional DIC changes are more complex than previously thought and challenging the dominance of anthropogenic sources in global DIC change.

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Section: Biological Effects On Quantifying the Bcpmentioning

confidence: 99%

The Changing Biological Carbon Pump of the South Atlantic Ocean

Delaigue,

Sulpis,

Reichart

et al. 2024

Preprint

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“…This general pattern may also held at some point for diatom silica, since some experiments have suggested that dissolved protease from environmental bacteria appear to digest by enzymatic hydrolysis some of the proteins embedded in the silica matrix, accelerating the dissolution of the frustules (Roubeix et al, 2008). This effect would be different from the better known hydrolytic attack to the exopolysaccharides and other organic layers that externally cover the frustules of diatoms and that avoid a direct contact with the seawater that otherwise would cause their rapid dissolution (Bidle and Azam, 1999;Toullec and Moriceau, 2018). Such external organic covers have never been reported from sponge silica, despite most sponges having part of their spicules directly exposed to the seawater and despite those spicules not dissolving during the lifetime of the sponges.…”

Section: Dissolution Patterns and Their Causesmentioning

confidence: 99%

On the dissolution of sponge silica: Assessing variability and biogeochemical implications

et al. 2022

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The dissolution of the biogenic silica that constitutes the skeletons of silicifying organisms is an important mechanism for regenerating dissolved silicon in the ocean. The silica skeletons deposited to the seafloor after the organisms die keep dissolving until becoming definitively buried. The low dissolution rate of sponge skeletons compared to that of diatom skeletons favors their burial and makes sponges (Phylum Porifera) to function as important silicon sinks in the oceans. However, it remains poorly understood whether the large variety of siliceous skeletons existing in the Porifera involves similar variability in their dissolution rates, which would affect the general conceptualization of these organisms as silicon sinks. Herein we investigated kinetics of silica dissolution for major types of skeletons in the three siliceous lineages of Porifera, following standardized digestion conditions in 1% sodium carbonate with orbital agitation at 85°C. The results are compared with those of a previous study conducted under identical conditions, which considered diatom silica, sponge silica, and lithogenic silica. Unexpectedly, the silica of homoscleromorph sponges dissolved only a bit slower than that of freshly cultured diatoms and as fast as diatom earth. However, the rest of sponge skeletons were far more resistant, although with some differences: the isolated spicules of hexactinellid sponges dissolved slightly faster than when forming frameworks of fused spicules, being hexactinellid frameworks as resistant to dissolution as the silica of demosponges, irrespective of occurring in the form of isolated spicules or frameworks. The experiments also indicated that the complexation of sponge silica with aluminum and with chitin does not increase its resistance to dissolution. Because the rapidly-dissolving homoscleromorph sponges represent less than 1% of extant sponges, the sponge skeletons are still conceptualized as important silicon sinks due to their comparative resistance to dissolution. Yet, the turnover of silica into dissolved silicon will always be faster in environments dominated by hexactinellids with isolated spicules than in environments dominated by other hexactinellids and/or demosponges. We discuss whether the time required for a given silica type to completely dissolve in 1% sodium carbonate could be a predictor of its preservation ratio in marine sediments.

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