Recycling and Burial of Biogenic Silica in an Open Margin Oxygen Minimum Zone

Abstract

An extensive data set of biogenic silica (BSi) fluxes is presented for the Peruvian oxygen minimum zone (OMZ) at 11°S and 12°S. Each transect extends from the shelf to the upper slope (∼1,000 m) and dissects the permanently anoxic waters between ∼200 and 500 m water depth. BSi burial (2,100 mmol m−2 yr−1) and recycling fluxes (3,300 mmol m−2 yr−1) were highest on the shelf with mean preservation efficiencies (34% ± 15%) that exceed the global mean of 10%–20%. BSi preservation was highest on the inner shelf (up to 56%), decreasing to 7% and 12% under anoxic waters and below the OMZ, respectively. The data suggest that the main control on BSi preservation is the rate at which reactive BSi is transported away from undersaturated surface sediments by burial and bioturbation to the underlying saturated sediment layers where BSi dissolution is thermodynamically and/or kinetically inhibited. BSi burial across the entire Peruvian margin between 3°S to 15°S and down to 1,000 m water depth is estimated to be 0.1–0.2 Tmol yr−1; equivalent to 2%–7% of total burial on continental margins. Existing global data permit a simple relationship between BSi rain rate to the seafloor and the accumulation of unaltered BSi, giving the possibility to reconstruct rain rates and primary production from the sediment archive in addition to benthic Si turnover in global models.

Active Silica Diagenesis in the Deepest Hadal Trench Sediments

“…Therefore, the relatively low Si turnover rates at MBR05 could be explained by limiting amounts of Al and Fe oxide-rich detrital phases, as indicated by lowest detrital fraction at this site compared to the other two bSiO 2 -bearing cores (Table S6 in Supporting Information S1). The negative correlation between asymptotic DSi values and the ratio of detrital fraction to bSiO 2 in a variety of marine environments highlights the potential important role of lithogenic materials in promoting production of secondary authigenic aluminosilicates (Dale et al, 2021;Dixit & Van Cappellen, 2003).…”

“…Yet, bSiO 2 dissolution is often accompanied by the formation of authigenic aluminosilicates (i.e., reverse weathering), thereby potentially involving in atmospheric CO 2 levels over geological timescales (Dunlea et al., 2017; Michalopoulos & Aller, 1995; Rahman et al., 2016). Unraveling the fate of bSiO 2 (recycling vs. preservation) in the sediments represents an important component of the marine Si budget, thereby contributing to understanding the cycles of other pertinent elements, such as carbon (Dale et al., 2021). While the importance of silica diagenesis in balancing the marine Si cycle has been recognized and studied mostly in estuarine and continental margin environments, very few data exist in deep‐sea settings which comprise the majority of the seafloor area.…”

Benthic Macrofauna Community Bioirrigation Potential (BIPc): Regional Map and Utility Validation for the South-Western Baltic Sea

“…Suitable data on dissolved nutrients fluxes at the sediment–water interface and measured irrigation rates, which could be effectively used to validate the utility of bioirrigation indices, are scarcely available. Published global estimates, such as those based on relationships between bottom water oxygen and nitrogen loss [ 46 ], fluxes of phosphorus [ 47 ] and biogenic silica [ 48 ] appeared to be too coarse in spatial resolution when compared to our investigation. Apart from negligible sampling size, the weak relationship between estimated BIPc values in this study and irrigation volumes from Powilleit and Forster [ 43 ] (based on a handful of stations) could be associated with the poor performance of the index, or also with experimental artefacts arising during the measurements.…”

From biogenic silica and organic matter to authigenic clays and dolomite: Insights from Messinian (upper Miocene) sediments of the Northern Mediterranean

“…However, growing evidence from both modern and ancient sedimentary environments suggests that organic‐rich and oxygen‐poor conditions can be detrimental for the preservation of biogenic silica and even lithogenic silica, casting doubt on the general attribution of diatomaceous deposits to the establishment of anoxia (e.g. Hiebert & Bennett, 1992; Spagnoli & Bergamini, 1997; Souchu et al ., 1998; Belias et al ., 2007; Villnäs et al ., 2012; Abe et al ., 2014; Ekeroth et al ., 2016; Lehtimäki et al ., 2016; Siipola et al ., 2016; Huggett et al ., 2017; Petranich et al ., 2018; Dale et al ., 2020). In particular, under anoxic conditions, bacterially‐mediated anaerobic degradation of organic matter plays a critical role in modulating the pH of pore waters, a fundamental parameter for biogenic silica preservation (e.g.…”