Biogenic silica dissolution in seawater — in vitro chemical kinetics
62
Citation
60
Reference
10
Related Paper
Citation Trend
Keywords:
Frustule
Biogenic silica
Saturation (graph theory)
Dissolved silica
Diatom production is mainly supported by the dissolution of biogenic silica (bSiO2) within the first 200 meters of the water column. The upper oceanic layer is enriched in dissolved and/or colloidal organic matter, such as exopolymeric polysaccharides (EPS) and transparent exopolymeric particles (TEP) excreted by phytoplankton in large amounts, especially at the end of a bloom. In this study we explored for the first time the direct influence of TEP-enriched diatom excretions on bSiO2 dissolution. Twelve dissolution experiments on fresh and fossil diatom frustules were carried out on seawater containing different concentrations of TEP extracted from diatom cultures. Fresh diatom frustules were cleaned from the organic matter by low ash temperature, and fossil diatoms were made from diatomite powder. Results confirm that newly formed bSiO2 dissolved at a faster rate than fossil diatoms due to a lower aluminium (Al) content. Diatom excretions have no effect on the dissolution of the newly formed bSiO2 from Chaetoceros neogracile. Reversely, the diatomite specific dissolution rate constant and solubility of the bSiO2 were positively correlated to TEP concentrations, suggesting that diatom excretion may provide an alternative source of dSi when limitations arise.
Biogenic silica
Frustule
Cite
Citations (9)
Biogenic silica
Dissolved silica
Paleolimnology
Sediment core
Frustule
Cite
Citations (76)
Frustule
Biogenic silica
Cite
Citations (26)
Oxygen isotope values of diatom silica ( δ 18 O diatom ) are increasingly used as paleoclimate proxies; however, the magnitude and timing of post‐mortem alteration of δ 18 O diatom values has been unclear. In freshwater diatom silica from a human‐made pond in northern New Mexico, post‐mortem alteration of δ 18 O diatom values occurs within one year of sediment burial. Diatom silica collected antemortem has an average δ 18 O diatom value of 21.5‰ (VSMOW, σ = 1.3, n = 23), whereas diatom silica from two sediment cores from the same freshwater environment records significantly higher δ 18 O diatom values (28.9‰, σ = 0.8, n = 13). The difference in ante‐ and post‐mortem δ 18 O diatom values indicate post‐mortem alteration of diatom silica oxygen that results in a >7‰ increase in δ 18 O values. This study demonstrates that δ 18 O diatom values reach mature values within 0.5 years of frustule death. Initial diatom δ 18 O values that record growing conditions are rapidly overwritten during silica maturation, and the mature diatom δ 18 O values approach isotopic equilibrium for quartz‐water. The rapid post‐mortem alteration of diatom δ 18 O values explains much of the disparate data regarding silica‐water fractionation for diatom silica and has a profound effect on the use of diatom silica δ 18 O values as a paleoclimate proxy in lacustrine and marine environments.
Frustule
Biogenic silica
Dissolved silica
Cite
Citations (37)
Summary Diatom populations and silica concentrations were monitored at frequent intervals in the shallow, eutrophic Loch Leven over a 27‐day period (October 1972) and the influences of the inflows, outflow and the sediment were assessed. Changes in dissolved and particulate silica are accounted for by incorporating the results into a silica budget. During this period processes affecting silica within the loch were more important than those outside. The incorporation of diatom frustules into the sediments and the release of dissolved silica from the sediments appeared to be of particular importance. Evidence suggests that dissolution of the frustules of some planktonic diatom species was also important.
Biogenic silica
Dissolved silica
Cite
Citations (48)
Frustule
Biogenic silica
Marine ecosystem
Cite
Citations (5)
Abstract Diatoms are a major group of phytoplankton that account for approximately 40% of the ocean carbon fixation and the vast majority of biogenic silica production through the construction of their cell walls (termed frustules). These frustules accumulate and are partially preserved in the ocean sediments. Diatom growth and nutrient utilization in high‐nitrate, low‐chlorophyll regions of the world’s oceans are mostly regulated by iron availability. Diatoms acclimate to iron limitation by decreasing cell size. The associated increase in surface area‐to‐volume ratio and decrease in diffusive boundary layer thickness may improve nutrient uptake kinetics. In parallel, cellular silicon (Si) contents are elevated in iron‐limited diatoms relative to nitrogen (N) and carbon (C). Variations in degree of silicification and nutritional requirements of iron‐limited diatoms have been hypothesized to account for higher cellular Si and/or lower cellular N and C, respectively. However, in some diatoms, frustule silicification does not significantly change when cells are iron‐limited. Instead, changes in the Si‐containing valve surface area relative to volume within these diatoms is hypothesized to be responsible for the variations in the cellular Si : N and Si : C ratios. In particular, some examined iron‐limited pennate diatoms have reduced widths relative to their lengths (i.e. lower length‐normalized widths, LNW) compared to iron‐replete cells. In the pennate diatom Fragilariopsis kerguelensis , the mean LNWs of valves preserved in sediments throughout the Southern Ocean (a well‐characterized iron‐limited region) is positively correlated with satellite‐derived, climatological net primary productivity in the overlying waters. Because of the specific morphological changes in pennate diatom frustules in response to iron availability, the valve morphometerics (e.g. LNWs) can potentially be used as a diagnostic tool for iron‐limited diatom growth and relative changes in the Si : N (and Si : C) ratios in extant diatom assemblages as well as those preserved in the sediments.
Frustule
Biogenic silica
Carbon fibers
Cite
Citations (94)