Biogenic silica accumulation
| Biogenic silica accumulation (light–dark bottles) |
|---|
| Approach: change in BSi concentration in light vs. dark incubation bottles |
| Context: incubation, in situ and lab |
| Spatial scale: point sample |
| Temporal scale: hours to days |
| Units: µmol BSi L-1 d-1; (x)mol BSi cell-1 d-1 |
| Community captured: bulk or size-fractionated |
| Co-measurements: ambient [Si(OH)4], PAR, temperature |
Method Overview
Net biogenic silica (BSi) accumulation is measured as the change in BSi concentration in incubation bottles over time. Samples are incubated in both light and dark bottles; the difference between initial and final BSi concentrations in the light bottle reflects net BSi accumulation (gross production minus dissolution). In the dark bottle, the BSi change reflects only dissolution. Together, light and dark measurements can be used to estimate both gross BSi production and BSi dissolution rates. BSi concentration is typically measured by alkaline digestion (NaOH at 80°C) followed by colorimetric or ICP-OES determination of dissolved silicic acid.
Scale of measurement
The method integrates over the full incubation period rather than providing an instantaneous rate.
Data generated
Net BSi accumulation rate (µmol BSi L-1 d-1); combined with dark bottle dissolution rates, gross BSi production can be estimated. Useful as an independent complement to 32Si-based production measurements.
Units & currency
Units are µmol BSi L-1 d-1 or (x)mol BSi cell-1 d-1. The currency is biogenic Si.
Sample size
Typical samples are 0.5–2.3 L in volume.
Repositories & databases
Limitations
Bulk BSi measurements include both living cells and dead frustules (lithogenic contamination must also be subtracted), so rates normalized to BSi contain uncertainty. Non-steady state conditions during the incubation can cause the dissolution rate to change over time. Bottle effects may arise.
Example Applications & Protocols
Classic examples
Recent applications
- Latour et al. (2023) Characterisation of a Southern Ocean deep chlorophyll maximum: response of phytoplankton to light, iron, and manganese enrichment [1]
Common calculations/conversions
- Net BSi accumulation (µmol BSi L-1 d-1) = ([BSi]final − [BSi]initial) / incubation time (light bottle).
- BSi dissolution = ([BSi]initial − [BSi]final) / incubation time (dark bottle).
- Gross production ≈ net accumulation + dissolution.
References
- ↑ Latour, P., et al. (2023). Characterisation of a Southern Ocean deep chlorophyll maximum: response of phytoplankton to light, iron, and manganese enrichment. Limnology and Oceanography Letters, 9(2), 145–154. https://doi.org/10.1002/lol2.10366