Silica Dynamics in Marine Phytoplankton Systems

Marine phytoplankton exert a profound control on the ocean’s silicon cycle through the uptake of dissolved silica and the formation of biogenic silica structures, notably the frustules of diatoms. Silicic acid (Si(OH)₄) in surface waters is consumed during frustule synthesis, linking silica availability to primary production and the biological carbon pump. Variations in silicic acid concentration, governed by ocean circulation, upwelling and remineralisation, ultimately influence the timing and magnitude of phytoplankton blooms and the export of organic carbon to the deep sea. Recent advances have revealed that, alongside diatoms, smaller phytoplankton groups—including picocyanobacteria and picoeukaryotes—can accumulate significant silica pools, challenging long-held paradigms. Biosilicification rates are modulated by nutrient co-limitation (for example iron or phosphate), ambient pH and temperature, and may vary with phylogenetic identity. The interplay of these factors determines the distribution of biogenic silica standing stocks, the efficiency of its export via sinking aggregates and the recycling of silica in the upper ocean. This dynamic system underpins global nutrient budgets and influences carbon sequestration, with practical implications for climate models and biogeochemical prediction.

Research from Nature Portfolio

Recent studies have demonstrated that termination of high-latitude diatom blooms is often driven by silicic acid limitation rather than nitrate depletion, with the onset of silica stress coinciding with enhanced diatom mortality and accelerated sedimentation. In Arctic spring blooms, the drawdown of silicic acid to limiting levels has been shown to control the timing of bloom decline and to promote the export of both senescent and dead cells, thereby coupling silica limitation directly to carbon sequestration. Analysis of surface pCO₂ dynamics reveals that silica availability exerts a primary control on bloom progression, highlighting the need for explicit representation of silicic acid supply in predictive models of polar ecosystems.

Silica Dynamics in Marine Phytoplankton Systems publication trend

The graph below shows the total number of articles in silica dynamics in marine phytoplankton systems across all publications each year (not limited to Nature Index journals).

Technical terms

Biogenic Silica (bSi): Silica incorporated into or produced by organisms, chiefly diatom frustules and other siliceous structures.

Dissolved Silica (dSi): Silicic acid and related dissolved forms of silica available for uptake by phytoplankton.

Frustule: The rigid, often ornamented cell wall of a diatom composed of biogenic silica.

Biosilicification: The biological process by which organisms take up dissolved silica and deposit it as structured silica.

Picophytoplankton: Photosynthetic planktonic organisms smaller than 2 µm, including picoeukaryotes and picocyanobacteria.

Nutrient Limitation: The state in which the scarcity of an essential nutrient, such as silicic acid, constrains phytoplankton growth.

References

1. Silicic acid limitation drives bloom termination and potential carbon sequestration in an Arctic bloom. Scientific Reports (2019).
2. A Large Silicon Pool in Small Picophytoplankton. Frontiers in Microbiology (2022).
3. A study of the influence of iron, phosphate, and silicate in Si uptake by two Synechococcus strains. Frontiers in Marine Science (2024).
4. Picophytoplankton is the main contributor to living carbon and biogenic silica stocks in the oligotrophic Eastern Indian Ocean. Frontiers in Marine Science (2024).
5. Biogenic silica accumulation in picoeukaryotes: Novel players in the marine silica cycle. Environmental Microbiology Reports (2023).