Diatom populations in an upwelling environment decrease silica content to avoid growth limitation.

Area of Science:

• Marine biology
• Oceanography
• Biogeochemistry

Background:

• Diatoms are key primary producers in oceans, crucial for global carbon and silicon cycles.
• Their rapid growth is vital for marine ecosystems, especially in dynamic regions.
• Understanding diatom adaptive strategies is essential for predicting ocean productivity.

Purpose of the Study:

• To investigate diatom adaptive strategies to silicic acid stress off coastal California.
• To quantify the relationship between silicon concentration, silica production, and diatom growth rates.
• To assess the impact of these adaptations on community composition and biogeochemical cycles.

Main Methods:

• Utilized fluorescent dye to measure single-cell silica production rates.
• Measured silicification (silica per unit area) and growth rates in diatoms.
• Analyzed in situ silicic acid concentrations and their effects on different diatom taxa.

Main Results:

• Diatoms decrease silicification (shell thickness) to maintain growth rates under silicon limitation.
• This physiological response is consistent across taxa, but the degree of limitation varies.
• Silicon stress did not alter community composition or the contribution of specific taxa to silica production.

Conclusions:

• Diatom adaptation to silicon stress involves reduced frustule thickness, impacting cell density and biogeochemical cycles.
• This strategy presents an ecological tradeoff, increasing predation risk but maximizing cell abundance for resource pulses.
• These adaptations enhance diatom persistence in variable ocean habitats, supporting their role as primary producers.