[P003] Poster

12:10 PM - 1:00 PM JST(3:10 AM - 4:00 AM UTC)

[P02-231] Potential competition for silicic acid between marine diatoms and cyanobacteria

○Takeshi Ikeda^1,2, Touwa Moriki¹, Akio Kuroda¹ (1. Hiroshima Univ. (Japan), 2. JST PRESTO (Japan))

Keywords:

Biomineralization,Cyanobacteria,Diatoms,Silica,Silicon cycle

Silicon (Si), the second most abundant element in the Earth's crust after oxygen, is an important mineral for certain organisms. The oxidized form of silicon, silicon dioxide or silica (SiO₂), is the primary building material in the skeletal structures of diatoms, radiolarians, and siliceous sponges. Silica is also utilized by some higher plants (e.g., rice and horsetail) to alleviate biotic and abiotic stresses. In all these organisms, silicon is taken up from the surroundings as soluble silicic acid (Si[OH]₄), a biologically available form of silicon in nature. Silicic acid is then polymerized and deposited as insoluble silica through a biological process called biosilicification (silica biomineralization).
The global silicon cycle is closely related to the carbon cycle, because silicic acid is an essential nutrient for the growth of diatoms, which are major primary producers in the ocean. Marine diatoms contribute to up to 20% of global CO₂ fixation, and their silica frustules serve as a ballast to enhance downward fluxes of the synthesized organic carbon from the surface ocean to the depths, thus contributing to the sequestration of CO₂ from the atmosphere.
Although previously unrecognized, marine cyanobacteria have recently been reported to produce silica from silicic acid, suggesting their involvement in the silicon cycle. In this study, we investigated the potential competition for silicic acid between marine diatoms and cyanobacteria.