Impact Of Growth Stress On Diatom BSiO2 Structure And Recycling

The silicic acid availability determines the occurrence of diatom bloom, and as diatoms are main vessels of the carbon to the deep ocean, influences also the biological pump of carbon and its variability. Remineralization of diatom frustules in the surface layer is an important source of silicic acid. Despite the importance of this process, dissolution is still poorly represented: while it has long been recognized that dissolution is a two-steps process, the community generally uses a simple exponential equation. To ameliorate this representation we tried to understand the mechanisms involved by using long term experiments on fresh diatom. Impact of external factors on bSiO2 dissolution have been studied for many years but silicification is overall a biological process. diatom silicification is sensitive to stresses encountered during growth in most oceanic areas like nutrients or light limitations, and like grazing. By monitoring the dissolution of diatom frustules formed under different nutrient conditions, we had 2 objectives. We expected to better understand the mechanisms involved in the 2-steps dissolution and secondly, we expected to address the impact of nutrient limitation on bSiO2 dissolution. Our results suggested that two different biogenic silica phases coexist in the frustule. These two phases have different dissolution rate constants, and both are affected by nutrient limitation. Moreover the proportion of each phase that constitute the frustule also changes when diatoms have grown under different nutrient limitations. Overall, nutrient limitations tested in this study, tend to increase the preservation of the biogenic silica formed.