Silica Use Through Time: Macroevolutionary Change in the Morphology of the Diatom Fustule

Abstract

Diatoms have evolved an obligate requirement for silica for their ornamented cell wall. Diatom productivity and subsequent burial of their siliceous remains on the ocean floor is a major control on the marine silica cycle. The ecological success of the diatoms over the Mesozoic and Cenozoic is associated with biogeographic shifts in siliceous sponges, decreasing silicification in the radiolarians, and a global decrease in oceanic silicic acid concentrations. We review what is known about the evolutionary advantages of the silica frustule and how selection pressures, including decreasing silicic acid concentrations, changes in growth limiting nutrients other than Si, CO₂, irradiance, predation and viral pressures have shaped the morphology of the frustule over the Mesozoic and Cenozoic.

Keywords:

• biomineralization
• diatom
• macroevolution
• silicon
• silicic acid

We thank the reviewer for their helpful comments, Jim Ehrman and Mount Allison's Digital Microscopy Facility for their help with the SEMs, and Andrew Irwin for help with Fig. 2 and constructive comments. ZVF was supported by NSERC, CFI, NBIF and Mount Allison University. BK was supported by the PlanktonTech Helmholtz Virtual Institute and Harvard University.