Silicifiers are among the most important organisms on planet Earth. They are able to take advantage of the abundance of silicon (the second-most-abundant element in the Earth’s crust) to build silica structures, which can help for protection against predators, for motility, or for facilitating the penetration of light and nutrients. At the same time, silicifiers have a paramount impact on the cycling of silicon, carbon and other nutrients in marine waters.
The SILICAMICS transdisciplinary conference focuses on the marine realm, for which numerous unknowns still remain regarding the global marine silica cycle. Marine diatoms have dominated over siliceous sponges and radiolarians over the last 150 M years. Today diatoms play a key role in the trophic networks of the most productive coastal and open-ocean ecosystems, as well as in the biology-mediated transfer of CO2 from the surface to the ocean interior (i.e. the biological carbon pump). The physiology and biochemistry of biosilicification have been studied in diatoms and other silicifiers but many gaps remain regarding mechanisms, evolutionary significance, variations in response to environmental change and the impact of these processes on marine biogeochemistry. Moreover, benthic diatoms and their role in coastal ecosystems have been largely overlooked despite significant contributions to coastal primary production. Along the same vein, the roles of other siliceous organisms, such as benthic sponges, rhizaria and silicoflagellates in the silica cycle, are starting to be better constrained at a global scale.
In the last two decades, the genomes of several diatom species have been sequenced. Scientific programs (such as Tara Oceans and the Gordon and Betty Moore Foundation’s projects) have provided additional DNA sequence information from diatoms as well as from other silicifying organisms. Genomics data can now be exploited to address fundamental research questions about the role of different silicifiers in coastal and open-open ecosystems, and their controls on C, N, P, and Si biogeochemical cycles. The interactions between silicifiers and other organisms are starting to be elucidated at different spatial and temporal scales, and their impact on nutrient cycling and ecosystem functioning are now being addressed. It is an exciting time to study the biology of ocean silicification processes.