The silica cycle in the modern ocean
The silica cycle in the modern ocean
Abstract:
In the marine world, element Si is unique as it is required for the growth of diatoms and of some sponges, and utilized by radiolarians-rhizarians, silicoflagellates, several species of choanoflagellates, and accumulated by some picocyanobacteria. At the same time, silicifiers have a paramount impact on the marine cycling of silicon and other nutrients (N, P,..) and carbon. So, to better understand the Si cycle in the world ocean is a crucial issue for marine biogeochemistry.The marine silica budget compiled by Tréguer & De La Rocha (2013), which questioned its steady state in the modern ocean, needs revisiting to incorporate recent advances that have notably changed estimates for net Si inputs (submarine groundwater inputs of dissolved silicon, easily dissolvable amorphous silica to the ocean, inputs from the dissolution of terrestrial lithogenic silica in ocean margin sediments, polar inputs from subglacial lakes and melting ice), net Si outputs (reverse weathering removal fluxes, siliceous sponges). Herein, first we show that assuming steady state the Si annual budget can be balanced at 13.1 T mol-Si year-1. Second, from new estimates of biological fluxes we show that other silicifiers than pelagic diatoms might significantly impact the silica cycle at global scale.