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Title

The marine silicon cycle in the light of sponge silica: a global review

AuthorsMaldonado, Manuel ; López-Acosta, María ; García-Puig, Marta ; Sitjà, Cèlia ; Ercilla, Gemma
Issue Date30-Jun-2017
Citation10th Sponge World Conference: 130 (2017)
AbstractThe cycling of silicon (Si) in the ocean interacts with many relevant chemical, biological and ecological pro-cesses, including control of primary production1and removal of atmospheric CO2. It also intertwines with the cycling of other relevant elements, such as carbon (C), nitrogen, phosphorus, iron, etc. Because of this importance, there is wide interest in quantifying the “journey of Si” through the world’s oceans. The classi-cal biogeochemical model proposed to this aim rests on two major assumptions: 1) Si circulates in the ocean under the biological control of planktonic diatoms that use it to elaborate their skeletons of biogenic silica (BSi), with other Si- using organisms (sponges, radiolarians, silicoflagellates, choanoflagellates, etc) making negligible contributions to the global fluxes; and 2) the marine Si cycle is under steady state, being the Si an-nually leaving the ocean —by burial of BSi in sediments— compensated by an equivalent Si flux entering the ocean in the form of dissolved silica (DSi). However, these two basic assumptions of the cycle have recently been challenged, with evidence suggesting that the equilibrium between Si inputs and outputs in the current cycle model is lost and that Si users other than diatoms could be responsible for such a situation. Our study reveals that the classical view of a Si cycle revolving exclusively around diatoms and their biological features has led to an oversimplification of the biological circuitry, failing to notice a secondary - but relevant - circuit fueled by siliceous sponges. The accommodation of the sponge circuit into the global marine Si cycle causes a major disruption of its classical diatom-biased conceptual frame. Unlike diatoms, sponges occur only in the benthic compartment, have life spans that extend from decades to centuries or even millennia, produce BSi skeletons without connection to the phototrophic production of organic C, and their BSi dissolves at much slower rates than that of diatoms. As a consequence, sponges slow down current diatom-based estimates of Si recycling rates and residence times, favor Si burial, and decouple predicted connections between the Si and C cycles. Importantly, the quantified deposition rate of sponge spicules to the marine sediments and their subse-quent burial increase the Si outflux from the ocean up to a value in which the equilibrium between Si inputs and outputs in the global ocean budget is restituted, a steadiness broken if the global model accommodates exclusively diatom-based fluxes
Description10th Sponge World Conference, 25-30 June 2017, Galway, Ireland.-- 1 page
Publisher version (URL)http://www.conference.ie/Conferences/menu.asp?menu=2398&Conference=489
URIhttp://hdl.handle.net/10261/178102
Appears in Collections:(ICM) Comunicaciones congresos
(CEAB) Comunicaciones congresos
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