Dissolved silicon (DSi) is a key marine nutrient. Sponges and diatoms are relevant DSi consumers, but sponges appear to have a less efficient uptake system that requires higher ambient DSI concentrations for maximum uptake. We experimentally tested whether a sponge adapted to live at the intertidal (Hymeniacidon perlevis) also shows such a need for high DSi. Under laboratory conditions, sponges were exposed to both the natural DSi concentration (10 lM) and much higher levels (25, 40, and 70 lM) for 36 h, being water samples taken at 6 h intervals to infer DSi uptake. Uptake rates shifted over time (particularly in high DSi treatments) and showed moderate interindividual variability. Average DSi uptake rate at 70 lM was twice higher than those at 40 and 25 lM, which in turn were not significantly different from each other, but were twice higher than the uptake rate at 10 lM. Therefore, H. perlevis needs, for efficient uptake, ambient DSi concentrations two to four times higher than the maximum available in its natural habitat. From an eco-physiological point of view, it means that the skeletal growth in the populations of H. perlevis is chronically limited by DSi availability, a limitation that may favor sponge evolution toward skeletal slimming.

The research has been supported by funds from the International Program for Scientific Cooperation between the Spanish Council for Scientific Research (CSIC) and the Chinese Academy of Science (CAS), two Spanish Ministry Grant (MICINN; BFU2008-00227/BMC; BFU2011-24936), the program of Dalian Municipal Science and Technology Bureau (2009J22DW037), and ‘‘The Start-up Foundation for the Doctor’’ from the Dalian Institute of Chemical Physics (S201011).

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Peer reviewed