The importance of sponge spicules in the turnover of biogenic silica (BSi) in the detritic bottoms of the Eastern Ligurian Riveria was evaluated. This study made evident that: i) sponge spicules represent the main component of the BSi both in the sediments and in the trapped matter; ii) a correlation exists between the sponge biomass present on the overhanging cliff and the amount of sponge spicules found in the sediment below; iii) inside the sediments, a superficial layer characterized by intensive silica dissolution processes can be observed; and iv) the amount of spicules collected is not constant throughout the year.