Water was collected using a CTD rosette sampler. 125 mL seawater were collected at every station from the surface to 200 m (plus one deep profile (1700 m) at station 5). Samples were stored in plastic bottles at 4°C on board until laboratory analysis.

Dissolved orthosilicic acid Si(OH)₄) was quantified using Mullin and Riley’s (1965) spectrophotometric method.

Mullin, J.B. and Riley, J.P. (1965). The spectrophotometric determination of silicate-silicon in natural waters with special reference to seawater. Anal. Chim. Acta, 46, 491-501.