Updated on June 3, 2003

UBO work examples

Dissolution experiments on various forms of biogenic silica (BSi) are being carried out, so as to parameterize the water column transformation model developed by Participant 7 (NIOO). Using either batch or flow-through reactors, dissolution kinetics of Biogenic Silica (BSi) are measured comparatively on free cells and on these cells, either embedded in copepod fecal pellets (Figure 1) or within aggregates (Figure 2).

Figure 1: Aggregates of the diatom Skeletonema costatum.
Photo: Courtesy of Brivaëla Moriceau working in cooperation with Dr. Uta Passow, AWI, Bremerhaven/Germany.

Figure 2: The copepod Calanus helgolandicus.
Photo: Courtesy of Dr. Morgane Gallinari.

Additional experiments are planned, to characterize the dissolution properties (kinetics, solubility) of the various elements that constitute diatom frustules. A degradation experiment has already been conducted, which has shown that the solubility of BSi decreases by some 40% after the diatom has lost 50% of its Si content. This experiment will be repeated with different species, presenting variable silicification degrees.
Results will serve to parameterize the dissolution properties of the BSi that reaches the seabed, in the dynamic model of BSi early diagenesis developed together with Participant 2 (CEA-DSM).