Sulfur assimilation by Oxyrrhis marina feeding on a 35S-DMSP-labelled prey.

A laboratory grazing experiment was conducted with the aim of quantifying the sulfur assimilation by a herbivore protist feeding on a dimethylsulfoniopropionate (DMSP)-containing phytoplankter. When supplied with dissolved (35)S-DMSP, cultures of an axenic strain of the diatom Thalassiosira pseudonana took up 60-95% of the added radioisotope and accumulated it untransformed in the cytoplasm. Radiolabelled diatom cells were offered as prey to the heterotrophic dinoflagellate Oxyrrhis marina.