Dimethylsulfoniopropionate and dimethylsulfoxide in Posidonia oceanica

The present work aims at determining the natural variability of dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) contents in the seagrass Posidonia oceanica, which is the largest producer of these molecules reported to date among coastal autotrophs. Seagrass leaf samples were collected during a period of 3.5 years in the pristine Revellata Bay (Calvi, northwestern Corsica, France). The DMSP content ranged from 25 to 265 μmol.gfw−1; DMSO from 1.0 to 13.9 μmol.gfw−1.The dynamics of the two molecules were closely linked, the DMSO content being equivalent to 3.5% of the DMSP content,all leaf samples considered (n = 423 samples and 414 DMSP(O) data pairs). The annual growth cycle of the seagrass dilutedthe initial stocks of the two molecules. Temperature indirectly affected molecule content dynamics through their directeffect on the seagrass productivity and biomass. Inter-annual variations in DMSP(O) content in relation to shallow watertemperature might further indicate that DMSP(O) could have been involved in the physiological response of P. oceanica to heat stress. Finally, middle-aged leaf tissues with an organosulfur molecule content similar to the average value calculated for the seagrass leaf bundle appeared to be the best choice of sample material to study DMSP and DMSO in that species. More research is needed to elucidate the biosynthetic pathways of these molecules in seagrasses, the evolutionary reasons for such a high production in P. oceanica and the physiological functions they play.