Abstract
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 diluted the initial stocks of the two molecules. Temperature indirectly affected molecule content dynamics through their direct effect on the seagrass productivity and biomass. Inter-annual variations in DMSP(O) content in relation to shallow water temperature 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.
Highlights
Haas (1935) showed that the red macroalgae Polysiphonia fastigiata and P. nigrescens when exposed to air emitted dimethyl sulphide (DMS)
DMSP and DMSO contents were correlated in C. nodosa and Z. marina confirming the finding of Richir et al (2020) that DMSP and DMSO are correlated in marine autotrophs
Recent work on P. oceanica and the present study demonstrated this seagrass species was the largest producer of DMSP and DMSO reported to date among coastal autotrophs, and most probably the major contributor to the dissolved DMS(P,O) pool in coastal waters of the oligotrophic Mediterranean
Summary
Haas (1935) showed that the red macroalgae Polysiphonia fastigiata and P. nigrescens when exposed to air emitted dimethyl sulphide (DMS). It was unlikely that DMS was stored as such in the macroalgae, given the small size of the molecule and its high diffusivity. This suggested the occurrence of a precursor sulphonium compound, identified as DMSP by Challenger and Simpson (1948). de Mora et al (1996) speculated a direct biosynthetic pathway on the basis of evidence gathered in Antarctic melt-water ponds that contained relatively high levels of dissolved DMSO but low concentrations of DMS and very little dissolved DMSP. In the coastal waters of North Island, New Zealand, Lee and de Mora (1996) speculated that algal photosynthetic processes may have played a role in the rapid daytime production of dissolved DMSO that could not have only resulted from photo- and bacterial oxidation of DMS. In the coastal waters of North Island, New Zealand, Lee and de Mora (1996) speculated that algal photosynthetic processes may have played a role in the rapid daytime production of dissolved DMSO that could not have only resulted from photo- and bacterial oxidation of DMS. Simó et al (1998) confirmed the biogenic production of DMSO by marine microalgae in laboratory cultures of Amphidinium carterae and Emiliania huxleyi
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