Year: 2010
Type: dissertation
Abstract: Dimethylsulphoniopropionate (DMSP) is the biogenic precursor of the climatecooling gas dimethylsulphide (DMS). DMSP is produced by certain phytoplankton groups including dinoflagellates. DMSP is a multifunctional compound potentially acting as an osmolyte, cryoprotectant, antioxidant, methyl donor, grazer deterrent and overflow exudate but its primary biological role and the variation in DMSP content in dinoflagellates remain unclear. As dinoflagellates can be sensitive to agitation, the methods for DMSP measurements in cultures were assessed and the measurement of total DMSP as a surrogate for intracellular DMSP was retained for most experiments. I collected all the published DMSP data in dinoflagellates and measured DMSP in 9\nspecies. The obtained dataset proposed a summary of DMSP concentrations in dinoflagellates which spread over 6 orders of magnitude with an average of 242 mM (n=61) and include the widest and highest DMSP concentrations reported in phytoplankton. The DMSP content was analysed in relation with various biological criteria that determine the wide diversity of the dinoflagellate group. Bioluminescent species and species holding haptophyte-like plastids have significantly lower DMSP concentrations whereas higher concentrations were found in Mediterranean species. The role of DMSP was further investigated in the heterotrophic dinoflagellate Crypthecodinium cohnii by testing the effect of abiotic parameters on its DMSP content. DMSP acted as an osmolyte with a short-term response to hyperosmotic shock and long-term response to hypoosmotic shock. Concentrations also increased with growth as a result of glucose depletion suggesting that DMSP might replace glucose-derived osmolytes. The DMSP adjustment of cultures transferred into glucose-depleted or repleted media appeared to be exceptionally fast (<1 min). Nitrogen limitation also increased DMSP concentrations, possibly due to DMSP acting as an overflow metabolite for excess sulphur or as an antioxidant under starvation stress. Overall the results strongly support the contribution of the dinoflagellate group to the DMSP production.
Author: Caruana, A
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Life below water
Open Access status: green
OpenAlex ID: W11583467