Red coralline algae as a source of marine biogenic dimethylsulphoniopropionate

The biogenic gas dimethylsulphide (DMS), derived from dimethylsulphoniopropionate (DMSP), plays an important role in the Earth's albedo, and thus climate regulation, through the formation of aerosols and cloud condensation nuclei. It is estimated that biogenic sources of DMS contribute 42% (mean) of the atmospheric sulphur burden and, significantly, > 90% of that contribution is derived from marine sources. Phytoplankton, macroalgae and corals are thought to be the main producers of marine biogenic DMSP. Red coralline algae (known as maerl or rhodoliths) cover extensive areas of seabed, yet despite their widespread global distribution, maerl-forming coralline algae have received little or no attention regarding their DMSP productivity. In the present study we report for the first time the occurrence of DMSP in 2 species of maerl. DMSP concentrations were found to average 1914 nmol g(-1) for soft tissue and estimated to be 637 mu mol m(-2) for maerl beds. In incubation experiments, maerl led to a dissolved DMSP (DMSPd) increase at a rate of 57.4 to 767.6 nmol m(-2) d(-1) in surrounding seawater, indicating that maerl contributes to DMSPd concentrations in the adjacent water column. Results show that maerl beds are a previously undiscovered source of DMSP in the marine environment. Further study is warranted to assess the significance of maerl as a source of DMSP and the role coralline algae may play in the biogenic sulphur cycle.