Concentrations of dimethylsulphide (DMS) and its precursor compound dimethylsulphoniopropionate (DMSP), two sulphur compounds that are involved in the formation of clouds, were measured for mucus ropes, coral mucus, surface films and sediment pore waters collected from three coral reefs in the Great Barrier Reef, Australia. The concentrations of DMS (61–18 665 nm) and DMSP (1978–54 381 nm) measured in mucus rope samples are the highest yet reported in the marine environment. The values exceed concentrations of DMS and DMSP reported from highly productive polar waters and sea ice algal communities. Concentrations of DMSP in coral mucus ranged from 1226 to 25 443 nm, with mucus from Acropora formosa containing the highest levels of DMSP. Dimethylsulphide and DMSP in surface microlayer samples from three coral reefs were two to four times subsurface (0.5 m) concentrations. In coral-reef sediment pore waters, concentrations of DMS and DMSP were substantially higher than water-column concentrations, suggesting that coral sediments may be a significant source of these two compounds to reef waters. Overall, the results strongly suggest that coral reefs in the Great Barrier Reef are significant sources of these two sulphur substances.
Community structure, biomass and productivity of epilithic algal communities on the Great Barrier Reef: dynamics at different spatial scales