Background
Dimethylsulfide (DMS) is a climatically-important trace gas of the atmosphere that is derived from its biological precursor dimethylsulfoniopropionate (DMSP, produced by various species of marine phytoplankton) that is believed to play a major role in helping to maintain earth's temperature within bounds conducive to the continued existence of life.  This CLAW hypothesis, named for the four scientists who formulated it - Charlson, Lovelock, Andreae and Warren (Charlson et al., 1987) - begins with an initial impetus for warming, such as an increase in the air's CO2 content, which induces an increase in the productivity of marine phytoplankton that results in a greater production of DMSP and its release to the atmosphere as DMS, where gas-to-particle conversions increase the air's population of cloud condensation nuclei and, ultimately, the albedo or reflectance of marine stratus and altostratus clouds via a narrowing of the cloud droplet spectrum and a decrease in the mean radius of the cloud droplets, both of which phenomena counteract the initial impetus for warming and thus contribute to an important negative feedback loop that may significantly slow global warming or possibly even stop it altogether (see Dimethyl Sulfide in our Subject Index).

Within this context, Broadbent and Jones note that "Jones et al. (1994) and Broadbent et al. (2002) reported that corals in the Great Barrier Reef (GBR) contain significant amounts of DMSP in their zooxanthellae, suggesting that coral reefs are potentially significant sources of DMS to the water column of reef areas and that coral reefs themselves may be significant sources of atmospheric DMS to the marine boundary layer (Jones and Trevena, 2005)."  In this paper, Broadbent and Jones further explore the possibility that coral reefs may be major participants in the bio-stabilization of earth's climate.

What was done
Concentrations of DMS and DMSP were measured within mucus ropes, coral mucus, surface films and sediment pore waters collected from Kelso Reef, One Tree Reef and Nelly Bay Reef in Australia's GBR.

What was learned
Broadbent and Jones state that "the concentrations of DMS and DMSP measured in mucus ropes and surface-water samples at One Tree Reef and Kelso Reef are the highest yet reported in the marine environment," exceeding concentrations measured in "highly productive polar waters (Fogelqvist, 1991; Trevena et al., 2000, 2003), and sea ice algal communities (Kirst et al., 1991; Levasseur et al., 1994; Trevena et al., 2003)."  More specifically, they report that "concentrations of DMS ranged from 61 to 18,665 nM and for DMSP, from 1,978 to 54,381 nM, representing concentration factors (CF = concentration in the mucus ropes divided by the concentration in seawater from 0.5 m depth) ranging from 59 to 12,342 for DMS and 190 to 6,926 for DMSP."  In addition, they report that "concentrations of DMSP in coral mucus were also exceptionally high, with mucus from Acropora formosa containing the highest levels of DMSP."  Last of all, they observed that DMS and DMSP concentrations were substantially higher than water-column concentrations in both surface microlayer samples and coral-reef sediment pore waters.

What it means
"Overall," in the words of Broadbent and Jones, "the elevated concentrations of DMS and DMSP in mucus ropes, coral mucus, surface films and sediment pore waters strongly suggest that coral reefs in the GBR are significant sources of these two sulphur substances," which in turn suggests that coral reefs may figure prominently in the CLAW phenomenon that helps to keep earth's temperature from rising too high.

Reference
Broadbent, A.D., Jones, G.B. and Jones, R.J.  2002.  DMSP in corals and benthic algae from the Great Barrier Reef.  Estuarine, Coastal and Shelf Science 55: 547-555.

Charlson, R.J., Lovelock, J.E., Andrea, M.O. and Warren, S.G.  1987.  Oceanic phytoplankton, atmospheric sulfur, cloud albedo and climate.  Nature 326: 655-661.

Fogelqvist, E.  1991.  Dimethylsulphide (DMS) in the Weddell Sea surface and bottom water.  Marine Chemistry 35: 169-177.

Jones, G.B. and Trevena, A.J.  2005.  The influence of coral reefs on atmospheric dimethylsulphide over the Great Barrier Reef, Coral Sea, Gulf of Papua and Solomon and Bismarck Seas.  Marine and Freshwater Research 56: 85-93.

Kirst, G.O., Thiel, C., Wolff, H., Nothnagel, J., Wanzek, M. and Ulmke, R.  1991.  DMSP in ice algae and its possible role.  Marine Chemistry 35: 381-388.

Levasseur, M., Gosselin, M. and Michaud, S.  1994.  A new source of dimethylsulphide (DMS) for the Arctic atmosphere: ice diatoms.  Marine Biology 121: 381-387.

Trevena, A.J., Jones, G.B., Wright, S.W. and Van den Enden, R.L.  2000.  Profiles of DMSP, algal pigments, nutrients and salinity in pack ice from eastern Antarctica.  Journal of Sea Research 43: 265-273.

Trevena, A.J., Jones, G.B., Wright, S.W. and Van den Enden, R.L.  2003.  Profiles of dimethylsulphoniopropionate (DMSP), algal pigments, nutrients, and salinity in the fast ice of Prydz Bay, Antarctica.  Journal of Geophysical Research 108: 3145-3156.