Breathe deeply when you are near the ocean and you'll pick up the scent of the sea. That vaguely rotten aroma, accented by salt, comes from a molecule called dimethylsulfide, or DMS. But that scent offers only a hint of the fascinating, far-reaching roles DMS and its precursor molecule, dimethylsulfoniopropionate (DMSP), play in the environment.
DMSP is synthesized by phytoplankton--the microscopic marine plants at the heart of the ocean food web--for a variety of beneficial uses. Scientists think DMSP acts as an antioxidant to neutralize potentially damaging chemicals generated by cellular processes and ultraviolet radiation from the sun. It may also be used to regulate the pressure inside phytoplankton cells in response to changes in seawater temperature and salinity. In addition, there is evidence that DMSP can function as a chemical signal within the marine food web.
DMSP also serves as food for bacteria that graze on phytoplankton. They can convert DMSP into DMS, the distinctly aromatic gas. When DMS wafts back into the atmosphere, it reacts with oxygen and creates fine aerosol particles. These provide a surface for water molecules to cluster around and begin to form clouds. It has been proposed that organisms can affect the climate around them by producing DMS.
DMSP is only one molecule in the complex mixture of compounds found in the ocean. To really know how the whole marine ecosystem operates, we have to learn more about the molecules that marine organisms produce, respond to, and use. It's easy to imagine a complex chain reaction where the availability (or non-availability) of DMSP made by phytoplankton shifts the molecules produced by bacteria--which, in turn, would send different chemical ripple effects throughout the food web and the entire environment.
Gaze out at the ocean on a clear day, and it's easy to forget that, within it, a vast number of...