Emiliania huxleyi x 10,000. This microscopic marine organism
has a high output of DMS.
Marine algae and DMS
Marine algae are able to cope with salty conditions
by the production of dimethylsulphonio proprionate (DMSP). This
substance is electrically neutral, carrying a positive charge associated
with sulphur, and a negative charge associated with the propionic
acid ion, on the same molecule. The internal neutralization of its
ionic charges renders it non-toxic, and cells that are able to substitute
a large proportion of betaine for salt are able to reduce the osmotic
pressure between the cell interior and the external sea water. (see
The sulphur cycle
When marine algae die or are eaten, the sulphur
betaine decomposes easily to yield the acrylic acid ion and dimethyl
sulphide (DMS). Onshore breezes carry the dimethyl sulphide inland
where atmospheric gases decompose it into a non-sea salt sulphate
aerosol comprised of sulphate and methane sulphonate. In this form
sulphur is deposited on the ground, thereby enhancing the growth
of land plants, and also increasing the rate ot rock weathering.
The increased flow of nutrients to the oceans is of obvious benefit
to marine organisms, and so the sulphur cycle is perceived as mutually
beneficial to both land- and sea-based ecosystems.