Putting the spotlight on organic sulfur

Marine microbes are the engines that drive global biogeochemical cycling in the oceans. They produce and cycle a dissolved organic matter (DOM) reservoir that is roughly as big as the atmospheric carbon dioxide pool ( 1 ). Interactions between DOM and marine microbes may also play a key role in the evolving climate through changes in remineralization rates ( 2 ). Historically, DOM has been thought of mainly in terms of its carbon, nitrogen, and phosphorus content. On page 456 of this issue, Ksionzek et al. ( 3 ) investigate the large pool of dissolved organic sulfur (DOS) compounds in the ocean and show that these compounds also play a key role in ocean biogeochemistry.