Sulfur and phytoplankton: acquisition, metabolism and impact on the environment

Summary Sulfur emission from marine phytoplankton has been recognized as an important factor for global climate and as an entry into the biogeochemical S cycle. Despite this significance, little is known about the cellular S metabolism in algae that forms the basis of this emission. Some biochemical and genetic evidence for regulation of S uptake and assimilation is available for the freshwater model alga Chlamydomonas . However, the marine environment is substantially different from most freshwaters, containing up to 50 times higher free sulfate concentrations and challenging the adaptive mechanisms of primary and secondary S metabolism in marine algae. This review intends to integrate ecological and physiological data to provide a comprehensive view of the role of S in the oceans. Contents Summary 371 I Introduction 371 II Atmospheric sulfur deposition 372 III Sulfur in aquatic ecosystems 372 IV Sulfur acquisition by algae 373 V Assimilation and reduction of sulfate by algae 374 VI Interactions between S and C, N, P metabolism 376 VII Regulation of sulfur metabolism 377 VIII Sulfur release by algae: the role of DMS 377 IX The pathway of DMSP biosynthesis 378 References 379