Is DMSP synthesis in chlorophycean macro-algae linked to aerial dispersal?

Dimethylsulphoniopropionate (DMSP) has been proposed to be a compatible (os motic) solute in marine macro-algae, allowing adaptation to changes in the osmotic pressure of the growth medium. However, whilst DMSP undoubtedly doe s contribute substantially to the overall osmotic pressure of the cytoplasm , several studies have demonstrated that its intracellular concentration is not directly regulated by the osmotic pressure of the growth medium. Thus, DMSP does not behave as a compatible solute sensu stricto and therefore it s role may not be strictly osmotic. Recently, HAMILTON & LENTON (1998) proposed that DMS emissions associated w ith blooms of DMSP accumulating marine phytoplankton may be linked to an ae rial mode of dispersal via the induction of cloud formation and local conve ctive winds. Only micro-algae were discussed. All macro-algae, however, als o have unicellular stages as gametes or spores which could become windborne . In this paper, we review the literature on the life histories, growth cycle s and ecology of marine DMSP synthesising chlorophycean macro-algae, in ord er to assess whether a similar dispersal mechanism may exist within this gr oup. Whilst only direct experimental evidence can resolve if these macro-al gae are dispersed or not by an aerial mechanism, many features of their gro wth, reproductive and life cycles are consistent with such a mechanism. Suc h an aerial dispersal mechanism might represent an especial ecological adva ntage in this group, allowing colonisation of areas separated by land masse s or denied to normal waterborne dispersal routes by directional currents.