Spora and Gaia: how microbes fly with their clouds

Abstract

We hypothesise that marine algae and various common microbes of the atmosphere (spora) use chemical induction of water condensation to enable or increase their wind dispersal between their aquatic, terrestrial or epiphytic growth sites. Biogenic chemical cloud condensation nuclei (CCN) and ice nuclei (IN), sometimes co-occurring in single species (e.g. Pseudomonas syringae), release heat energy of phase change, thus contributing to local air movements that can be used both for lofting and for lateral dispersal of their producers. The phase-change catalysis may occur on the microbial surface (e.g. P. syringae) or may happen more distantly through the release of chemical precursors for suitable ions (e.g. plankton-derived dimethylsulphide [DMS] forming atmospheric sulphate). Small phytoplankton and bacteria take off from water through bubble-burst processes especially in “white-caps”, these often themselves caused by convective winds. Selection for local induction of wind is likely to be most effective at the level of clonal microbial patches. Algal blooms having high DMS emission may represent attempts to create winds for dispersal; if so, algal cell changes occurring in such blooms may have features convergent to terrestrial dispersal cyclomorphoses of aphids, locusts, subcortical insects and others. It is already established that biogenic cloud formation occurs on a scale fully capable of affecting world climate. This fact features prominently in the Gaia Hypothesis. However, in contrast to the evolutionary scenario for microbe dispersal that we present, the claim of an adaptive function at the world level still lacks an explanatory mechanism.