A bank of microscopic forms on disturbed boulders and stones in tide pools

Disturbed marine habitats contain banks of microscopic forms that develop into macroscopic vegetation under adequate conditions. This study examined seasonal species turnover, time-space community development and species-area relationships of an assemblage of microscopic forms, on boulders and stones in 2 tidal pools in central Chile (32 degrees 46' S; 71 degrees 33' W). A total of 25 taxa were found in the assemblage, with low species turnover throughout the year. The assemblage contained about twice the number of species present in the water column and about half the number present in the macroscopic vegetation. Species present in the macroalgal vegetation and in the water column accounted for 70% of the taxa in the assemblage; the remaining 30% suggested propagule sources outside the study area. Colonization and succession experiments indicated that the banks were formed by ephemeral and perennial species. Most perennials are slow-growing and crustose, of low-colonizing capacity; the bank seemed more important for the survival of these perennial species than for fugitive forms. Species richness in the bank correlated with the surface area of boulders. For areas larger than 40 cm(2), species richness was significantly higher on individually sampled stones than on equivalent surfaces subsampled from larger boulders, suggesting that, species richness follows predictions of the intermediate disturbance hypothesis. The number of species was high, suggesting that disturbance affects the macroscopic expression of diversity rather than the total number of species.