Competition between three estuarine benthic diatom species in mixed cultures

Three species of intertidal diatoms were kept in unialgal and mixed cultures forming mats on the surface of clean sand. Interaction between the species was studied by 25 d incubation in serially diluted cultures, allowing natural population densities to be maintained. Abundance of species in mixed cultures was primarily determined by their capacities to thrive under inorganic carbon limitation (and associated conditions) and by their capacity to produce inhibitory substances. The range of physico-chemical conditions exploited by the test species narrowed considerably during interaction with a competitor. The relevance of the experiments for the interpretation of distribution patterns of estuarine diatom species is discussed as is the limited information available on mechanisms for carbonfixation in these organisms