The interactions of certain littoral diatoms with young plants of marine algae

The interactions of certain littoral diatoms with young algal plants were studied from various aspects. The distribution of littoral diatoms on the shores of the Isle of Cumbrae, Scotland was also investigated. Diatom community in the littoral area is probably related largely to the temperature and length of sunshine period. Both the association and interactions of diatoms with macroalgae would seem to involve complex physico-chemical actions. The similarity of epiphytic diatom assemblages on various macroalgae varies with the seasons. For laboratory studies, certain common diatoms in the littoral area were isolated from natural materials. The results of experimental studies indicated that interactions did occur when diatoms and young plants of marine algae associated, particularly in the very early stage of spore and zygote attachment on the substratum. The principal features of these interactions vary greatly with algal species studied, and are affected by physico-chemical factors. The various interactions would seem to be due mainly to algal extracellular substances and to the mechanical attachment of diatom cells on the germinated spores and zygotes. The antidiatom activities of fucoid germlings and red algal sporelings, as well as the effects of diatom mucilaginous material on the morphogenesis and growth rate of algal sporelings and germlings, were examined in detail. Transformation of photosynthetic products (as dissolved organic matter) between certain littoral diatoms and red algal sporelings was demonstrated by 14C labelled carbon compounds under different experimental conditions. The diatom interactions are of ecological importance in view of the wide distributions of these organisms in nature