M. Le Blanc

Algal plating as a tool for investigating allelopathy among marine microalgae

Chemical interactions among marine microalgae were studied in cultures of pennate diatoms on agar plates. Nine marine and freshwater pennate diatoms were surveyed as potential bioassay organisms; Cylindrotheca fusiformis was most favourable for assays because of its rapid and even growth on agar. Diatom and bacterial bioassays were used to screen cell and filtrate extracts of 14 microalgal cultures. A number of these algal species, which were grown axenically, produced extractable, intracellular and/or extracellular substances that inhibited the growth of C. fusiformis. Our results suggest that the culturing of pennate diatoms on a solid medium can provide a simple bioassay for screening algal extracts which potentially contain growth inhibitors involved in microalgal allelopathy.