Environmental influences on akinete germination of Anabaena circinalis and implications for management of cyanobacterial blooms

Certain cyanobacteria, including the noxious bloom-forming species Anabaena circinalis Rabenhorst, produce thick-walled reproductive structures (akinetes) which may serve as a resting stage and ensure survival during adverse growth conditions. The effect of certain environmental variables (temperature, salinity and desiccation) on akinete germination of A. circinalis was investigated under laboratory conditions, to determine the conditions under which germination was inhibited. The overall aims were to provide a broader understanding of the life history and ecology of this species and to assess suppression of akinete germination as a potential management strategy for control of cyanobacterial blooms in the lower Murray River, Australia. The results indicated a marked threshold of temperature and salinity tolerance for germination of A. circinalis, but the latter was not within a range that could be successfully manipulated in a natural ecosystem. However, it was found that desiccation of akinetes for moderately short periods can significantly impair their capacity to germinate. It is, therefore, speculated that allowing periodic drying of shallow wetlands adjacent to the Murray River and in other areas may reduce the size of the inoculum for population growth by reducing viability of akinetes in surface sediments.