Desiccation and temperature tolerance of green and red Haematococcus lacustris (Chlamydomonadales, Chlorophyta) akinetes

Freshwater green algae of the Haematococcus lacustris species complex are known for their ability to accumulate the secondary carotenoid astaxanthin, which has various industrial applications. Survival of H. lacustris in harsh environments is facilitated by the formation of desiccation-tolerant akinetes, which are thick-walled, resistant cells. In this study, we compared the desiccation tolerance of green and red akinetes and investigated the effect of different desiccation periods and extreme temperatures on their viability. We used the effective quantum yield of the photosystem II as an indicator of how akinetes respond to environmental stress. We also examined the ultrastructure of the akinetes using electron microscopy. Both green and red akinetes survived desiccation at all dehydration rates tested. The effective quantum yield of the green akinetes was generally higher than that of the red akinetes throughout the experiment. Moreover, desiccated red akinetes were able to survive different additional stresses, even exposure to extreme temperatures of − 80 °C and 55 °C. Red akinetes that had not been previously desiccated tolerated freezing better than high temperature. These findings contribute to our understanding of the desiccation tolerance of Haematococcus akinetes and have implications for the global distribution of this alga.