Effects of drought and salt stresses on man-made cyanobacterial crusts

►In the natural setting, the M. vaginatus not only occupies masses of crust biomass, but also plays significant role in the cementing of BSCs. ►As a common dominant species in BSCs, the M. vaginatus has been chosen as an inoculation in constructing or regenerating BSCs in some researches. ►Therefore, we constructed the man-made cyanobacterial crusts with M. vaginatus in our experiment. ►The strain used in the current study was isolated from the BSCs in Qubqi Desert at Dalateqi region of Inner Mongolia Autonomous Region, where it is routinely exposed to drought, salt stress and wide fluctuations in temperature in conjunction with high radiation. ►In the previous studies, it has been demonstrated that the M. vaginatus could adapt to a variety of stress conditions, including drought, salinity and so on. ►In the present work, we further comparatively studied the effects of drought and salt stress on the algal crusts, distinguished the difference in drought stress and salt stress. ►The results showed that the crust growth and photosynthetic activity was significantly inhibited by the stress conditions (P < 0.05), and the inhibitory effect increased with increasing stress intensity and treated time. ►Compared with the salt stress, drought completely stopped the crust metabolic activity, so the crust biomass was conserved at a higher level, which meant the drought itself might provide the crusts some protection, especially when the crusts simultaneously suffered drought and salt stresses. ►That is very important for the survival of crusts inhabited in the high-salt areas. In addition, to some extent the crusts could adapt to the stress conditions through metabolic adjustment. ►In our experiment, we found the accumulation of exopolysaccharides (EPS) increased under stress conditions within a certain threshold. ►These results would help us to understand the adaptability of BSCs to the stress conditions, and provide some theoretical support for the constructing man-made crusts in the drought and high-salt areas.