The sensitivity for salinity increase in the drought resistant cyanobacterium Crinalium epipsammum SAB 22.89

Abstract

In the coastal dunes of the Netherlands phototrophic organisms are colonising the sand surface (De Winder et al. 1989a). In previous studies the response of the three representative organisms, the cyanobacteria Crinalium epipsammum and Tychonema sp. and the green alga Klebsormidium flaccidum, to re- and dehydration (De Winder et al. 1989b, 1990b) was investigated. Equilibration with water-saturated air did only enable photosynthesis when this was granted by the water-retention characteristics of the physical environment of the samples. Rehydration enabled the recovery of photosynthesis of desiccated samples on substrata with a good water retention only. Photosynthetic activity is thus ascertained at environmental conditions of non-liquid water when this is enabled by a “compatible matrix”. The cyanobacterial strains showed a recovery of photosynthesis instantaneously. In contrast, rewetted cells of the green alga showed a recovery of photosynthesis only after a time-lag. During controlled dehydration K. flaccidum and to a lesser extent C. epipsammum proved to be able to maintain full carbon-fixing activity until the water content of its surroundings approached zero. Tychonema sp. appeared to reduce its activity in response to becoming dehydrated. The experiments described substantiated the view on the ecology of these drought tolerant organisms. The cyanobacteria as the initial colonizers inhabiting the barren sand are able to react quickly to changing water availability, by an on and off switching of their metabolism. As a result of the growth of the cyanobacteria the water retention of the top soil is improved to conditions were the green alga K. flaccidum is adapted.