Autecology of a filamentous alga, Ctenocladus circinnatus (Chlorophyceae), in saline environments

Six highly saline habitats in arid regions of British Columbia, Nevada, and California with the chaetophoralean Ctenocladus circinnatus Borzi were investigated to characterize the unique environment of this alga. Seasonal patterns within three of these habitats were analyzed to reveal those parameters determining the restricted distribution of Ctenocladus. Sodium was the dominant cation in combination with any major anion, such as SO4−, CO3−, HCO3−. Seasonal salinity fluctuations of the water solutions were large (< 10– > 100 millimhos). Ctenocladus tolerated these high salinities and temperatures (−3 to 28 °C) as akinetes formed early in the summer and they survived as akinetes until dilution of the water solutions the next spring. The period for optimum vegetative development was short (6–12 weeks) because of an increase in salinity and temperature of the waters.Akinete germination in the laboratory was optimal between 9 and 26 °C and temperatures above 34 °C destroyed akinetes. Conversely, the freezing of akinetes produced no adverse affects. Laboratory studies showed germination and vegetative development retarded at pH below 8.0 with akinetes destroyed below 7.0. Light is essential for germination with low light intensities (214 lx) stimulating germination. Light intensities above 12 000 lx destroyed akinetes within 5 days. Sexual reproduction in both the field and laboratory was absent. The significance of the akinete and lack of sexual reproduction are correlated with laboratory and field data and the restricted distribution of Ctenocladus.