The Effects of Salinity on Growth and Distribution of Four
Freshwater Diatom Species


Attayeb A. Hayati
Biology Department, Faculty of Science, American University of Beirut, Lebanon.
Present address: King Faisal University Dammam Teacher`s College, P. O. Box 2375,
Dammam 31451, Saudi Arabia. E-mail: attayebh@yahoo.com

                                                                                   Abstract

The upper and lower salinity limits of Nitzschia acicularis, Nitzschia pusilla, Nitzschia palea and Synedra acus, which were isolated from the Damour River, Lebanon, were determined from laboratory cultures. Growth responses of the investigated diatoms showed maximum growth in the enriched Damour River natural water (salinity = 0.24 ppt). With an increase in salinity there was a gradual decrease in the growth until the upper limit was reached. At higher salt concentrations near the upper limit a lag phase was observed, during the first two days of the growing culture, where the growth was greatly declined. This reduction in growth can be attributed to high osmotic stress experienced by the investigated diatoms when transferred to flasks containing salinities near the extremes of their tolerance. The investigated diatoms appear to be very resistant and capable of adaptation to
new situations because they grew better after this two days lag period. The results of this study also showed that all the investigated diatom species have broader salinity tolerance limits than those reported in the literature and this would enable their distribution at localities with higher or lower salinities than those typical of the Damour River, Lebanon.

.Key words: Salinity, Nitzschia acicularis, Nitzschia pusilla, Nitzschia palea, Synedra acus.




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