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During the period of February 2004 to April 2005, 74 samples from various forms of algal vegetations were collected from different periphytic freshwater habitats in Sultanate of Oman. These habitats include water streams of Aflaj systems, springs, wadis and rocky mountain regions of El-Dakhilia, Al-Dhahirah, Al-Batinah, Al-Sharquyah, and Muscat. Thirty cyanobacterial taxa were identified based on their morphological characteristics. Distribution analysis of the cyanobacterial flora in correlation with the studied areas obviously emphasized that the locality of Al-Taeen was the richest site, while localities of Bahla, Al-Hamra, Wadi Al-Moudin, Wadi Tanouf in Nazwa were the poorest sites by the diversified cyanobacterial flora. The microscopic identification of the natural assemblages of the biotopes of the studied localities indicated the presence of seventeen taxa of chlorophytes. The autecology of green algae revealed that the appearance and existence of rhizobenthic Chara canescens and the unbranched filaments of Rhizoclonium heiroglyphieum strongly confirmed the hardness of water habitats of Jalan area in Al-Sharquyah. On the other hand, water habitats of Nazwa area were found to be the suitable environments favoring the growth and dominancy of freshwater periphytic chlorophytes. Fifteen diatom taxa were identified from the investigated localities. The autecology of the identified diatom taxa of oligohalobien type (indicators for freshwater habitats), except Biddulphia laevis and Achnanthes brevipes var. intermedia of mesohalobien type of salinity. This observation added strength conformity for the hardness of water of Jalan locality.

Proteins of 15 isolates of T. longbrachiatum and T. harzianum were compared by polyacrylamid gel electrophoresis (PAGE) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Gels were stained with silver nitrate. Protein banding patterns of the isolates were subjected to cluster analysis by the unweighted pair-group method based on arithmetic mean (UPGMA).

Experiments were carried out to determine the effects of some environmental factors causing the phenomenon of algal blooming in the upper lake of Wadi El-Raiyan under laboratory conditions. Microcystis aeruginosa and M. flos aquae were isolated from Wadi El-Raiyan Lakes. Mono-clonal culture of each species was kept in 100-ml BG11 media in the laboratory for 5 days. The algal growth was measured by the determination of chlorophyll a and cell count to understand the succession patterns of both species in relation to the tested environmental conditions. The best photoperiod cycle was found to be (14:10 hrs) and the growth of the two species increased with increasing light intensities up to 45µ E m-2 s-1. Salinity and the growth of tested species exhibited a significant inverse relationship, increased salinity inhibiting algal growth. Water pH range from 7 to11 was suitable for growth of both species, while a pH below or above this range caused a significant decrease in growth. High nitrogen sources entering into Wadi El-Raiyan Lake may be one of the reasons for the blooming of the tested microalgae. The toxic effects of the bloom-forming species impact the economic fish resources of the lake leading to fish kills.