spatial distribution of asterionella formosa hassall, cyclotella ocellata pantocsek and fragilaria crotonensis kitton in the zayandehrud reservoir dam, iran

the main diatomic structure-forming species of the zayandehrud reservoir was investigated by collecting samples from the surface, five, seven and 10 m depths from january 2011 to october 2012 along four linear transects. asterionella formosa hassall, cyclotella ocellata pantocsek and fragilaria crotonensis kitton were revealed as the three structure-forming species among diatomic algae in the reservoir. the number of these diatomic cells increased from the reservoir banks to its central areas, but their abundance was non-uniformly distributed at the 10-meter water column at different sites, except for c. ocellata that showed a practically uniform distribution at the peak of its maximum growth. overall, the frequency and cover of these structure-forming diatoms changed under the influence of different abiotic variables such as electrical conductivity (ec) and nitrate (no3-n).