Factors possibly affecting growth of Microcystis aeruginosa and M. flos aquae isolated from Wadi El-Raiyan Upper Lake Egypt under laboratory conditions

Abstract

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.