Microalgal diversity in response to differential heavy metals-contaminated wastewater levels at North Nile Delta, Egypt

Abstract

Background:The most hazardous wastewater sources in the northern part of the Middle Nile Delta, Egypt; receiving a massive amount of agricultural, industrial, and sewage drainage are Kitchener drain which is one of the tallest drainage systems, and Burullus Lake which represents the 2nd largest Egyptian coastal lake.Results: The current work is to determine the abundance and frequency of cyanophytes, chlorophytes, and bacillariophytes and the correlation between them and environmental abiotic components.Among sixty nine microalgal species, 19 species are belong Cyanophyta, 26 belong Chlorophyta and 24 belong Bacillariophyta.Genus Scenedesmus (Chlorophyta) was the most abundant in the study area (13 species), followed by Genus Oscillatoria (9 species) and Genus Navicula (7 species).Nostoc muscorum and Chlorella vulgaris were the most common and recorded in all sites (100% of the locations) under study.The application of the two-way indicator species analysis (TWINSPAN) and detrended correspondence analysis revealed agglomerating of 4 groups (communities) at 4th level of classification and reasonable segregation between these groups.Zinc, cadmium and lead were showed the highest levels (0.26 ± 0.03, 0.26 ± 0.06, and 0.17 ± 0.01 ppm, respectively). Conclusions:The correlation analysis between water and community variables indicated a high negative correlation of total algae richness with nickel (r = -0.936,p < 0.01).Cyanophyta and Bacillariophyta were correlated negatively (r = -0.842,p < 0.01).However, Chlorophyta showed a negative richness with each of Ni and Pb (r = -0.965,-0.873, respectively) on one hand and a high positive correlation was revealed (r = 0.964) with all environmental variables on the other hand.