2. Materials and methods
2.1. Sampling area
The samples of water and sediments were collected from Lake Tana, Amhara regional state, Ethiopia. The sampling area was located at a latitude of 12 (12° 0′ 0 N) and a longitude of 37.33 (37° 19′ 60 E). The lake was the source of Blue Nile with a total surface area of 3 600 km2, a volume of 28.00 km3 and an average elevation of 1 911 m above the sea level[24].