Comprehensive Insight into Lake Nasser Environment: Water Quality and Biotic Communities—A Case Study before Operating the Renaissance Dam

Marian G Nassif,Abd Ellatif M Hussian,Mohamed E Goher,Walid Aly,Mohamed A Fetouh,Mahmoud H Hegab,Eman I Abdel-Aal,Amany M Haroon,Soaad A Sabae,Agnieszka Napiórkowska-Krzebietke,Usama M Tahoun,Seliem M El-Sayed

doi:10.3390/w13162195

Abstract

This study focused on the monitoring and assessment of aquatic ecosystem functioning based on the abiotic and biotic features of Lake Nasser in the post-flood and pre-flood periods as the last ones before water storing behind the Grand Ethiopian Renaissance Dam. The physicochemical parameters, distribution and structure of biotic communities, including bacteria, phytoplankton, zooplankton, macrophytes, epiphytes and fish were analyzed at 15 sites. The values of most parameters (primarily temperature, total suspended solids, pH, orthophosphates, carbonates, sulphates and some cations) were higher in the pre-flood period, whereas higher values of conductivity, total dissolved solids, total solids, nitrites, nitrates, chemical oxygen demand, bicarbonates and chlorophyll a were recorded in the post-flood period. Cyanobacteria-dominated phytoplankton and total coliform bacteria were more abundant in the pre-flood period, and especially at sites 10–15, whereas higher abundances of zooplankton were recorded in the post-flood period. All these changes in parameters were significantly differentiated, and only the concentrations of dissolved oxygen, biochemical oxygen demand, ammonium and silicates were at similar level in both periods. The study also indicated that environmental factors had affected the macrophyte distribution and the adaptation of the invasive species Myriophyllum spicatum to thrive under different environmental factors in the lake. Besides, macrophytes provided the habitat to other aquatic organisms, especially epiphytes, and also helped maintaining the good water quality, nutrient cycling and stabilizing rivers’ and lakes’ banks. Generally, these conditions were rather favorable for biological processes and fish production.

Highlights

The construction of the Aswan High Dam (AHD, 1959–1970) in the southern part of Egypt resulted in the creation of one of the largest manmade lakes in the world
The total zooplankton was more abundant in the post-flood period; it might have been due to the flood which facilitated the hatching of the resting eggs lying dormant in littoral zones
Current studies were provided to monitor and assess water quality based on the abiotic and biotic parameters including the physicochemical parameters, distribution and structure of bacteria, phytoplankton, zooplankton, macrophytes, epiphytes and fish at the selected sites in Lake Nasser during both the post-flood and pre-flood periods. These periods were the last ones before the storing of the water behind the Grand Ethiopian Renaissance Dam (GERD), which already started

Summary

Introduction

The construction of the Aswan High Dam (AHD, 1959–1970) in the southern part of Egypt resulted in the creation of one of the largest manmade lakes in the world. The AHD became a multipurpose storage reservoir to provide adequate summer water, hydropower, flood protection and improved river navigation. The whole reservoir extends for about 496 km, including 292 km for Lake Nasser and 204 km for Lake Nubia [1]. Lake Nasser, like other lakes in arid regions, is considered an “amplifier lake” in terms of its dramatic response to climate changes [2]. Each change can lead to dramatic shifts in the lake biota and in the composition of sediments accumulating on the lake bottom. The water resources in Egypt are very limited, any future activities and perturbations on the lake should be carefully considered before implementation. The area around the lake should be kept as a natural desert

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Discussion

Conclusion