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.

Microalgae are one of the most effective sources of renewable energy production. It can grow at high rates and capable of producing oil along the year. Microalgae biomass was first suggested as a feedstock for biofuel production and received early attention for commercial application. Microalgae are expected to be a vital raw material for amino acids, vitamins and productions of valuable byproducts. The cultivation of microalgae is known to be the most gainful business in the biotechnological industry. It is a waste less, environmentally pure, energy and resource saving route. Biodiesel production from algal lipid is non-toxic and highly biodegradable. Conversion of biomass to biofuel can be achieved by different methods which are broadly classified into: thermal, chemical and biochemical methods, in addition to the large number of different agents for decomposing and hydrolysing. We can obtain the low-cost energy production from the wastewater treatment by using microalgae. Finally, biodiesel production by microalgae in Egypt is not practical at the economical level. In order to improve biodiesel fuel quality, the alga must be subjected to genetic engineering for up-regulation of fatty acid biosynthesis and/or by down-regulation of β-oxidation. Economically, the algal biomass must be processed for bio-refinery to maximize its utilization for different applications.

The Wadi El-Rayan is a depression in the Fayoum oasis collecting agricultural drainage water from the Fayoum. Since 1973, this drainage water formed two man-made lakes. Twenty years ago, a third lake, called Lake Magic was formed. Since this newly formed lake was not yet studied, in January of 2019 we conducted research related to its physico-chemical (ion composition, nutrients, heavy metals, etc.) and biological (phyto-, bacterio- and zooplankton) characteristics. The depth of the lake ranged from 1.5 to 9.0 m, water transparency was up to 4.0 m, and the water temperature was 13.6 °C. The average salinity was 29.1 g/l, and the salinity of drainage waters from agricultural fields was 2.9 g/l. A total of 28 phytoplankton species was identified belonging to Bacillariophyceae (eight species), Dinophyceae (three species), Cyanobacteria (seven species), Chlorophyceae (nine species) and Conjugatophyceae (one species). Chlorophyllacontent varied from 14.3 to 24.2 μg/l. In zooplankton, there were three species of Ciliophora, five of Rotifera, and two Copepoda as well as Nematoda and Cirripedia larvae. Salinity in Lake Magic was much higher than in drainage waters coming in the lake. This is a result of a strong salinity increase in Lake Magic after its creation due to climate aridity, and salinity may markedly increase during the next 20 years along with the sharp changes of the lake's ecosystem.

This study aimed to enhance Nile Tilapia growth using Chlorella vulgaris as a food additive in the biofloc system. Different concentrations of C. vulgaris were tested in four different treatments compared to control. The growth rate of Nile tilapia was parallel with C. vulgaris addition to the treatments. The best productive value (growth performance) for Nile Tilapia was recorded in T1 that was distinctly superior to the other treatments. The use of C. vulgaris in the biofloc system decreased feed conversion ratio (FCR) values; whereas the most significant value was observed at T1. Phytoplankton structure in Nile Tilapia gut was predominated with C. vulgaris representing 67.7% of the total phytoplankton crop. Statistical analysis also approved that the most important factor affecting Nile Tilapia growth was C. vulgaris addition, and some other chemical variables that affect phytoplankton’s growth such as PO4. In addition, muscle protein ratio of Nile Tilapia increased with increasing C. vulgaris concentrations. Our data concluded that increasing C. vulgaris concentration improved the growth performance of Nile Tilapia under the biofloc condition.

The Nile River, known as the "giver of life," serves as Egypt’s main source of fresh water. A total of 28 sites along the Nile River were selected during the winter and summer of 2022 to illustrate spatial–temporal variation and indicate potential sources of pollution. The study showed that all chemical and physical parameters are within permissible limits. Based on the abiotic parameters, discriminant analysis (DA) classified the collected Nile sites into three groups (A, B, and C). Group A included the southern sites characterized by high transparency and low levels of electrical conductivity (EC), pH, dissolved oxygen (DO), biological oxygen demand (BOD), and chemical oxygen demand (COD). Group B included the middle sites and was characterized by the relatively high means of EC, total dissolved solid (TDS), pH, DO, BOD, and COD. Group C included the northern sites, which are characterized by low transparency and the highest value of nutrients and EC. A total of 113 phytoplankton species belonging to seven phyla were recorded, while a total of 52 zooplankton species were recorded. The lowest abundance and diversity of phytoplankton and zooplankton were detected at the southern sites, which increased gradually to attain the highest density and diversity in the northern sites. The submerged macrophyte species were recorded in the study area with low species diversity, and Myriophyllum spicatum was the dominant one. 98 epiphytic diatoms and 30 species of macroinvertebrates attached to macrophytes were recorded. The blood parameters of Oreochromis niloticus were within normal limits except for those collected from the Greater Cairo governorate sites in the north. The study showed an improvement in Nile water quality due to increased water levels and water discharged into the Nile.

Through managed enclosure experiments conducted in Lake Nasser during autumn 2023, how zooplankton grazing rapidly reshapes phytoplankton communities was addressed. Four treatments were tested: a zooplankton-free control, natural zooplankton density (Treatment A), double density (Treatment B), and triple density (Treatment C). Across the 45 identified phytoplankton species, Cyanophyceae dominated (42% of total density), followed by Bacillariophyceae (31.5%) and Chlorophyceae (18.7%). Within 72 hours, intense grazing pressure in Treatment C reduced total phytoplankton density by 57%, from 2.8 × 10⁶ to 1.2 × 10⁶ cells/L. Zooplankton exhibited clear selective feeding, strongly targeting Bacillariophyceae—particularly Cyclotella glomerata, Synedra ulna, and Melosira granulata—as well as Chlorophyceae, while Cyanophyceae showed greater resistance to grazing. These findings highlight the pivotal role of zooplankton in structuring phytoplankton assemblages and underscore their potential as a biomanipulation tool for managing eutrophic lakes through targeted grazing control.