Egyptian Journal of Aquatic Research最新文献

Introduction of farmed non-native fish strains into ecosystems outside their native range has raised global concerns. We investigate the presence of Oreochromis niloticus in the southernmost part of Lake Tanganyika. DNA was extracted from tissue samples and analysed using microsatellite DNA markers. We confirm the O. niloticus from the observed morphological features of the samples collected and the analysis using genetic markers. Although the species is native to the lake, it is unclear if the fish now being sampled are indigenous or escaped from aquaculture facilities 15–20 years ago. The genetic diversity was similar statistically, though higher in O. tanganicae, followed by wild O. niloticus and least in farmed O. niloticus. There was no evidence of hybridisation between O. niloticus and native O. tanganicae. We recommend a comprehensive investigation to ascertain the origin of the O. niloticus, which, though rare, is present in catches. Due to known introductions, conservation measures must be set up to protect the genetic purity of O. tanganicae since O. niloticus is known to hybridise with other Oreochromis species and it is not known whether the farmed non-native strain is capable to establish such hybridization more than the wild native strain.

One of the most useful water streams in Egypt is the Ismailia Canal. However, despite its significance, numerous factories discharge their waste into the canal, causing a drastic decrease in its water quality and fauna. In this respect, this study aims to evaluate the negative impact of fertilizer discharge on community structure, zooplankton biodiversity, and water quality in the Ismailia Canal. Four stations were selected, where the Canadian Water Quality Index and the Metal Index were used to determine the point source of contamination at each station. As revealed in the Canadian WQI results, Stations (3) and (4) have marginal water quality, but no metal pollution was shown in the Metal Index results of the study area. The Canonical Correspondence Analysis (CCA) was also applied. The zooplankton community structure and biodiversity were examined, where their total density recorded an average of 598,854 ind./m³. Nineteen zooplankton species—belonging to the groups: Rotifera, Cladocera, Copepoda, and Nematoda—were identified. Rotifera was predominant, representing 97.05% of the total zooplankton density. Although Station (3) had the highest diversity index, there was a special abundance of organic matter bio-indicators. That is why mandatory laws and management plans had to be enforced to mitigate the canal deterioration.

This study aims to assess shoreline change rates at al-Gamil Beach, west of Port Said City on the northeastern Mediterranean coast of Egypt. The study area is characterized by two main tidal inlets connected Lake EL-Manzala by the sea and other coastal protection structures. Given that the al-Gamil coastline shall be monitored to explore erosion and sedimentation changes along the shoreline, multi-temporal satellite images and an ArcGIS-based DSAS model application were utilized to identify and measure changes to the coastline. Five Landsat images covering the study area were used to identify patterns of coastline accretion and erosion. These images were corrected geometrically and radiometrically to help the investigation process of coastline change rates. The three DSAS statistical models: Linear Regression Rate, End Point Rate, and Net Shoreline Movement were used to assess the shoreline change rate. Based on these findings, the shoreline has alternate exposure to accretion and erosion at varying rates, where the average rate of accretion is nearly +9 m/year, while the maximum rate of erosion is about −27 m/year.

The aquaculture industry is facing a growing need for a cost-effective, sustainable, and highly nutritious alternative to fish meal (FM) due to the increasing gap between supply and demand. This study investigated the effect of substituting (FM) with probiotics (Spirulina platensis) in fish feed on the survival, growth, and biochemical parameters of Oreochromis niloticus. Live tilapia fingerlings were stocked in 100-l glass aquaria. The feeding regimen consisted of four controls: commercial feed (C), formulated feed with FM (FMR₀), and formulated feeds with 25% and 50% replacement of FM (FMR₂₅, and FMR₅₀), respectively. The trial groups included FMR₂₅S₅ (25% FM replacement with 5% Spirulina), FMR₅₀S₅ (50% FM replacement with 5% Spirulina), FMR₂₅S₁₀ (25% FM replacement with 10% Spirulina), and FMR₅₀S₁₀ (50% FM replacement with 10% Spirulina). The trial period lasted for 24 weeks. Weight gain (WG) was most pronounced in FMR₅₀S₁₀ (p < 0.05). The SGR (specific growth rate) was highest for FMR₅₀S₁₀, FMR₅₀S₅, and FMR₅₀. A similar pattern was exhibited in the FMR₅₀S₁₀ group for length gain (LG). The protein efficiency ratio (PER) values were maximum in FMR₅₀, FMR₅₀S_5, and FMR₅₀S₁₀. FMR₂₅S₁₀, FMR₀, and FMR₂₅ exhibited the highest feed intake (FI) (p < 0.05). Trial diets supplemented with Spirulina enhanced the activities of SOD, CAT, and MPO. FMR₂₅S₁₀ exhibited the highest GPx activity and appreciable flesh quality. Collectively, S. platensis enhanced growth and feed utilization and modulated biochemical endpoints in feeds.

Natural zeolites and composites containing zeolites, with their distinctive physicochemical properties, show great promise and have been applied across various industries, including agriculture, aquaculture, water and wastewater treatment, air purification, and petrochemicals. Recent years have witnessed significant advancements in the use of these inorganic adsorbents. The growing environmental concerns related to heavy metal contamination in water sources underscore the need for effective remediation strategies to protect ecosystems and human health. This review explores the diverse applications of natural zeolites and zeolite composites in the context of removing heavy metals from polluted water. A special focus is also given to the structural attributes, composition, and effectiveness of zeolites and zeolite composites. The review delves into their extensive utilization, with insights into their adsorption capabilities and mechanisms influencing performance. In addition, the review highlights the potential significance of these materials in aquaculture systems, particularly their role in mitigating waterborne heavy metal contaminants and enhancing environmental sustainability. By synthesizing current research findings, this review offers a comprehensive perspective on the multifaceted roles of natural zeolites and zeolite composites in heavy metal remediation in polluted water and their relevance in aquaculture practices.

Metals enter aquatic systems directly from anthropogenic sources, natural, and atmospheric deposition. Sediment is an essential component of aquatic ecosystems; it serves as a habitat for a variety of aquatic organisms. Due to their non-biodegradability, metals are among the most harmful pollutants in aquatic environments. The purpose of this study is to evaluate the levels of Mn, Fe, Cu, Pb, Zn, Ni, Cd, and Co verified from a total of 29 surface sediment samples collected along the western Mediterranean coast of Egypt in 2020—i.e., from Abu Qir Bay, al-Mex Bay, and Marsa Matrouh. It also aims to assess the ecological risk related to metal levels in sediments. The results revealed that metals followed a decreasing concentration sequence on average: Fe > Mn > Zn > Pb > Co > Ni > Cu > Cd. Both the geo-accumulation index (I_geo) and the pollution load index (PLI) showed that Abu Qir Bay sediments are moderately polluted; al-Mex Bay sediments are slightly polluted and Marsa Matrouh sediments are unpolluted. A multivariate statistical analysis was used, including Pearson correlation analysis and clustering heatmap, where the results are classified into two clusters according to their sources.

In this study, a simple and eco-friendly approach to biosynthesizing silver nanoparticles (AgNPs), mediated by an aqueous extract of Laurencia papillosa, was successfully developed. The formed nanoparticles (NPs) were characterized by UV–visible spectroscopy, X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), and energy dispersive analysis of X-rays (EDAX). The particles showed a crystalline spherical shape with a size ranging from 6.9 to 15.0 nm. By using a central composite design (CCD) based on response surface methodology (RSM), several experimental parameters such as pH, incubation period, and concentration of algal extract were improved. The optimized AgNPs were used as an adsorbent for iron, zinc, manganese, and copper removal from fish aquaculture effluents. The removal percentage was 97.1%, 43.3%, 5.6%, and 2.4% for Fe, Mn, Zn, and Cu respectively. The results imply that AgNPs have the potential to be used as bioadsorbents for heavy metal removal.

The purpose of this study is to assess long-term trends in Chl-a and SST in major fishing zones associated with fish production over an 18-year period (2002–2019) in the Gulf of Suez, Gulf of Aqaba, and the Red Sea proper. The study found that seasonal SST mean values ​​differed significantly (P < 0.01) when compared across seasons. Chl-a (mg/m³) exhibited variation between winter and summer (P = 0.01). Regarding regional variability, SST differed significantly between the three regions (P ≤ 0.01), while Chl-a showed no significant difference between the Gulf of Aqaba and the Red Sea, otherwise, chlorophyll exhibited significant variation between the gulfs of Suez and Aqaba (P < 0.01) and the Gulf of Suez and the Red Sea (P < 0.01). The current study found that the total catch varied seasonally in the studied regions from 2010 to 2015. Seasonal (2010–2015) and annual (2002–2019) time series analyses of fish production variance indicated significant zonal production trends. On the other hand, annual trends showed a gradual decline in the total catch from 2002 to 2015, followed by an increased trend until 2019.

Polychlorinated biphenyls (PCBs) are persistent organic pollutants. They were widely used and distributed in the environment causing endocrine disruption, carcinogenicity, and immunotoxicity. The toxic heavy metal, Hexavalent chromium Cr(VI), co-exists with PCBs leading to ecological deterioration and health problems. Thus, bioremediation of the coexisting PCBs and Cr(VI) is essential for the environment and public health. In this study, three bacterial strains identified as Bacillus safensis, Bacillus cereus, and Bacillus vietnamenesis, were isolated. As revealed, various strains belonging to the genus Bacillus degraded PCBs. However, this study can be considered the first report on isolated strains as PCB-degraders that resist Cr(VI) as co-contaminants. All strains had the biphenyl dioxygenase (bphA) gene and grew on PCBs as the sole carbon and energy source and completely remediated 5 mg/l Cr(VI) individually within 24 h. The three isolates showed different response mechanisms to Cr(VI) that enabled Bacillus safensis and Bacillus cereus to grow on PCBs and Cr(VI) as co-contaminants. Bacillus vietnamensis recorded the highest growth on PCBs, but could not grow on PCBs with Cr(VI). Therefore, Bacillus safensis and Bacillus cereus are concluded to be good candidates for bioremediation of PCBs and Cr(VI) as co-contaminants, while Bacillus vietnamensis is more suitable for bioremediation of either PCBs or Cr(VI) individually.

This study investigates groundwater resources in the El-Omayed area on the northwestern coast of Egypt. The aim is to assess the extent and severity of saltwater intrusion in the shallow aquifer system, as well as its potential impacts on groundwater resources. A combined geophysical and hydrochemical approach was adopted in this investigation. Across the study area, 32 vertical electrical soundings were conducted, along with two electrical resistivity tomography profiles. Sixteen water samples were collected, and then chemically analyzed to evaluate water quality, seawater intrusion, and source of salinity. The results of geophysical interpretation revealed the existence of a thin, shallow freshwater-bearing layer (42–95 Ω.m), predominantly situated in the central parts of the area, followed by saltwater saturated layers of (0.9–2.1 Ω.m) affected by the Mediterranean Sea invasion. The eastern portion of the aquifer also recorded a relatively high seawater intrusion. As evidenced by the actual data gathered from drilled wells, the study area can be divided into three distinct zones: fresh, brackish, and saltwater zones. The study identified the most suitable sites to establish new groundwater wells, in addition to identifying the source of salinity through the investigation of the geochemical properties of water samples.