This study was conducted to evaluate the impact of human activities on the ecological health and food chain at the shores of four Nile Islands in Great Cairo including El-Qeratten, El-Waraq, El-Zamalek, and El-Manial. Water quality, bacteria, phytoplankton, benthic algae, zooplankton, macrobenthic invertebrates, and bony fishes were examined at each island shore over two seasons including the lowest and the highest flow (February and July 2020, respectively). The obtained results showed that the average values of most of the chemicals in Nile Island’s water were within the Egyptian water quality limits. Discriminant analysis of physicochemical factors revealed a similarity between El-Waraq and El-Qerateen and between El-Manial and El-Zamalek. El-Qeratten was the most polluted island. It has the highest total and fecal coliform bacteria count (3.155 and 3.050 Log MPN/100 mL, respectively). El-Zamalek shores have the highest phytoplankton (33,582 cells × 104 L−1) and zooplankton count (310,891 organisms × m−3) and phyto-biochemical values. Biochemical analysis of phytoplankton demonstrated the richness of the bulk by protein (> 85% of biomass), indicating that phytoplankton has a high nutritional value. Elevated zooplankton count was recorded at El-Zamalek, which coincided with the peak of phytoplankton abundance. Mollusca were the dominant macrobenthic invertebrates on most of the island’s shores. Bony fishes were represented by 27 species and two crustaceans. The levels of the metals in fish samples were compared with the food safety guideline endorsed by the World Health Organization and Food and Agriculture Organization (WHO/FAO) to evaluate the toxicity level.
The live food (phytoplankton and zooplankton) is a very important food source in fish farming, particularly for early larval stages. Therefore, the present study was carried out to determine the consumption rate (grazing (G) and ingestion (I) rates) of three zooplankton species of different size, Brachionus plicatilis, Acanthocyclops trajani, and Heterocypris salina. Five different concentrations (10, 20, 30, 40 and 50 x10 4 cells/ml) of the most common cultured phytoplankton species (Chlorella vulgaris) were utilized as fed for these species. The optimal concentration of the green algae that nourish the zooplankton species with minimum leftover that could affect the water quality was determined. The results revealed that grazing and ingestion rates of B. Plicatilis and H. salina showed linear regression with algal concentrations (p < 0.008; R 2 =0.72 and 0.82,) and (p <0.001; R 2 = 0.969 and 0.964), respectively.Their consumption rates values increased markedly with increasing the concentration of C. vulgaris. On the other hand, the consumption rate of A. trajani were independent of algal concentrations (p ≥ 0.09 and 0.07; R 2 = 0.07 and 0.05, respectively), and reached their maximum values at 30x 10 4 cell /ml. The study concluded that C. vulgaris is a suitable food for B. Plicatilis and H. salina while it is not for A. trajani, where its feeding behaviour still needs more in-depth studies.
Lake Qarun is a closed saline lake in the northern part of El-Fayoum Depression of Egypt. The objective of this work is to give a complete picture of lake biotic factors to alarm on dinoflagellates blooming phenomenon and to compare between chlorophyll a values measured by Fluorometer and Spectrophotometer. Monthly patterns in Chlorophyll a concentrations were measured during the period from May 2015 to April 2016, using two different methods; by fluorometric and spectrophotometric techniques. Phytoplankton species in Lake Qarun are heterogeneously distributed all over the year; dinoflagellates were the main dominant group, chlorophyll a frequently accumulated as distinct peak (336 μgl-1) in July 2015. The phenomenon of dinoflagellated blooming of Prorocentrum micans, Gymnodinium lantzschii and Exuviaell aapora that turning the lake water to brown in colour, is recorded annually. The two methods used in detection of chlorophyll a during this work are accurate and simplified bring the picture in Lake Qarun. Actually, results of fluorometer are more sensitive and higher than those of spectrophotometer. In fact, high salinity, agricultural drainage water from drains and aquaculture activities turned the lake to variable, sensitive aquatic ecosystem, affecting significantly on phytoplankton structure and blooming dynamics determination. There is no record of toxicity effects or mass fish mortality in the lake due to this phenomenon.
Thalassiosira are commonly used algae in mass production (Muller-Feuga, 2000). Certain species from different phytoplankton classes could overcome stress in natural environment, as they can exceed other microalgae classes, sometimes they vigorously grow and forming bloom generating secondary metabolites in the surrounding aquatic environment (Taheri et al., 2017). Influence of pH factor on the metabolic activity, biochemical constituents and ultrastructure of various algae was tested by (Sharma et al., 2012, Safafar et al., 2016. Also light intensity, temperature and minerals affect growth of cyanobacteria detected by (Katoli et al., 2015). There is a relation between phytoplankton uptake of inorganic carbon during photosynthesis process and increase pH of the surrounding environment (Hansen, 2002). However, in the algal culture medium pH is considered one of the most important factors influence optimal algal growth, it controls algal metabolism and affects its bioactive products biosynthesis (Liu and Lee, 2000). Chlorella spp. and Scenedesmus spp. are green phytoplankton commonly incorporated in food industries because of its high protein and lipid content, (Barka and Blecker, 2016). Nannochloropsis spp. of phytoplankton belongs to Eustigmatophyceae. Although its first record was in marine water (Vareltzis and Undeland, 2012) it commonly recorded in both fresh and marine environment. This species gained its importance from its high biochemical constituents and its possible mass production. A laboratory study about Chlorella spp. use as safe protein source for consumption and dietary supplementation and as natural food for some zooplankton species was tested by (Hegab et al., 2019) and concluded that Chlorella vulgaris is used as food source for Brachionus plicatilis and Heterocypris salina. Zooplankton species grazing and ingestion rates were mainly depending on Chlorella densities. Chlorella vulgaris, Scenedesmus quadricauda and Nannochloropsis oculata are known to be used in biodiesel production (Metsoviti et al., 2019) and as feed for fish (Pulz and Gross, 2004). Optimization of the conditions of algal cultivation may lead to production of algal biomass in adequate microalgae quantity (Vasileva et al., 2015).The major scope is using of algae as feed to higher planktons and other organisms in the food web. Microalgae proteins are one of the most important sources of protein to fill the gap in usual protein sources (Barka and Blecker, 2016). Micro algal protein content of Spirulina paltensis constitutes (50-65%) compared to fish protein (24%), (Moorhead et al., 2011). Chlorella vulgaris protein constitutes (43-58% of its dry weight) differs by culture conditions (Safi et al., 2014). Algal usage in different industries in cosmetics, food products enlarge the need for mass production of algae, so there is a growing interest for focus studies on the algal optimum condition needed for optimum growth. So, this study investigate the growth response and total biochemical content of three species of phytoplankton cultu...
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