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The relationship between phytoplankton and fish in nutrient-rich shallow Lake Qarun, Egypt

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Napiórkowska-Krzebietke A. , Hussian A. E. M. , Abd El-Monem A. M. , El-Far A. M.

tom Vol. 45, No. 4

539--553

The present study focused on the determination of the baseline data and correlations between biological and physicochemical variables, including the assessment of trophic conditions in Lake Qarun. The concentrations of nutrients were high, with the maxima usually in the east subarea (total nitrogen 6.40 mg dm-3, mineral nitrogen 2.34 mg dm-3, orthophosphates 0.22 mg dm-3). A total of 134 phytoplankton species were recorded. Bacillariophyceae and Dinophyceae co-dominated spatially and seasonally in phytoplankton assemblages. The highest phytoplankton density (935 × 104 cells dm-3) and chlorophyll a content (69.3 μg dm-3) were recorded in the east subarea of the lake, whereas the largest total and dominant fish (Mugil cephalus and Solea spp.) were in the west. Tilapia zillii and Engraulis encrasicolus were most abundant in the east and in the middle part, respectively. When phytoplankton density decreased from the east toward the west subarea, the Secchi disk depth increased. The TLI-based assessment indicated hypereutrophic waters at most sites of Lake Qarun. Statistically significant positive or negative correlations were found between the dominant fish species: T. zillii and Solea spp., and the phytoplankton density, Dinophyceae density, concentrations of TP, chlorophyll a, ammonium, nitrite and nitrate. Such correlations may be helpful to better understand how to enhance the sustainable fish production.

Biosorption of some toxic metals from aqueous solution using non-living algal cells of Chlorella vulgaris

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Goher M. E. , Abd El-Monem A. M. , Abdel-Satar A. M. , Ali M. H. , Hussian A.-E. M. , Napiorkowska-Krzebietke A.

nr 3

Dead cells of Chlorella vulgaris were used experimentally to remove cadmium (Cd2+), copper (Cu2+) and lead (Pb2+) ions from aqueous solution under various conditions of pH, biosorbent dosage and contact time. C. vulgaris was isolated from Lake Manzala, (Egypt) and then cultivated outdoors, in growth media, maintaining pH of nearly 7.5. After cultivation, the cells were harvested by coagulation and prepared to make an experiment with different variants of pH, contact time and adsorbent dose. The adsorption specific characteristics of C. vulgaris were examined using Fourier Transformation Infrared Spectroscopy (FTR) and Scanning Electron Microscopy (SEM). The FTIR and SEM data showed vibration frequency changes for the peaks corresponding to the surface functional groups and morphological changes of C. vulgaris, respectively, after its exposure to metal ion solution. The maximum removal efficiency for copper and lead at ambient room temperature was recorded at pH 5 and 20-minute contact time, while the contact time of 120 minutes at pH 6 created the most suitable conditions for cadmium biosorption. On the other hand, 2 g dm-3 of C. vulgaris under optimum conditions was sufficient to remove 95.5%, 97.7% and 99.4% of Cd2+, Cu2+ and Pb2+, respectively, from a mixed solution of 50 mg dm-3 of each metal ion. The removal trend was in order of Pb2+ > Cu2+ > Cd2+. The results suggested that the biomass of C. vulgaris is an extremely efficient and environmentally friendly biosorbent for the removal of Cd2+, Cu2+ and Pb2 from aqueous solutions, which may be applied on a large, industrial scale.