Mahmoud Abdel-Radi Dar

The Red Sea’s near-shore zones are considered nurseries and grazing grounds for the various economic fish species. To illustrate the relation between human health and seafloor sediments, the geological and geochemical properties of seafloor sediments were investigated in near-shore zones at Marsa Alam and Hurghada cities along the Red Sea. The obtained data illustrated that the sediment nature at Hurghada is primarily of biogenic origin, as indicated by the high carbonate contents; however, the sediment nature at Marsa Alam is attributed mainly to the terrigenous origin. Accordingly, the studied heavy metals at both localities showed different feeding sources; Marsa Alam sites showed high levels of Fe, Mn, Zn, Ni, and Cu attributed to terrigenous inputs; however, the high averages of Cd and Pb at Hurghada indicating influence from land-based and anthropogenic activities. The calculated risk assessment parameters and carcinogenic risk (ILCR) do not indicate any significant risk. Geochemically and as indicated by the statistical parameters: correlation coefficient, PCA, and Geo-accumulation (Igeo); Mn, Zn, Cu, and Ni were found to be mainly associated with Fe in the same source of accumulation and similar geochemical forms. However, the adsorption over sediment particles and/or assimilation inside the carbonate lattices are possible occurrences of Cd, Pb, and partially Ni. The calculated risk assessment parameters and carcinogenic risk (ILCR) do not indicate any significant risk to marine organisms and human consumption.

The heavy metals were measured in edible parts and shells of five edible bivalve species; Venerupis corrugata, Venerupis sp., Venerupis aurea, Ruditapes decussatus, and Paratapes undulatus collected from Timsah Lake, Suez Canal, Egypt. Ruditapes decussatus showed the highest average of flesh weight and exhibited the highest accumulation averages of Mn, Ni, and Pb. Paratapes undulatus recorded the highest averages of Fe, Zn, Cu, Cd, and Co in their flesh. According to the WHO guidelines, Fe levels in the edible parts of V. corrugata, R. decussatus and P. undulatus exceed the permissible limit of 100 µg/g. In contrast, Cu and Zn metals concentrations are below the permissible limits of 30 and 1000 µg/g, respectively. The levels of Pb and Ni surpass the permissible limits (0.2 and 0.35 µg/g) in all the studied species. Meanwhile, Cd levels are below the permissible limit (0.07 µg/g) in all species, except for P. undulatus. Furthermore, P. undulatus had the highest shell weight average and the highest averages of the mineralized; Fe, Mn, Zn, Cu, Ni, Pb, and Cd. Zn recorded the highest mineralization ratio (metal _shell /metal _flesh ) in the shells of R. decussatus, P. undulates, and V. corrugata (11.38, 6.26, and 5.18, respectively). However, Cd and Fe showed high mineralization ratios in the shell lattices of P. undulatus (7.17, 6.22), suggesting that some bivalve species have demonstrated differential abilities to mineralize certain metals within their shells.

Alginates are one of the most important compounds of brown seaweeds. These compounds are employed in the food area, because of their important rheological properties, such as viscosity, gelling, and stabilizing features and as dietary fiber source. In this study, five species of dominant brown seaweeds were collected in the Red Sea (Padina boergesenii, Turbinaria triquetra, Hormophysa cuneiformis, Dictyota ciliolata, and Sargassum aquifolium) so as to characterize the alginate yield and its properties. The analysis demonstrated differences in the alginate yield among the seaweeds. The highest yield of alginate was recorded in the species T. triquetra (22.2 ± 0.56% DW), while the lowest content was observed in H. cuneiformis (13.3 ± 0.52% DW). The viscosity from the alginates varied greatly between the species, whereas the pH varied slightly. The alginate exhibited a moisture content between 6.4 and 13.1%, the ash content ranged between 12.3 and 20% DW, the protein reached values from 0.57 to 1.47% DW, and the lipid concentration varied from 0.3 to 3.5% DW. Thus, the phytochemical analysis demonstrated that the extracted alginates can be safely applied in the food industry. Furthermore, the alginate yield reveals the potential application of these seaweeds as a nutraceutical raw source, which can be exploited by the food industry.

Biosorption is the most favourable technique for the treatment of heavy metals as it is fast, powerful, and low cost, it takes place in a wide range of temperatures as well as it can be used for almost all types of heavy metals. In this study, the biosorption technique adsorbs Cu2+ and Zn2+ on the dried macroalgae (Halimeda opuntia and Turbinaria turbinata) in a batch system. Experimental parameters affecting the biosorption process are initial metal ion concentrations (5, 10, 15 and 25 mg/L), pH between (4.5 and 5.2), biomass dosage (1 gm) and agitation speed 150 rpm applied at contact time (30, 60 and 120 min). The significant-high average removals of Cu2+ by H.opuntia (> 96%) were recorded in concentrations of 10, 15 and 25 ppm at 120 min and the highest average removals by T.turbinata (81.07%, 78.32% and 74.7%) were recorded in concentrations of 5, 10 and 15 ppm at 120 min. The lowest average removal of Cu2+ 89.22% was recorded by H.opuntia and 49.9% was recorded by T.turbinata in a concentration of 25 ppm at 30 min. In the same way, significant-high average removals (>94%) were recorded in a concentration of 10 ppm at 120 min for H.opuntia and in a concentration of 5 ppm by at 60 min for T.turbinata. In conclusion, the dead biomass of marine algae can provide a promising and low-cost technique for removing heavy metal pollutants in medical industries.

The finest sediment group (FSG) including (Ø3, Ø4 and <Ø4) and the bulk sediment samples were used to estimate the leachable forms of Fe, Mn, Zn, Cu, Ni, Pb, Co and Cd at Adabiya and El Zaitiya harbours in the Suez Bay at the northern tip of Suez Gulf using flame atomic absorption spectrophotometer (AAS). FSG was representing the essential constituents of the seafloor sediments with averages of 70.62% from the total sediments at El-Zaityia Harbour and 70.38% at Adabiya Harbour indicating the deposition under calm oceanographic conditions. Fe was the metal carrier for the different heavy metals, the average leachable forms of Fe and Zn in the FSG (50924.94; 377.61 µg/g) about two folds in the bulk sediment (27153.9; 180.47µg/g) at El Zaityia Harbour and about three folds in the FSG (43965.42; 456.94 µg/g) which more than the bulk sediments (17777.75; 134.62 µg/g) at Adabiya Harbour. In the same Matter, the averages of leachable forms of Mn, Cu, Ni and Pb in the FSG recorded about three folds (532.15; 195.38, 54.60, 145.94 µg/g) at El Zaitiya Harbour and (476.88; 109.42, 47.35, 67.11 µg/g) Adabiya Harbour than the recorded averages in the bulk sediment (182.43; 67.01, 19.01, 62.80 µg/g) at El Zaitiya Harbour (155.56, 35.14, 15.78, 20.27 µg/g) and Adabiya Harbour respectively.