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Distribution and community structure of microphytoplankton in relation to increasing anthropogenic impact along coastal waters of Jeddah, the central Red Sea

Al-Amri Aisha A., Qari Huda A., El-Sherbiny Mohsen M.

Oceanological and Hydrobiological Studies

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2020

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Vol. 49, No. 2

193--205

EN

Seasonal distribution and diversity of surface phytoplankton have been studied in relation to anthropogenic activities at seven locations along the coastal waters of Jeddah, Saudi Arabia in 2017. The concentration of nitrite, nitrate, ammonia, phosphate and silicate varied over wide ranges: 0.04–20.27, 0.05–29.3, 0.22–78.16, 0.02–25.90 and 43–24.50 μmol l-1, respectively. Inorganic nutrients, phytoplankton biomass and density were at eutrophic levels at two lagoon locations (4 and 5), while other coastal locations showed oligotrophic characteristics of the Red Sea. Phytoplankton biomass was positively correlated with all measured inorganic nutrients. The total phytoplankton density varied between 52.4 × 103 and 40800 × 103 cells m-3 (average 6249.9×103 ± 10797×103 cells m-3). A total of 174 species of phytoplankton (95 diatoms, 75 dinoflagellates, 3 cyanophytes and 1 silicoflagellates) were recorded in this study, with the dominance of diatoms (95.1%). Higher densities observed at lagoon locations were mainly due to the proliferation of the diatom species Skeletonema costatum and Chaetoceros decipiens. In terms of diversity, dinoflagellates were more numerous than diatoms in July, otherwise mostly diatoms dominated. On the other hand, cyanophytes were more abundant in November. Based on the present study, anthropogenic activities (especially sewage effluent) in Jeddah coastal waters had a significant impact on the phytoplankton densities and diversity.

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Geochemical fractionation of heavy metals in sediments of the Red Sea, Saudi Arabia

Al-Mur Bandar A.

Oceanologia

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2020

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No. 62 (1)

31--44

EN

The geochemical fractionation of heavy metals, including Mn, Fe, Cu, Pb, Zn, Cd and Ni, collected from the surface sediments of the Jeddah coastal zone of the Red Sea in Saudi Arabia was determined using a sequential extraction technique. The data obtained from the five fractions indicated that the concentration of metals varies among different locations in the study area. The total metal concentrations (%) in the exchangeable (F1), carbonate (F2), reducible (F3) and organic-bound (F4) fractions were measured to determine the mobility of each studied metal. The sum of the two fractions F3 and F4 represented 70% of the Cu, 72% of the Zn and 36% of the Pb. However, the sum of the three fractions F2, F3 and F4 represented 76%, 74%, 68% and 58% of the Cd, Ni, Fe and Mn, respectively. Approximately 46% of the total copper was related to organics, which could reflect a high mobility of copper in these sediments. The maximum mobility of metals in the sediments was confirmed by the bioavailability factor (BF), which was within the ranges of 0.47-0.93, 0.34-0.92, 0.62-0.95, 0.69-0.95, 0.24-0.82, 0.54-0.98, and 0.60-0.95 for Fe, Mn, Cu, Zn, Pb, Cd, and Ni, respectively. Based on the BF, the metals exhibited the following order: Cu ≈ Zn > Cd ≈ Ni ≈ Fe > Mn > Pb. The high levels of BF for the studied metals could reflect the potential for toxic metals to be easily released into the marine environment. The risk assessment code for Cd showed a medium risk in five sediment samples of the northern and southern regions and a high risk to the aquatic environment in the other sediment samples. However, the speciation of Fe, Mn, Cu, Zn, Pb and Ni in the studied sediments exhibited low to medium risks to the aquatic environment.

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Spatial and temporal distribution of heavy metals in coastal core sediments from the Red Sea, Saudi Arabia

Al-Mur B. A., Quicksall A. N., Al-Ansari A. M. A.

Oceanologia

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2017

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No. 59 (3)

262--270

EN

Jeddah is the most industrialized city on the west coast of Saudi Arabia and is under increasing influence of human activities. Heavy metals data were obtained from four near-coast Red Sea sediment cores in close proximity to Jeddah. Chromium, manganese, iron, copper, zinc, and lead were analyzed from depth-resolved sections of each core via heavy acid digestion and inductively coupled plasma-mass spectrometry (ICP-MS). The average concentrations of all four sites were 245.96 mg kg−1, 478.45 mg kg−1, 8506.13 mg kg−1, 251.82 mg kg−1, 623.09 mg kg−1, and 362.75 mg kg−1, respectively. The depth-resolved results showed that highest concentrations of Mn, Cu, and Pb were found in the top 15 cm of the core profile distributions compared to other depth sub-samples. Heavy metal concentrations in core sediments are increased near central Jeddah and have become higher in recent years. The results of enrichment factor calculations indicate little anthropogenic supply of Mn and Cr while Pb, Zn, and Cu show strong anthropogenic input. The Pollution Load Index was higher in the two sites closer to central Jeddah where power and desalination plants and wastewater release are known. This indicates that the area has suffered from heavy metal pollution compared to other non-industrialized sites in the Red Sea. Heavy metal contaminations due to anthropogenic activity should be taken into account to protect the Red Sea during future growth. The results of this work should be considered as a baseline for heavy metals monitoring in the sediments of the Red Sea coast near Jeddah, Saudi Arabia.