This study investigated seasonal variation, spatial distribution, sources, composition and potential ecological risks of 16 polycyclic aromatic hydrocarbons (PAHs) in Red Sea coastal water. Surface seawater samples were collected at fourteen different locations. The sum of 16 PAHs concentrations in Red Sea showed clear variation between seasons, ranged from 1.08–6.10, 0.79–50.86, 1.37–54.47 and 0.21–7.18 μg/L in summer, autumn, winter, and spring respectively. PAHs levels in Red Sea coastal waters were relatively high at certain sites during autumn and winter seasons. They could be classified as highly polluted by PAHs contaminants (>10 μg/L). According to the diagnostic ratios measured, the majority of PAHs in this study originated from pyrogenic sources, while minor amounts originated from petrogenic sources. Four rings PAHs accounted for more than 64% of the total PAHs studied. PAHs pose a high ecological risk along the period of study, according to the ecological risk assessment by Risk quotients (RQNCs and RQMPCs).

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Recently, the marine ecology in the Red Sea coast has been altered due to various anthropogenic activities that led to an accumulation of heavy metals (HMs) in its sediments. To evaluate the spatial and temporal distribution and the ecological risk assessment along the study area of the Egyptian Red Sea coast, fourteen samples of sediments were collected during spring and autumn in 2015. The present study aimed to address chromium, zinc, nickel, total carbonate and organic matter in the sampled sediments to assess the risk. In both seasons, the descending order of metal concentrations was Zn > Cr > Ni. The level of studied metals was compared to the background and sediment quality guideline (SQG) values. Results revealed that an adverse biological effect in some sites was possible. Zinc, for instance, recorded higher averages than those of the background and those detected along worldwide coasts. Additionally, to evaluate pollution, methodologies such as the enrichment factor (EF), contamination factor (CF), pollution index (PI) and modified pollution index (MPI) were calculated and interpreted.