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Updated: May 10, 2026

Determination of Total Lipid and Lipid Classes in Marine Samples
Published on: December 11, 2021
Lipid composition variability in surface sediments of rural open-leaky versus urban closed lagoons, Red Sea coast,
Hattan A Alharbi1, Ahmed I Rushdi2, Mubarak T Al-Otaibi1
1Department of Plant Protection, College of Food and Agriculture Sciences, King Saud University, P.O. Box 2460, Riyadh, 11451, Saudi Arabia.
Abstract:
Red Sea lagoons are vital ecological and economic ecosystems, with the relatively pristine AlWajh Lagoon contrasting the urbanized and polluted Obhur Lagoon, underscoring the need for conservation and restoration. This study aims to investigate the differences in composition and spatial distribution of major lipid compounds in surface sediments from these two contrasting coastal ecosystems: the open-leaky AlWajh lagoon and the closed Obhur lagoon. The analysis identified a diverse array of organic compounds, including n-alkanes, n-alkanoic acids, n-alkanols, sterols, anthropogenic plasticizers and petroleum biomarkers. Distribution, composition, and diagnostic ratios of these lipids were used to apportion organic matter sources and assess environmental conditions in both lagoons. The lipid profiles revealed significant differences in organic matter provenance. In the AlWajh lagoon, n-alkanes showed a strong microbial and petrogenic signature, characterized by a low carbon preference index (CPI ~ 0.41) and high low-molecular-weight to high-molecular-weight (LMW/HMW) ratios (mean = 12.7). Aquatic biota was the primary source for n-alkanoic acids and n-alkanols (81-83%). AlWajh's organic matter was dominated by anthropogenic (52.10%) and aquatic (46.03%) sources, with minor terrestrial input. Conversely, the Obhur lagoon exhibited a stronger terrestrial influence in its n-alkane profile (CPI = 2.06; LMW/HMW = 0.66), with terrestrial sources contributing 37.39% of n-alkanols. Obhur also showed higher petroleum contamination, evidenced by elevated unresolved complex mixtures (UCMs) (mean U:nCB ratio = 7.24) and the presence of hopane and sterane biomarkers. Anthropogenic inputs were dominant in Obhur (63.85%), followed by aquatic (25.95%) and terrestrial (10.24%) contributions. Plasticizers, specifically dibutyl phthalate, accounted for a low and similar percentage of total extractable organics in both lagoons (4.48-4.57%). Sediment lipid profiles from AlWajh and Obhur lagoons (shaped by aquatic and petroleum inputs in the former, and petroleum, marine, and terrestrial sources in the latter) reveal diverse natural and anthropogenic compounds, reflecting complex biogeochemical and environmental interactions. These findings provide insights into the distinct sources and degradation pathways of organic matter in open and closed coastal ecosystems, supporting environmental monitoring initiatives.
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