Long-chain aliphatic wax esters isolated from the sponge Chalinula saudensis (Demospongia) along the Jeddah coast of the Red Sea

A esponja Chalinula saudensis ocorre ao longo da costa de Jeddah, Arabia Saudita, mas apenas recentemente foi isolada e identificada. No presente estudo a matéria orgânica total da esponja foi extraída por solventes e o extrato foi separado por partição sucessiva através do emprego de hexano e água, clorofórmio e água e finalmente t-butanol e água. A camada contendo clorofórmio foi então separada por cromatografia em sílica. Os resultados mostraram a presença de ésteres de quatro ácidos graxos de cadeira longa (C28H56O2, C30H60O2, C32H62O2 e C36H70O2), sendo que o segundo deles foi também identificado nos corais Millepora dichotoma e Millepora platyphylla. Não se tem evidência da presença dos demais compostos em outros organismos marinhos, embora haja relatos para ésteres semelhantes de cadeia longa, mas contendo diferentes cadeias alifáticas e diferentes pesos moleculares. Os compostos isolados em C. saudensis são geralmente ceras e sua presença na esponja tem importância não só nas rotas de biosíntese, mas servem como isolantes nas variações sazonais adversas.The sponge Chalinula saudensis, which occurs along the Jeddah coast, has only recently been isolated and identified. In this study, the total crude organic matter of the sponge was extracted by solvents. The total crude extract was further separated by partitioning it with hexane and water, then with water and chloroform, and finally with water and t-butanol. The chloroform layer was subjected to separation by preparative layer chromatography on silica. One fraction contained four long-chain fatty acid esters, C28H56O2, C30H60O2, C32H62O2 and C36H70 O2. The second ester, C30H60O2, has been identified in the fire corals Millepora dichotoma and Millepora platyphylla. The others have not previously been reported from marine organisms; however similar long-chain esters with different long aliphatic chains and with different molecular weights have been identified from other marine organisms. These compounds are normally waxy and their presence in Chalinula saudensis plays a vital role in the biosynthetic pathways. They also act as insulators against seasonal variations

Formation of Zn- and Fe-sulfides near hydrothermal vents at the Eastern Lau Spreading Center: implications for sulfide bioavailability to chemoautotrophs

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Fecal sterols and pahs in sewage polluted marine environment along the eastern Red Sea coast, South of Jeddah, Saudi Arabia

404-410Water and sediment samples were takes near the sewage discharge point on the eastern Red Sea Coast of Jeddah and analyzed for PAH and fecal sterols like coprostanol, cholesterol and cholestanol. PAH were estimated spectrofluorometrically and then further analyzed by GC-MS. Sterols were derivatized by BSTFA into their corresponding trimethyl silyl derivatives and then analyzed by gas chromatography and quantified with standard sterols. PAH ranged from 1.5 to 6.5 g 1-1 in eight stations. Concentration of coprostanol in water samples showed a maximum of 8.2 g 1-1 at station XVIII and minimum 0.1 g 1-1 at station 10C. The analysis of the sediment samples indicated much higher values for fecal sterols. It was found to be 785 g 1-1 in sediment and 6.5 g 1-1 in the water samples at station XVIII. PAH did not show any distinct increase in the sediment samples. According to Grimaldt equation the value of r* (5 / 5 + 5) was determined. Out of a total of sixteen samples, fourteen samples had a value of 0.7 or higher than 0.7. This indicate a definite and a positive sewage contamination infecting almost the whole area studied. The GC-MS of the PAH indicate the presence of phenanthrene, benzophenone and 2,4-diisoprophyl naphthalene, methylnaphthalene, and 9-H-methylene flourene. Present study infers that the sewage; either untreated or partially treated is dumped into the sea

The effective adsorption of arsenic from polluted water using modified Halloysite nanoclay

The presented research applied the modified Halloysite nanoclay to boost the adsorption efficacy of heavy metals from the water. To improve As (III) adsorption effectiveness from water, the study assessed the characteristics of the prepared materials and improved the experimental conditions. The study was optimized the experimental condition with a dosage of 1 g/L, contact time of 90 min, the solution pH of 8, and the initial concentration of 5 ppm of As (III). The optimization was performed in distilled water and later the experiments were conducted in the real polluted water. The modified Halloysite nanoclay’s physical characteristics were investigated using techniques like X-ray diffraction, scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, and surface area analysis. The experimental result shows the adsorption efficiency of 82.4 % of As (III) at the optimized condition during the usage of modified Halloysite nanoclay. To create a suitable mathematical model for a better description of the interactions between pollutants and solid adsorbents, it is helpful to analyze the process kinetically. The removal process of As (III) was studied kinetically and the observation shows the pseudo-second order kinetics

TRANSITION FROM A CONTINENTAL TO AN OCEANIC RIFT IN THE NORTHERN RED SEA

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Relationship between extracellular low-molecular-weight thiols and mercury species in natural lake periphytic biofilms

The uptake of mercury by microorganisms is a key step in the production of methylmercury, a biomagnifiable toxin. Mercury complexation by low molecular weight (LMW) thiols can affect its bioavailability and thus the production of methylmercury. Freshwater biofilms were sampled in the summer using artificial Teflon substrates submerged for over a year to allow natural community colonization in the littoral zone of a Boreal Shield lake. Inside biofilms, concentrations of different extracellular thiol species (thioglycolic acid, L-cysteine-L-glycine, cysteine, and glutathione) were up to three orders of magnitude greater than in the surrounding water column, potentially more readily controlling mercury speciation than in water column. All biofilm thiols except thioglycolic acid were highly correlated to chlorophyll a, likely indicating an algal origin. Extracellular total mercury represented 3 ± 1% of all biofilm mercury and was preferentially found in the capsular fraction. Levels of LMW thiols of presumed algal origins were highly correlated with total mercury in the mobile colloidal fraction of biofilms. We propose that periphytic phototrophic microorganisms such as algae likely affect the bioavailability of mercury through the exudation of LMW thiols, and thus they may play a key role in the production of methylmercury in biofilms