Entity

Time filter

Source Type


Lakkis S.,Lebanese University | Lakkis S.,National Center for Marine science
Cahiers de Biologie Marine | Year: 2012

Hundreds of Indo-Pacific marine species either from benthic or pelagic environments were introduced from the Red Sea into the East Mediterranean, through the Suez Canal pathway, since its opening to navigation in 1869. Most of those have succeeded to establish stable populations along the Levantine Basin coast. During the last 50 years and after the functioning of Aswan High Dam in 1965 and the deepening of the Suez Canal, the invasion process increased and introduced species of Eritrean and Indo-Pacific origin were mostly doubled. This is due not only to human activities, but also to the climate change inducing global warming and thus hydrological changes which occurred in the entire Levantine Basin and traduced by increment of seawater temperature and salinity (AT ∼ 0.40 °C, △S ∼ 0.35). Out of 350 fish species so far recorded in the Lebanese coast, 60 are introduced in the area where they established populations. From 240 macrophytes species present along the Lebanese coast, 20 tropical species have invaded the Levantine coast where they established populations along the Lebanese coast. About 15% from 400 phytoplankton species and 20% from approximately 1000 zooplankton species are introduced into the Mediterranean. This process of invasion is still continuing, so we notice more tropical newcomers in the Levantine Basin. The impact of invasion on local biodiversity is questionable. There may be a negative effect with regard to the competition between introduced and native species. Inversely positive effect could be the consequence of invasion with regard to the macro-ecology and biogeography. However, none of the studies so far conducted in this respect has identified any extinction of a native species due to the influence of any invader. This phenomenon reflects certain " Tropicalization" of the East Mediterranean Basin, enhancing the invasion of exotic species into the new marine environment. This is due probably, not only to the man-made activities, but also to the climate change inducing global warming noticed during the last decades. Source


Flouty R.,Lebanese University | Flouty R.,National Center for Marine science
Desalination and Water Treatment | Year: 2016

Of the unicellular green algae species, Chlamydomonas reinhardtii has only recently gained greater attention for the treatment of heavy metal contamination in aqueous solutions. In the present study, C. reinhardtii was used to remove Cu and Pb metal ions from the Litani River in Lebanon. Three samples were collected from three different sites located along the tributaries of Litani. Short-term (40 min) metal biouptake experiments were performed using 0.2 g L−1 of freeze-dried and living algal cells. In the studied samples, dead cells showed higher removal efficiency for both metal ions than living cells. The percentage removal of dead algae for Cu (28.66%) is about 1.8 times higher than that of living cells (16%). For Pb, biosorption (23.4%) is about 2.75 times higher than bioaccumulation (8.5%). Water chemistry significantly affects metal speciation, bioavailability, and biouptake by living and dead cells. As predicted by Visual MINTEQ program, only very small fractions of Cu and Pb were present as free ions with the majority being bound to humic substances (HS) or carbonate ligands. PbCO3 and CuCO3 dominated in water samples containing very low amount of organic compounds. As stated by the free ion activity model (FIAM) and the biotic ligand model (BLM), Cu uptake seems to increase with an increase in the free Cu2+ concentration in water and it is dependent on ligands complexation and co-cations competition effects. However, equilibrium models cannot explain the bioaccumulation results obtained for Pb. Although further investigations are needed, the obtained results are very promising as a starting point for a potential application of these micro-organisms as an efficient and economic biomaterial for the removal of heavy metals from metal-contaminated freshwaters. © 2016 Balaban Desalination Publications. All rights reserved. Source


Flouty R.,Lebanese University | Flouty R.,National Center for Marine science | Estephane G.,Lebanese University
Journal of Environmental Management | Year: 2012

A comparative evaluation of bioaccumulation and biosorption of Cu (II) and Pb (II) ions by algal cells of Chlamydomonas reinhardtii was conducted in single and binary metal systems. Experiments were performed in solutions containing 5 × 10-7 M of free metal at 30 °C and pH 6. Algal cells were used in the concentration of 0.2 g/L. Both processes tend to be more important as contact time between heavy metals and algal cells increases. Under studied conditions, dead cells showed higher removal efficiency than living cells for both metal ions. Removal efficiency of Pb increases from 8% to 40% when comparing the results obtained by living cells and dead cells. For Cu (II) ions, the removal efficiency of dead cells was about 2 times higher than living cells (55% vs. 28%). Living cells showed similar bioaccumulation capacity for both ions. Synergistic and antagonistic effects between copper and lead were observed in binary metal systems which imply that bioaccumulation process is much more dynamic than assumed in the equilibrium models. In contrast, dead algal cells showed a higher affinity for Pb (II) ions compared to Cu (II) ions and no competitive effect was observed in the biosorption of copper and lead by the inert cells in binary metal mixtures. Biosorption of Cu (II) and Pb (II) seems to occur at different binding sites on the surface of algal biomass. The obtained results showed that the mostly advantageous process of metal ions binding is biosorption and the biomass of C. reinhardtii is suitable for the development of an efficient and economic biosorbent for the removal of heavy metals from aqueous environments. © 2012 Elsevier Ltd. Source


Flouty R.,Lebanese University | Flouty R.,National Center for Marine science
Environmental Engineering and Management Journal | Year: 2015

The removal efficiency of algal biomass Chlamydomonas reinhardtii for Pb and Cu metal ions was evaluated in single and binary metal systems. Biosorption experiments were performed in solutions containing 0.2 g L-1 of algal biomass at 30oC and pH 6. Initial metal ion concentrations ranged from 10-7 M to 10-6 M. Thermal analysis of the biosorbent indicated that algal cells are composed of groups containing C, H, N, and S. The presence of ionisable functional groups responsible for biosorption of metal ions on algal cells was confirmed by FT-IR analysis. Biosorption of lead seems to be more sensitive toward modification in carboxyl groups than amino groups, while copper showed the opposite trend. Under studied conditions, the removal efficiency of algal cells for Cu is higher than for Pb in single monometallic systems. Biosorption of copper and lead seems to occur at independent binding sites on the surface of algal biomass. Pb ions are adsorbed on specific sites with high affinity independent of Cu, whereas, two types of active sites are involved in the biosorption of copper; high affinity specific sites independent of Pb and low affinity sites dependent on the presence of Pb. The potential of algal biomass as biosorbent has been established by the available data, and more research and development of algal biosorption process is needed. © 2015, Gh. Asachi Technical University of Iasi. Source


Flouty R.,Lebanese University | Flouty R.,National Center for Marine science | Khalaf G.,National Center for Marine science
Ecotoxicology and Environmental Safety | Year: 2015

Ni, Pb and Cu uptake by Chlamydomonas reinhardtii has been quantified in single and binary metal systems in order to test some of the key assumptions of the biotic ligand model (BLM). Experiments were performed in solutions containing 5×10-7M of free metal at 30°C and pH 6. Nickel internalization fluxes (Jint) were measured in the presence of various concentrations of lead or copper from 5×10-8M to 5×10-6M at pH 6.0. Competition experiments did not show a straightforward antagonistic competition, as would be predicted by BLM. Synergistic and antagonistic effects were observed in binary metal systems which implies that bioaccumulation process is much more dynamic than assumed in the equilibrium models. Ni uptake decreased significantly in the presence of Cu2+ concentrations higher than 5×10-7M. However, a maximum value of Ni uptake was observed at 5×10-7M Pb2+. Cu2+ was shown to compete strongly with Ni for uptake, having a higher binding affinity to Ni transport sites (KCu-Rs=106.95M-1) than to Cu transport sites (KCu-Rs'=106.22M-1). In contrast, the effect of Pb2+ on Ni uptake could not be explained by a simple competitive equilibrium with the transport sites of Ni such as the BLM. On the other hand, internalization fluxes of Cu and Pb were nearly constant in the absence and in the presence of Ni, implying that nickel had no effect on the uptake of copper or lead. The calculated affinity constant of Cu to Ni transport sites in the presence of Ni was similar to that obtained in the absence of Ni (K'Cu-Rs'=106.22M-1). It was further concluded that Cu and Pb did not interact with the same active sites on the cell surface. Ni and Cu were shown to interfere with Mg and Na transporters, while Pb uptake was thought to occur by the Ca pathway. © 2014 Elsevier Inc. Source

Discover hidden collaborations