Dynamique des populations microphytobenthiques couplée à leur composition biochimique au sein du réservoir Allal El Fassi (Maroc)

L'étude du métabolisme des populations microphytobenthiques par le biais des principaux constituants cellulaires à savoir les glucides, les protéines et les lipides a été réalisée du mois d'août 1996 au mois de juillet 1997 au sein du réservoir Allal El Fassi, situé sous climat semi-aride.Les résultats issus d'un échantillonnage sur substrats artificiels permettent de montrer que :- la température, l'oxygène, l'azote et le phosphore influencent l'orientation métabolique des populations microphytobenthiques ;- les plus fortes concentrations en glucides, en protéines et en lipides correspondent à des populations estivales ;- les lipides sont susceptibles de fournir une estimation satisfaisante de la biomasse microphytobenthiques ;- le métabolisme du microphytobenthos s'oriente vers la synthèse préférentielle des protéines.Most of the works achieved so far in semi-arid lakes have been focused especially on the dynamics, structure and metabolic of phytoplankton. However, this issue has not been addressed in term of metabolic microphytobenthic cells activity. With an aim increasing the relative scientific knowledge relating to the functioning of lacustrian ecosystems in the Maghreb for which the data are still very fragmentary, special attention has been granted to the study of the microphytobenthos metabolism, by means of determining essential cellular constituents (carbohydrates, proteins and lipids) of the reservoir Allal El Fassi.The Allal El Fassi reservoir is about 47 km of Fez. It was built in 1992, and is 7 km long, 0.7 km wide and 34 m maximum depth. The reservoir is classed as mesotrophic and used for irrigation, recreation and to supply drinking water.The study was conducted between August 1996 and July 1997. Samples were taken vertically from the deepest point of the reservoir by means of a Van-Dorn sampler from seven depths: Near the surface, - 2 m, - 5 m, - 10 m, - 15 m, - 20 m and close to the bottom. The samples were analysed for physical, chemical and metabolism of Diatom. Analysis of Nitrogen and phosphate was done following Golterman method and oxygen dissolved by the Winkler method.Given the advantage that presents the artificial substrata (polyethylene leaves) for sample of periphyton, we have opted for the utilization of these substrata similar to these already used by WATANABE et al. (1988). These substrata are submerged during four weeks at different depths.The evaluation of the microphytobenthic biomass has been carried out according to the method of LOHMAN (1908) after enumerations to the microscope Olympus following the technique of LECLERCQ (1984).The dosage of the carbohydrates has been undertaken according to the method of MOAL et al. (1985), while concentrations of proteins have been determined according to the method of LOWRY (1951) and lipids have been extracted according to the method chloroform/methanol.The results show that microphytobenthic biomass presents important fluctuations since extreme values are respectively 0.25·104 µg·cm-2 and 14.95·104 µg·cm-z.Carbohydrates and lipids concentrations (mean=4.52 µg·cm-z and 2.27 µg·cm-z, respectively) are clearly less high than those of proteins (mean=81.84 µg·cm-2). This result indicates that the metabolism of the microphytobenthos of the Allal El Fassi reservoir is oriented towards the preferential protein synthesis. The vertical distribution of proteins, carbohydrates and lipids concentrations shows a well marked stratification, maximal concentrations generally recorded between 0 and 5 m. These high concentrations are attributed to the development of Niztchia, Navicula, Cymbella, Cyclotella, Melosira and Cocconeis.Proteins and carbohydrates concentrations were significantly correlated (r=0.84, p=0.01 at 0m and r=0.52, p=0.10 at 5 m). On the opposite, concentrations of lipids have no correlation neither with those of proteins, nor with those of the carbohydrates.The correlation between the lipids concentrations and the microphytobenthic biomass, is highly significant (r=0.48, p=0.10). This correlation results notably into the fact that lipids visualise well the evolution of the microphytobenthic biomass. However, no significant correlation was found between proteins, carbohydrates concentrations and biomass microphytobenthic.Many works prove the influences of some environmental factors namely light intensity and the temperature on the biochemical composition of the microphytobenthic. In this way, we observe that in period of high temperature, the synthesis of lipids is important. The positive correlation between temperature and lipids (r=0.48, p=0.10) support the observed increase in the concentrations of this variable with increasing temperature. Nevertheless, no significant correlation was found between proteins and carbohydrates concentrations and temperature, which suggests that the synthesis of these components is made independently from this factor. Oxygen dissolved and nitrogen intervene equally in the synthesis of lipids

Évolution nycthémérale des composantes biochimiques du phytoplancton de la retenue du barrage Idriss premier (Fès, Maroc)

The diel changes of the biochemical composition of the phytoplankton were studied in the Idriss first reservoir (located on the Inaouen river at thirty Km from the city of Fes, Morrocco) during September 1994. Several biomass and metabolic indicators (proteins, carbohydrates, lipids, chlorophyll a and primary production) were assessed every fourth hour over tow days (7, 8 and 9 September). Since the Protein/Carbohydrates ratio (P/C) is largely recognised as a good integrator of the metabolic functions of the cells, we examined its distribution pattern concomitantly with aforementioned parameters. The results demonstrated enhanced P/C ratios clearly indicating that nutrients were sufficiently available for growth. In addition, this index showed a diel significant variation with levels higher in the night than in the day. Moreover, these results suggest that phytoplankton species during the night used the day-synthesised carbohydrates to insure the cell metabolic functioning. The P/C presents relatively high values in proposition to the ones that have been recorded in temperate regions, and seems to be related to azotic inputs of the Inaouen river

Screening for childhood lead poisoning in the industrial region of Fez, Morocco

International audienceThe study objectives were to estimate lead poisoning prevalence among children living next to an industrial area, to compare it to that in a control population, and to establish clinical and biological follow-up of the poisoned children. This is a descriptive cross-sectional study including 150 children (exposed and unexposed) performed between January 2012 and April 2013. It was meant to determine blood lead levels (BLLs) in children considered to be an exposed population (EP N 90), living in the industrial area Ain Nokb Fez compared with BLLs of children of other areas belonging to the same city supposed to be unexposed [UP (N&nbsp;=&nbsp;60)]. A sociodemographic questionnaire was obtained, and a blood lead analysis was performed. Clinical and biological follow-up has been performed of poisoned children. The sample consisted of 90 EP children with an average age of 6.82&nbsp;±&nbsp;3.32&nbsp;years and male-to-female sex ratio (SR) of 1.5 and 60 UP children with an average age of 6.45&nbsp;±&nbsp;3.29&nbsp;years and an SR of 1.2. Among the 150 children recruited, the average of BLLs was 58.21&nbsp;±&nbsp;36&nbsp;µg/L (18-202.3&nbsp;μg/L). The average of BLLs in EP children (71&nbsp;±&nbsp;40&nbsp;µg/L) was statistically greater (p&nbsp;&lt;&nbsp;0.0001) than that registered in UP children (38&nbsp;±&nbsp;13&nbsp;µg/L). All poisoned children belonged to the EP group at a prevalence of 21.1&nbsp;%. The clinical and biological examinations of poisoned children showed a few perturbations such as anemia, hypocalcaemia, and deficiencies in magnesium and iron. No renal disease or objective neurological disorders were observed. In the follow-up of the children with BLL ≥100&nbsp;µg/L (19 cases). BLL monitoring showed a significant decrease in average of blood concentration ranging from 136.75&nbsp;±&nbsp;32.59 to 104.58&nbsp;±&nbsp;32.73&nbsp;µg/L (p&nbsp;&lt;&nbsp;0.0001) and in lead poisoning prevalence (p&nbsp;&lt;&nbsp;0.001), which decreased to 7.8&nbsp;% from 21.1. Our study showed a high prevalence of lead poisoning (21.1&nbsp;%) in EP children. The relocation of the industrial site associated with corrective and preventive measures has contributed to a decrease of exposure and lead poisoning prevalence in the aforementioned population.</p