الجماهيرية العربية الليبية الشعبية الاشتراكية العظمى

1. الجماهيرية العربية الليبية الشعبية الاشتراكية العظمى جامعة قاريونسكلية العلومقسم النبات

3. Some Ecological Aspects of Posidoniaoceanica (L.) Delile on the Eastern Libyan Coasts • بعض الأوجه الإيكولوجية • لنبات تبن البحر Posidoniaoceanica(L.)Dlile بالساحل الشرقي من ليبيا

5. ABSTRACT • The current study investigates the effect of some environmental factors including habitat type, water depth and pollution with some heavy metals on the population biology of Posidoniaoceanica (L.) Delile at two sites, Garyounis and Deryanah on the Libyan coast during 2007/2008.

6. ABSTRACT • The mean population density of P.oceanicawas very similar at the two sites (4.9 and 4.7 colony/25m2 for Benghazi and Deryanah respectively). • However, at Garyounis, the colonies showed longer diameters (39 m), shorter plants (26. 3cm) and fewer leaves per colony (191.1) compared to Deryanah where they measured 3 m and 48.5 cm in diameter and in height respectively and had 405.6 leaves per colony. As the water depth increases (5, 10 and 15m) plant density, colony diameter and plant height remain largely unchanged, whereas the number of leaves increases.

7. ABSTRACT • The Soil contents of Cr and Pb were much higher in Garyounis compared to Deryanah. Colony diameter was positively correlated with Cr contents (+0.75) while, the number of leaves was negatively correlated with Cr (-0.75) and Pb (-0.63) contents.

8. More investigations are still needed to evaluate the environmental factors affecting its ecology and the economic importance of P.oceanicaand per especially the anthropogenic activities.

9. Introduction • Seagrass may serve as heavy metal reservoirs (Malea, 1994), have been described excellent bioindicators (Pergent-Martini et al., 2005) due to their high sensitivity to changes in the environment, and specially to human impacts (Short and Wyllie-Echeverria, 1996).

10. Introduction • The meadows constituted by the seagrass Posidonia oceanica (L.) Delile are widely recognized as key ecosystem in coastal habitats (Hemminga and Duarte, 2000), and considered one of the most important ecological assemblages of Mediterranean coastal systems (Buia et al., 2000).

11. Introduction • Pergent et al., (2007) reported the fact thatPosidonia oceanica grows very slowly, suggest that these structures started to form themselves several hundreds of years ago. • In Mediterranean basin a serious, long lasting, seagrass decline (Krause-Jensen et al., 2004) occurred, mainly associated to the increasing of anthropogenic pressure along the coastline, which enhanced turbidity, sedimentation and pollution (eg., Duarte et al., 2004).

12. Introduction • Seagrass are not a preferential source of food for herbivores because of their high C/N ratios, their high content in cellulose and the presence of chemical deterrents (Verges et al., 2006). • The metals measured for the study were selected because Cr and Pb are generally characterized as toxic elements, whereas Zn is toxic only at high levels (Malea, 1994).

13. Introduction • The aim of this study was to establish the vegetation structure of Posidonia oceanica (L.) Delile at Garyounis and Deriana coasts, the interaction between their contents of some heavy metals (Cr, Pb and Zn) and some morphological parameters.

15. The study area included two striated fine sandy coasts far from each other about 45 Km at the eastern coast of Libya (Fig. 1). They were Garyounis coast (20° 02´ N and 32° 01´ E) at Benghazi city and Deriana one (53° 12´ 32´´ N and 38° 18´ 20´´ E) 40 Km. eastern of Benghazi. • Garyounis coast suffer from strong anthropogenic loads especially sewage and the different activities of its ports, meanwhile, Deriana coast have 10 Km of salt marshes. The mean of salinity of Sea water was 37%, with mainly weak western waves (1.5 Km/h.), the tides also neglected (30-60 Cm) with a relatively high humidity (reached 73% at August).

16. The data were collected by diving to different depths (5, 15 and 20m) during the period of 1/5/2007 and 1/9/2007. Personal GPS Garmin 12 was used as global positioning system (Latitude and Longitude). • Quadrats method (at least three 5×5 m2) through 1 mile. Three sites (each 0.5 mile) were chosen along three lines in north direction as sampling sites (for replications) at different depths (5, 15 and 20m) to cover the study area.

17. Deriana Garyounisnis • Fig. (1): Benghazi coast showing the study area (Admiral British navy modified by the authors) Admiral, J. P.; Clarke, C. B. (1996) Deriana

18. 20 m 1 ميل بحري 25 m2 15 m m 5

21. The data describing some morphological parameters (Number, height and diameters, and leaves number) and soil contents of heavy metals (Cr, Pb and Zn) by atomic absorption were analyzed according to the following general linear model of SAS (2005): • Y ijk = U + L i + D j + (LD) ij + e ijk • Where: • Y ijk = Observation. • U = Overall mean. • L i = Effect of Locations (1Garyounis and 2Deriana). • D j = Effect of Depth (5, 15 and 20). • (LD) ij = Interaction. • e ijk = error.

22. Results and discussion

23. Results and discussion The results illustrated in table (1) evaluated significantly that, the colonies of P. oceanica growing in Garyounis coast as compared to that of Deryanah coast showed obviously longerdiameter (38.96 vs 2.79 m), shorter plants (26.33 vs 48.54 cm), lower leaves number (191.11 vs 405.56/m2) and no significant similar colonies number (4.89 and 4.67/m2, respectively).

24. ** = significant at p ≤ 0.01 n. s. = not significant

25. ** = significant at p ≤ 0.01 n. s. = not significant

26. Results and discussion • Garmen et al., (2002) recorded • more or less similar results of colonies diameter of P. oceanica (40m) at ecologically similar area (Malta coast).

27. Results and discussion • Pergent, et al., (2007) noticed that the entrance of Ain Al-Ghazala lagoon at the eastern coast of Libya did not suffer any anthropogenic activities and had relatively pure sediment; the diameters of P. oceanica colonies averaged 20-30 m and can reach almost 70 m in several sectors.

28. Results and discussion • Height of blades depended mainly on light density and photosynthesis process (2005 شرف،) • and reached its maximum length at summer (Monica et al., 2006).

29. Results and discussion • Pergent, et al., (2000) and Buia and Mazzella, (2000) reported that the endemic P. oceanica natural density of blades was 1000/m2 • while, Mohamed and Denizot, (1984) recorded 750 blade/m2 at Deryanah coast but less than that number at different Benghazi coasts.

30. Results and discussion • The relative reduction of P. oceanica density may be due to the presence of Caulerpales which are considered as strong competitors and their production of toxic substances, which inhibit their grazing (Piazzi et al., 2005).

31. Generally, as the water depth increased the number of leaves significantly increase while, the diameter, number of colonies and the plant height remained more or less constant with non significance.

32. Results and discussion • Flena et al., (2003) revealed that anthropogenic and industrial wastes negatively affected the growth and density of P. oceanica (especially leaves numbers) in Italy Island which was much similar to the study area.

33. Results and discussion • Hemminga et al., (2000) proved that P. oceanica had high degree of dynamic elasticity to adaptwithrough conditions enable its sensed layers to grow well till 10-30 m depth.

34. Results and discussion • The results of interaction between all these items and plant parameters showed significance only with the number of colonies. • These may be due to the sensitivity of P. oceanica to many factors especially low salinity, high temperatures and tides (Pergent et al., 2007).

35. Results and discussion • The overall means of sediment contents of the tested heavy metals (mg/kg soil) Cr (1.18), Pb (14.17) and Zn (0.27) were independent (p≤ 0.05) of location, depth and their interactions, • with the exception of the water content of Cr and Pb which were much higher in Garyounis coast as compared with Deryanah coast (Table 2).

36. Results and discussion • These may be due to the high level of anthropogenic activities especially sewage near Garyounis coast. Although Libyan coasts had low levels of heavy metals (Cd, Mn, Ni and Cu) and relatively high level of Zn (27.3 mg/g-1) along Benghazi coasts حمودة و ويلسون, 1989) ).

37. ** = significant at p ≤ 0.01 n. s. = not significant.

38. Results and discussion • Simple correlation coefficients between the concentrations of some heavy metals and some plant parameters showed generally and obviously that,: • the colonies diameter was positively correlated with Cr (+0.75) at p ≤ 0.001 • while, the number of leaves was negatively correlated with Cr (-0.75) at p < 0.001 and Pb (-0.63) at p ≤ 0.01 (Table 3).

39. * = significant at p ≤ 0.05 ** = significant at p ≤ 0.01 *** = significant at p ≤ 0.001

40. وفــــــــــــوق كــــــل ذي عــلـــــــــــم عـــلــــــــــيـــم صــــدق الله العظـيـــم الآية (76) من سورة يوسف