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Abstract Seagrass beds and mangrove forests represents the main productive ecosystems among the marine habitats, additionaly, they provide numerous services and goods for creatures. Urbanization and industrialization intensively developed since few decads ago on Egyptian Red Sea coast, especially at Hurghada and Safaga Coastal zone. There is low attention from botanists to the changes in seagrasses and mangrove on Red Sea Coast. Therefore the present work aimed to integrate between the traditional methods (field study) and modern methods (Remote Sensing Techniques) for monitoring seagrasses beds and mangrove forests and studing the periodical changes of the seagrass beds and mangrove forests corresponding to the progressive anthropogenic impacts. In addition, to assess using the seagrasses beds as biomonitoring agent for heavy metals pollution in coastal zone of Hurghada and Safaga. To achieve the target of the study, field monitoring for 41 stands of Seagrasses beds in Hurghada and Safaga were carried out from 2013-2015. Florestive composition of the stands was studied and the biodiversity indices were calculated. Seagrasses density, biomass photosynthetic pigments were estimated. Multiple satellite images of the spectra and the field data were used to estimate seagrasses species distribution in two training and applied sites. In addition, + ETM, TM, MSS, OLI and Spot satellites for determination the temporal changes of seagrasses cover areas from 1972 to 2014 were used . The analysis and image processing using software: ERDAS 2010 and Arc GIS10.3 Seawater, sediments and seagrasses tissues were collected from four sites located in Hurghada and Safaga to investigate the possibility of using seagrasses as bioindicator for heavy metals pollution. The main results can be summarized as follow: Field monitoring identified five species of seagrasses in the 41 stands; Halophila stipulacea (Forssk.) Asch., Halodule uninervis (Forssk.) Boiss., Halophila ovalis (R.Br.) Hook. f., Thalassodendron ciliatum (Forssk.) Hartog and Syringodium isoetifolium (Forssk.) Hartog. All recorded seagrasses are belonging to tropical indo-pacific bioregion. Application of TWINSPAN and DECORANA, as classification and ordination techniques to the 41 stands resulted in five vegetation groups. Diversity indices indicated that Hurghada and Safaga coastal zone are poor in seagrasses diversity. Integration between field monitoring and remote sensing technique, the spectral signature of the recorded species were determined and seagrasses distribution was mapped in training site (NIOF in Hurghada) and applied one (Safaga Fishing Port in Safaga) and the coverage area of the four seagrasses were determined.Field study confirmed by using remote sensing technique indicated that H. stipulacea seagrasses has the highest distribution in Hurghada and Safaga. In addition Remote sensing technique indicated that H. uninervis has the highest coverage area among the four recorded seagrasses. Satallite images clarified the changes in coverage areas of seagrasses and mangrove habitats parallel to human urbaniziation along the Red Sea Coast. The images showed that the seagrasses beds coverage area reduced by 69.8% in Hurghada area between 1972 - 2014 and 25.4% in Safaga area between 1973 - 2014. Also the coastal fringe mangrove in Um dehais showed reduction percentage of 98.7 and 52.7% from 2002 to 2015 and 1984 to 2015, while mangrove coverage area increased by 59.6 and 127.2% in Abu Monqar Island from 1973 to 2015 and Sharm El bahari from 1984 to 2015, respectively. The highest reduction in seagrasses and mangrove coverage area occured from 1990 to 2004, the period where the Red Sea Coast showed the highest stress of urbanization. Heavy metals analysis in seawater indicated that Fe is the dominant metal. The results indicated that water contains low concentrations of heavy metals which are in order, Fe>Mn>Cu>Pb>Zn>Cd. Mechanical analysis of sediments in the four sites showed that all sediment samples in the 41 sites contain high percentage offine granule (Ø3, Ø4 and Ø5) averaged 62.91-92.20% followed by the medium granules. Highest percentage of silicates and TOM were recorded in SFP site while that of carbonates were recorded in Wadi Quiah. Noticeably, high fluctuation in the concentrations of each heavy metal in the same site indicate variation in heavy metals resources. Iron is the main metal in the three fine fractions of sediments (Ø3, Ø4 and Ø5). The dominant order of heavy metals in the fine granules of the sediments in the studied sites was Fe>Zn>or<Mn>Cu>or<Pb>Cd. The results showed that SFP sediment contains highest concentrations of the most heavy metals. The results clarified that the concentrations of heavy metals in seagrasses organs vary from species to species and from site to site, which sustains that there are a lot of overlapping environmental factors which control the absorption of elements, not only the concentration of the element in the sediment and water. Correlation coefficient cleared that there are significant positive correlation between the concentrations of some heavy metals in sediment and in seagrasses tissues; as, Fe and Pb for H. stipulacea and H. ovalis, Fe For H. uninervis, and Cu and Cd For Th. ciliatum. Significant negative correlation was detected between Fe, Cu and Zn in sediment and in H. ovalis organs.The results indicated that H. uninervis had the capability to bioconcentrate Cu and Cd in their leaves; H. stipulacea had high ability to bioconcentrate Cd in their roots, rhizomes and leaves; H. ovalis concentrated Cu and Pb in leaves but Cd in rhizomes and Th. ciliatum bioconcentrated Cd with higher BCF value in rhizomes. On the other hand, the four seagrasses didn’t show tendency to bioconcentrate Fe, Mn and Zn. So, the four seagrasses can be used as bioindicator for Cu, Pb and Cd pollution. Translocation factor results indicated that H. stipulacea and H. uninervis seagrasses had high ability to translocate the heavy metals from roots to rhizomes but showed low tendency to translocate them from rhizomes to leaves. While H. ovalis and Th. ciliatum showed tendency to translocate the heavy metals from roots to rhizomes as well as translocation them from rhizomes to leaves. Translocation of heavy metals from roots to rhizomes is highly active in SFP for H. stipulacea and H. uninervis and from roots to rhizomes and rhizomes to leaves for H. ovalis. Correlation between heavy metals in plant tissues with their concentration in sediment of SFP which contain highest concentration of heavy metals denoted that high concentrations of heavy metals in sediment can activate the translocation of heavy metals from roots to rhizomes and from rhizomes to leaves depending on the seagrass species.The highest density of H. stipulacea and H. uninervis was recorded in SFP but recorded the lowest biomass. While, H. ovalis recorded its highest density and biomass in SFP site. H. stipulacea, H. uninervis and H. ovalis contain their highest chl a content in Gasous sites and chl. b in Hurghada, but their highest carotenoids content in SFP. This result indicated that seagrasses were affected by bioconcentration of heavy metals in their tissues however they have the ability to resist their risks by increasing carotenoids in their tissues. Recommendation: - Expanding the use of remote sensing technique conjunction with field monitoring to map of vegetation in terrestrial, aquatic and marine ecosystem. - Using seagrasses as biomonitor for heavy metals pollution especially Cu, Pb and Cd. - New legislation should be enacted to reduce pollution and maintain ecological diversity of the Red Sea coast. - The completion of monitoring temporal variations of environments under study to define the critical areas which are under the threats caused by human activity to manage and conserve them. |