الفهرس 
Marine ecosystems lossOnly 14 pages are availabe for public view
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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.