الفهرس 
LITERATURE REVIEWOnly 14 pages are availabe for public view
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Abstract
SUMMARY
Coastal lakes, like Idku, are dynamic resource ecosystems that are threatened by natural and human impacts, Lake Idku is one of the five Egyptian northern lakes, which is not stable because it is subjected to huge inputs of terrigenous and anthropogenic pollutants from drain discharge, sewage, and agricultural runoff, as well as reclamation programs.
Although the dangers that the lake is exposed to, the decision makers and users of the lake believe that the aquatic plants are useless, so the disinfection operations were carried out by removing all the plants without taking into account their environmental importance.
Surveys of macrophyte communities are commonly hindered by limited accessibility through field study area and this is because of large size and environmental conditions of lakes, such as shallow water in some places. So, remote sensing is a valuable tool for assessment of macrophyte stands and associated ecological parameters. With the advance of sensor technology and processing techniques, vegetation characteristics such as species composition, coverage area, Production, and even chemical composition can be determined by analysis of radiometric data.
The present work carried out the following objectives points:
• Mapping the spatial distribution of physicochemical parameters of water and sediment and heavy metals’ pollution indices using GIS.
• Mapping the distribution and the coverage area for the aquatic macrophytes using remote sensing.
• Estimating the biomass and production of aquatic macrophytes.
• Investigating the nutrients budget of the study plants and their phytoremediation potential to absorb and accumulate pollutants from the lake.
• Determining the forage quality of the study macrophytes to be used as animal fodder.
• Investigating the C-sequestration potential (CSP) of the study macrophytes.
Twelve stations were selected in this study for sampling. Physicochemical parameters and heavy metals were analyzed for water and sediment, besides sediment-heavy metals’ pollution indices were calculated and all parameters were interpolated using GIS techniques, while plant samples were analyzed for inorganic and organic nutrients, heavy metals and nutritive values, in addition, to the vegetation measurements and carbon sequestration potential.
The important results of the study:
The south part of the lake had the highest water pH, while the east part had the highest NO2 and NO3, in addition the western section had the highest concentrations of water Ca, Mg and K, in contrast with the eastern section, which had the highest P content.
The water of the north-western section of the lake was highly polluted with the investigated heavy metals compared with the other lake’s sections.
The sediment of the north-western section of the lake had the highest EC, pH, Ca, and K, while the south-western section had the highest contents of sediment Mg, OM and P.
The north-western section of the lake had the highest contents of sediment Fe, Cd and Ni, while the western section had the highest sediment Pb.
Based on the GIS technique, the sediment of lake Idku is polluted with heavy metals especially in the western and the middle sections of the lake.
The heavy metals contamination degree of the sediment ranged between moderate to very high degree of contamination.
Nine macrophytic species (E. stagnina, P. coloratum, P. australis, T. domingensis, V. cuspidata, E. crassipes, L. stolonifera, P.stratiotes, C. demersum) were recorded and selected for the present investigation in Lake Idku.
P. australis had the highest coverage area, while C. demersum had the lowest.
It is worth noting that the biomass of the above-ground parts of all the study macrophytes in Lake Idku was higher than those of the below-ground parts.
The statistical analysis (ANOVA 1) showed highly significant variation (p < 0.01) in the biomass of all investigated plant species (except C. demersum and V. cuspidata) among the different study stations.
It is serious to mention that the emergent species like P. australis, T. domingensis and V. cuspidata had higher biomass and production than the other study species. The study species were descendingly arranged based on their production, as follows: P. australis ˃ T. domingensis ˃ V. cuspidata ˃ P. coloratum ˃ E. stagnina ˃ P. stratiotes ˃ E. crassipes ˃ C. demersum.
The statistical analysis (ANOVA 1) of the inorganic nutrients in the below- and above-ground parts of the nine study species indicated significant variation in the investigated shoot nutrients and root K among the study species. The highest concentration of Ca was recorded in the above-ground tissues of T. domingensis. Besides, the highest K content was recorded in the L. stolonifera shoots. Moreover, the highest Mg content was recorded in the below-ground parts of E. crassipes and E. stagnina, respectively.
The analysis of the heavy metals indicated significant variation in all the investigated metals (except Ni) in the below-ground parts, while no significant variation in the above-ground parts of all the recorded species. L. stolonifera shoots had the highest content of Fe, while its roots had the highest value of Cd. In addition, P. stratiotes roots had the highest Pb concentration, while C. demersum tissues had the highest Ni concentration.
The descriptive statistical analysis of the bioaccumulation factor (BF) showed that all the study species had BF greater than the unit for all investigated heavy metals. E. crassipes had the highest BF of Fe and Ni. Besides, P. stratiotes had the highest BF of Pb and Cd, while the lowest was recorded by V. cuspidata and P. coloratum, respectively. Moreover, V. cuspidata had the lowest BF of Fe. The study species were arranged in descending order according to their BF as follows: P. stratiotes > E. crassipes > C.demersum > P.coloratum > E. stagnina > T. domingensis > P. australis > L. stolonifera > V. cuspidata for Pb; E. crassipes > P. stratiotes > L. stolonifera > C. demersum> E. stagnina > T. domingensis > P. coloratum > P. australis > V. cuspidata for Fe; P. stratiotes > E. crassipes > V. cuspidata > L. stolonifera > E. stagnina > P. australis > T. domingensis > C. demersum > P. coloratum for Cd; and E. crassipes > P. stratiotes > L. stolonifera > C. demersum > E. stagnina > P. coloratum > V. cuspidata > P. australis > T. domingensis for Ni.
The translocation factor (TF) of heavy metals from the below-ground parts to the above-ground parts showed that P. stratiotes had the highest TF for Cd and Ni. Besides, V. cuspidata had the highest TF for Pb and Fe. Moreover, T. domingensis and E. crassipes had low translocation ability of Ni. The study species were arranged descendingly according to their TF as follows: V. cuspidata > P. australis > P. coloratum > L. stolonifera > E. crassipes > T. domingensis > E. stagnina > P. stratiotes for Pb; V. cuspidata > L. stolonifera > P. stratiotes > P. australis > P. coloratum > T. domingensis > E. crassipes > E. stagnina for Fe; P. stratiotes > P. coloratum > P. australis > E. crassipes > T. domingensis > L. stolonifera > E. stagnina > V. cuspidata for Cd; and P. stratiotes > P. coloratum > T. domingensis > P. australis > E. crassipes > E. stagnina > L. stolonifera > V. cuspidata for Ni.
The statistical analysis (ANOVA I) of organic nutrients revealed significant variation in all the investigated variables among the study species. T. domingensis recorded the highest value of ether extract (EE). In addition, E. crassipes recorded the highest soluble carbohydrates (NFE) value. Moreover, L. stolonifera had the highest value of TP, and V. cuspidata had the highest crude fibers (CF) value. Furthermore, C. demersum had the highest value of ash content.
The statistical analysis (ANOVA I) of the nutritive data indicated significant variation in the investigated variables among the different studied species. It was found that E. crassipes had the highest values of digestible energy (DE), metabolized energy (ME), and net energy (NE). In addition, the highest value of gross energy (GE) was recorded by V. cuspidata. Moreover, T. domingensis recorded the highest value of total digestible nutrients (TDN). Furthermore, L. stolonifera had the highest value of digestible crude proteins (DCP).
The results of the organic carbon percentage of the different tissues of the study species indicated that the above-ground parts had OC percentage greater than the below-ground ones.
The different tissues of the study emergent species had carbon sequestration potential (CSP) greater than floating and submerged species. The highest CSP was recorded in the above-ground tissues of P. australis, while the lowest was recorded in the below-ground parts of E. crassipes.
The CSP of the study species based on their total biomass in the whole lake as estimated using the remote sensing technique showed that P. australis can sequester about 19214.14 t carbon from the whole lake during the study sampling in autumn. However, C. demersum can sequester the least amounts (0.61 t). Based on the CSP, the study species fell in the order P. australis ˃ T. domingensis ˃ V. cuspidata ˃ P. coloratum ˃ E. stagnina ˃ E. crassipes ˃ P. stratiotes ˃ C. demersum.