Total and Bio-Available Phosphorus in Sediments and Its Contribution to Lake Nasser Eutrophication, Egypt | ||||
| Egyptian Journal of Aquatic Biology and Fisheries | ||||
| Article 3, Volume 21, Issue 3, July 2017, Page 29-44 PDF (876.25 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/ejabf.2017.3727 | ||||
 View on SCiNiTO | ||||
| Author | ||||
Mohsen Yousry Darwish 
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| Nile Research Institute | ||||
| Abstract | ||||
| Phosphorus has negatively influences on the ecosystem and causes eutrophication. To assess the degree of eutrophication it is necessary to know not only the total P content in the sediments, but also its bio-available forms. The main objectives of this study are to assess the distribution of total phosphorus in bed sediment along Lake Nasser, to characterize the phosphorus bioavailable forms in surface sediments, to examine the relationship between phosphorus concentration and other sediment properties and to assess the potential contribution of bioavailable phosphorus in eutrophication. To achieve these objectives, superficial sediment and water samples were collected along Lake Nasser during May 2016. The sediment samples were analyzed for total phosphorus, water soluble phosphorus, plant available phosphorus and grain size distribution. For water, dissolved oxygen, total phosphorus, Chlorophyll-a and transparency are analyzed. The results showed that, the total phosphorus in sediment samples ranged from 550 to 704 mg/kg and showed a temporal variation comparing with the data recorded during May 2009 (P= 0.046). Water soluble-phosphorus (WSP) and plant available phosphorus ranged from 1 to 3.25 mg/kg and 13.8 to 26.9 mg/kg, respectively, which represented 0.15 % - 0.46% and 2.06% - 4.59% of the total sedimentary phosphorus. The total phosphorus, transparency and chlorophyll-a in water ranged from 40 to 60 µg/l, from 1.3 to 2.8 m and from 2.4 to 32 µg/l respectively. The total phosphorus concentration in bottom layer of water column recorded higher values than that in the surface layer and ranged from 55 to 100 µg/l. The results also show that, the depletion of dissolved oxygen concentration near the bottom layer (2.15 mg/l) may enhance the release of P from the sediments. The high positive correlation was found between total phosphorus in sediment and WSP in sediment, clay and TP in water. However, total phosphorus in sediment has strong negative correlation with sand. It’s worth mentioning that, WSP in sediment has a positive correlation with total phosphorus in water, indicated that WSP fraction can release phosphorus easily and increasing the total phosphorus in water. Based on Trophic State Index Calculation (TSI), Lake Nasser ranged from mesotrophic to light eutrophic state. It is recommended that dredging the surface sediments from the sedimentation zone have a positive effect in improving water quality where, dredging removes substantial amount of P stored in sediments. | ||||
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