Abstract
Sediment cores were collected from nine wetland lakes in Morocco, Tunisia and Egypt for the CASSARINA project investigating environmental change in Northern African wetlands. The cores were dated radiometrically by using natural (210Pb) and artificial (137Cs and 241Am) radionuclides. At sites in Morocco and Tunisia with mean annual rainfall totals ranging from 500–1000 mm yr−1, fallout records were generally satisfactory and it was possible to develop independent sediment chronologies based on the radiometric data alone. At the Egyptian sites, rainfall was less than 200 mm yr−1 and fallout records were much less distinct. At these sites the radiometric data could only be used to give an indication of mean sedimentation rates during the past 30–40 years. By using a combination of fallout radionuclide, pollen, and macrofossil stratigraphic records it was however possible to determine a credible sediment chronology spanning the major part of the 20th century. Applying this chronology to records of spheroidal carbonaceous particles (SCP) from the same sediment cores, the onset of significant levels of atmospheric pollution in the Nile Delta is dated in all three cores to the mid 1950s. Results from a number of lakes (Sidi Bou Rhaba, Ichkeul and Korba) revealed high and accelerating siltation rates, threatening their continued existence beyond the next few decades. In contrast, sedimentation rates at all three Nile Delta sites appear to have declined in recent decades, most probably due to the impact of the Nile barrages.
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Appleby PG (1998) Dating recent sediments by 210Pb: Problems and solutions. Proc. 2nd NKS/EKO-1 Seminar, Helsinki, 2-4 April 1997, STUK, Helsinki, 7-24
Appleby PG, Nolan PJ, Gifford DW, Godfrey MJ, Oldfield F, Anderson NJ and Battarbee RW (1986) 210Pb dating by low background gamma counting. Hydrobiologia 141: 21-27
Appleby PG and Oldfield F (1978) The calculation of 210Pb dates assuming a constant rate of supply of unsupported 210Pb to the sediment. Catena 5: 1-8
Appleby PG and Oldfield F (1983) The assessment of 210Pb data from sites with varying sediment accumulation rates. Hydrobiologia 103: 29-35
Appleby PG, Richardson N and Nolan PJ (1991) 241Am dating of lake sediments. Hydrobiologia 214: 35-42
Appleby PG, Richardson N, and Nolan PJ. (1992) Self-absorption corrections for well-type germaniun detectors. Nucl. Inst. Methods B71: 228-233
Birks HH, Peglar SM, Boomer I, Flower RJ, Ramdani M, with contributions from Appleby PG, Bjune AE, Patrick ST, Kraïem MM, Fathi AA and Abdelzaher HMA (2001a) Palaeolimnological responses of nine North African lakes in the CASSARINA Project to recent environmental changes and human impacts detected by plant macrofossil, pollen, and faunal analyses. Aquat Ecol 35: 405-430
Birks HH, Birks HJB, with contributions from Flower RJ, Peglar SM and Ramdani M (2001b) Recent ecosystem dynamics in nine North African lakes in the CASSARINA Project. Aquat Ecol 35: 461-478
El-Shenawy, MA (1994) Azolla filiculoides, a new effective dinitrogen fixer Lake Edku, Egypt. Bull. Nat. Inst. Oceanogr. & Fish. A.R.E. 20, pp. 83-97
Fathi AA and Abdelzaher HMA (2000) Site descriptions for the Egyptian lakes and results of water chemistry and phytoplankton for CASSARINA lakes. Final CASSARINA Results Report. Botany Department, El Minia University, El Minia, Egypt
Flower RJ, Stevenson AC, Dearing JA, Foster IDL, Airey A, Rippey B, Wilson JPF and Appleby PG (1989) Palaeolimnological studies of three contrasted sub-humid environments in Morocco. J. Palaeolimnol. 1: 293-322
Flower RJ (2001) ChAnge, Stress, Sustainability and Aquatic ecosystem Resilience In North African wetland lakes during the 20th century: an introduction to integrated biodiversity studies within the CASSARINA Project. Aquat Ecol 35: 261-280
Flower RJ, Dobinson S, Ramdani M, Kraïem MM, Ben Hamza C, Fathi AA, Abdelzaher HMA, Birks HH, Appleby PG, Lees JA, Shilland E and Patrick ST (2001) Recent environmental change in North African wetland lakes: diatom and other stratigraphic evidence from nine CASSARINA sites. Aquat Ecol 35: 369-388
Mehringer PJ, Petersen KL and Hassan FA (1979) A pollen record from Birket Qarun and the recent history of the Fayum, Egypt. Quat Res 11: 238-256
Peglar SM, Birks HH, and Birks HJB, with contributions from Appleby PG, Fathi AA, Flower RJ, Kraïem MM, Patrick ST and Ramdani M (2001) Terrestrial pollen record of recent land-use changes around nine North African lakes in the CASSARINA Project. Aquat Ecol 35: 431-448
Pennington W, Cambray RS and Fisher EM (1973) Observations of lake sediments using fallout 137Cs as a tracer. Nature 242: 324-326
Ramdani M, Flower RJ, Elkhiati N, Kraïem MM, Fathi AA, Birks HH and Patrick ST (2001a) North African wetland lakes: characterization of nine sites included in the CASSARINA Project. Aquat Ecol 35: 281-302
Ramdani M, Elkhiati N, Flower RJ, with contributions from Birks HH, Kraïem MM, Fathi AA and Patrick ST (2001b) Open water zooplankton communities in North African wetland lakes: the CASSARINA Project. Aquat Ecol 35: 319-333
Robbins JA (1978) Geochemical and geophysical applications of radioactive lead. In: Nriagu JO (ed.) Biogeochemistry of Lead in the Environment. Elsevier Scientific, Amsterdam, pp. 285-393
Rose NL (1994) Characterisation of carbonaceous particles from lake sediments. Hydrobiologia 274: 127-132
Shawky S and El-Tahawy M (1999) Distribution pattern of 90Sr and 137Cs in the Nile delta and the adjacent regions after Chernobyl accident. Appl. Radiation Isotopes 50: 435-443
Stevenson AC and Battarbee RW (1991) Palaeoecological and documentary records of recent changes in Garaet el Ichkeul: a seasonally saline lake in N.W. Tunisia. Biol Cons 58: 275-295
Stanley, DJ (1988) Subsidence in the Northeastern Nile Delta: Rapid rates, possible causes and consequences. Science 240: 497-500
Stanley, DJ (1990) Recent subsidence and northeast tilting of the Nile Delta, Egypt. Marine Geology 94: 147-154
Waterbury J (1979) Hydropolitics of the Nile valley. Syracuse University Press, Syracuse
Zahran MA and Willis AJ (1992) The Vegetation of Egypt. Chapman & Hall, New York
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Appleby, P., Birks, H., Flower, R. et al. Radiometrically determined dates and sedimentation rates for recent sediments in nine North African wetland lakes (the CASSARINA Project). Aquatic Ecology 35, 347–367 (2001). https://doi.org/10.1023/A:1011938522939
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DOI: https://doi.org/10.1023/A:1011938522939