Benthic foraminifera as bioindicators of heavy metal pollution in Lake Burullus, Egypt
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ORIGINAL PAPER
Benthic foraminifera as bioindicators of heavy metal pollution in Lake Burullus, Egypt Sherif M. El Baz
Received: 30 April 2014 / Accepted: 1 September 2014 # Saudi Society for Geosciences 2014
Abstract A study of benthic foraminiferal assemblages is carried out on 30 sediment samples collected from Lake Burullus to assess the response of the benthic foraminifera to the polluted sediments. The lake has been contaminated by industrial waste, mainly trace elements, as well as by agricultural effluent. Benthic foraminifera are the most common microorganism found in the surface sediments in the shallow and marginal marine environments. They are very sensitive to slight environmental changes and can reflect the health of the ecosystem they inhabit. Many studies assume or conclude that foraminiferal assemblages and the frequency of deformed tests are proxy indicators of pollution. X-ray microanalysis reveals that deformed specimens contain higher levels of heavy metals (Mn, Cu, and Hg) than non-deformed ones. This strongly suggests that heavy metals are responsible for the abnormalities in foraminiferal tests. Sediment samples were analyzed for the concentrations of Mn, Cu, Fe, Zn, V, Sr, Hg, Ni, Pb, Co, and Cr. Results show that the collected samples contain different concentration of the tested heavy metals. Keywords Benthic foraminifera . Heavy metals . Abnormalities . Egypt
Introduction Lake Burullus lies on the eastern side of Rosetta branch of the Nile River, occupying a central position along the Mediterranean Nile delta coast of Egypt. It extends between longitudes 30° 30′ and 31° 10′ E and latitudes 31° 21′ and 31° S. M. El Baz (*) Faculty of Science, Geology Department, Damietta University, New Damietta, Egypt e-mail: [email protected]
35′ N (Fig. 1). It is the second largest lake of the Nile delta coastal lakes and is about 53 km long, 13 km wide. Water depths range from 0.5 to 2.5 m. The eastern sector of the lake is the shallowest, showing an average depth of 0.8 m. The Lake is connected to the sea at its northeastern edge through the Burullus inlet, which is about 250 m wide and 5 m deep. It receives agricultural drainage water mostly from eight drains (Burullus, Baltim, El Gharbia, Nasser, and drains 7, 8, 9, and 11) and only one canal (Brimbal Canal). Due to the high inflow of fresh water to the lake through the drains, the lake water salinity becomes very low ranging from 1.235 to 2.535 g/l (ARE-UNEP, 2002). Industrial, agricultural, and domestic wastes discharges have increased the levels of heavy metals in the lake. Heavy metals are of the serious pollutants in natural environment due to their toxicity, persistence, and bioaccumulation problems (El Nemr 2003). Cadmium, mercury, lead, copper, and zinc are regarded as serious pollutants of aquatic ecosystems because of their environmental persistence, toxicity, and ability to be incorporated into food chains (Frstner and Wittman 1983). Benthic foraminifera are the most common microorganism found in the surface sediments in the sh
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