Ecological Indicators 58 (2015) 445–457 Contents lists available at ScienceDirect Ecological Indicators j o ur na l ho me page: www.elsevier.com/locate/ecolind Distribution and assessment of heavy metals in the aquatic environment of Lake Manzala, Egypt Ahmed A. Elkady a , Stephen T. Sweet b,∗ , Terry L. Wade b , Andrew G. Klein c a Food Toxicology & Contaminants Department, National Research Centre, Dokki, Cairo, Egypt b Geochemical and Environmental Research Group, Texas A&M University, College Station, TX 77845, USA c Department of Geography, Texas A&M University, College Station, TX 77843, USA a r t i c l e i n f o Article history: Received 13 October 2014 Received in revised form 15 April 2015 Accepted 1 May 2015 Keywords: Heavy metals Residue profile Lake Manzala Egypt a b s t r a c t Analysis of trace metals from sediment and fish collected from eight locations in Lake Manzala, Egypt, during May, June and July of 2011, indicated anthropogenic impacts. The highest concentrations of metals, except Mn and Sr, were detected at Bahr Al-Baqar (S1) which drains from Cairo. At the other sampling locations, the concentrations of selected trace metals fall below the levels of concern while the geo- accumulation index (I geo ) suggests unpolluted conditions for the majority of the studied metals at most sites. However, near the Bahr Al-Baqar (S1) drain concentrations of Ag, Hg and Zn fall above the Long and Morgan’s (1990) effects range low (ERL) while Pb was above their effects range median (ERM). I geo values suggest unpolluted to moderately polluted condition for As and Sn, moderately polluted conditions for Zn, moderate to extremely polluted conditions for Ag, and severely to extremely polluted conditions for Pb at Bahr Al-Baqar. Two sites (Legan, S5, and Al-Ginka, S8) were indicated by I geo as moderately polluted for Ag while two other sites (West of Bashar, S3, and Al Dehdy, S6) were indicated as unpolluted to moderately polluted for Ag. The Legan and Al-Ginka sites were also indicated as being moderately polluted for Zn. Similar to the sediments, the highest concentrations of metals in fish tissue were from Bahr Al-Baqar (S1). Al concentrations at all sites were comparable to concentrations known to cause lesions in fish. At all sites concentrations of selected trace metals in fish tissue were below the limits set by the FAO. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Lake Manzala is the largest of the Nile Delta lakes. It is located on the northeastern edge of the Nile Delta, 170 km from Cairo and 15 km west of Port Said (Fig. 1). Several decades ago the surface area of Lake Manzala was 1698 km 2 , however, by 1988 it was reduced to 770 km 2 (Saeed and Shaker, 2008) due to continuous land reclama- tion projects and it may be further reduced to 469 km 2 in the future. Lake Manzala is brackish, eutrophic, elongated, and shallow with an average depth of 1.2–1.5 m (El-Kholy et al., 2012). Freshwater inputs to the lake are not sufficient to provide adequate flushing to the sea, therefore trace metals entering the system are expected to accumulate over time. Lake Manzala is an important fisheries resource in the Nile River Delta, accounting for over 30 percent of all commercial and recre- ational fish landed and consumed in Egypt. However, Lake Manzala ∗ Corresponding author. Tel.: +1 9794589338. E-mail addresses: sweet@gerg.tamu.edu, s-sweet@exchange.tamu.edu (S.T. Sweet). has been classified as one of the most polluted Lakes in Egypt (Wahaab and Badawy, 2004). Accumulation of bioactive metals in fish is controlled by different metabolic pathways that control metal uptake and concentration in fish tissue. The concentrations of these metals in the fish reflect the environmental conditions where they are living. Environmental pollution in Lake Manzala and its main drainage channels have previously been documented by measuring the concentrations of selected trace metals in fish and sediment samples (Badawy and Wahaab, 1997; Bahnasawy et al., 2011). Soltan et al. (2005) studied heavy metal accumulation in two species of tilapia (nilotica and galilea) in Lake Nasser along with water, sediment and aquatic plants. Authman (2008) proposed using O. niloticus as a biomonitor of heavy metal exposure in a study in the Sabal drainage canal where he found the concentrations of heavy metals exceeded the toler- ance level for human consumption. Sources of contaminants to Lake Manzala include untreated sewage, atmospheric deposition, agri- cultural and industrial wastes which may impact human health when fish are consumed. Heavy metals of environmental concern include arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), silver (Ag), http://dx.doi.org/10.1016/j.ecolind.2015.05.029 1470-160X/© 2015 Elsevier Ltd. All rights reserved.