International Journal of Scientific and Research Publications, Volume 3, Issue 9, September 2013 1 ISSN 2250-3153 www.ijsrp.org Distribution of Trace Metals in Two Commercially Important Fish Species (Tilapia Zilli and Oreochromis Niloticus) Sediment and Water from Lake Gudbahri, Eastern Tigray of Northern Ethiopia Mulu Berhe Desta 1 and Mehari Muuz Weldemariam 1 1 Department of Chemistry, College of Natural and Computational Sciences, Mekelle University Abstract- Distribution of trace metals (Zn, Cu and Cr) in water; bottom sediment and two fish species (Tilapia zilli and Oreochromis Niloticus) collected from Lake Gudbahri were analyzed using Varian AA240FS Atomic Absorption Spectrophotometry in order to ascertain their suitability for consumption and other domestic uses. Results indicated that Tilapia zilli contained the highest concentration of Zn (84%) of the detected heavy metals, followed by Cu (15%), while Cr (1%) was the lowest value. Similarly, Nile Tilapia contained the highest concentration of Zn (77%), followed by Cu (21%). Bioaccumulation factors of Nile Tilapia were Cu (409), Zn (110), Cr (57) and Tilapia zilli showed 345.5, 112 and 28.6 for Cu, Zn and Cr respectively. The distribution of heavy metals in sediment and water samples were in the order of magnitude as by Zn>Cr>Cu and Zn>Cu>Cr respectively whereas the order of heavy metals concentration in fish samples were found to decrease in sequence as Zn>Cu>Cr. The levels of the heavy metals concentration were compared with permissible limit values provided by WHO, FEPA and various national and international agencies. These levels of heavy metals accumulated in the two fish species might be due to the increase in agricultural influx waters, domestic wastes and some anthropogenic activities. Keywords: Heavy metals, Tilapia zilli, Oreochromis Niloticus, Bioaccumulation factor, % Bioavailability, Lake Gudbahri I. INTRODUCTION Water pollution has become a global problem. Contamination of aquatic ecosystems with Heavy Metal (HMs) has long been recognized as a serious pollution problem. When fish are exposed to elevated levels of metals in a polluted aquatic ecosystem, they tend to take these metals up from their direct environment [1]. Metal contamination may have deleterious effects on the ecological balance of the recipient environment and diversity of aquatic organisms [2]. During the last decades the rapid economic development of Africa has led to an increase in environmental pollution [3-5]. Heavy metals released into the environment find their way into aquatic systems as a result of Agricultural practices – for instance, the use of fertilizers and pesticides for the control of pests in the cultivation of coffee, cotton, tea and sugarcane and other activities such as mining and industry as well as growth of the human population have increased the discharge of waste effluents into lakes and rivers rendering it environmentally unstable. Consequently, aquatic organisms may be exposed to elevated levels of heavy metals due to their wide use for anthropogenic purposes [6]. Heavy metals are non-biodegradable and once discharged into water bodies, they can either be adsorbed on sediment particles or accumulated in aquatic organisms. Fish may absorb dissolved elements and heavy metals from surrounding water and food, which may accumulate in various tissues in significant amounts [7] and are eliciting toxicological effects at critical targets. Also, fish may accumulate significant concentrations of metals even in waters in which those metals are below the limit of detection in routine water samples [8], therefore, fish might prove a better material for detecting metals contaminating the freshwater ecosystems. Various studies were conducted on the levels of heavy metals in different water bodies [9-14]. Toxic heavy metal can cause dermatological diseases, skin cancer and internal cancers (liver, kidney, lung and bladder), cardiovascular disease, diabetes, and anemia, as well as reproductive, developmental, immunological and neurological affects in the human body. It is also possible that environmental toxicants may increase the susceptibility of aquatic animals to various diseases by interfering with the normal functioning of their immune, reproductive and developmental processes [15]. Long exposure to water