ISSN: 2578-4994
Authors: Amusat AI*
Heavy metal is always a concern when introduced in high amount into the body of water particularly the sediment that serves as favourable sinks due to bioaccumulation which indirectly affects the organisms of the aquatic ecosystems. Therefore, this study investigated seasonal variation of heavy metal concentrations of water and sediment samples of Erelu reservoir and their impacts on its macro-invertebrates. Water samples were collected monthly in the morning across the three selected stations between 800am-10am from June 2013-May 2015. Heavy metal concentrations were determined using AAS model Analyst PGP 10. Macro-invertebrates were collected using Van-veen grab of 66.6cm3 surface area, dip-net and sweep nets of mesh sizes (500μm and 250μm) were used for insects on water surface and on vegetation surrounding the reservoir. Macro-invertebrates collected were sorted, counted and identified with standard aquatic taxonomic keys. Data collected were analysed using paired t-test of significant and Pearson’s Correlation Coefficient and paired t-test at α0.05. The results showed that Fe(mg/L), Zn(mg/L) and Cr(mg/L) in water samples were significant (p<0.05) across seasons and stations while Pb (mg/kg) and Zn (mg/kg) in sediment samples were significant (p<0.05) between seasons and across stations respectively. Zinc(mg/L) had strong relationship with Iron (r= 0.894**) in water samples while Cadmium mg/kg had positive significant (p<0.05) relationship with Iron (r=0.837**) and Chromium mg/kg (r= 0.839**) in sediment samples respectively. Lead had positive correlation with Odonata (r= 0.743*); Zinc related with Unionidea (r= 0.691*) and Cadmium significantly correlated with Capitellida (r= 0.826**) in water samples respectively. Lead had relationship with Hygrophila (r= 0.683*); Iron with Capitellida (r= 0.691*) and Sorbeoconcha (r= 0.692*); Zinc with Diptera (r= 0.680*); Chromium with Pulmonata (r= 0.779*) and Unionidea (r= 0.878*) while Cadmium related significantly (p<0.05) related with Capitellida (r= 0.854**) in sediment samples respectively. The result indicated that the heavy metals both in sediment and water samples has greater influence on macro-invertebrate abundance.
Keywords: Taxonomic keys; Variation; Odonata; Sorbeoconcha; AAS; Aquatic Ecosystem
