Abstract:
Contamination of water and sediment of aquatic reservoirs with heavy metals is the main
ecological problem world over. The present study was conducted to investigate the seasonal
variations in heavy metal concentrations of water and sediment samples of Erelu reservoir (Oyo
Town, Nigeria) and their impacts on its macro-invertebrates. Water samples were collected
monthly in the morning across the seven selected stations. Heavy metal concentrations were
determined using Atomic Absorption Spectrophotometer. Macro-invertebrates were collected
and identified with standard methods. Data collected were analysed using paired t-test and
Pearson’s Correlation Coefficient(r). The results showed that the heavy metal concentration in
water was in the order of Zn>Pb>Fe>Cr>Cd (mg/L) where asPb>Fe>Zn>Cd>Cr during dry
season. Likewise, the concentration in sediment was in the order of Fe>Pb>Cr>Cd>Zn during
wet season whereas Pb>Fe>Zn>Cr>Cd during dry season respectively. Fe (mg/L), Zn(mg/L) and
Cr(mg/L) in water samples were significantly different (p<0.05) across seasons and stations
while that of Pb (mg/kg) and Zn (mg/kg) in sediment samples were also significantly different
(p<0.05) across stations respectively. Zinc(mg/L)in water samples strongly related with Iron (r=
0.894**) while Cadmium mg/kg significantly (p<0.05) related with Iron (r=0.837**) and
Chromium mg/kg (r= 0.839**) in sediment samples respectively. Water sample Lead had
positive correlation with Odonata (r= 0.743*); Zinc related with Unionidea (r= 0.691*) while
Cadmium related significantly with Capitellida (r= 0.826**) respectively. However, Lead, Iron,
Zinc, Chromium and Cadmium of sediment samples related significantly (p<0.05) with majority
of macro-invertebrate orders respectively. The result indicated that the heavy metals in sediments
were higher in values compared to those in water samples and there were significant seasonal
variations. Sediment samples have greater influence on macro-invertebrate abundance of Erelu
Reservoir compared to that of water samples |
