Assessment of the bio-tolerance and environmental risks of Oreochromis.niloticus, and Ipomoea aquatica in Agodi Reservoir. Nigeria

Concentration of heavy metals in O. niloticus in Agodi Reservoir

Concentration of heavy metals in O. niloticusTable 1. From the table, the metal bioaccumulation followed the order Mn>Fe>Zn>Cu>Co>Pb>Cd>Cr>Ni. All metals, except Co, Ni and Cr, were above the threshold limits for heavy metal contamination in fishes.²⁵(Table 1). Cd, Co and Ni also showed higher bioaccumulation rates in the wet season than in the dry. The dry season’s mean concentrations of Cr, Cu and Fe, Mn and Pb varied from 0.000.00 up to 2.189.54, 5.544.78 and 13.6418.64 respectively.

Table 1 Concentration in Heavy Metals (mg/kg). O. niloticus in Agodi Reservoir.

Environmental risks from heavy metals in O. niloticus in Agodi Reservoir

The ERQ of heavy Metals O. niloticusTable 2 contains the following information. The Table shows that all the metals, except Co, Cr, Ni, presented a high level ecological risk to the aquatic biota, as their ERQ values exceeded one (1). Mn (501.50) and Fe (858.19) had ERQ values of 533.27 and 858.19 respectively in the dry and the wet seasons. These were very high relative to other metals with high ERQ (Table 2). Pb, Zn and Cu also had ERQs of 6.89, 4.55, and 1.09 in the wet season. In contrast, Zn, Cd, and Cu had ERQs of 6.21, 4.75, and 1.85 in the dry season. High ERQs were also observed for Zn as well as Mn throughout the study period. ERQ values were also higher in the wet than the dry seasons, except for Cd, Co, and Ni (Table 2).

Table 2 Ecological risk quotient of heavy metals O. niloticus in Agodi Reservoir.

Concentration of heavy metals in I. aquatic in Agodi Reservoir

Concentration of heavy metals in I. aquaticaTable 3 displays the results. The table showed that the metal bioaccumulation followed the order Fe>Zn>Mn>Cu>Pb>Cd>Co>Cr>Ni. Some metals (Cd. Cu. Fe. Mn. and Pb) were higher then the threshold limits.²⁵Co, Cr, Ni, Zn and Ni were found to be more harmful than the threshold limit. The bioaccumulation of Cr and Fe, Ni, Pb and Mn was higher in the wet than the dry seasons, while Co, Cu and Mn were higher in the dry than the wet seasons. The average concentrations of Co, Cr and Cu, Fe, Ni, Pb, and Zn from dry to wet seasons range from 0.2210.20 to 0.130.23.

Table 3 Concentration of Heavy metals (mg/kg). I. aquatic in Agodi Reservoir.

Agodi Reservoir plant: Ecological risk from heavy metals

The ERQ of heavy Metals I. aquaticaTable 4 shows the results. Table 4.

Table 4 Ecological Risk Quotient for Heavy Metals I. aquatic in Agodi Reservoir.

The ERQ values of Fe (533.27, 858.19) and Mn (551.50 and 955.55) were very high in comparison to other metals with high ERQ (Table 4,). Pb, Cu, and Zn also had ERQs values of 6.89 and 4.55 respectively in the wet seasons, while Cd, Zn, and Cu had ERQs values of 6.21 and 4.75 during the dry. High ERQ values were also recorded for Zn, Mn, and Pb throughout the study period. Fe and Cu were also nearly obtained throughout the study period. ERQ values were also higher in the dry season than in the wet, with the exception of Cr, Fe and Mn (Table 4).

Tolerance of heavy metals Oreochromis niloticus Ipomoea aquatic

The tolerance of O. niloticus(Fish) I. aquaticaFig.1 shows the relationship between cadmium and plant in the dry and wet seasons. Figure 1. This shows that fish tolerated spikes in dry season (11.69%/kg in December) or wet season (0.47mg/kg May). I. aquaticaAugust (0.99mg/kg) was below threshold, while April (1.10mg/kg). Fig.2 shows that the concentrations in cobalt (Co), were within the tolerance of O. niloticusIn November; 14.75 mg/kg) The dry season I. aquaticaIn June (Wet season), there was a spike of 0.65 mg/kg. Fig.3 shows that the concentrations of chromium and chromium (Cr), were not above the threshold of either. O. niloticus I. aquaticaIn the dry season, but the concentration was beyond what was tolerable O. niloticus(14.58mg/kg June) I. aquatica(1.00 mg/kg April) in the rainy season

Fig. 4 also showed that both the fish and the plant had Cu levels within the tolerance of the organisms. Figure5 also revealed this. O. niloticusIt did not bioaccumulate Fe beyond the acceptable limit in the dry season. However, it did experience an increase in August (1332.33mg/kg). The concentration was also elevated in I. aquaticaThe threshold level was 135.8mg/kg in Feb., but it was above the tolerance of the plant in April (1910.50mg/kg); wet season. The bio-tolerance of O. niloticus(Fish) I. aquatica(Plant) to manganese(Mn) in the dry and wet seasons (as shown in Fig.6) showed that no concentration was above the tolerance of O. niloticusDespite the high concentrations recorded in the wet seasons, the fish were able to survive. However, the concentration of 1003.08mg/kg recorded in August (dry season), was higher than the fish’s tolerance limit. The figure also revealed that February’s values (144.75mg/kg), as well as April’s (112.25mg/kg), were both above the fish’s tolerance. I. aquaticaIn the dry and wet seasons, respectively.

The tolerance limit for nickel (Ni), was exceeded by the concentrations of nickel (Ni), in April (3.46mg/kg), and May (0.38mg/kg). O. niloticus I. aquaticarespectively (Fig.7). The Pb concentrations in August (1.61mg/kg), and May (13.50mg/kg), were both above the tolerance limit. O. niloticusThe concentrations were different in the dry and moist seasons. However, the toxic concentration in October (93.10mg/kg), was only found in the dry season. I. aquatica (Fig.8). High concentrations of Zinc (Zn), were recorded in O. niloticusThe concentrations were within the tolerance of fish, even though the August 446.29mg/kg level was below the threshold. However, the concentration for I. aquaticaFebruary’s concentration of 178.27mg/kg was above the tolerance level of the plant (Fig.9)