Metal accumulation in muscle and oxidative stress response in the liver of juvenile Oreochromis niloticus from contaminated sediment under a simulation of increasing temperature

Abstract

In the present study, a mesocosm experiment with contaminated sediment and clean groundwater using juvenile Oreochromis niloticus was set up to assess the effect of increasing temperature on bioaccumulation of metal in fish muscles (cadmium, chromium, nickel, and lead) and enzymatic activities in fish liver [reduced glutathione (GSH), glutathione reductase (GR), superoxide dismutase (SOD), glutathione transferase (GST), and glutathione peroxidase (GSH Px)]. The trend of temperature variation was Control 1 (0 Watts) < 60 Watts < 100 Watts < Control 2 (200 Watts). After 72hrs, there was no observed mortality in Controls 1 and 2; however, the % Survival in 0 Watts reduced to 90.0 ± 4.0 %. Furthermore, 60, 100 and 200 Watts had lower rates of survival at 46.0 ± 6.9, 36.0 ± 13.1, and 24.0 ± 11.1 % respectively. The calculated bioaccumulation factors (BAFs) for metals was in the trend: Pb > Cd > Cr > Ni. Mean metal pollution index (MPI) in fish muscles was lowest at 0 watts (24hrs - 7.86 ± 1.72, 72hrs - 25.77 ± 4.56) and highest at 100 watts (24hrs - 39.45 ± 1.91, 72hrs - 55.82 ± 1.05). Controls 1 and 2 showed no significant difference in the concentration of GSH and GR while showing a significant difference in GST and GSH Px concentrations after 24 and 72 hrs. Pearson’s correlation showed that GSH was inhibited by water temperature and, Cd, Cr, and Pb concentrations in surface water and fish. Therefore, an increase in ambient temperature in an already contaminated environment will increase the bioavailability of metal contaminants leading to an increase in bioaccumulation and exacerbation of oxidative stress in juvenile tilapia.