Impact of heavy metals on the food web in the Mediterranean lagoon, Lake Burullus, Egypt

Research on the impact of heavy metals and their accumulation in ecosystem elements of Lake Burullus is still scarce. Therefore, this study focuses on the relationship between the levels of heavy metals in the lake water, plankton communities and Nile tilapia (Oreochromis niloticus). The mean annual concentrations of Fe, Zn, Cu, Mn, Pb and Cd in water and fish samples were 527.8, 366.7, 162.6, 137.3, 119.8 and 3.6 μg l⁻¹, and 70.8, 43.6, 8.05, 1.2, 0.14 and 0.045 μg g⁻¹ dry weight (d.w.), respectively. The study demonstrated the relationship between the accumulation of metals in fish muscles and their levels in the lake water (p < 0.05; r = 0.7–0.9), with the metal content in O. niloticus muscles being mostly below the permissible limits. The obtained results showed that the levels of the metals in the lake water are not correlated with phytoplankton and zooplankton, and their groups, except copper and zinc, are negatively correlated with phytoplankton (r = −0.45 and −0.58, respectively). The study concluded that the concentrations of the analyzed metals in Lake Burullus did not reach the effective levels that would have a significant impact on the distribution of phytoplankton and zooplankton, or a hazardous effect on O. niloticus and its safety for human consumption.