Environmental monitoring: Tobara fish as bioindicators of heavy metal pollution in a coastal ecosystem

This study aims to evaluate the liver, gill, and muscle tissue heavy metal accumulation of the thin lip mullet (Chelon ramada) from Ain Ziana Lagoon, Benghazi. The heavy metals included zinc, copper, lead, and manganese. Between September 2021 and August 2022, specimens were collected on a monthly basis. They were identified using DNA barcoding, namely the CO1 gene, which is associated with the sequence that is BankIt in the NCBI gene bank (accession number OR533708). The research tracked the lagoon's physicochemical characteristics, finding that heavy metal concentrations spiked in the summer and that water temperature, pH, and salinity varied throughout the year. Except for copper in the winter, lead, manganese, and copper levels were all above acceptable limits, according to a comparison with EPA (2005) regulations. On the other hand, zinc levels were under these limitations. The amounts of all metals in the sediment regularly exceeded the limits set by the EPA. Zinc and manganese levels in fish tissues were within the approved ranges according to WHO and FAO standards but lead and manganese levels were far higher than allowed, indicating possible pollution from sewage or industrial sources. There were noticeable seasonal patterns in bioaccumulation, especially during the warmer months, but manganese did not exhibit a distinct pattern. Also noted that the thin lip mullet's mineral absorption and release capacities varied with the different seasons and tissues. Lastly, the Metal Pollution Index (MPI) showed that there was a larger possibility for bioaccumulation in the liver, gill, and muscle during the study period.