Abstract
<title>Abstract</title> <p> Parasitic helminths have emerged as promising bioindicators for monitoring heavy metal pollution in aquatic ecosystems. This study investigated the bioaccumulation of four heavy metals (Cu, Zn, Pb, and Cd) in three groups of parasitic helminths (Trematoda, Nematoda, and Cestoda) isolated from the commercially important Brushtooth lizardfish ( <italic>Saurida undosquamis</italic> ) along the Misurata coast, Libya. A total of 88 fish samples were collected during the hot and cold seasons of 2022, revealing a 100% infection prevalence across all seasons. Heavy metal concentrations in the isolated helminths were analyzed using Atomic Absorption Spectrophotometry (AAS). The results indicated that Copper (Cu) was the predominant metal across all helminth groups, while Cadmium (Cd) and Lead (Pb) exhibited group-specific accumulation patterns. Trematodes and Cestodes exhibited a significantly higher capacity to accumulate toxic metals (Pb and Cd) compared to Nematodes, which showed more stable accumulation patterns and a preference for essential metals. Seasonal variations influenced metal distribution, with generally higher concentrations observed during the cold season, particularly in Cestodes. The distinct accumulation capacities, especially the high bioconcentration of toxic metals in Trematoda and Cestoda, highlight their potential as sensitive and reliable bioindicators for marine heavy metal pollution. This study provides the first baseline data on the use of helminth parasites from <italic>S. undosquamis</italic> for environmental biomonitoring in the Libyan Mediterranean coast. </p>