Heavy Metals Contamination and Their Impacts on Fish Responses in Porong River, East Java, Indonesia

: The presence of heavy metals and other contaminants may indicate the presence of a biological response in aquatic animals. This research investigates the heavy metal contamination and water quality on the immune response (IL-1 β ) of wader fish ( Barbonymus gonionotus ) in response to the presence of contaminants in the waters of the Porong River. The location area was selected because of its diverse utilization surrounding the river, including residential areas, industrial zones, and agricultural practices. The research procedure includes water quality measurements, plankton analysis, heavy metals exposure, and immune response (IL-1β) detection by PCR. In general, the waters of the Porong River were found to be polluted based on the assessment of water quality, as indicated by the measurement of CO 2 , TDS, TSS, and salinity parameters surpassing the established threshold values. In the waters of the Porong River, the metals Cu, Hg, Cd, and Pb exhibited a descending order of penetrating power as follows: Cu > Hg > Pb > Cd. Conversely, in the sediment samples, the order of penetrating power was Cu > Pb > Cd > Hg. The PCR amplification results indicated the presence of IL-1β response in all examined fish, suggesting that it could be attributed to water contamination throughout the entire sampling site. In addition, the heavy metals contamination in the waters of the Porong River resulted in high expression of IL-1β in the fish sample. The findings lead to the conclusion that the waters of the Porong River are classified as polluted based on the measurements of water quality parameters, namely CO 2 , TDS, TSS, and salinity, which surpass the threshold values established according to Government Regulation (PP) of the Republic of Indonesia Number 22 of 2021.