The impacts of palm oil mill effluent (POME) on aquatic animals – a mini-review

This review synthesizes and critically evaluates the deleterious ecotoxicological impacts of palm oil mill effluent (POME) on aquatic animals. As the primary byproduct of the palm oil industry, POME presents a significant environmental hazard due to its complex and highly concentrated composition, characterized by elevated biochemical oxygen demand, chemical oxygen demand, high concentrations of suspended solids, and a suite of potentially toxic heavy metals (cadmium, copper, mercury, and lead). Extant toxicological investigations have elucidated the adverse effects of both acute and chronic POME exposure on a range of aquatic animals. These effects encompass disruptions in growth, respiration, integumentary pigmentation, hematological profile, antioxidative enzyme activity, reproduction, behavior (including feeding and mating), and early developmental stages. Reviewed studies spanned POME concentrations from 1.565 ppm to 1 ppt, with exposure durations ranging from 10 to 45 days. Furthermore, the impacts of suspended solids within POME were assessed, revealing significant negative consequences on reproductive behaviors and output, as well as visual acuity, at turbidity levels between 20 and 100 nephelometric turbidity units (NTU) with exposure durations from 15 minutes to 15 hours. Notably, current POME ecotoxicological research is taxonomically circumscribed to a limited number of model species, including tilapia, zebrafish, hybrid catfish, and Siamese fighting fish, across various life stages. Consequently, future research must expand the taxonomic and life-stage breadth of investigations to corroborate and refine our understanding of POME’s impacts on aquatic ecosystems. The findings presented herein offer salient, evidence-based insights that can inform the development of effective POME remediation strategies, thereby mitigating the ecological risks posed to aquatic biota.