Male-biased sensitivity to wastewater effluent exposure in Harpagifer antarcticus from Fildes Bay, King George Island

Antarctica has experienced a growing human presence in recent decades, with year-round scientific and military stations concentrated along the coast. Wastewater effluents from these settlements represent a growing concern, as they contain pharmaceuticals and personal care products (PPCPs) capable of disrupt endocrine functions in aquatic organisms at environmentally relevant concentrations. This study evaluated the impact of wastewater exposure on the gonadal transcriptome of the Antarctic fish Harpagifer antarcticus , collected nearby human settlements and research stations in Fildes Bay, King George Island. Chemical analysis revealed bioaccumulation of diclofenac, carbamazepine, and fluoxetine in fish muscle. Morphological endpoints indicate significant decreases in male gonadosomatic index (GSI) at impacted sites. Molecular analysis suggested disruption of genes related to reproduction. Females displayed significant overexpression of zp at impacted sites, while males from contaminated areas showed increased expression of both zp and esr1 .Transcriptomic analysis revealed a male-biased response, with enriched GO terms associated to sperm motility, nervous system function, and immune and inflammatory regulation, as well as chemical homeostasis and lipid metabolism. Females were less impacted, exhibiting transcriptomic alterations mainly linked to metabolic homeostasis. Together, these findings suggest that male H. antarcticus are particularly sensitive to wastewater-derived contaminants, with transcriptional shifts serving as early warning signals of impaired reproduction, physiology, and population resilience. This study highlights the vulnerability of Antarctic coastal ecosystems to anthropogenic pressures and underscores the urgent need for improved wastewater management in this fragile environment. • Transcriptomic alterations were studied in Harpagifer antarcticus inhabiting Fildes Bay, King George Islands. • The PPCPs most abundant in Harpagifer antarcticus muscle were diclofenac, carbamazepine, and fluoxetine. • Male exhibited reduce gonad size and stronger DEGs at sites exposed to wastewater compared to females. • The principal molecular alterations in gonads were related to reproduction function and sperm movement. • Transcriptomic signatures revealed additional effects on nervous system function, immune regulation in males.