Stress-dependent shifts in genotoxic sensitivity of Arctic zooplankton

Abstract

The Arctic Ocean is increasingly exposed to multiple stressors, including rising temperatures and metal pollution. Zooplankton, as central components of the Arctic food web, exhibit varying sensitivities to these stressors depending on their ecological niches. This study compares acute and sublethal genotoxic responses of two ecologically distinct Arctic zooplankton species; surface-dwelling Acartia longiremis and deeper-dwelling Calanus spp.; to combined copper (Cu) and temperature stress. Morphological analysis (antenna colour) and DNA barcoding revealed the Calanus spp. assemblage was dominated by C. finmarchicus (74.3%) with fewer C. glacialis (25.7%). Acute exposure to elevated temperature (11 °C) or Cu (20 μg/L) resulted in greater mortality in A. longiremis than in Calanus spp. Sublethal exposure to the individual and combined stress for 24 h showed a contrasting pattern as revealed by DNA damage analysis and targeted gene expression. Genotoxicity appeared linked to oxidative stress, DNA damage through strand breaks and cross-links, and impaired defense and repair mechanisms with species-specific differences in stress response pathways. A. longiremis showed higher acute sensitivity, while Calanus spp. were more susceptible to sublethal genotoxic effects. These findings highlight that zooplankton from distinct microhabitats within the same Arctic ecosystem can exhibit different vulnerabilities and mechanistic defences to co-occurring stressors.