Polar cod in a changing environment: multidisciplinary approaches to study population dynamics

The Polar cod (Boreogadus saida Lepechin, 1774) is a key forage species in the Arctic food web, transforming the energy from low to high trophic levels. Its life cycle depends on the Arctic environment, its seasonal ice coverage and low water temperatures. Because the Arctic will experience massive changes as the ice melts due to climate changes, large impacts on the Polar cod distribution and connectivity are expected. In a context of fragile ecological balance, we explore connectivity among populations of Polar cod across the Svalbard and Iceland regions. This investigation requires a multidisciplinary approach that would disclose how adaptation and plasticity contribute to the species coping with climate change. Preliminary analyses of a SNPs dataset generated with ddRAD-seq revealed limited genetic differentiation between Svalbard and Iceland individuals, suggesting high connectivity across the study area. Nonetheless, a small set of loci appears to be under divergent selection, indicating potential signals of local adaptation despite overall genomic homogeneity. Besides genetic data, we expect that epigenetic variation, obtained by profiling DNA methylation patterns between regions, might disclose plastic responses to different environmental parameters. These ongoing analyses may detect subtle and short-term differentiation signals that remain undetected through classical genomic analyses, and we anticipate having initial findings to report at the conference. By integrating genomic and epigenomic approaches, this study seeks to improve our understanding of Polar cod resilience and hence to safeguard the stability of Arctic marine ecosystems under rapid climate change.