Whole genome sequencing reveals interbay population structure of Saccharina latissima (sugar kelp) in western Iceland

The nearshore macroalgae Saccharina latissima (eng. sugar kelp, ice. beltisþari) is abundant across the boreal arctic marine region and has been receiving increased focus around Iceland and other countries bordering the Northern Atlantic Ocean for aquaculture and ecological engineering potential. While the ecological and economic importance of nearshore macroalgae has become increasingly clear, the amount of population connectivity is poorly understood. Genetic, and especially genomic, data for this group are exceptionally depauperate. We here report the first population genomic level analysis of S. latissima in Iceland, comparing individuals sampled across two of the largest bays on the island, Faxaflói and Breiðafjörður. We see a clear segregation of the northernmost and southernmost sites, with a secondary split between inner and outer bay sites. These patterns suggest a dynamic biogeography impacting the population structure of S. latissima across relatively short distances (less than 150 km) in western Iceland and highlights the potential for local selection pressures to shape genetic composition across small geographic scales.