Improving the farm while protecting the wild: understanding drivers of genetic differentiation in kelp

Summary

While the deployment of improved seaweed strains optimized for size, growth rate, and disease resistance remains largely confined to Asia, selective harvest of parent material to improve farming is more widespread. Precautionary management with respect to the issue of “escaped” genetic material from farms has usually come in the form of radius-based restrictions on where parent material for farmed kelp can be sourced. This assumes distance is the primary driver of genetic differentiation and can limit access to the best available cultivation strains. Previously, studies have utilized a small number of markers to suggest that environment may be more important than distance in determining genetic population structure. Here, I present genetic profiles composed of >1 million single nucleotide polymorphisms (SNPs) from a new whole genome sequencing effort of farmed and wild sugar kelp (Saccharina latissima) from the Norwegian coastline. By comparing populations from different environments, cultivation methods, and geographic regions, these profiles paint a more complete picture of the drivers of genetic differentiation, highlighting cultivation method as an influence greater than distance, even at scales greater than 100km. Considering this new information, alternative management structures are required to facilitate strain development while protecting wild populations. These results apply to kelp farmed anywhere in the world, especially areas with complex coastlines, providing foundational knowledge for the expansion of kelp farming at regional to national scales.