Minimising Risks of Reduced Genetic Diversity in Marine Restoration

Marine habitat restoration is expanding globally and increasingly relies on aquaculture and hatchery-based propagation, yet the genetic consequences of producing and outplanting large numbers of habitat-forming organisms remain poorly evaluated. A lack of best-practice guidelines and insufficient genetic monitoring creates risks including bottlenecks, inbreeding and domestication, with long-term impacts possible for both restored and remnant populations. Here, we assessed the impacts of hatchery processes on genetic diversity and domestication in the kelp, Ecklonia radiata, by genotyping wild donor populations and their hatchery-bred F ₁ cohorts. Despite using ~100 donor adults per site, hatchery-bred F ₁ individuals showed clear reductions in genetic diversity. On average, neutral heterozygosity declined by ~20%-30%, and more than half of the percentage of polymorphic loci was lost, indicating strong genetic drift and erosion of potentially locally adapted variation. Moreover, a small number of outlier loci were strongly associated with hatchery conditions, indicating early selection and domestication responses within a single generation. F ₁ cohorts also exhibited elevated inbreeding and sharp reductions in effective population size (N _e falling from ~500 in the wild to as low as 21 in the hatchery). These findings demonstrate that unmonitored propagation can rapidly alter the genetic composition of foundation species under hatchery conditions, potentially undermining adaptive capacity and field performance. Incorporating genetic guidelines and monitoring into restoration programs will be essential to support long-term persistence and evolutionary resilience.