Contrasting patterns of kelp-associated bacterial community dynamics between farmed and wild Saccharina latissima throughout an aquaculture season
Seaweed farming is the world's fastest growing aquaculture sector. To facilitate the productive and sustainable expansion of the industry, whilst minimising deleterious ecosystem impacts, it is essential to understand the processes influencing seaweed health and yield. In the UK, the cultivation of sugar kelp (Saccharina latissima) has expanded in recent years, although it remains relatively small-scale. In 'wild' populations of kelp species, including S. latissima, it is well established that associated bacteria play key roles in the development, growth and environmental resilience of their kelp host. The effects of farming associated differences in growth conditions, such as increased stocking density, surface suspended culturing and monocultures, on these kelp-microbiome relationships remain poorly understood. Using 16S rRNA sequencing, we characterised bacterial communities associated with two farmed and one wild population of S. latissima, in the Western English Channel (southwest UK) across a typical growing season. Kelp-associated bacterial communities were distinct from those in surrounding seawater and differed consistently between farmed kelp and the wild population. Diversity and composition followed site-specific seasonal trajectories that diverged between the farmed kelp and the wild population and became increasingly dissimilar as the season progressed. Together, these findings show that cultivation does not simply mimic the dynamics observed in the wild kelp population but instead, it generates distinct, context dependent microbiome trajectories. Such patterns are likely shaped by a complex interplay between several factors, including synchronised early succession, fouling intensity, and local environmental conditions, which requires further investigation linking specific drivers to observed microbiome shifts. Future aquaculture development could consider microbial monitoring and undertaking active microbiome-based management strategies to support the sustainability, resilience, and productivity of the expanding seaweed aquaculture industry.
Seaweed farming is the world's fastest growing aquaculture sector. To facilitate the productive and sustainable expansion of the industry, whilst minimising deleterious ecosystem impacts, it is essential to understand the processes influencing seaweed health and yield. In the UK, the cultivation of sugar kelp (Saccharina latissima) has expanded in recent years, although it remains relatively small-scale. In 'wild' populations of kelp species, including S. latissima, it is well established that associated bacteria play key roles in the development, growth and environmental resilience of their kelp host. The effects of farming associated differences in growth conditions, such as increased stocking density, surface suspended culturing and monocultures, on these kelp-microbiome relationships remain poorly understood. Using 16S rRNA sequencing, we characterised bacterial communities associated with two farmed and one wild population of S. latissima, in the Western English Channel (southwest UK) across a typical growing season. Kelp-associated bacterial communities were distinct from those in surrounding seawater and differed consistently between farmed kelp and the wild population. Diversity and composition followed site-specific seasonal trajectories that diverged between the farmed kelp and the wild population and became increasingly dissimilar as the season progressed. Together, these findings show that cultivation does not simply mimic the dynamics observed in the wild kelp population but instead, it generates distinct, context dependent microbiome trajectories. Such patterns are likely shaped by a complex interplay between several factors, including synchronised early succession, fouling intensity, and local environmental conditions, which requires further investigation linking specific drivers to observed microbiome shifts. Future aquaculture development could consider microbial monitoring and undertaking active microbiome-based management strategies to support the sustainability, resilience, and productivity of the expanding seaweed aquaculture industry.