Sophie Corrigan1,2, Charles R. Tyler1, Ross A. Brown1, Ian G. C. Ashton3, Cat Wilding2, Carly Daniels3, Dan A. Smale2
1College of Life and Environmental Sciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter, Devon, EX4 4QD, UK.
2 Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB
3 College of Engineering, Mathematics and Physical Sciences, University of Exeter, Penryn Campus, Cornwall, TR10 9FE, UK.
Seaweed farms are expanding rapidly in Europe, in response to increasing demand for seaweed-derived products for human food, cosmetics, agriculture and industry. Seaweed farming may offer additional ecosystem services, such as habitat provisioning and elevated local biodiversity, which could benefit other marine industries including fisheries by providing breeding or feeding grounds to fish species. The habitat value of seaweed farms has largely remained unquantified, however, with most research focusing on mitigating detrimental biofouling, rather than highlighting the potential contributions of farm-associated biodiversity to healthy ecosystem functioning. We monitored the development and diversity of epibiont assemblages on sugar kelp (Saccharina latissima) from a farm in southwest UK, and compared these assemblages to those found on wild kelps. We found significant increases in epibiont abundance and diversity on farmed kelps over and beyond their growing season, reaching an average of 6196.3 ± 450.4 SE individuals per kelp and 9.7 ± 0.17 SE taxa present by August 2020. Assemblages on farmed kelps were dominated by amphipods, bivalves and bryozoans, which are detrimental to crop quality, yet contribute to bioremediation and provisioning of food for higher trophic levels, such as commercial fish species recorded at the farm. Wild kelps hosted significantly fewer epibionts (87.2 ± 56.0 SE), but had a higher taxonomic richness (13.3 ± 0.42 SE), suggesting seaweed farms may offer novel habitats in coastal areas. Increased understanding of epibiont assemblage development could improve the habitat value of seaweed farms, while optimising crop yield for farmers as an example of sustainable ecosystem-based aquaculture.