Textile substrate seeding of Saccharina latissima sporophytes using a binder: An effective method for the aquaculture of kelp

Abstract

The macroalga Saccharina latissima holds promise as a widespread crop in northern Europe. Currently, seeded lines are cultured for 1–2 months within a hatchery until they become ≥1 mm sporophytes, which are then outplanted to a farm. Textiles are being developed as a cultivation substrate for macroalgae, however due to their large surface area, these need either direct in-situ seeding at the farm or a very short, high turnover hatchery period. Two materials, Kuralon twine and non-woven textile, were seeded using three S. latissima developmental stages: meiospore, gametophyte or juvenile sporophyte. The gametophyte and sporophyte stages were applied using a binder solution to adhere them to the materials. These were outplanted at a seaweed farm in the Sound of Kerrera, UK. After 5 weeks, fronds were significantly larger (45 ± 25 mm) and more abundant (20 ± 8·20 cm−1) when seeded with sporophytes over gametophytes or meiospores (8 ± 10 mm and 2 ± 2·20 cm−1). This reflects the growth advantage of outplanting juvenile sporophytes, since they are larger and more developed when outplanted. Higher fouling of filamentous algae was seen on the non-woven textile but this did not appear to affect growth. After four months, sporophyte seeded materials had the largest fronds and the greatest fresh mass of 2.1 ± 0.8 kg·20 cm−1, equivalent to simultaneously deployed hatchery reared twine (2.0 ± 0.1 kg·20 cm−1). Gametophyte seeding achieved 0.8 ± 0.6 kg·20 cm−1 while meiospore seeding achieved only 0.1 ± 0.1 kg·20 cm−1. No difference was found between growth on Kuralon twine or non-woven textile (p > 0.05), showing that both are suitable growth substrates. Seeding of juvenile sporophytes onto textile using the binder is demonstrated to be a successful method for the cultivation of S. latissima, and may require only 1% of the hatchery tankage, once optimised. It is expected that this method is transferable to the cultivation of other kelp species.