Sexual Propagation in the Green Seaweed Codium tomentosum—An Emerging Species for Aquaculture

Codium tomentosum holds a variety of bioactive compounds, high nutritional value and health benefits, which makes it a valuable natural resource for the food, cosmetic and pharmaceutical industries. Currently, C. tomentosum is farmed at a small-scale targeting niche markets, and further expansion of production is limited by a lack of optimised propagation and cultivation methods. This study aims to identify the conditions required to control key production parameters including gametogenesis, gamete release and suitable culture conditions for the early stages of development of C. tomentosum. Wild specimens of C. tomentosum were collected on the Aguçadoura shore, north of Portugal. Gametogenesis was successfully induced in infertile specimens cultured under a short-day photoperiod (8 h:16 h; L:D). Gamete release was optimised through a combination of hydric shock and ultrasounds, with the highest gamete yield obtained after a 2 h 30 min desiccation period, followed by re-hydration and a series of three ultrasounds. Germlings, precursors of the adult C. tomentosum, grew faster when cultured under a lower light intensity (20 μmol m−2 s−1) compared to higher intensities (40 and 60 μmol m−2 s−1) in every light spectrum; additionally, the growth of germlings exposed to the lowest light intensity was significantly higher under white, red and green light spectra compared to blue light. The results on key production parameters constitute an important contribution to the establishment of nursery protocols based on sexual reproduction for aquaculture of the species.