Porphyra umbilicalis in applied and basic research: reproductive phenology, development, seed stock culture, and a field trial for aquaculture

Royer, Charlotte; Redmond, Sarah; Lai, Chu; Brawley, Susan

From the abstract: "Porphyra umbilicalis is being developed in the North Atlantic for aquaculture; however, information on nursery stock establishment and maintenance is needed, including when to collect spores (phenology), how to maintain healthy seed stock over multiple generations, and whether reproductively mature blades can be stored at low temperature (-20 °C) for immediate use 'on demand' to seed lines and nets. We evaluated whether spore damage would occur by documenting early developmental patterns of germlings from cold-stored parent blades to control blades. Phenological studies over 300 km of Maine, USA, shore indicated that successful NS production by P. umbilicalis peaks in winter, is greatly reduced in summer, and may be affected by amphipod (Apohyale prevostii) grazers in fall and spring. The pattern of early cell division in germinating neutral spores was affected by donor parent (blade) for a few minor patterns of cell division, but not by cold storage (-20 °C) of reproductive blades for 6 weeks. Linear development was about four times more common in neutral spore germlings than bilateral development, but variations in pattern of cell division were observed, and these may help to explain the variable morphology of the adult blade. The minimal time required to grow neutral spores to reproductively mature blades in laboratory culture was 62 days; vigorous water motion provided by aeration and immobilization of blades by holdfast clips (versus tumbling) were essential to spore production. Seeded lines produced blades of harvestable size with a substantial understory in a preliminary field trial."