Physiological studies of cultured New England nori, Porphyra umbilicalis Kutzing and Pyropia leucosticta (Thuret) Neefus & J. Brodie, and implications for their use in integrated multi-trophic aquaculture systems

Successful aquaculture of any crop requires detailed knowledge of the optimum conditions for growth as well as an understanding of its life history. The expansion of a seaweed aquaculture industry in New England is partially hampered by the lack of complete knowledge of the physiology and biology of native seaweeds. Species of the red seaweed Porphyra and Pyropia, known by the Japanese name "nori", are the most valuable maricultured seaweeds in the world. The goals of these studies were to determine the optimum temperatures, photoperiods, and light levels for production of two local nori species Porphyra umbilicalis and Pyropia leucosticta, determine which environmental factors triggered development and release of conchospores to complete the life history of Py. leucosticta, and assess whether blades of P. umbilicalis were viable after long-term freezing. Both P. umbilicalis and Py. leucosticta grew optimally (>10% day-1) at 10-15°C, 12:12 L:D, and above 110 mumol photons m-2 s-1. Pigment and protein content in both species generally decreased with increasing light level, although the effect of light level on phycobilin content was dependent on photoperiod. Detailed information on the growth rate, photosynthetic efficiency of photosystem II, pigment and protein content of P. umbilicalis and Py. leucosticta grown under 32 combinations of temperatures, photoperiods, and light levels are reported. Development of conchosporangial filaments in the sporophyte generation of Py. leucosticta and release and germination of conchospores were found under all temperatures, photoperiods, and nitrogen concentrations tested (18 total combinations). Blades of P. umbilicalis showed 100% survival after up to 12 months of frozen storage, recovering to pre-freezing growth rates rapidly following rehydration. Hence, freezing is a suitable form of preservation for P. umbilicalis and can be utilized to ensure sufficient supply of seed stock for tank-based cultivation. My results add to the existing knowledge of the physiology and biology of P. umbilicalis and Py. leucosticta from New England. Ultimately, these results will help interested nori growers maximize production and successfully cultivate P. umbilicalis and Py. leucosticta..