Porphyra cultivation in Alaska: conchocelis growth of three indigenous species

Abstract

Experiments were performed to determine the range and optima of environmental conditions under which indigenous species of Alaskan Porphyra can grow. Growth of the conchocelis phase of Porphyra abbottae, P. torta and P. pseudolinearis was measured, when cultured in enriched media, under long days (16 h light) and varying conditions of irradiance (20, 40, 80 and 160 μmol photons m⁻² s⁻¹), temperature (7, 11, 15 and 19 °C) and salinity (5, 10, 20, 30 and 40‰). Optimal growth (7.6% increase in volume day⁻¹) of P. abbottae occurred at 11 °C, 80 μmol photons m⁻² s⁻¹ and 30‰. Porphyra torta grew best (6.5% day⁻¹) at 15 °C, 80 μmol photons m⁻² s⁻¹ and 30‰. Porphyra pseudolinearis generally had higher growth rates than the other two species with optimal growth (8.8% day⁻¹) occurring at 7 °C, 160 μmol photons m⁻² s⁻¹ and 30‰. For all three species salinity between 20 and 40‰ had little effect on growth, but there was virtually no growth at salinity of 10‰ and below. Irradiances between 20 and 160 μmol photons m⁻² s⁻¹ generally had little effect on growth rates. However, growth of P. abbottae increased with irradiance at 7 °C but was inhibited at irradiances over 40 μmol photons m⁻² s⁻¹ at 15 °C and higher. Porphyra torta also showed growth inhibition at 15 °C and higher irradiances. Porphyra pseudolinearis appeared to be the most robust species with respect to tolerance to extremes of salinity and irradiance.