Effects of temperature and ammonium on growth, pigment production and nitrogen uptake by four species of Porphyra (Bangiales, Rhodophyta) native to the New England coast

Porphyra is one of the world's most valued maricultured seaweeds and has been cultivated for several hundred years in Asia. The objective of this study was to produce critical information as a guide for the selection of an appropriate Porphyra species from coastal New England for the development of a land-based aquaculture system. Four Northwest Atlantic Porphyra species: P. leucosticta, P. amplissima, P. linearis and P. umbilicalis, were cultivated for 1 and 2 weeks at saturated light intensities ( 100 150 mu mol photons m(-2)s(-1)) and six combinations of ammonium (25 and 250 mu moles L-1) and temperature (10, 15 and 20 degrees C). Specific growth rate (SGR) increased with decreasing temperature in P. leucosticta, P. linearis and P. umbilicalis and increased with increasing temperature in P. amplissima. The SGR of all species was greater at the higher ammonium concentration. Porphyra linearis had the highest SGR, increasing in biomass by approximately 16% day(-1). Phycoerythrin (PE) content was higher at 10 degrees C and 250 mu moles L-1 in all species except P. amplissima. The PE content, measured as fresh weight (FW), of P. linearis (29 mg g(-1) FW-1) and P. umbilicalis (26 mg g(-1) FW-1) was significantly higher than the other two species. Tissue nitrogen content of all species measured in dry weight was on average 1.45% higher at 250 mu moles L-1 than at 25 mu moles L-1 ammonium concentration. Porphyra umbilicalis had the highest tissue nitrogen contents (6.76%) at 10 degrees C and 250 mu moles L-1 ammonium. Based on these results, P. linearis and P. umbilicalis should be considered as potential candidates for bioremediation with finfish and shellfish mariculture.