Effect of irradiance on bioremediation capacity of the red algae Chondrus crispus and Palmaria palmata

To investigate the illuminance requirements for the culture of red algae in finfish effluent, both Chondrus crispus and Palmaria palmata were assessed simultaneously at three irradiances. Apical tips, 3.5 cm length, were stocked at 2 g L −1 in 1-L glass flasks with enriched seawater in two 24-day experiments, at 10 and 14 °C, respectively. Palmaria grew up to 70 % better and up took more nutrients than Chondrus under five of the six experimental conditions, except at 14 °C and low irradiance (daily photon dose of 3.4 mol photon m −2 day −1 ). Specific growth rate of both species at high irradiance, 13.1 and 17.2 mol photon m −2 day −1 , at each trial, 10 and 14 °C, respectively, was 40 and 20 % better than at medium irradiance, but nutrient uptake was similar at both medium and high irradiance. Chondrus growth rate was higher during Experiment 2 (14 °C and 17.2 mol photon m −2 day −1 ) than during Experiment 1 (10 °C and 13.1 mol photon m −2 day −1 ), while Palmaria growth rate was similar in both trials, but always significantly higher than Chondrus . In the range 10–14 °C, Palmaria is the best candidate for integration with Atlantic halibut juveniles ( Hippoglossus hippoglossus ).