Nutrient Removal by Palmaria palmata and Chondrus crispus in Bioremediation of Aquaculture Effluent

Abstract

Palmaria palmata and Chondrus crispus were cultured in the lab at three levels of temperature and two of nitrate, representative of commercial Atlantic halibut farming conditions. Productivity and nitrogen removal by P. palmata were greatest at temperatures <10°C. Productivity of C. crispus was greatest at >10°C, while nitrogen removal was unaffected by temperature, 6-17°C. When cultured in various nitrate and ammonium combinations, nitrogen uptake was highest when available as ammonium. Both species took up 89-100% of ammonium in 24 hours, but only 23-37% and 55-87% of nitrate was taken up by P. palmata and C. crispus, respectively. When P. palmata was integrated with halibut recirculating aquaculture, productivity and nutrient removal were compromised during summer. During winter, <11°C, nitrogen removal by P. palmata was relatively stable at 2.3 gN m-2 d-1. For 50% nitrogen removal from halibut aquaculture during winter, a finfish: seaweed biomass of 1: 1 would be required.