Open-sea cultivation trial of the red alga, Palmaria palmata from seeded tetraspores in Strangford Lough, Northern Ireland

Abstract

Cultivation of Palmaria palmata was performed by a technique introduced in this paper of tetraspore release and attachment to culture string. Optimal conditions for laboratory growth were investigated with respect to irradiance and nutrient media. The length of laboratory culture required for the growth and development of attached sporelings was also investigated, prior to deployment of seeded strings on a longline structure in Strangford Lough, Northern Ireland. Of sporelings grown in 5, 10, 25 and 50 μmol m − 2 s − 1 , those at the lower irradiances (5 and 10 μmol m − 2 s − 1 ) were significantly longer than those at higher irradiances after 12 weeks. Sporeling length was also significantly greater at lower irradiances when in F/2 nutrient media with additional vitamin solution, compared with F/2 medium without the vitamin solution. Seeded string was held in the laboratory for 2, 4, 6, or 8 weeks. After 3 months at sea, the 2-week strings had fewer visible plants and had shorter plants than the 4, 6 and 8-week strings, but plants on all strings were similar in length after 7 months at sea. The demand for P. palmata as a snack food in Northern Ireland regularly outstrips the supply obtainable from natural populations. The technique of seeding string with tetraspores is proposed as one method of commercially cultivating P. palmata on a large scale.