Development of simplified and more cost-effective hatchery techniques for macroalgae seedling production

Supervisor: Tim Atack (Ardtoe Marine Laboratory)
There is considerable interest in the culture of seaweeds as a source of biomass, platform chemicals, food, fertilizers and other valuable products. The farming of seaweeds will require a reliable supply of hatchery produced seedlings but, in order to compete in the market, the cost of production of seaweeds will have to be minimised. However, current laboratory-scale seaweed hatchery techniques for sporophyte production and nursery culture are time consuming, expensive, and are not scalable to commercial levels. The purpose of this project is thus to investigate possible simplified and more effective techniques for the reliable and cost-effective production of seaweed seedlings, focussing on the kelps Laminaria digitiata and Saccharina latissima. Different types of tumble culture were tested. The first one was carried on outdoors in 100 litre bags. These sporophytes were developed until the bag attained maximum capacity and then the largest and most vigorous were transferred to conical-shaped tanks. The results with bag culture were promising but there is a big limitation regarding the size of the seaweeds and the bag capacity. The development of sporophytes was rapid in the cone tanks but epiphyte growth was triggered by the high temperatures. Other individuals were placed under different wavelengths to determine the best light for the growth of young sporphytes. One of the bottlenecks of large-scale seaweed culture is to produce mature individuals out of the natural maturation season. To examine the blades of L. digitata and S. latissima individuals were cut in different sizes and locations to induce the maturation. Two environments were used: a tank placed outdoor and another indoor. The results of outdoor cultivation were unsuccessful, with maturation of only one S. latissima. The results were positive indoors, but only for L. digitata, with a successful release of spores. The proper selection of mature individuals could shorten the culture and produce a higher quality final product. The commercial production of gametophytes and sporophytes ready for seedling was the final part of the study. To attain this objective, bags used for micro algae culture were utilised to produce a large quantity of gametophytes within a shorter operational time, space required and daily maintenance. Moreover, it is possible to use the same original gametophyte culture with the desirable sporophyte characteristics using aliquots from a previous bag. Four consecutive bags of 40 litres capacity were produced.