Kati Michalek1, Adrian K. A. Macleod1, Michael Ross1, Richard Abell1, Michele S. Stanley1
1The Scottish Association for Marine Science (SAMS), PA37 1QA Oban, Scotland
Interest and demand in cultivating seaweeds has been growing rapidly in Western Europe, driven by the continuously developing expertise and markets for a variety of food and non-food applications. The Scottish Association for Marine Science (SAMS) has been operating an experimental seaweed farm for almost ten years, conducting industry-driven research to improve seaweed cultivation methods for optimal biomass yields and quality.
To identify the optimum time for harvest we followed biomass yield, morphology, composition, and trace elements in two cultivated kelp species (Saccharina latissima and Alaria esculenta) at nine consecutive harvest times between March and July 2020. Yields and biochemical composition differed across species and harvest times, affected by prevailing environmental conditions (temperature, light, and nutrient levels) that vary throughout but also across cultivation cycles. In addition, specific growth rates of A. esculenta peaked earlier in the season than S. latissima. This was also reflected in the temporal difference for maximum yields (early-June for A. esculenta and early July for S. latissima) whilst progressing biofouling pressure increasingly affected yield and quality estimates.
Our results highlight the dramatic variability in kelp performance throughout the harvest season as well as the complex relationships with environmental cultivation conditions. The optimal harvest time will vary depending on the intended application, with an early harvest recommended for food applications (low fouling pressure, heavy metal and iodine accumulation) and a later harvest for maximised yields and carbohydrate contents.