The yield and quality of multiple harvests of filamentous Ulva tepida

Species of the genus Ulva are used for human consumption due to their nutritional qualities and we assess a new filamentous species, Ulva tepida. A critical step is to quantify the yield and quality of biomass over multiple harvests to ensure consistency throughout the production cycle. To do this, ropes were seeded with U. tepida and harvested fortnightly over 6 weeks of outdoor cultivation with biomass yield and quality quantified for each harvest. This cycle was repeated a further two times. The yield of biomass was not significantly different between harvests (13.6–23.0 g dry weight (dw) m-1 rope), however, the final harvest was highly variable. Consequently, we recommend a production cycle of two harvests. The quality of biomass, as determined by the key biochemical parameters for these two sequential harvests, was consistent. Carbohydrates were the major component (45 % dw) and were primarily dietary fibre (27 % dw) consisting of insoluble (18 % dw) and soluble (9 % dw, equates to ulvan) fibre, with consistent values between harvests. Protein, as the sum of amino acids (17 % dw), was also consistent between harvests. Similarly, the content of ash (31 % dw) and lipids (3 % dw), as well as the composition of minerals and fatty acids was consistent. These results quantify, for the first time, no negative effects of multiple harvests on the yield and quality of biomass and support this technique to optimise productivity and quality.