Effect of Ulva prolifera fragment size on the biomass of developing green algae

Green tides are on the rise in the world's ocean recently, and Ulva is one of the most important genera to develop this marine disaster. However, the rapid biomass accumulation of this genus is quite complex, so in this study we utilized the different sizes of U. prolifera fragments (0.015, 0.03, 0.05, 0.075, 0.1, 0.2, 0.5, 1, and 2 mm) to explore the relationship between fragment size and green algae biomass. Compared with the relative growth rate (RGR) of the smallest algal fragment size (0.015 mm), the RGR and yield were increased by 25.41% and 0.10%, respectively, for 2-mm algal fragments. The J, I and P phases of the rapid induction curve of chlorophyll fluorescence (OJIP curve) increased significantly in the biggest fragment compared to the smallest algal fragment size. The chlorophyll (Chl) a and b contents in the biggest algal fragment size increased by 46.68% and 41.36%, respectively, compared with the smallest algal fragment size. The Chl a/b ratio also increased significantly in the biggest fragment. Thus, multiple factors can produce algal fragments of varying sizes in U. prolifera, resulting in rapid proliferation under natural conditions. This is among the important factors contributing to the rapid accumulation of U. prolifera biomass.