Ascertaining the interactions of brown seaweed-derived biostimulants and seawater temperature on spore release, germination, conchocelis, and newly formed blades of the commercially important red alga Neopyropia yezoensis?

Seaweed-derived extracts are commonly used as biostimulants in agriculture and, more recently, to cultivate other types of seaweeds. Here, we examined if Ascophyllum marine plant extract powder (aka AMPEP) and Kelpak® influenced changes in the life history of the commercially important, Neopyropia yezoensis. N. yezoensis was cultured in von Stosch enriched (VSE) medium with different concentrations (0, 0.001, and 1 mL L−1) of AMPEP and Kelpak® for up to six days. Cultivars were then allowed to grow in VSE at either 15, 20, or 25 °C, 12:12 L:D photoperiod, and 100 μmol photon m−2 s−1 of PAR for up to 42 days. Spore release, germination, and appearance of newly formed blades per treatment were tracked and quantified using photographs. Results showed that temperature was the main factor driving the transition between developmental stages. However, interactive effects were observed. The concentration of 0.001 mL L−1 Kelpak® seemed to promote early germination and formation of conchocelis tufts at 15 °C. The same concentration of AMPEP and Kelpak® at 20 °C appeared to have a delayed positive effect on blade formation. These preliminary results do not show significant evidence that the application of Kelpak® and AMPEP, as tested, could affect the transition between life stages or provide enhancements on thermal tolerance.