Effects of biostimulants, AMPEP and Kelpak on the growth and asexual reproduction of Pyropia yezoensis (Bangiales, Rhodophyta) at different temperatures

Abstract

Acadian marine plant extract powder (AMPEP) and Kelpak are commercial biostimulants derived from brown algae <i>Ascophyllum nodosum</i>. This study was to determine if AMPEP and Kelpak can induce thermal resistance in<i> Pyropia yezoensis</i>. <i>P. yezoensis</i> blades were exposed to different concentrations (control: 0, low: 0.001, high: 1 ppm) of AMPEP and Kelpak at 10°C for 6 and 7 days, respectively. Those blades were then cultivated in von Stosch enriched seawater medium at different temperatures (10, 15, 20, and 25°C) with 12 : 12 L : D photoperiod and 100 μmol m<sup>-2</sup> s<sup>-1</sup> of photosynthetically active radiation for additional 15 days. Results showed that P. yezoensis reproduced archeospores at 20 and 25°C at all biostimulant conditions within 15 days. At lower temperatures (10 and 15°C), only AMPEP-treated <i>P. yezoensis</i> reproduced archeospores. <i>P. yezoensis</i> exposed to 1 ppm Kelpak exhibited higher phycoerythrin and phycocyanin contents than control and 0.001 ppm conditions at 15°C. AMPEP-treated conditions showed higher phycoerythrin and phycocyanin contents than control at 10°C. These results suggest that AMPEP and Kelpak may not enhance the thermal resistance of <i>P. yezoensis</i>. However, AMPEP stimulated archeospores release at lower temperatures. The treatment of AMPEP and Kelpak also increased the pigment contents in <i>P. yezoensis</i>. These results suggest that the use of seaweed-derived biostimulants can provide some economic benefits in <i>P. yezoensis</i> aquaculture. The enhancement of archeospores formation by AMPEP at lower temperature may also increase the productivity since <i>Pyropia</i> farming relies on the accumulation of secondary seedings via asexual reproduction.