Periodical drying or no drying during aquaculture affects the desiccation tolerance of a sublittoral Pyropia yezoensis strain

Abstract

Germplasm degeneration causes serious problems for the Chinese Pyropia yezoensis industry. A subtidal P. yezoensis strain was introduced into aquaculture. The desiccation tolerance of this strain is compared by using “periodically drying” and “never drying” culture protocols. The thalli with periodical drying tolerated ~70% relative water loss (RWL) while those cultured without “drying” endured ≤50% RWL. Pigment contents were higher in the thalli with periodical drying than those farmed without drying. Chlorophyll a and carotenoid levels from both systems decreased significantly at RWL = 20%, were steady at RWL = 20–50%, and decreased at RWL = 60%. Phycoerythrin, phycocyanin, and soluble proteins (SPs) contents from the periodically drying system decreased significantly at RWL = 20%, while those from the never drying system remained steady at RWL = 0–50%. For (phycoerythrin + phycocyanin): SPs from either system increased during dehydration and peaked at the critical point of desiccation tolerance. Superoxide dismutase (SOD), catalase, and peroxidase activities peaked at RWL = 40–50% in the never drying system and 60–70% in the periodically drying system. The results suggested that SOD, catalase, and peroxidase played important roles in desiccation tolerance of this strain. Phycoerythrin, phycocyanin, and carotenoid could dissipate the excess energy as heat or directly scavenge reactive oxygen species. Thus, no significant malondialdehyde was accumulated during dehydration. In conclusion, with and without periodically drying during P. yezoensis farming affected the desiccation tolerance, pigments and SP contents, and antioxidase activities. The subtidal strain seemed to prefer the never drying culture protocol in terms of SPs content and SOD, CAT, and POD activities.