Antioxidant metabolism in the intertidal red seaweed Stictosiphonia arbuscula following desiccation

Seaweeds grow in distinct vertical bands on the seashore and it is well known that their ability to recover physiological processes following desiccation is correlated to their shore position. Despite this, little is known of the cellular mechanisms by which intertidal seaweeds limit membrane damage during desiccation and subsequent rehydration. In this study, specimens of the intertidal red seaweed Stictosiphonia arbuscula were placed in sealed tanks and maintained at different relative humidities (control, RH 90-100%; moderate desiccation, RH 70-80% and severe desiccation, RH 40-50%) for 12, 24 or 48 h. Membrane damage and antioxidant metabolism was examined immediately following specimen rehydration. Amino acid leakage, through the plasmalemma, was greater for desiccated low-band specimens than high-band specimens, indicating greater membrane damage. In addition, low-band specimens produced more hydrogen peroxide and lipid hydroperoxides than high-band specimens. This indicates that, upon rehydration, high-band populations have a greater ability to reduce the build-up of hydrogen peroxide, limit lipid peroxidation and hence membrane and protein damage, than low-band populations. The greater ability to prevent or reduce the production of reactive oxygen species was not due to a larger antioxidant pool, but rather increased activity of the enzymes required to regenerate ascorbate and glutathione. These findings suggest that antioxidant metabolism is one of the defence mechanisms that protect S. arbuscula from cellular damage due to desiccation.