Reactive oxygen production and damage in intertidal Fucus spp. (Phaeophyceae)

The research described in this paper was designed to test the hypothesis th at the differential stress tolerance associated with the vertical zonation of intertidal seaweeds is attributable to reactive oxygen metabolism, To do so, we measured the production of, and damage caused by, reactive oxygen i n three species of intertidal brown seaweeds-Fucus spiralis L., F. evanesce ns C, Ag., and F. distichus L.-that differ in their ability to withstand fr eezing, desiccation, and high light stress. Fucus spiralis is the most stre ss-tolerant species and F. distichus the least. Reactive oxygen production was determined by measuring the production of H2O2 and the oxidation of dic hlorohydrofluorescein diacetate to dichlorofluorescein, Damage caused by fr eezing, desiccation, and high-light stress was assessed by measuring variab le fluorescence (F-v/F-m) and lipid peroxidation. Production of reactive ox ygen increased following freezing, desiccation, or high-light stress. Ln ge neral, the data were consistent with the hypothesis that reactive oxygen me tabolism is involved in stress tolerance. The production of reactive oxygen was relatively low in unstressed seaweeds, and there was little difference between species. Fucus distichus showed the greatest increase in reactive oxygen production after desiccation and freezing stress. Fucus evanescens p roduced more reactive oxygen production after desiccation than F. spiralis, Although F, evanescens and F. spiralis produced similar amounts of reactiv e oxygen after freezing, this treatment resulted in an increase in lipid pe roxidation only in F. evanescens (and F. distichus).