Changes in antioxidant enzyme activities, malondialdehyde, and glutathione contents in the dinoflagellate Lingulodinium polyedrum (Dinophyceae) grown in batch-cultures

Catalase (CAT; EC 1.11.1.6) and ascorbate peroxidase (APX; EC 1.11.1.11) activities, as well as malondialdehyde (MDA) and reduced glutathione (GSH) and oxidized glutathione (GSSG) contents, were determined during the growth of the unicellular marine alga Lingulodinium polyedrum (Stein) Dodge in batch‐cultures. CAT and APX activity peaks were detected at the beginning of algal exponential growth, although declining trends were subsequently identified in both enzymes, with a slight increase in CAT activity at the end of the experimental period. MDA content attained maximum values from day 0–3 and at the end of the experimental period (day 21), declining halfway from day 10–14. GSH and GSSG contents presented the highest values at the beginning of the growth curve, decreasing from day 3 onwards. Despite the depletion of the GSH pool, an upward trend was observed in the (GSH) (0.5 GSSG + GSH)^?1 ratio, indicating that the L. polyedrum cells were able to maintain an increasing redox potential along exponential and linear growth phases in their efforts to prevent oxidative stress.