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Oxidative stress parameters in relation to temperature and other factors have been analysed in Hypnea musciformis, the red seaweed from Anjuna beach, Goa, with an aim to understand its susceptibility to the changing seasons. The results indicate that elevated temperature, sunshine and dessication during peak summer in May enhanced the activity of lipid peroxide, hydrogen peroxide and antioxidants such as catalase, glutathione and ascorbic acid. Statistical tests using multivariate analysis of variance and correlation analysis showed that oxidative stress and antioxidants maintain significant relation with temperature, salinity, sunshine and pH at an individual or interactive level. The dissolved nitrates, phosphates and biological oxygen demand in ambient waters and the trace metals in seaweeds maintained sufficiently low values to provide any indication that could exert contaminant oxidative stress responses. The present field studies suggest that elevated antioxidant content in H. musciformis offer sufficient relief to sustain against harsh environmental stresses for its colonization in the rocky intertidal zone.

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-Oxidative stress and antioxidant defence systems were assessed in a marine red alga Porphyra vietnamensis Tanaka et Pham-Hoang Ho, from India. Lipid peroxidation (LPX) and hydrogen peroxide (H 2 O 2 ) were measured as oxidative stress markers. Antioxidant defences were measured as catalase (CAT), glutathione S-transferase (GST) and ascorbic acid (AsA), in order to understand their dissimilarity with respect to environmental conditions (pollution levels) from selective locations along the central west coast of India. Levels of LPX, H 2 O 2 , CAT and GST were significantly higher in samples collected from Dona Paula than in samples from Malvan and Kunkeshwar, while a lower concentration of AsA was found in samples from Dona Paula. Heavy metals such as Cd, Pb and Hg in higher concentrations in these areas than in other sites were also observed. Variation of oxidative stress indices in response to the accumulation of heavy metals within P. vietnamensis could be used as molecular biomarkers for the assessment and monitoring of environmental quality in ecologically sensitive marine habitats.