THE INFLUENCE OF SEASONS ON METAL DISCOMBOBULATION OXIDATIVE STRESS IN SENTINEL ORGANISMS IN SOUTHAFRICAN URBAN FORESTSA NAUDÉ, R.G. SNYMAN, J.L. MARNEWICK AND J.P. ODENDAALAbstract Variations in Al, Fe and Mn concentrations in soil, leaf litter, moss, lichen and pill millipedes, as well as the induced oxidative stress effect of metals on the organisms, between the dry and the wet season within two Afromontane forests in the Western Cape were investigated. The two forests in the closest proximity of the Cape Town city centre and urban pollution sources were chosen to determine the difference of metal contamination between the dry, hot and cold, wet season. Three sampling sites were chosen within each forest at different altitudes on Table Mountain, as well asa control site, where the soil, leaf litter and each organism were randomly collected in both the dry and the wet seasons for metal and biochemical analysis. The metals in the wet season in both of the forests showed higher concentrations, as did the forest closest to the Cape Town city centre.This is indicative of higher levels of pollution due to increased anthropogenic activities in the wetseason. Oxidative stress in organisms was apparent in the varying tGSH levels, of which the dryseason mostly revealed the higher concentrations. Oxidative lipid damage (measured as MDA) levels were generally increased during the wet season when the metal concentrations were higher as a result of prominent brown haze episodes in winter. Urban forest ecosystems in urban cities may suffer irreparable damage resulting from metal contamination, more so in the colder wet season. |