Photochemical degradation of dissolved organic carbon: Hydrogen peroxide production and potential effects on plankton in the Beagle Channel (Tierra del Fuego)

The production of hydrogen peroxide (H2O2) based on solar radiation was analyzed in waters of the Beagle Channel at the mouth of the Lapataia River, Ushuaia, Tierra del Fuego. Between October and November 2004, we incubated the samples in coincidence with the spring stratospheric ozone depletion, which regularly produces an increase in the doses of ultraviolet radiation B (RUVB, 280-320 nm). Significant differences were observed in the photo-oxidation of dissolved organic carbon (COD) comparing the exposure to the total solar radiation against the exposure to > 295 nm and to > 320 nm wavelengths. Such effect was observed with RUVB doses higher than 21 kJ m(-2). No biological degradation was observed in absence of sunlight. It was determined a maximum H2O2 concentration of 40 nM in average after exposure to the solar radiation, regardless of the dose received. The photo-production of H2O2 in waters of the Beagle Channel showed low levels, probably due to the low COD concentrations, to its weak reactivity, or to both. Considering that only high concentrations of H2O2 induce oxidative damage, we failed to find potential oxidative effects on the studied plankton communities from the Beagle Channel when were exposed to the highest H2O2 concentrations previously observed.