Integrated biomarker response in Mytilus chilensis exposed to untreated urban discharges along the coast of Ushuaia Bay (Beagle Channel, Argentina).

The short-term effects of coastal untreated effluents from Ushuaia Bay, Beagle Channel, on the biochemical and physiological biomarkers of Mytilus chilensis were assessed. An integrated biomarker response (IBR) index was calculated as a helpful tool to represent the general stress of the experimental organisms. Cultured mussels were exposed during 96 h to three coastal sites impacted by sewage effluents. At the beginning (T0) and every 24 h, mussels were subsampled from each site and different biochemical and physiological biomarkers were determined. There was no mortality registered in the experiments during the 96 h. However, biochemical and physiological biomarkers presented significant variations. Lipid peroxidation mean levels in mussels decreased in mantle and increased in digestive gland with respect to T0 in almost all cases. Acetylcholinesterase activity was inhibited in all sites, reaching a maximal decrease of 35% with respect to T0. Catalase remained stable and glutathione-S-transferase was activated. Oxygen consumption and ammonia excretion rates increased in organisms from two sites and, consequently, O:N ratio decreased, denoting a symptom of stress. IBR values showed the existence of different stress levels between exposed and unexposed mussels. These results exhibited an alteration of the general metabolism of mussels exposed for a short period of time to untreated coastal wastewater, suggesting the use of these organisms as early indicators of changes in the environmental quality of coastal waters of Ushuaia Bay.

Quality of UVR exposure for different biological systems along a latitudinal gradient.

The exposure of organisms to ultraviolet radiation (UVR) is characterized by the climatology (annual cycle) and the variance (anomalies) of biologically-weighted irradiances at eight geographical locations in austral South America, from 1995-2002. The net effect of UVR on biological systems is a result of the balance of damage and repair which depends on intensity and duration of irradiance and is modulated by its variability. The emphasis in this study is on day-to-day variability, a time scale of importance to adaptive strategies that counteract UVR damage. The irradiances were weighted with DNA- and phytoplankton photosynthesis-action spectra. Low latitude sites show high average UVR. For all sites, the frequency of days with above average irradiances is higher than below average irradiances. Persistence in anomalies is generally low (

Multichannel radiometer calibration: a new approach.

The error in irradiance measured with Sun-calibrated multichannel radiometers may be large when the solar zenith angle (SZA) increases. This could be particularly detrimental in radiometers installed at mid and high latitudes, where SZAs at noon are larger than 50 degrees during part of the year. When a multiregressive methodology, including the total ozone column and SZA, was applied in the calculation of the calibration constant, an important improvement was observed. By combining two different equations, an improvement was obtained at almost all the SZAs in the calibration. An independent test that compared the irradiance of a multichannel instrument and a spectroradiometer installed in Ushuaia, Argentina, was used to confirm the results.