Arctic "ozone hole" in a cold volcanic stratosphere

Highlighting the Importance of Water Alkalinity Using Phosphate Buffer Diluted With Deionized, Double Distilled and Tap Water, in Lowering Oxidation Effects on Human Hemoglobin Ozonated at High Ozone Concentrations in vitro

In autohemotherapy, it is important to find a way to lower the effects of oxidation, especially at high concentrations of ozone. One of the parameters, other than ozone concentration, which can have a significant effect on the stability and rate of decomposition of ozone at high concentrations, is the presence of ions in water. A number of spectroscopic techniques including intrinsic fluorescence, circular dichroism and UV–VIS were used as well as SDS-PAGE, Native-PAGE dynamic light scattering and water ion analysis, in order to investigate the effects of two relatively high concentrations of ozone on purified human hemoglobin (Hb) in phosphate buffer and diluted versions with deionized, double distilled and tap water in vitro. Purified human Hb and not whole blood human Hb was used in this study, since the addition of water to the whole blood would have caused the RBCs to lyse, affecting the purification of Hb for further analysis. Therefore, using purified Hb, it was possible to investigate the effects of dilution of 50 mM phosphate buffer to 10 mM phosphate buffer with different water types including non-ion containing deionized and double distilled water as well as ion-containing tap water, when ozonated at 55 and 80 μg/ml ozone. The fundamental changes in the secondary and tertiary structures of Hb were seen to be related to non-ozonated Hb samples diluted with deionized and double distilled waters, respectively. Generally, Hb oligomerization was more likely to occur at the higher concentration of ozone (80 μg/ml) and in samples where phosphate buffer was diluted with non-ion containing deionized and double distilled waters and not the ion-containing tap water. This could be explained by the presence of water alkalinity or bicarbonate ions in tap water, which can scavenge free radicals and reduce Hb oxidation/oligomerization. Therefore, it was concluded that Hb could best withstand high concentrations of ozone in the presence of the undiluted 50 mM phosphate buffer followed by phosphate buffer diluted with tap water, containing bicarbonate ions.

Ultraviolet-B Radiation Effects on the Structure and Function of Lower Trophic Levels of the Marine Planktonic Food Web

The impact of UV-B radiation (UVBR; 280-320 nm) on lower levels of a natural plankton assemblage (bacteria, phytoplankton and microzooplankton) from the St. Lawrence Estuary was studied during 9 days using several immersed outdoor mesocosms. Two exposure treatments were used in triplicate mesocosms: natural UVBR (N treatment, considered as the control treatment) and lamp-enhanced UVBR (H treatment, simulating 60% depletion of the ozone layer). A phytoplankton bloom developed after day 3, but no significant differences were found between treatments during the entire experiment for phytoplankton biomass (chlorophyll a and cell carbon) nor for phytoplankton cell abundances from flow cytometry and optical microscopy of three phytoplankton size classes (picoplankton, nanoplankton and microplankton). In contrast, bacterial abundances showed significantly higher values in the H treatment, attributed to a decrease in predation pressure due to a dramatic reduction in ciliate biomass (approximately 70-80%) in the H treatment relative to the N treatment. The most abundant ciliate species were Strombidinium sp., Prorodon ovum and Tintinnopsis sp.; all showed significantly lower abundances under the H treatment. P. ovum was the less-affected species (50% reduction in the H treatment compared with that of the N control), contrasting with approximately 90% for the other ones. Total specific phytoplanktonic and bacterial production were not affected by enhanced UVBR. However, both the ratio of primary to bacterial biomass and production decreased markedly under the H treatment. In contrast, the ratio of phytoplankton to bacterial plus ciliate carbon biomass showed an opposite trend than the previous results, with higher values in the H treatment at the end of the experiment. These results are explained by the changes in the ciliate biomass and suggest that UVBR can alter the structure of the lower levels of the planktonic community by selectively affecting key species. On the other hand, linearity between particulate organic carbon (POC) and estimated planktonic carbon was lost during the postbloom period in both treatments. On the basis of previous studies, our results can be attributed to the aggregation of carbon released by cells to the water column in the form of transparent exopolymer particles (TEPs) under nutrient limiting conditions. Unexpectedly, POC during such a period was higher in the H treatment than in controls. We hypothesize a decrease in the ingestion of TEPs by ciliates, in coincidence with increased DOC release by phytoplankton cells under enhanced UVBR. The consequences of such results for the carbon cycle in the ocean are discussed.