Resumo

HERNANDEZ, E. A.  e  MAC CORMACK, W. P.. Changes in viability of two Antarctic marine bacteria exposed to solar radiation in the water column: influence of vertical mixing. Rev. argent. microbiol. [online]. 2007, vol.39, n.3, pp.177-183. ISSN 0325-7541.

The effect of UV radiation on two Antarctic marine bacterial strains (UVps and UVvi) was studied in the water column of Potter Cove (South Shetland, Antarctica). Quartz flasks were filled with the bacterial suspensions and exposed to solar radiation at 0 m, 1 m and 3 m depth. Assays using flasks exposed to direct solar radiation and others using flasks covered with/by interferential filters which discriminate between UVA and UVB, were performed. In other assays, a vertical mixing of 4 m/h was simulated. Both strains showed a significant decrease in viability (expressed as colony - forming units) when exposed to a surface UVB dose of 8.4 kJ m^-2. Studies with interferential filters showed a significant decrease at 0 and 1 m depth under both UV treatments. The UVps strain appeared to be more sensitive to UVB than to UVA. Damage produced by UVB was attenuated by the vertical mixing when the surface UVB dose was 4.8 kJ m^-2. This effect was not observed when surface UVB dose was 7.7 kJ m^-2. These results show that the negative effect caused by UVB radiation on the bacterioplankton would be significant only in the first meter of water column of the Antarctic coastal waters with high levels of suspended particulate material.

Palavras-chave : Marine bacteria; Antarctica; UV radiation; Vertical mixing.

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