The vertical mixing as a regulating factor of the UVR effects on bacterioplankton from an Antarctic marine coastal environment

HERNANDEZ E.; FERREYRA G.; VAZQUEZ S.; RUBERTO L.; CORIA S.; MAC CORMACK W.

Buenos Aires, Argentina

Congreso; XXXI SCAR and Open Science Conference; 2010

The effect of UV radiation on the viability of the culturable bacterioplanktoncommunity (CBC), and two of their isolated components (Arthrobacter UVvi and BizioniaUVps), was studied in the water column at Potter Cove, Antarctica. Quartz flasks containing CBC from 0 and 30 m were exposed to solar radiation under a simulated vertical mixing of 4 m h-1 between 0 and 4 m depth. Surface controls were also included. Similar experiments using UVps and UVvi strains were performed. In these experiments interferential filters were used to discriminate photosynthetic active radiation (PAR), UVA and UVB. Deleterious effects of UV were observed at surface on both, isolates strains and the CBC. However, CBC from 30 m showed to be more resistant to UV than the surface assemblage. UVps was more sensitive than UVvi, while surface CBC exhibited an intermediate UV sensitivity. The vertical mixing produced an attenuating effect when the surface UVB dose was lower than 5 kJ m-2. The negative effects attributed to UVB were higher than those caused by UVA. The results suggested that CBC inhabiting waters above the pycnocline (located at 5–10 m depth) are more adapted to UV than those living below the pycnocline. Studies showed that when water column of Potter Cove are stratified, the impact of UV on the marine bacterioplankton is only significant in the first 4 meters depth. These results support the evidence of a strong UVattenuating effect associated to the high levels of suspended particulate matter present in this coastal Antarctic environment.