INVESTIGADORES
FERREYRA Gustavo Adolfo
artículos
Título:
Impact of the ultraviolet radiation on two isolated Antarctic marine bacteria
Autor/es:
HERNÁNDEZ, E.A., G.A. FERREYRA AND W.P. MAC CORMACK
Revista:
Reports on Polar and Marine Research
Referencias:
Año: 2008 vol. 571 p. 311 - 319
Resumen:
The annual depletion of the ozone layer selectively reduces absorption of ultraviolet-
B radiation (UVB, 280-320 nm), resulting in higher UVB irradiance on the
Antarctic surface (Staehelin et al. 2001). It was reported that the UVB is
responsible of significant detrimental biological effects on aquatic environments
(Vincent and Neale 2000, Booth et al. 2001a, Biggs and Moody 2003). Ultraviolet
A radiation (UVA, 320-400 nm) may also be responsible for certain types
of photobiological damage (Kim & Watanabe 1994, Sommaruga et al. 1997).
UVA can affect bacterial viability and activity (Helbling et al. 1995), either
directly or indirectly via production of oxidant compounds from dissolved organic
matter. However, the major part of the studies dealing with the effect of UV
radiation (UVR) on aquatic organisms has been focused on phytoplankton
assemblages, the effect on the aquatic bacteria being less investigated. Bacteria
play a key role in mineralization of nutrients and provide a trophic link to
higher organisms (Azam et al. 1983; Ducklow et al.1992). This role is crucial in
the Southern Oceans, where phytoplankton stocks are low and the spring algal
blooms is scarce or do not develop (Karl 1993). Marine bacteria seem to be
more susceptible than other planktonic organisms to the effects of UVR (Jeffrey
et al. 1996). The lack of UV-protective compounds in marine bacteria other than
cyanobacteria could be one of the causes of this susceptibility (Cockell and
Knowland 1999). Reports about changes in species composition of marine
bacterial communities under UVB stress (Arrieta et al. 2000) reflect the different
sensitivity that different members of these communities has to the UVR stress.
Solar radiation has not only detrimental effects on bacterioplankton. Crucial
roles in DNA-damage repair has been found for UVA and PAR (Kaiser and
Herndl 1997) as activators of the photoenzymatic repair mechanisms. This fact
determines a complex relationship between positive and negative effects of
solar radiation on marine bacteria which largely depends on the characteristics
of the environments under study. In this work, two Antarctic marine bacteria
were isolated from surface water at Potter Cove, Antarctica and used as biological
models in different experimental designs in order to analyse their
response to solar radiation exposure. In a first step, the effects of PAR, UVA
and UVB on the isolated strains were evaluated at different time periods in days
with different irradiance regimes. In a second step, the role of the water column
as attenuating factor was analysed by exposure of the bacterial strains at three
depths in the water column: surface, 1 m and 3 m. Finally, the effect of a simulated
vertical mixing of 4 m h-1 on the bacterial survival was evaluated.-1 on the bacterial survival was evaluated.