INVESTIGADORES
FERREYRA Gustavo Adolfo
artículos
Título:
The effects of UV radiation on photosynthesis in an Antarctic diatom (Thalassiosira sp.): Does vertical mixing matter?
Autor/es:
HERNANDO, M.P. AND G.A. FERREYRA
Revista:
JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY
Editorial:
Elsevier
Referencias:
Año: 2005 vol. 325 p. 35 - 45
ISSN:
0022-0981
Resumen:
The reduction of Antarctic stratospheric ozone results in significant increases in ultraviolet B radiation (UVB-R, 280320
nm) reaching oceans surface, potentially damaging phytoplankton. Several studies refer to the negative direct and indirect
effects of UVB-R and ultraviolet A (UVA-R, 320400 nm, which is not modified by ozone concentration) on different
targets within algal cells. There are, however, internal and external processes, like vertical mixing, which can in part
counteract such effects. The hypothesis that vertical mixing is a significant factor reducing the negative effects of ultraviolet
radiation (UV-R, 280400 nm) on planktonic algae photosynthesis was tested at Potter Cove (South Shetland Is.,
Antarctica). Three laboratory (solar simulator, SOLSI) and two field (natural Sun exposure) experiments were conducted.
Vertical mixing was studied exposing cells of Thalassiosira sp., a typically bloom forming diatom in Antarctic waters, to
variable light conditions simulating 6 h cycles (Mix treatment), whereas incubations at two fixed depths were used as
controls (0.5 and 5 m, Sfix and Dfix treatments, respectively). Light effects were studied for each of the previous exposure
conditions considering three treatments: PAR-T (exposure to PAR, photosynthetic active radiation, 400700 nm), UVA-T
(exposure to PAR and UVA-R) and UVB-T (exposure to PAR, UVA-R and UVB-R). During SOLSI experiments no
significant differences were found between the different light treatments under simulated normal and medium ozone
concentrations. Under low ozone conditions, 40% reduction in photosynthesis was observed in the UVB-T for surface
incubations. In contrast, no significant differences were observed among the light treatments under mixing conditions. Field
and laboratory experiments showed similar results. However, during one of the field experiments when ozone was low, not
only Sfix but Mix incubations presented a significant reduction in photosynthesis, suggesting that vertical mixing under such
conditions was not efficient enough to prevent harmful UVB-R effects. On the other hand, during a day with high insulation
and normal ozone, but with elevated absorption of light in the water column, no significant effects of any of the studied
factors were detected.Thalassiosira sp., a typically bloom forming diatom in Antarctic waters, to
variable light conditions simulating 6 h cycles (Mix treatment), whereas incubations at two fixed depths were used as
controls (0.5 and 5 m, Sfix and Dfix treatments, respectively). Light effects were studied for each of the previous exposure
conditions considering three treatments: PAR-T (exposure to PAR, photosynthetic active radiation, 400700 nm), UVA-T
(exposure to PAR and UVA-R) and UVB-T (exposure to PAR, UVA-R and UVB-R). During SOLSI experiments no
significant differences were found between the different light treatments under simulated normal and medium ozone
concentrations. Under low ozone conditions, 40% reduction in photosynthesis was observed in the UVB-T for surface
incubations. In contrast, no significant differences were observed among the light treatments under mixing conditions. Field
and laboratory experiments showed similar results. However, during one of the field experiments when ozone was low, not
only Sfix but Mix incubations presented a significant reduction in photosynthesis, suggesting that vertical mixing under such
conditions was not efficient enough to prevent harmful UVB-R effects. On the other hand, during a day with high insulation
and normal ozone, but with elevated absorption of light in the water column, no significant effects of any of the studied
factors were detected.fix and Dfix treatments, respectively). Light effects were studied for each of the previous exposure
conditions considering three treatments: PAR-T (exposure to PAR, photosynthetic active radiation, 400700 nm), UVA-T
(exposure to PAR and UVA-R) and UVB-T (exposure to PAR, UVA-R and UVB-R). During SOLSI experiments no
significant differences were found between the different light treatments under simulated normal and medium ozone
concentrations. Under low ozone conditions, 40% reduction in photosynthesis was observed in the UVB-T for surface
incubations. In contrast, no significant differences were observed among the light treatments under mixing conditions. Field
and laboratory experiments showed similar results. However, during one of the field experiments when ozone was low, not
only Sfix but Mix incubations presented a significant reduction in photosynthesis, suggesting that vertical mixing under such
conditions was not efficient enough to prevent harmful UVB-R effects. On the other hand, during a day with high insulation
and normal ozone, but with elevated absorption of light in the water column, no significant effects of any of the studied
factors were detected.fix but Mix incubations presented a significant reduction in photosynthesis, suggesting that vertical mixing under such
conditions was not efficient enough to prevent harmful UVB-R effects. On the other hand, during a day with high insulation
and normal ozone, but with elevated absorption of light in the water column, no significant effects of any of the studied
factors were detected.