INVESTIGADORES
FERREYRA Gustavo Adolfo
artículos
Título:
Photoacclimation to long-term UVR exposure of natural Sub-Antarctic phytoplankton communities: fixed surface incubations vs mixed mesocosms
Autor/es:
HERNANDO, M., I. SCHLOSS, S. ROY AND GUSTAVO FERREYRA
Revista:
PHOTOCHEMISTRY AND PHOTOBIOLOGY
Editorial:
American Society for Photobiology
Referencias:
Año: 2006 vol. 82 p. 923 - 935
ISSN:
0031-8655
Resumen:
Solar UVB radiation (280320 nm) is known to have detrimental
effects on marine phytoplankton. Associated with the
seasonal ozone hole in Antarctica, stratospheric ozone depletion
occasionally influences the sub-Antarctic (Beagle
Channel, Argentina) region, enhancing levels of UVB. The
primary objective of this work was to study the effects of
several (i.e. 610) days of exposure to UVB on the taxonomic
composition and photosynthetic inhibition of local phytoplankton
communities. For different light treatments, fixeddepth
incubations placed in an outdoors water tank were
compared with incubations in 1900 L mesocosms, where
vertical mixing was present. Phytoplankton growth was
inhibited by UV radiation (UVR) in fixed-depth experiments
but not in the mixed mesocosms. Under fixed and mixed
conditions alike, photosynthesis was significantly inhibited by
UVB at the beginning of the experiment but no longer after
several days of exposure, suggesting that cells had acclimated
to radiation conditions. There was a change in species composition
in response to UVR exposure in both experiments,
which likely explained acclimation. In the community exposed
to fixed conditions this change was from a phytoflagellatedominated
assemblage to a community with high relative
abundance of diatoms after 6 days of exposure. UVA was responsible
for most of the observed growth inhibition; however,
the reduction in photosynthesis was produced by UVB.
The reasons behind this variability in responses to UVR are
associated with species-specific sensitivity and acclimation,
and the previous light history of cells. In the community exposed
in mesocosms, an assemblage codominated by phytoflagellates
and diatoms was observed at the beginning of
the experiments. After 10 days of exposure, green algae
(Eutreptiella sp.) had increased, and phytoflagellates were the
dominant group. The synthesis of mycosporine-like amino
acids (MAAs), antioxidant enzymes and photosynthetic
antenna pigments, in relation to repair and protection
processes, may explain the reduced inhibition of both growth
and photosynthesis that was observed in the phytoplankton
community after several days of exposure. For environments
such as the Beagle Channel seasonally exposed to the ozone
hole, the results obtained from the fixed-depth experiments
show that species can cope with UVR by means of MAA
synthesis, while mixing would primarily promote a change
in species composition and defense strategies.i.e. 610) days of exposure to UVB on the taxonomic
composition and photosynthetic inhibition of local phytoplankton
communities. For different light treatments, fixeddepth
incubations placed in an outdoors water tank were
compared with incubations in 1900 L mesocosms, where
vertical mixing was present. Phytoplankton growth was
inhibited by UV radiation (UVR) in fixed-depth experiments
but not in the mixed mesocosms. Under fixed and mixed
conditions alike, photosynthesis was significantly inhibited by
UVB at the beginning of the experiment but no longer after
several days of exposure, suggesting that cells had acclimated
to radiation conditions. There was a change in species composition
in response to UVR exposure in both experiments,
which likely explained acclimation. In the community exposed
to fixed conditions this change was from a phytoflagellatedominated
assemblage to a community with high relative
abundance of diatoms after 6 days of exposure. UVA was responsible
for most of the observed growth inhibition; however,
the reduction in photosynthesis was produced by UVB.
The reasons behind this variability in responses to UVR are
associated with species-specific sensitivity and acclimation,
and the previous light history of cells. In the community exposed
in mesocosms, an assemblage codominated by phytoflagellates
and diatoms was observed at the beginning of
the experiments. After 10 days of exposure, green algae
(Eutreptiella sp.) had increased, and phytoflagellates were the
dominant group. The synthesis of mycosporine-like amino
acids (MAAs), antioxidant enzymes and photosynthetic
antenna pigments, in relation to repair and protection
processes, may explain the reduced inhibition of both growth
and photosynthesis that was observed in the phytoplankton
community after several days of exposure. For environments
such as the Beagle Channel seasonally exposed to the ozone
hole, the results obtained from the fixed-depth experiments
show that species can cope with UVR by means of MAA
synthesis, while mixing would primarily promote a change
in species composition and defense strategies.Eutreptiella sp.) had increased, and phytoflagellates were the
dominant group. The synthesis of mycosporine-like amino
acids (MAAs), antioxidant enzymes and photosynthetic
antenna pigments, in relation to repair and protection
processes, may explain the reduced inhibition of both growth
and photosynthesis that was observed in the phytoplankton
community after several days of exposure. For environments
such as the Beagle Channel seasonally exposed to the ozone
hole, the results obtained from the fixed-depth experiments
show that species can cope with UVR by means of MAA
synthesis, while mixing would primarily promote a change
in species composition and defense strategies.