INVESTIGADORES
GONÇALVES Rodrigo Javier
congresos y reuniones científicas
Título:
Utilization of solar ultraviolet radiation by phytoplankton assemblages from the Southern China Sea
Autor/es:
E. W. HELBLING; K. GAO; R. J. GONCALVES; H. WU; V. E. VILLAFAÑE
Lugar:
Xiamen (China)
Reunión:
Otro; Annual Chinese Oceanographic Meeting; 2003
Resumen:
During May 2002 we carried out studies with
tropical phytoplankton assemblages from coastal waters off Southeast China to
assess the combined effects of solar ultraviolet radiation (UVR, 280-400 nm)
and mixing rates. Water samples were
taken daily and incubated under in situ and simulated in situ conditions under
three radiation regimes (PAR+UVR, PAR+UV-A and PAR only). Variable radiation regimes, to simulate the irradiance
field in the upper mixed layer (UML), were obtained by using a device
consisting of one fixed (static samples) and one rotating system (moving
samples). Solar UVR inhibited
phytoplankton photosynthesis in the water column (i.e., during in situ experiments),
and this inhibition (mean value at surface = 24%) decreased with depth so that
at 1.2 m there were no significant differences between radiation
treatments. At 1.8 m depth though, the
samples receiving UV-A had significantly higher carbon fixation than those
receiving only PAR. Simulated in situ
experiments showed that solar UVR stimulated phytoplankton photosynthesis under
fast mixing conditions (i.e., when the irradiance levels changed from 100% to
6% and back in less than 30 minutes).
With slower circulation periods, solar UVR reduced carbon fixation and
consequently the integrated inhibition within the UML approached the values
from the static samples. Previous model
predictions based on the interactive effects of UVR and mixing might have
underestimated phytoplankton photosynthesis in these regions. Overall, our results suggest a high
resistance of these coastal tropical assemblages to solar UVR as compared to
other regions of the planet.