INVESTIGADORES
VILLAFAÑE Virginia Estela
congresos y reuniones científicas
Título:
Time series study in a freshwater lagoon of Patagonia: Solar acclimation of phytoplankton measured by pulse amplitude modulated (PAM) techniques
Autor/es:
S BARBIERI, ELENA; J GONCALVES, RODRIGO; VIRGINIA ESTELA VILLAFAÑE; WALTER HELBLING, E
Lugar:
Aix-les-Bains, Francia
Reunión:
Congreso; 11th European Society for Photobiology Congress; 2005
Resumen:
A time series study conducted during 2000-2002 at Chiquichano Lagoon (43°14’S, 65°18’W, Trelew, Argentina), determined a microplankton bloom (>400 µg chl-a l-1) during summer.  A new study was initiated in February 2005 to evaluate the impact of solar radiation on photochemical parameters of phytoplankton assemblages throughout the year.  Samples are collected the evening before experimentation, pre-filtered to remove zooplankton (>100 µm), and kept in the dark (night time).  In the samples collected so far, chl-a varied between 100 - 700 µg chl-a l-1 and nanoplankton (<20 µm) accounted for 61 - 95%.  Samples are dispensed in quartz tubes under different radiation treatments (duplicates): a) PAB (280-700 nm), uncovered tubes; b) PA (320-700 nm), tubes covered with a cut-off filter at 320 nm, and c) P (400-700 nm), tubes covered with cut- off filter at 395 nm.  The tubes are exposed to solar radiation in a water-bath for temperature control.  The effect of solar radiation on photosystem II is monitored throughout the day by measuring the photosynthetic quantum yield (Y) and other parameters with a Water-PAM fluorometer (Walz).  Additionally, samples are taken at local noon and at the end of experiments (evening) to evaluate recovering in the dark.  A significant decrease in Y was determined at high irradiances as compared to the initial values in all treatments, and the Y values at noon were 19%±12, 24%±14 and 42%±16 of the initial in the PAB, PA and P treatments, respectively.  A significant recovery is observed when cells are transferred to dim light, but it is not complete, even after 20 hours, when Y reached 70%±22; 74%±18 and 81%±14 of the initial value in the PAB, PA and P, respectively, thus indicating that some chronic damage persisted in the cells.  The samples with high chl-a concentration, i.e., > 400 µg chl l-1, were the most inhibited, suggesting a “dark” acclimation of these samples in an environment with high attenuation of solar radiation.