PHOTOSYNTHETIC DYNAMICS OF PHYTOPLANKTON FROM THE CHUBUT RIVER ESTUARY (ARGENTINA) THROUGHOUT TIDAL CYCLES

CÉSAR D. MEDINA; DANIEL E. PÉREZ; JORGE E. MARCOVECCHIO; MARCOS LAGUNAS; VIRGINIA E. VILLAFAÑE; E. WALTER HELBLING

Bahía Blanca, Argentina

Congreso; Estuarine and Coastal Sciences Association (ECSA) 44 Symposium - Science and management of estuaries and coasts: A tale of two hemispheres,; 2008

Since June 2007 we are evaluating the impact of solar radiation on photochemical quantumyield (Y) of phytoplankton from the Chubut River Estuary (43°S, 65°W), on monthlybimonthlybasis and throughout tidal cycles (12 hs of duration). Together withmeasurements of several photosynthetic parameters (measured with a pulse amplitudemodulated fluorometer – PAM) we collect samples for chlorophyll-a, taxonomiccomposition and cellular abundance, dissolved organic matter, temperature, conductivityand inorganic nutrients (NO2-, NO3-, SiO42- y PO43-). We determined large variability in themeasured variables throughout the year due to the presence of the different water massespresent in the estuary: river, marine and mixing zone. Particularly, Y was highly variable,not only throughout the annual cycle, but also within a single cycle considered. Thisvariability in Y was strongly associated to the taxonomic composition of the community:Although in general nanoplankton numerically dominated the samples, the diatomsAulacoseira granulata and Odontella aurita characterized the river and marine community,respectively. From the comparison of Y with physical and chemical data we conclude thatY is a good indicator of mixing condition in the water column as well as of the previouslight history of phytoplankton cells.