Short-term variability in the phytoplankton and and physico-chemical variables in a high-tidal regime, Bahía Blanca Estuary, Argentina

GUINDER, V. A.; POPOVICH, C. A.; PERILLO, G. M. E.

BRAZILIAN JOURNAL OF OCEANOGRAPHY

INST OCEANOGRAFICO

Año: 2009 vol. 57 p. 249 - 258

1679-8759

Hourly measurements of phytoplankton and physico-chemical variables were carried out at a fixed point in the inner zone of the Bahía Blanca Estuary in order to evaluate the short-term variability over a tidal cycle. Our results showed that the chlorophyll a concentration, cellular abundances and dissolved nutrient concentrations markedly fluctuated among hours with an irregular pattern. On the other hand, phytoplankton species composition and particulate suspended matter concentration (PSM) varied coupled with tidal advection and resuspension processes. As winds velocities were very low over the sampling period, tidal currents were responsible for vertical turbulences in the water column. Consequently, bottom sediments and phytobenthic species were resuspended into the plankton habitat. PSM concentration in the surface water increased towards high tide, while in the bottom it was maxima at the beginning of the flood. Diatoms behaved as relatively passive particles with respect to tidal advection and their cells sizes and shapes might be related with the species distribution. This short-term study gathers evidence to suggest that the tidal scale variability of phytoplankton composition in this high-energy regime is especially affected by resuspension and advection processes, and cellular size and shape seem to play a major role on those effects.