Spatial Variability of Phytoplankton and Environmental Factors in a Temperate Estuary of South América (Atlantic Coast, Argentina).

CECILIA POPOVICH; JORGE MARCOVECCHIO

CONTINENTAL SHELF RESEARCH

Elsevier

Lugar: Amsterdan (Holanda); Año: 2008 vol. 28 p. 236 - 244

0278-4343

AbstractA spatial and temporal study on data collected along the longitudinal gradient of the Principal Channel of Bahı´a Blanca estuary,Argentina, was carried out during 1992–1993. At nine stations, phytoplankton abundance, chlorophyll a (Chl-a) concentration,inorganic nutrient levels, Secchi disk depth, euphotic depth:mixing depth ratio (Zeu:Zm), salinity and temperature were recorded.Phytoplankton abundance, Chl-a concentration and nutrient levels decreased towards the outer zone of the estuary. The inner zone(stations 1 and 2), which was characterized by high turbidity, high nutrient concentrations and high Zeu:Zm (40.16, [critical mixingratio]), registered the highest phytoplankton abundance and Chl-a concentrations. Temporal variability of data was also noteworthy inthis zone. The highest biomass values thus corresponded to June, July, August and the beginning of spring (18 mg Chl-a L1 and9106 cells L1) concomitantly with a diatom bloom. In the middle zone (stations 3–6), a strong phytoplankton biomass decrease wasobserved and it coincided with both deep-mixed depths and low Zeu:Zm (o0.16). The outer zone (stations 7–9), which was characterizedby low phytoplankton biomass values and low nutrient levels all along the year, was the area mostly influenced by waters from theadjacent continental shelf. In view of the above, it can be concluded that the most important primary production in the Bahı´a Blancawould be produced in the shallow inner zone during winter, being the spatial reach of the phytoplankton biomass principally limited toestuarine waters. Presumably, less than 5% of such biomass may reach the coastal area of the estuary.