“Nutrients and organic matter distribution in Mar Chiquita coastal lagoon tidal plains. The tide effect”

BELTRAME, M. ORNELA; DE MARCO SILVIA G.; MARCOVECCHIO JORGE E.

Buzios, Brasil

Simposio; 4th International Symposium Geochemistry in Tropical Countries,; 2004

Both the direction adn the magnitude of inorganic nutrients and organic matter exchange fluxes between the water column and the associated tidal plains during the dairy tidal cicle is at present one of the most attended topics within environmental coastal studies. This process together with the corresponding hydrographic conditions define the role of this type of environments: functioning as nutrients and organic matter sink or as a source of these compounds to the Coastal Zone. In this way an experimental design was applied in Mar Chiquita Coastal Lagoon (Buenos Aires province, Argentina) wich included two sampling stations: the first one named Confluencia, on the main brach of the Coastal lagoon; and the second, named Cangrejo Stream, on an marginal one. Water samples (column water and porewater) were obteined, with a one-an-hour frequency basis, during a whole tidal cycle as well as in situ measurements were carried out. Inorganic nutrients (nitrate, nitrite, ammomium, phosphate, silicate) and particulated organic matter (POC) were determined in both column and pore waters, while temperature, salinity/conductivity, pH, turbidity and dissolved oxygen were in situ measured within the water column. Both the NO3 and the NO2 levels have shown to be higher in water column than in pore water. Unlike this, NH4 has shown an inverse effect, with variation ranges between 5.1-16-5 µmol/L withim thw water column and 22.8-224 µmol/L in the pore water. In the same way, both the PO4 and SiO2 have also presented the distribution trend previously described for ammonium. In addition,pore water organic matter levels were always higher than those of water column. Considering this scenario, nutrients and organic matter dynamics within the system, as well as their net fluxes and processes affecting their accurrence were fully discussed.