Environmental water quality assessment in Guaratuba bay, state of Paraná, southern Brazil

An environmental assessment of the estuarine waters of Guaratuba bay, Paraná State, Brazil, is provided through the analysis of physical-chemical, biological and hydrographic dynamics. Twelve stations with a bi-monthly frequency (from October/2002 until August/2003) were sampled during spring and neap tides for the determination of pH, Secchi depth, CO2 saturation, dissolved oxygen, chlorophyll, suspended particulate matter and dissolved inorganic nutrients (nitrate, nitrite, ammonium, phosphate and silicate). Based on the evaluation of six parameters (chlorophyll, Secchi depth, CO2 saturation, dissolved inorganic nitrogen and phosphorus and dissolved oxygen), Guaratuba Bay shows a low to medium trophic status, i.e. from meso- to oligotrophic, and a predominant heterotrophic metabolism, meaning that respiration overcomes primary production. Horizontal stratification was observed during the rainy season, while during the dry season the system showed more homogeneous conditions. Inorganic and/or organic matter in Guaratuba Bay seem to be controlled mainly by the seasonality of precipitation and/ also by ebb and flood tidal phase variations