Influence of seasonality on the estuarine waters of an amazonian ¨"Furo¨" (Arrozal – Barcarena, Pará, Eastern Amazon)

Abstract

Seasonality and anthropic influence are reflected in the physicochemical parameters, nutrients, and chlorophyll a of the estuarine waters of the Furo do Arrozal (Barcarena, Pará). Water samples were collected at eight fixed stations at the end of the rainy and dry seasons. The results changed from the end of the rainy to the dry season: transparency increased from 44 to 73 cm, and turbidity from 1 to 22 NTU; electrical conductivity (EC) rose from 0.01 to 0.06 mS/cm; suspended solids varied from 1 to 14 mg/L; pH values were higher at both mouths (Acará/Pará), 10.4 and 10.5; ammoniacal nitrogen and nitrate reached maximum values of 1.24 mg/L (P8/rainy) and 2.7 mg/L (P1/dry), respectively; nitrite remained stable (0.01 mg/L); phosphate reached a maximum value of 0.08 mg/L (rainy); total phosphorus ranged from 0.05 to 0.12 mg/L (dry); silicate ranged from 1.31 to 5.94 mg/L (rainy); and chlorophyll a increased from 7.36 mg/m³ (rainy) to 33.3 mg/m³ (dry). Along the margins of the “Furo” lie the city of Barcarena and nearby riverside communities influenced by the waters of the Pará and Acará estuaries.