Abstract

BLANCO, Juan F.. STREAM PHYSICO-CHEMISTRY AT GORGONA ISLAND NATURAL NATIONAL PARK, TROPICAL EASTERN PACIFIC. Actu Biol [online]. 2009, vol.31, n.91, pp.123-140. ISSN 0304-3584.

Biogeochemical studies in Colombian streams are scarce, for this reason I measured several physico-chemical variables, along with total dissolved organic carbon, total nitrogen, total phosphorous, chloride and sulfur to determine the influence of geologic, atmospheric and biotic processes during low and high rainfall periods. Volcanic lithology (basalts and ultramafic intrusives) is seemly responsible for the occurrence of saline (conductivity > 500 µmhos/cm), neutro-alkaline (pH < 8,5) and phosphorus-rich (< 200 µg/l) waters. Marine aerosols are possibly responsible for chloride inputs (> 2 mg/l). The dissolved organic carbon was higher in mature forest (> 60 mg/l) than in secondary forests and shrublands (< 60 mg/l). The low concentration of sulfates suggests that industrial and volcanic gas emissions do not exist, although underwater gas-bubbling is noticeable at La Azufrada reef. Increased rainfall and discharge altered element concentrations depending on their nature and basin features.

Keywords : chloride; dissolved organic carbon; Gorgona Island; hydrologic disturbance; phosphate; physico- chemistry.

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