Synoptic Survey of Surface Water Isotopes and Nutrient Concentrations, Páramo High-Elevation Region, Antisana Ecological Reserve, Ecuador

Abstract

Here we provide baseline information on water isotopes and nutrient concentrations for channelized streams and wetlands from a páramo ecosystem in Antisana Ecological Reserve, Ecuador. Water samples were collected from wetland areas and compared to the nearby Rio Tumiguina. Stream water samples were also collected downstream from glacial source areas for 7 km (Rio Tumiguina) and 10 km (Rio Antisana). Water samples from the gauging station on the Rio Tumiguina (n = 4) and nearby wetlands (n = 4) showed significant differences for some nutrients and little difference for other nutrients. Nitrate (NO₃-N) concentrations were below 14 μg L⁻¹ (1 μmol L⁻¹) at both sites and not significantly different. Concentrations of ammonium (NH₄-N) in both stream water and wetlands were much higher than NO₃-N concentrations. For example, NH₄-N concentrations in stream water of 195 μg L⁻¹ (14 μmol L⁻¹) were 17 times that of NO₃-N concentrations. In contrast to NO₃-N and NH₄-N, there was a significant difference (P < 0.001) between concentrations of soluble reactive phosphate (SRP), with concentrations of SRP in the Rio Tumiguina of about 263 μg L⁻¹ (8.2 μmol L⁻¹) and below detection limits in wetlands. Dissolved organic carbon (DOC) concentrations in the Rio Tumiguina of 0.4 mg L⁻¹ were quite low compared to the 23 mg L⁻¹ of DOC from the páramo wetlands. At both stream transects, the δ¹⁸O values decreased from glacial signatures of about – 17± near the glacial terminus to – 13± at distances of 7 to 10 km. Nitrate concentrations were at or below detection limits at all sampling sites. Ammonium concentrations were higher than NO₃-N concentrations in all samples. Concentrations of dissolved organic phosphorus (DOP) were almost as high as dissolved organic carbon (DOC) near the glacial outlets. Concentrations of dissolved organic nitrogen (DON) and DOC were near detection limits near the glacial outlets and then increased downstream.