Investigating seasonal hydrology and its relationship with microbiological indicators in the Apex River watershed (Iqaluit, Nunavut)

Abstract

Climate change in permafrost regions is projected to alter water resource distribution and water quality. The aim of this study was to characterize seasonal hydrology and dissolved organic matter (DOM) abundance and composition in the Apex River watershed in order to (1) identify water sources and pathways and (2) explore possible relationships between seasonal hydrology, DOM, and standard microbiological indicators (total coliforms (TC) and Escherichia coli). Discharge was measured at four sites in the Apex River (AR, CF, ET, and WT) from June 10th – August 28th, 2015. Water samples were collected three times weekly from June 8th - August 28th at the four sites and analyzed for DOC concentrations and DOM composition. Fluorescence spectroscopy and parallel factor (PARAFAC) analysis revealed the presence of five fluorescent components: three humic and two protein-like. DOM exports from the smaller east tributary (ET) exhibit predominantly protein-like (autochthonous) while DOM from the larger west tributary (WT) demonstrates humic-like (allochthonous) and protein-like (autochthonous) fluorescence. Autochthonous DOM is derived from microbial activity within water bodies while allochthonous DOM is derived from terrestrial sources. The rapid response of discharge to inputs indicates that snowmelt and precipitation runoff primarily follows overland pathways. Evidence of different timing of labile DOC availability between the Apex River outflow (AR), compared to ET, implies that controls on autochthonous DOM inputs differ between the two sites. TC densities show a correlation with protein-like fluorescence and biological freshness index (BIX). Results contribute to background knowledge which policy-makers can use to establish policies that ensure the sustainability of Iqaluit’s water resources.