Organic carbon spiraling in an Idaho river

Abstract

In running water ecosystems, the use of community attributes to infer biological integrity is widespread. In contrast, functional variables like energy flow and elemental cycling have received considerably less attention. In this study, we quantify organic carbon spiraling in four reaches of the Middle Snake River (MSR). We calculated organic carbon (OC) turnover rates (KOC), mean velocities (VOC), and turnover lengths (SOC) by quantifying suspended and benthic pools of organic carbon and measuring metabolic rates using both open-system and chamber approaches. Ultra-fine particulate organic carbon (UPOC) dominated both transported and benthic OC in all study reaches. KOC was lowest where benthic standing stocks were greatest and KOC was elevated in summer relative to spring and fall. VOC was negatively correlated with benthic OC standing stock and greatest in spring and early summer when river discharge was highest. Turnover lengths (SOC) ranged from 11–108 km and were strongly related to temporal patterns in VOC. Comparison of the Snake River with other river systems suggests that MSR is more retentive and homogeneous than rivers of similar size in North America.