Research Article

Quantifying spatiotemporal rhythm of stream metabolism along human disturbance gradients

Department of Environmental Engineering, Bolu Abant Izzet Baysal University, Bolu, 14030 Turkey

^* Corresponding author: miraceryigit@hotmail.com

Received: 8 November 2019
Accepted: 27 May 2020

Abstract

This study aimed at investigating the effects of the urban wastewater treatment plant (WTP) discharges on the metabolism of Büyüksu Stream (Bolu, Turkey), and modelling the metabolism components as a function of measured environmental variables. Dissolved oxygen (DO) and water temperatures (T_w) were measured to estimate montly stream metabolism in the four reaches: Before and after discharges of the WTP, and the headwaters of Abant Creek and Mudurnu Creek feeding Büyüksu Stream. The DO and T_w measurements were performed for 17 months between August 2015 and December 2016. Metabolism components of community respiration (R_c), gross primary production (GPP) and net ecosystem metabolism (NEM) were estimated by using the two-station method. According to naturality gradient (reach disturbance gradients: before and after discharges, and headwaters of the creeks), mean metabolism components were compared by performing the one-way analysis of variance. The comparison results showed that the WTP discharges increased the average R_c from −30.6 g O₂ m⁻² day⁻¹ to −130.9 g O₂ m⁻² day⁻¹, and had no significant impact on the average GPP, statistically (15.6 and 9.1 g O₂ m⁻² day⁻¹ before and after discharges, respectively). Validations of the multiple non-linear regression models of NEM and R_c gave coefficients of determination of 74.9% and 66.6%, respectively.