Threshold Responses of Macroinvertebrate Communities to Stream Velocity in Relation to Hydropower Dam: A Case Study from The Guayas River Basin (Ecuador)

Thi Nguyen,Minar Damanik Ambarita,Koen Lock,Marie Forio,Luis Dominguez-Granda,Natalija Suhareva,Pieter Boets,Peter Goethals,Christine Van Der Heyden,Thu Hoang,Gert Everaert

doi:10.3390/w10091195

Abstract

The Guayas River basin is one of the most important water resources in Ecuador, but the expansion of human activities has led to a degraded water quality. The purpose of this study was (1) to explore the importance of physical-chemical variables in structuring the macroinvertebrate communities and (2) to determine if the thresholds in stream velocity related to macroinvertebrate community composition could be identified in the Guayas River basin. Thus, macroinvertebrates and physical–chemical water quality variables were sampled at 120 locations during the dry season of 2013 in the Guayas River basin. Canonical correspondence analysis (CCA) was performed to identify relevant physical–chemical characteristics of the river influencing the distribution of the macroinvertebrate communities. Threshold indicator taxa analysis (TITAN) was used to discriminate between the macroinvertebrate community related to stagnant waters (Daule–Peripa reservoir) and to running waters. CCA indicates that the most important environmental factors influencing the distribution of macroinvertebrate communities were stream velocity, chlorophyll concentration, conductivity, temperature and elevation. Tipping points for the macroinvertebrate community were defined by stream velocity at 0.03 m/s and 0.4 m/s, i.e., stagnant-water (including dam-related reservoirs) taxa start to quickly decrease in abundance and frequency at 0.03 m/s while running-water taxa start to quickly increase in abundance and frequency at 0.03 m/s until a stream velocity of 0.4 m/s. The results provide essential information to define environmental flows to further support water management plans of the Guayas River basin. Information obtained will be useful for management of similar rivers in South America, as well as the rest of the world.

Highlights

Rivers are ecosystems, which provide great ecological value [1]
There was one sampling site located at the tributary of the Daule River, which had the highest observed values of dissolved oxygen (DO) (13.6 mg/L), chlorophyll (66.8 μg/L) and conductivity (1981 μS/cm)
Our results show that good water quality was observed at sampling sites with a high elevation, low temperature, high stream velocity and low concentrations of chlorophyll

Summary

Introduction

Rivers are ecosystems, which provide great ecological value [1]. They are an important source of renewable water supply for humans and freshwater ecosystems [2] and provide many ecosystem services such as sources of drinking water and recreational areas and provide nursing grounds and food for many organisms [3]. Freshwater organisms are impacted via various stressors, such as water pollution, erosion, alterations in stream hydrology and changing habitat structures [5]. The water needs for human and natural ecosystems are often considered as competing with each other [6]. Water managers and political leaders need to manage water to meet human requirements, protect endangered species and support freshwater ecosystems [6]

Objectives

Methods

Results

Conclusion