Changes in invertebrate assemblage structure as affected by the flow regulation of a páramo river

Universidad Nacional de Colombia – Sede Bogotá – Departamento de Biología – Cra 30 No. 45 – 03, Colombia

^* Corresponding author: jdgonzalezt@unal.edu.co

Received: 23 March 2016
Accepted: 19 July 2016

Abstract

Flow regulation can alter the structure and dynamics of lotic communities, especially in rivers with unpredictable high-flow events, such as those flowing through the Páramo, an endemic ecosystem of the high-altitude Neotropical Andes. This study evaluated how flow regulation affects invertebrate assemblage structure in a Páramo river. In both the wet and dry seasons, the study assessed flow history, water chemistry and mesohabitat characteristics in their relation to assemblage structures upstream (undisturbed reach) and downstream (disturbed reach) of a water diversion structure. The elimination of spates through flow regulation did not lead to a complete change in the assemblage components at the disturbed reach. Instead, it led to an assemblage structure with a greater genera-richness, a lower genera-evenness and a greater occurrence of certain genera, e.g., Pristina, Alotanypus, Polypedilum and Austrolimnius. These genera lacked resistance-resilience adaptations, which would allow them to survive in mesohabitat conditions resulting from increased hydromorphological stability, namely higher fine sediment retention, higher benthic organic matter (BOM) and lower hydraulic stress. Overall, the results of this study reinforce the assertion that, in Páramo rivers, the temporal dynamics of the natural flow regime significantly control the structure of invertebrate assemblages. Thus, to preserve these rivers' biotic assemblages, it will be necessary to implement new regulation plans that mimic their natural flow histories.