Spatial and Temporal Variation of Aquatic Macroinvertebrates in the Upper Gila River, New Mexico and Response to Drought, Wildfire and Monsoonal Flooding

Authors: Keith Gido, Webster Jordan, Sky Hedden, James Whitney, David Propst

Year: 2018

Abstract

Characterizing spatial and temporal variation in communities can provide insight into main factors driving community structure. Samples across space can capture variation attributed to environmental gradients, such as stream size, and samples across time can capture responses to variation in hydrologic conditions, including extreme events such as flooding and drought. Because disturbance is often unpredictable by nature, capturing the effects of a natural disturbance can be quite difficult, unless a study is already in progress. Two wildfires and an extreme monsoon occurred mid-way through a 2008-2016 study on the spatial and temporal variation in aquatic communities in the Gila River of New Mexico, providing an opportunity to witness how these events might structure macroinvertebrate communities. Aquatic macroinvertebrate community structure varied spatially along an elevational gradient with high elevation sites distinguished with higher abundance of two caddisfly families Polycentropodidae and Philopotamidae and low elevation sites characterized by higher abundance of the dragonfly family Libellulidae. Overall insect diversity decreased following the wildfires, although a few families, such as Chironomidae, were unaffected or increased in total biomass. Variable discharge over the 8-year study also had an effect, with Empididae, Nemouridae, and Taeniopterygidae becoming more abundant in flood years relative to other macroinvertebrate taxa. Responses of macroinvertebrate taxa was concordant with general patterns of habitat use; some riffle dwelling species performed well in wet years and some pool dwelling species performed well in dry years. Collectively, these patterns of variation might be used to predict benthic macroinvertebrate community response to spatial and temporal variation in environmental conditions.