Response of arid-land macroinvertebrate communities to extremes of drought, wildfire, and monsoonal flooding

Observing spatial and temporal variation in aquatic communities provides insight into factors driving community structure. These observations are particularly important as ecosystems are being challenged by new extremes associated with a changing climate. However, since the timing of disturbances is unpredictable, capturing their effects is difficult, unless a study is already gathering data prior to and after these events. During a 2008-2016 study on the spatial and temporal variation of aquatic macroinvertebrate communities in the Gila River of New Mexico, a severe drought from 2011 to 2013, two mega-wildfires in 2011 and 2012, and the third-largest monsoon flood on record in 2013 occurred, providing an opportunity to document how these disturbances structure macroinvertebrate communities. Taxonomic richness and biomass of many individual taxa decreased following the wildfires and the extreme flood, yet the total biomass of the macroinvertebrate community decreased only slightly. We also found an association between the response of some taxa to inter-annual variation in hydrologic conditions and habitat use. This was evidenced by an increase in the relative biomass of taxa associated with pool habitats, such as Nematoda and Ceratopogonidae during drought years, whereas taxa from riffle habitats, such as mayfly (Leptophlebiidae) and stonefly (Perlodidae) nymphs increased in biomass in relatively wet years. Two groups of stonefly nymphs (Nemouridae and Taeniopterygidae) notably increased following the large monsoonal flooding in 2013. Collectively, the observed responses of macroinvertebrates to extreme hydrologic, wildfire and climate disturbances suggest that increasing frequency of disturbance might result in directional changes in the macroinvertebrate communities due to taxa-specific responses to those events.

Automated summary

Observing the spatial and temporal variation in aquatic communities can provide insights into the factors influencing community structure. A study on the macroinvertebrate communities in the Gila River of New Mexico revealed the effects of drought, wildfires, and floods on these communities. The richness and biomass of different taxa changed, and there were associations between the responses of certain taxa and hydrologic conditions and habitat use.