Using macroinvertebrate recolonization to predict community recovery: Implications for the restoration of Kimball Creek

Many stream and river restoration practitioners rely on the "Field of Dreams" hypothesis in which manipulating the physical parameters to a habitat will invoke the desired ecological response. However, there is a need to understand the ability for these ecosystems to recover from disturbances related to restoration activities prior to implementation, particularly in ecosystems that have been so impaired they possess altered stable states and may display variable recovery patterns in response to restoration activities. Many future climate change scenarios predict altered hydrologic regimes that may also impede successful restoration attempts. Therefore, it is important to gauge ecosystem recovery potential prior to restoration with the objectives of 1) identifying ecosystems that may or may not respond positively to restoration, and 2) targeting ecosystems that can withstand extreme hydrologic events in order to properly plan and maximize available resources towards restoration projects. Using recolonization trays, we assessed the macroinvertebrate community recovery potential of a 3rd order stream in western Colorado, USA, in anticipation of an extensive restoration project. Experiments were conducted during the summers of 2012 and 2013, coinciding with the onset of an extended drought. We hypothesized that recolonized communities at our highly impaired stream reach (Degraded), when compared to a less impaired reach (Reference), would exhibit lower abundance and not resemble adjacent representative benthic communities. Additionally, we predicted community response at the Degraded reach would be more variable in the second year of drought resulting from reduced stream discharge and resource availability. PERMANOVA and nMDS analyses showed significantly different macroinvertebrate community assemblages between reaches in both years, as well as differences within reaches between years. Recolonized assemblages at both reaches did not fully resemble those from adjacent representative benthic assemblages at the end of the experiment in both years. However, as predicted, recolonized communities at the Degraded reach were most dissimilar from each other and surrounding benthos, especially in 2013, suggesting that community recovery in severely impaired stream reaches may be further hindered by drought conditions.