LAUSR

Micronized copper azole (MCA) wood preservative formulations include Cu in nano form, and relatively little is known about longer-term effects of Cu leached from MCA into wetland ecosystems. Here we tested the hypothesis that changes in soil microbiomes within reconstructed freshwater wetlands will be associated with exposure to elevated Cu concentrations originating from immersed MCA treated wood stakes. Eight replicate communities were assembled with Willamette Valley flood plain soil, and clonally propagated wetland plants within mesocosms. Inundated communities were equilibrated for 5 months before installation of MCA or control Southern Yellow Pine stakes (N=4 communities/experimental group). Soil samples were collected for 16S and ITS amplicon sequencing to quantify responses in prokaryotes and eukaryotes respectively at 15 timepoints, spanning 2 simulated seasonal dry downs, for up to 678 days. Physiochemical properties of water and soil were monitored at 20 and 12 timepoints respectively, over the same period. For both taxonomic groups of organisms, phylogenetic diversity increased and was positively correlated with elapsed days. Furthermore, there was significant divergence among eukaryotes during the second year based on experimental group. While the composition of taxa underwent succession over time, there was significantly reduced relative abundance of sequence variants from Gomphonema diatoms and Scutellinia fungi in communities where MCA wood stakes were present as compared to the controls. These focused microbiome shifts were positively correlated with surface water Cu and soil Cu concentrations, which were significantly elevated in treated communities. The reconstructed communities were effective systems for assessing potential impacts to wetland microbiomes after exposure to released copper. The results further inform post-commercialization risk assessments on MCA treated wood. This article is protected by copyright. All rights reserved.