Multi‐stressor impacts on fungal diversity and ecosystem functions in streams: natural vs. anthropogenic stress

Abstract

Biological assemblages are often subjected to multiple stressors emerging from both anthropogenic activities and naturally stressful conditions, and species' responses to simultaneous stressors may differ from those predicted based on the individual effects of each stressor alone. We studied the influence of land-use disturbance (forest drainage) on fungal decomposer assemblages and leaf decomposition rates in naturally harsh (low pH caused by black-shale dominated geology) vs. circumneutral streams. We used pyrosequencing to determine fungal richness and assemblage structure. Decomposition rates did not differ between circumneutral and naturally acidic reference sites. However, the effect of forest drainage on microbial decomposition was more pronounced in the naturally acidic streams than in circumneutral streams. Single-effect responses of fungal assemblages were mainly related to geology. Community similarity was significantly higher in the naturally acidic disturbed sites than in corresponding reference sites, suggesting that land-use disturbance simplifies fungal assemblages in naturally stressful conditions. Naturally acidic streams supported distinct fungal assemblages with many OTUs (operational taxonomic unit) unique to these streams. Our results indicate that fungal assemblages in streams are sensitive to both structural and functional impairment in response to multiple stressors. Anthropogenic degradation of naturally acidic streams may decrease regional fungal diversity and impair ecosystem functions, and these globally occurring environments therefore deserve special attention in conservation planning.

Environmental degradation results in contrasting changes in the assembly processes of stream bacterial and fungal communities

“…A number of studies have shown that microbial communities are sensitive to changes in local environmental conditions (Duarte et al , Tolkkinen et al ). Our results are in agreement with these previous studies since leaf packs in near‐pristine streams and anthropogenically altered streams supported distinct fungal and bacterial communities.…”

Effects of land use on the structure and function of leaf‐litter microbial communities in boreal streams

“…For example, increasing microbial biomass on leaf litter in nutrient enriched streams (Gulis & Suberkropp, ; Baldy et al ., ), successional shifts in fungal and bacterial groups during leaf‐litter decomposition (Das, Royer & Leff, ; Duarte et al ., ) and shifts in fungal and bacterial community composition in response to metal and other chemical contamination (Sridhar et al ., ; Duarte et al ., ; Solé et al ., ). Capitalising on advancements in DNA sequencing technologies, recent research has also aimed at better characterising the community composition of these leaf‐litter microbial communities in streams across different spatial scales and in the presence of anthropogenic disturbance (Tolkkinen et al ., , ; Heino et al ., ; Duarte et al ., ).…”

Consumption of terrestrial organic matter in the rocky intertidal zone along the central Oregon coast

“…, Tolkkinen et al. ). Coarse containers were constructed from rubber‐coated wire (2.5‐cm mesh), and leaves in open packs were sewn together with 6‐lb monofilament line (Fig.…”

“…2a). A 500-lm mesh is a good size to exclude detritivores yet prevent hypoxia (Flores et al 2013, Tolkkinen et al 2015. Coarse containers were constructed from rubber-coated wire (2.5-cm mesh), and leaves in open packs were sewn together with 6lb monofilament line ( Fig.…”