Amplicon libraries of 16S rRNA and amoA genes from a two-phase experiment in which we first establish outdoor soil mesocosms to assess the impact of separate Cu and polycyclic aromatic hydrocarbon (PAH) contamination gradients on total prokaryotic and ammonia oxidizing archaea (AOA) and bacterial (AOB) communities in two soils with contrasting properties over a 16-month period. We then subjected contaminated and uncontaminated soils to to drying and rewetting stress in laboratory microcosms to test effects of contamination legacy on drought resilience.
Microbial communities are potentially useful indicators of the status of soil functioning in response to anthropogenic disturbances. However, the effect of compounded disturbances is of increasing interest given the multiple threats to soils. We hypothesized that microbial communities under continuous exposure to soil contaminants will be more affected when confronted with drought than those in uncontaminated soil. To test this, we performed a two-phase experiment in which we first establish outdoor soil mesocosms to assess the impact of separate Cu and polycyclic aromatic hydrocarbon (PAH) contamination gradients on total prokaryotic and ammonia oxidizing archaea (AOA) and bacterial (AOB) communities in two soils with contrasting properties over a 16-month period. We then subjected contaminated and uncontaminated soils to drought conditions in laboratory microcosms to test whether contamination legacy altered microbial responses to drying and rewetting stress. We found that Cu and PAH contamination consistently altered the diversity and structure of all communities as well as AOA abundance and nitrification activity in both soils, whereas AOB abundances were more variable. In the second phase of the experiment, we found that the structure and diversity of total microbial communities in contaminated soils was consistently less stable in response to drought, although the legacy of Cu contamination was more pronounced. In contrast, ammonia oxidizing archaeal and bacterial communities responded differently to drying-rewetting stress across both soil and contamination types, though a consistent effect of Cu legacy was observed for nitrification activity. These results underscore the context-dependent nature of microbial community responses to stressors as well the increased impact of climate change on microorganism in contaminated soils.
Microbial communities are potentially useful indicators of the status of soil functioning in response to anthropogenic disturbances. However, the effect of compounded disturbances is of increasing interest given the multiple threats to soils. We hypothesized that microbial communities under continuous exposure to soil contaminants will be more affected when confronted with drought than those in uncontaminated soil. To test this, we performed a two-phase experiment in which we first establish outdoor soil mesocosms to assess the impact of separate Cu and polycyclic aromatic hydrocarbon (PAH) contamination gradients on total prokaryotic and ammonia oxidizing archaea (AOA) and bacterial (AOB) communities in two soils with contrasting properties over a 16-month period. We then subjected contaminated and uncontaminated soils to drought conditions in laboratory microcosms to test whether contamination legacy altered microbial responses to drying and rewetting stress. We found that Cu and PAH contamination consistently altered the diversity and structure of all communities as well as AOA abundance and nitrification activity in both soils, whereas AOB abundances were more variable. In the second phase of the experiment, we found that the structure and diversity of total microbial communities in contaminated soils was consistently less stable in response to drought, although the legacy of Cu contamination was more pronounced. In contrast, ammonia oxidizing archaeal and bacterial communities responded differently to drying-rewetting stress across both soil and contamination types, though a consistent effect of Cu legacy was observed for nitrification activity. These results underscore the context-dependent nature of microbial community responses to stressors as well the increased impact of climate change on microorganism in contaminated soils.