Steven Douglas Siciliano

• BSc, PhD
• Professor (Full) at University of Saskatchewan

Plants and their root microbiomes have co-evolved complex relationships that influence growth and development. While plant genotype is known to shape root microbiomes, a detailed understanding of this interplay remains limited. We used shotgun metagenomic sequencing to examine the composition, function, and microbial association networks of root ba...

Oribatid mites are one of the most abundant groups of microarthropods in soil. Oppia nitens, belonging to the family Oppiidae, one of the largest and most diverse families of oribatid mites, has been developed as a standardized model test organism for assessing soil contamination. However, the limited availability of genomic information for this sp...

Microbes are pervasive and their interaction with each other and the environment can impact fields as diverse as health and agriculture. While network inference and related algorithms that use abundance data from pyrosequencing can infer microbial interaction networks, the ambiguity surrounding the actual underlying networks hampers the validation...

Phosphorus (P) fertilizers promote soil petroleum‐hydrocarbon (PHC) bioremediation by correcting carbon‐to‐P ratio imbalances. While these inputs create conditions favorable to microbial growth, areas of a site or an entire site with low degradation rates (i.e., “stalled”) occur for unknown reasons. We hypothesized that soil conditions limit P bioa...

Incorporating the ecosystem services (ES) approach into soil ecological risk assessment (ERA) has been advocated over the years, but implementing the approach in ERA faces some challenges. However, several researchers have made significant improvements to the soil ERA, such as applying the species sensitivity distribution (SSD) to discern chemical...

Bacteria provide ecosystem services (e.g., biogeochemical cycling) that regulate climate, purify water, and produce food and other commodities, yet their distribution and likely responses to change or intervention are difficult to predict. Using bacterial 16S rRNA gene surveys of 1,381 soil samples from the Biomes of Australian Soil Environment (BA...

Soil invertebrates are an integral part of Arctic ecosystems through their roles in the breakdown of litter, soil formation, and nutrient cycling. However, studies examining soil invertebrates in the Arctic are limited and our understanding of the abiotic and biotic drivers of these invertebrate communities remains understudied. We examined differe...

Metal-impacted sites often need aggressive ecorestoration strategies to restore a functional plant-soil system. The use of biological soil crusts for soil stabilization, moisture retention and C and N input in disturbed and contaminated soils is becoming a more common ecorestoration practice. Biological soil crusts comprise cyanobacteria, fungi, li...

High Arctic soil organic carbon (SOC) is an important component in the global C cycle, yet there is considerable uncertainty in the estimates for the polar deserts and semi-deserts that dominate these regions. Some of this uncertainty in SOC estimates arises from the cryoturbic processes including diapirism that structure polar desert soils. Diapir...

Holobiont bacterial community assembly processes are an essential element to understanding the plant microbiome. To elucidate these processes, leaf, root, and rhizosphere samples were collected from eight lines of Brassica napus in Saskatchewan over the course of 10 weeks. We then used ecological null modeling to disentangle the community assembly...

Arctic soils are marked by cryoturbic features, which impact soil-atmosphere methane (CH4) dynamics vital to global climate regulation. Cryoturbic diapirism alters C/N chemistry within frost boils by introducing soluble organic carbon and nutrients, potentially influencing microbial CH4 oxidation. CH4 oxidation in soils, however, requires a spatio-...

Background The plant root-rhizosphere microbial community interactions play important roles in crop production as those interactions can be beneficial, detrimental, or neutral for the plant. In Brassica napus, our current understanding of root growth dynamics and dominance of bacterial taxa and their dynamics across growth stages is insufficient. I...

Purpose Our aim was to characterize the fungal root and rhizosphere microbiomes of genetically diverse Brassica napus lines in a temporally-intensive, multi-site field study to assess the relative contributions of plant genetics, growth stage and environmental conditions to microbiome composition and to identify fungi that were associated with yiel...

Microbial degradation of subsurface organic contaminants is often hindered by the low availability of both contaminants and nutrients, especially phosphorus (P). The use of activated carbon and traditional P fertilizers to overcome these challenges has proved ineffective; therefore, we sought to find an innovative and effective solution. By heating...

The plant root microbiome can enhance yield in crops, but whether this effect is due to one yield-promoting bacterial community consisting of key taxa, or multiple configurations of taxa with different traits is unclear. A changing climate and the need to reduce carbon-intensive agricultural inputs has spurred breeding programs to explore holobiont...

Aims Phyllosphere bacteria play critical roles in plant growth promotion, disease suppression and global nutrient cycling but remain understudied. Methods In this project, we examined the bacterial community on the phyllosphere of eight diverse lines of Brassica napus for ten weeks in Saskatoon, Saskatchewan Canada. Results The bacterial communit...

Effective bioremediation of hydrocarbons requires innovative approaches to minimize phosphate precipitation in soils of different buffering capacities. Understanding the mechanisms underlying sustained stimulation of bacterial activity remains a key challenge for optimizing bioremediationparticularly in northern regions. Positron emission tomograp...

Boron is an essential plant micronutrient responsible for several important functions. Boron availability in soils may be influenced by binding with soil organic matter (SOM), particularly with aromatic diol and polyphenol groups on SOM. The mechanism by which aromatic diols bind boron, however, remains unclear. The objective of this work is to fur...

This study investigated the influence of habitat quality (HQ) on the reproduction and bioenergetics (energy reserve and metabolic enzyme activities) of the oribatid mite, Oppia nitens, in response to cadmium (Cd). In the baseline toxicity test, Cd elevated the carbohydrate reserve of adult mites at intermediate Cd concentrations (88 and 175 mg Cd k...

Multiple metal-impacted soils are often realistic scenarios for risk assessments, but tools to address these are currently lacking. The objective of this work was to evaluate whether assuming concentration addition (CA) of metal mixture effects was conservative for prospective risk assessment of soils that were elevated mainly in Ni and Cu and some...

High Arctic polar deserts cover 26% of the Arctic. Climate change is expected to increase cryoturbation in these polar deserts, including frost boils and diapirs. Diapirism—cryoturbic intrusion into the overlying horizon—creates subsurface nutrient patches with low biodegradability and is thought to regulate greenhouse gas emissions, including the...

Positron-emitting nuclides have long been used as imaging agents in medical science to spatially trace processes non-invasively, allowing for real-time molecular imaging using low tracer concentrations. This ability to non-destructively visualize processes in real time also makes positron imaging uniquely suitable for probing various processes in p...

Sulfate adsorbs on Fe-oxide minerals by both inner- and outer-sphere modes, however, the time dependence of coexisting surface species is not clear. Using in situ attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), peak fitting and multivariate curve resolution (MCR) analyses, we quantify adsorption and desorption kinet...

The plant microbiome has been recently recognized as a plant phenotype to help in the food security of the future population. However, global plant microbiome datasets are insufficient to be used effectively for breeding this new generation of crop plants. We surveyed the diversity and temporal composition of bacterial and fungal communities in the...

Soils are sources of the potent greenhouse gas nitrous oxide (N2O) globally, but emissions from permafrost-affected soils have been considered negligible owing to nitrogen (N) limitation. Recent measurements of N2O emissions have challenged this view, showing that vegetated soils in permafrost regions are often small but evident sources of N2O duri...

Soils provide numerous ecosystem services (ES) such as food production and water purification. These ES result from soil organism interactions and activities, which are supported by the soil physicochemical properties. Risk assessment for this complex system requires understanding the relationships among its components, both in the presence and abs...

The plant microbiome has been recently recognized as a plant phenotype to help in the food security of the future population. However, global plant microbiome datasets are insufficient to be used effectively for breeding this new generation of crop plants. We surveyed the diversity and temporal composition of fungal communities in the root and rhiz...

High Arctic polar deserts cover 26% of the Arctic. Increasing temperatures are predicted to significantly alter polar desert freeze‐thaw and biogeochemical cycles, with important implications for greenhouse gas emissions. However, the mechanisms underlying these changing cycles are still highly uncertain. Cryoturbic, carbon‐rich Bhy horizons (diapi...

Invasive plants can cause changes in the structure and function of the ecosystem being invaded. Any changes in ecosystem diversity and community composition will likely alter ecosystem services provided by that ecosystem. However, how these ecosystem services may change is poorly understood. To elucidate how these ecosystem services will change wit...

Phosphorus (P) fertilizers are crucial to achieve peak productivity in agricultural systems. However, the fate of P fertilizers via microorganism incorporation and the exchange processes between soil pools is not well understood. ¹⁸Oxygen-labelled phosphate (¹⁸O- Pi) can be tracked as it cycles through soil systems. Our study describes biological a...

Metal mixture toxicity across soil types is a daunting challenge to risk assessment. Here, we evaluated metal mixture toxicity in Oppia nitens, using ten fixed metal mixture ratios in five Canadian soils that closely matched some of the EU PNEC reference soils. Soils were dosed with five metals (Cu, Zn, Pb, Co, Ni) as single metals (ten concentrati...

The soil-air exchange of pesticides is one potential fate and exposure pathways, and this process is generally thought to be governed by soil properties and environmental conditions. The experimental determination of soil-air partitioning coefficient (Ksa) is laborious and costly and typically, Ksa's are predicted from a semiempirical or a simple l...

Modifying the rhizosphere microbiome through targeted plant breeding is key to harnessing positive plant–microbial interrelationships in cropping agroecosystems. Here, we examine the composition of rhizosphere bacterial communities of diverse Brassica napus genotypes to identify: (1) taxa that preferentially associate with genotypes, (2) core bacte...

Cadmium (Cd) is a heavy metal of concern in contaminated sites because of its high toxicity to soil biota and humans. Typically, Cd exposure is thought to be dominated by dissolved Cd in soil pore water and, thus, dermal uptake. In this study, we investigated the uptake, toxicity, and maternal transfer of Cd in a standard soil invertebrate, the ori...

The oribatid soil mite Oppia nitens C.L. Koch, 1836, is a model microarthropod in soil ecotoxicity testing. This species has a significant role in supporting soil functions and as a suitable indicator of soil contamination. Despite its significance to the environment and to ecotoxicology, however, very little is known of its biology, ecology, and s...

Nutrient availability is a key factor for the in situ bioremediation of petroleum hydrocarbon contaminated (PHC) soils. Phosphorus deficiencies in calcium rich PHC soils can often be challenging, as amendment P rapidly forms new mineral phases. In situ bioreactors were used to determine the chemical fate of several P amendments (ortho-P, tripolypho...

Positron emission tomography (PET) is a powerful tool for mapping the dynamic distribution of substances in visually opaque systems. A modular, scalable, transformable, and relocatable PET system is custom built to provide optimized flexible PET imaging for a wider variety of applications. In coordination with the purposely designed hardware, we de...

Metals are present as mixtures in the environment, yet testing such complex mixture poses design and technical challenges. One possible solution is the use of fixed ratios, i.e. rays of increasing metal concentrations. But fixed ratios rays are compromised when soils dosed with metal salts are leached due to metal-soil selectivity rules. Two alt...

Many emerging, and some legacy, pollutants pose risks to humans and ecosystems near the detection limits (DL) of existing analytical systems. As a result, site assessments and management options are often presented with data sets that are sparse, highly skewed, and left-censored. Existing analysis methods are unable to differentiate effects of trea...

When soil is frozen, biochar promotes petroleum hydrocarbon (PHC) degradation, yet we still do not understand why. To investigate microbial biodegradation activity under frozen conditions, we placed 60‐μm mesh bags containing 6% (v/v) biochar created from fishmeal, bonemeal, bone chip, or wood into PHC‐contaminated soil, which was then frozen to −5...

Soil habitat quality is thought to influence metal toxicity via changes in speciation and thereby toxicokinetics. Here, we assessed the toxicokinetic and toxicodynamic effects of habitat quality on mite, Oppia nitens when exposed to zinc (Zn) contaminated soils. Forty-seven soils were ranked into three habitat qualities; high, medium, and low based...

The development of microbial networks is central to ecosystem functioning and is the hallmark of complex natural systems. Characterizing network development over time and across environmental gradients is hindered by the millions of potential interactions among community members, limiting interpretations of network evolution. We developed a feature...

Sediment toxicity studies and ecological risk assessments on organic contaminants routinely apply organic carbon normalization to toxicity data; however, no studies examine its potential for use in soils with petroleum hydrocarbon (PHC) contamination. Limited studies in soil ecotoxicology assess the influence of species assemblages used in species...

Current soil remediation guidelines for metals reflect single generation laboratory studies, however in the field, organisms are exposed to metals for more than one generation. This study assessed the multigenerational effect of zinc on Oppia nitens under a pulse or continuous exposure scenario. Synchronized adult mites (parents) were exposed to si...

Previous studies have suggested that understanding soil metal speciation, rather than relying solely on total metal content, can improve the accuracy and utility of contaminated site risk assessments. Since soil properties and reaction time can alter metal speciation, then speciation should influence metal bioaccessibility. For example, under gastr...

Juveniles are generally considered more sensitive to contaminants than adults. However, it is unknown if the behavioral responses of juvenile soil invertebrates is different than the adults. The absence of juvenile or adult soil invertebrates in contaminated soils due to avoidance adversely impacts the soil quality. Here, we assessed the avoidance...

In the Yukon Territory, transmission rights‐of‐way (ROWs) are managed using brushing and mowing techniques alone. When cut, target species such as Populus tremuloides Michx. and Salix spp. grow rapidly shortening maintenance cycles. Long‐term vegetation control may be improved by integrating herbicide application. However, prior to implementation,...

https://doi.org/10.1088/1742-6596/1120/1/012077

In 2018 IEEE Nuclear Science Symposium and Medical Imaging Conference Proceedings (NSS/MIC), pages 1–3, 2018. https://doi.org/10.1109/NSSMIC.2018.8824574

Current environmental assessments for petroleum hydrocarbon (PHC) contaminated sites are dependent on discrete soil sampling to estimate the degree and extent of contamination, leading to unreliable and non-reproducible results. Incremental sampling methodology (ISM) involves collecting and combining samples within a targeted area and holds promise...

In recent years, laboratory soil toxicity testing has advanced with the introduction of ecologically relevant boreal forest soil invertebrate and plant species, as well as increased adoption of avoidance toxicity tests. In this study, we investigated the toxicity of a binary petroleum hydrocarbon (PHC) mixture to six agronomic and boreal forest pla...

The Nuclear Imaging Detector Development group at the Department of Physics, University of Regina is developing Canada's first positron emission tomography (PET) system for plant physiological function studies. In its current configuration the system consists of four detectors heads, each with active area of 48×48 mm2. In a typical arrangement the...

Undergraduate research poster on the impact of a Passive Anode-Cathode Technology on the degradation of benzene by anaerobic cultures.

Core Ideas Modification of Ca levels influences P adsorption. Citrate influences the adsorption equilibrium of P onto soil. Competitive adsorption of citrate and P is primary mechanism of interaction. In subsurface systems that have been contaminated with petroleum hydrocarbons (PHCs), the degradation by microbes is limited by nutrient availabilit...

Although petroleum hydrocarbons (PHCs) released to the environment typically occur as mixtures, PHC remediation guidelines often reflect individual substance toxicity. It is well documented that groups of aliphatic PHCs act via the same mechanism of action, nonpolar narcosis and, theoretically, concentration addition mixture toxicity principles app...

Phosphorus availability and cycling in microbial communities is a key determinant of bacterial activity. However, identifying organisms critical to P cycling in complex biodegrading consortia has proven elusive. Here we assess a new DNA stable isotope probing (SIP) technique using heavy oxygen-labelled phosphate (P¹⁸O4) and its effectiveness in pur...

Adsorption and precipitation reactions often dictate the availability of phosphorus in soil environments. Tripolyphosphate (TPP) is considered a form of slow release P fertilizer in P limited soils, however, investigations of the chemical fate of TPP in soils are limited. It has been proposed that TPP rapidly hydrolyzes in the soil solution before...

Understanding the relationships between below- and aboveground plant community diversity and composition is essential for understanding plant–soil linkages and feedbacks. Here we examine the patterns of belowground plant species richness, evenness, community composition, and individual species relative abundance with soil depth in a rough fescue gr...

Predicting mammalian bioavailability of PAH mixtures from in vitro bioaccessibility results has proven to be an elusive goal. In an attempt to improve in vitro predictions of PAH soil bioavailability we investigated how energetic input influences PAH bioaccessibility by using a high and low energetic shaking method. Co-inertia analysis (COIA), and...

Phosphorus (P) bioavailability often limits gasoline biodegradation in calcareous cold‐region soils. One possible method to increase P bioavailability in such soils is the addition of citrate. Citrate addition at the field scale may increase hydrocarbon degradation by: (i) enhancing inorganic and organic P dissolution and desorption, (ii) increasin...

Identifying the spatial scale at which particular mechanisms influence plant community assembly is crucial to understanding the mechanisms structuring communities. It has long been recognized that many elements of community structure are sensitive to area; however the majority of studies examining patterns of community structure use a single relati...

Mountain peatlands often have mineral horizons embedded within or buried below the peat, which affects substrate quality and soil properties in subsurface peat. However, their role in greenhouse gases (GHG) production and GHG responses to temperature and water table changes are uncertain. We conducted a laboratory microcosm experiment to assess the...

To integrate biochar as a practical and successful remedial amendment at northern landfarms, components of its formulation and application must be optimized for site‐specific environmental conditions. Different biochar amendments were applied to petroleum hydrocarbon (PHC)‐contaminated soil at two northern field sites (Iqaluit and Whitehorse) and i...

Plant associated microbial communities can produce growth promoting hormones, increase nutrient cycling, and suppress plant pathogens, leading increased plant productivity. If plants can be bred for these microbial communities this could lead to more sustainable agriculture. In this study, DNA was extracted from root and rhizosphere soil from 16 li...

Butte, Montana is part of the largest superfund site in the continental United States. Open-pit mining continues in close proximity to Butte’s urban population. This study seeks to establish baseline metal concentrations in the hair and blood of individuals living in Butte, MT and possible routes of exposure. Volunteers from Butte (n = 116) and Boz...

Moisture is critical for plant success in polar deserts but not by the obvious pathway of reduced water stress. We hypothesized that an indirect, nutrient-linked, pathway resulting from unique water/frozen soil interactions in polar deserts creates nutrient-rich patches critical for plant growth. These nutrient-rich patches (diapirs) form deep in h...

Although invasive plants can drive ecosystem change, little is known about the directional nature of belowground interactions between invasive plants, native roots, bacteria, archaea and fungi. We used detailed bioinformatics and a recently developed root assay on soils collected in fescue grassland along a gradient of smooth brome (Bromus inermis...

Petroleum hydrocarbon (PHC) degradation slows significantly during the winter which substantially increases the time it takes to remediate soil in Arctic landfarms. The aim of this laboratory trial was to assess the potential of a meat and bonemeal (MBM) biochar to stimulate PHC degradation in contaminated soil collected from Iqaluit, Canada. Over...

Aims We refine and test a next-generation sequencing assay for the molecular identification and quantification of plant roots from mixed-species samples. Methods We modified primers targeting the trnL intron to provide greater taxonomic resolution and developed an improved bioinformatics pipeline that can identify roots based on global, site-, and...

Managing phosphorus bioaccessibility is critical for the bioremediation of hydrocarbons in calcareous soils. This paper explores how soil mineralogy interacts with a novel biostimulatory solution to both control phosphorus bioavailability and influence bioremediation. Two large bore infiltrators (1 m diameter) were installed at a PHC contaminated s...

Microorganisms are vital in mediating the earth’s biogeochemical cycles; yet, despite our rapidly increasing ability to explore complex environmental microbial communities, the relationship between microbial community structure and ecosystem processes remains poorly understood. Here, we address a fundamental and unanswered question in microbial eco...

Archaea are ubiquitous and highly abundant in Arctic soils. Because of their oligotrophic nature, archaea play an important role in biogeochemical processes in nutrient-limited Arctic soils. With the existing knowledge of high archaeal abundance and functional potential in Arctic soils, this study employed terminal restriction fragment length polym...

Polycyclic aromatic hydrocarbon (PAH) bioavailability from ingested soils will vary between soils; however, the nature of this variation is not well characterized. Here, we used the juvenile swine model to link external exposure to internal benzo[a]pyrene (BaP) and anthracene exposure following oral PAH ingestion of 27 different impacted site soils...

Humans are commonly exposed to polycyclic aromatic hydrocarbons (PAHs), a family of compounds present as mixtures in the environment. This study exposed swine to PAH mixtures in single and subacute dose regimens and collected liver and ileum tissue to measure cytochrome P450 mRNA expression and enzyme activity as biomarkers of exposure and DNA addu...

Soil and dust ingestion is one of the major human exposure pathways to contaminated soil; however, pollutant transfer from ingested substances to humans cannot currently be confidently predicted. Soil polycyclic aromatic hydrocarbon (PAH) bioavailability is likely dependent upon properties linked to chemical potential and partitioning such as fugac...

Hypertension is considered to be the most important risk factor for the development of cardiovascular diseases. Beside life-style risk factors, exposure to lead and mercury species are increasingly discussed as potential risk factors. Although there are a few previous studies, the underlying mechanism by which exposure to lead and mercury disturb b...

Little has been published on the chemical exposures and risks of dental restorative materials other than from dental amalgam and composite resins. Here we provide the first exposure and risk assessment for gold (Au) alloy and ceramic restorative materials. Based on the 2001-2004 US National Health and Nutrition Examination Survey (NHANES), we asses...

Using data from the 2001 to 2004 US National Health and Nutrition Examination Survey (NHANES) on the number and placement of tooth restorations in adults, we quantified daily doses due to leaching of elements from gold (Au) alloy and ceramic restorative materials. The elements with the greatest leaching rates from these materials are often the elem...

Mitchell Peninsula is located towards the East of the Windmill Islands in eastern Antarctica. It is an ice-free polar desert, and knowledge of its soil microbial taxonomic composition is limited. In this study, we investigated the soil microbial taxonomic composition using multiplex 454 pyrosequencing targeting the bacterial 16S rRNA and the fungal...

Landscape heterogeneity impacts community assembly in animals and plants, but it is not clear if this ecological concept extends to microbes. To examine this question, we chose to investigate polar soil environments from the Antarctic and Arctic, where microbes often form the major component of biomass. We examined soil environments that ranged in...

In situ visible and near-infrared (vis-NIR) spectroscopy is a potential solution to the logistic constraints limiting the accuracy and spatial resolution of soil organic carbon (SOC) estimates for Arctic regions. The objective of our study was to develop a calibration model based on field-condition soils for in situ applications to predict SOC in H...

There are unusual patterns of greenhouse gas (GHG) net production in soil profiles of Arctic polar deserts. These deserts include frost boils that are symptomatic of permafrost‐associated soils. Some frost boils contain diapirs, intrusions of recently thawed, carbon‐ and water‐rich fine material pushed upward into the overlying active layer. Here w...