Impacts of Road Dust on Small Subarctic Lake Systems

Arctic regions have been experiencing increasing pressures from multiple environmental stressors, most notably rapid climate change and human development. Previous research has demonstrated the impacts of calcareous dust from gravel roads on surrounding vegetation and permafrost, whereas aquatic systems have remained largely unstudied. Here, we explore whether 1) the chronic generation of dust from the 740 km long Dempster Highway has affected water chemistry and diatom assemblages in lakes in the Peel Plateau region of the Northwest Territories, and 2) accelerated regional warming has affected these lakes. A suite of 27 water chemistry variables was assessed from 28 lakes along a 40 m – 26 km distance from the highway. Paleolimnological analyses of biological proxies (diatoms, visible reflectance spectroscopy-derived chlorophyll-a, and an index of chrysophyte scales to diatoms [S:D]) were undertaken on dated sediment cores from two lakes near the highway and one lake situated far from the highway, outside the expected range of dust transport. Conductivity and calcium exhibited a wide range of measurements across our 28 sites; lakes within 1 km of the highway generally exhibited higher ions and related variables than more distant lakes. Analyses of diatom assemblages indicated that the two shallower sites near the highway underwent modest compositional changes over the past approximately 100 years, whereas changes recorded at the farther site were more pronounced. The diatom records, supported by chlorophyll-a and S:D indices, indicated that changes in both the near and far lakes were consistent with warming, with little discernable impact from road dust. Whilst chemical changes associated with the half-century old highway corridor appear clear, they are not yet of sufficient magnitude to elicit a directional biological response in algal assemblages.Les régions de l’Arctique subissent de plus en plus de pressions en provenance d’agresseurs environnementaux, plus particulièrement le changement climatique rapide et le développement humain. Des recherches ont permis de démontrer les incidences de la poussière calcaire émanant des routes en gravier sur la végétation et le pergélisol environnants, mais les systèmes aquatiques ont fait l’objet de très peu d’études. Ici, nous explorons : 1) si la production chronique de poussière par la route de Dempster d’une longueur de 740 km a une influence sur la chimie de l’eau et les assemblages de diatomées dans les lacs de la région du plateau Peel, dans les Territoires du Nord-Ouest; et 2) si le réchauffement régional accéléré a un effet sur ces lacs. Un ensemble de 27 variables de chimie des eaux a été évalué à partir de 28 lacs sur une distance variant entre 40 m et 26 km de la route. Des analyses paléolimnologiques de substituts biologiques (diatomées, chlorophylle-a dérivée de la spectroscopie en réflectance visible (chl-a) et indice d’échelles de chrysophytes à diatomées [S:D]) ont été effectuées sur des carottes de sédiments datées, prélevées dans deux lacs situés près de la route et dans un lac situé loin de la route, à l’extérieur de l’étendue possible du transport de la poussière. Dans les 28 sites, les taux de conductivité et de calcium enregistrés se sont répartis sur une vaste gamme de mesures. De manière générale, les lacs se trouvant à moins d’un kilomètre de distance de la route avaient une plus forte teneur en ions et en variables connexes que les lacs plus éloignés. Les analyses d’assemblages de diatomées ont permis de constater que les deux sites moins profonds à proximité de la route avaient connu des changements de composition modestes au cours des cent dernières années environ, tandis que les changements enregistrés au site plus éloigné étaient plus prononcés. Les enregistrements de diatomées, taux de chl-a et indices S:D à l’appui, ont permis de constater que les changements caractérisant tant les lacs situés à proximité qu’à distance coïncidaient avec le réchauffement, et que l’incidence de la poussière de route était à peine perceptible. Bien que les changements chimiques liés au corridor routier d’un demi-siècle semblent clairs, leur ampleur n’est toujours pas suffisante pour obtenir une réponse biologique directionnelle dans les assemblages d’algues

Abruptly and irreversibly changing Arctic freshwaters urgently require standardized monitoring

1. Arctic regions support a wide variety of freshwater ecosystems. These naturally oligotrophic and cold-water streams, rivers, ponds and lakes are currently being impacted by a diverse range of anthropogenic pressures, such as accelerated climate change, permafrost thaw, land-use change, eutrophication, brownification and the replacement of northern biota with the range expansion of more southern species. 2. Multiple stressors are rapidly changing Arctic freshwater systems as aquatic habitats are becoming more suitable for species originating from more southerly regions and thereby threatening biota adapted to cold waters. The livelihoods of Indigenous Peoples of the north will be altered when ecosystem services associated with changes in biodiversity are affected. Unfortunately, monitoring of biodiversity change in Arctic freshwaters is currently inadequate, making it difficult, if not impossible, to predict changes in ecosystem services. 3. Synthesis and applications. We propose a three-step approach to better address and facilitate monitoring of the rapid ecological changes that Arctic freshwater ecosystems are currently experiencing as a result of climate change. First, we should increase our efforts in the monitoring of freshwaters across all Arctic countries by setting up a network of monitoring sites and devoting more effort to a broad-scale baseline survey using standardized methods. Second, we should enhance modelling efforts to include both ecological change and socio-economic development. These models should help pinpoint species, ecosystems and geographical areas that are likely to show abrupt changes in response to any changes. Third, we should increase interaction among scientists, policymakers and different stakeholder groups. In particular, Indigenous Peoples must be involved in the leadership, planning and execution of monitoring and assessment activities of Arctic freshwaters. The proposed approach, which is critical to detecting the effects of climate change in the circumpolar region, has broader applications for global coordination of Arctic freshwater biomonitoring. Through routine monitoring, standardization of methods, enhanced modelling of integrated scientific and socio-economic change, and increased collaboration within and among sectors, more effective monitoring and management of climate change impacts on freshwater biodiversity will be possible in the Arctic and globally

Abrupt climatic events during the last glacial-interglacial transition in Alaska

Evidence is mounting that abrupt climatic shifts occurred during the last glacial-interglacial transition (LGIT) in the North Atlantic and other regions. However, few high-resolution climatic records of the LGIT exist from the high latitudes of the North Pacific rim. We analyzed lake sediments from southwestern Alaska for biogenic silica, organic carbon, organic nitrogen, diatom assemblages, and compound-specific hydrogen isotopes. Results reveal climatic changes coincident with the Younger Dryas, Intra-Allerod Cold Period, and Pre-Boreal Oscillation. However, major discrepancies exist in the paleoclimate patterns of the Bolling-Allerod interstadial between our data and the GISP2 18O record from Greenland, and causes are uncertain. These data suggest that the North Pacific and North Atlantic experienced similar reversals during climatic warming of the LGIT but that the Bolling-Allerod cooling trend in the GISP2 18O record is probably not a hemispheric or global pattern

Biodiversity patterns of Arctic diatom assemblages in lakes and streams : Current reference conditions and historical context for biomonitoring

1. Comprehensive assessments of contemporary diatom distributions across the Arctic remain scarce. Furthermore, studies tracking species compositional differences across space and time, as well as diatom responses to climate warming, are mainly limited to paleolimnological studies due to a lack of routine monitoring in lakes and streams across vast areas of the Arctic. 2. The study aims to provide a spatial assessment of contemporary species distributions across the circum-Arctic, establish contemporary biodiversity patterns of diatom assemblages to use as reference conditions for future biomonitoring assessments, and determine pre-industrial baseline conditions to provide historical context for modern diatom distributions. 3. Diatom assemblages were assessed using information from ongoing regulatory monitoring programmes, individual research projects, and from surface sediment layers obtained from lake cores. Pre-industrial baseline conditions as well as the nature, direction and magnitude of changes in diatom assemblages over the past c.200 years were determined by comparing surface sediment samples (i.e. containing modern assemblages) with a sediment interval deposited prior to the onset of significant anthropogenic activities (i.e. containing pre-1850 assemblages), together with an examination of diatoms preserved in contiguous samples from dated sediment cores. 4. We identified several biotypes with distinct diatom assemblages using contemporary diatom data from both lakes and streams, including a biotype typical for High Arctic regions. Differences in diatom assemblage composition across circum-Arctic regions were gradual rather than abrupt. Species richness was lowest in High Arctic regions compared to Low Arctic and sub-Arctic regions, and higher in lakes than in streams. Dominant diatom taxa were not endemic to the Arctic. Species richness in both lakes and streams reached maximum values between 60°N and 75°N but was highly variable, probably reflecting differences in local and regional environmental factors and possibly sampling effort. 5. We found clear taxon-specific differences between contemporary and pre-industrial samples that were often specific to both ecozone and lake depth. Regional patterns of species turnover (β-diversity) in the past c.200 years revealed that regions of the Canadian High Arctic and the Hudson Bay Lowlands to the south showed most compositional change, whereas the easternmost regions of the Canadian Arctic changed least. As shown in previous Arctic diatom studies, global warming has already affected these remote high latitude ecosystems. 6. Our results provide reference conditions for future environmental monitoring programmes in the Arctic. Furthermore, diatom taxa identification and harmonisation require improvement, starting with circum-Arctic intercalibrations. Despite the challenges posed by the remoteness of the Arctic, our study shows the need for routine monitoring programmes that have a wide geographical coverage for both streams and lakes

No magic number: determining cost-effective sample size and enumeration effort for diatom-based environmental assessment analyses

Aquatic microorganisms are commonly used as indicators in environmental assessments. Two key aspects of sampling design for these studies are the number of sites sampled and the enumeration effort of organisms within samples. However, there has been no rigorous determination of a cost-effective balance between them. Here, we use regional diatom datasets from 207 to 493 lakes to determine the influence of sample size (lake number) and enumeration effort (valve count) on the accuracy and cost-effectiveness of commonly-used environmental assessment analyses. We find that both lake number and valve count can be considerably reduced from the original datasets. However, there is considerable variation among analyses, such that a single most cost-effective sampling configuration cannot be recommended. For weighted-averaging assemblage versus environment models we recommend 70-100 lakes and 200 valves for retaining high accuracy. For other analyses, we recommend iteratively building up datasets, using initially high (300 or more) and consistent valve counts, and using subsampling to determine when the influence of either lake number or valve count plateaus. This technique is applicable to other types of microorganisms used in environmental assessments.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

No magic number: Determining cost-effective sample size and enumeration effort for diatom-based environmental assessment analyses

Aquatic microorganisms are commonly used as indicators in environmental assessments. Two key aspects of sampling design for these studies are the number of sites sampled and the enumeration effort of organisms within samples. However, there has been no rigorous determination of a cost-effective balance between them. Here, we use regional diatom data sets from 207 to 493 lakes to determine the influence of sample size (lake number) and enumeration effort (valve count) on the accuracy and cost-effectiveness of commonly used environmental assessment analyses. We find that both lake number and valve count can be considerably reduced from the original data sets. However, there is considerable variation among analyses, such that a single most cost-effective sampling configuration cannot be recommended. For weighted-averaging assemblage versus environment models, we recommend 70–100 lakes and 200 valves for retaining high accuracy. For other analyses, we recommend iteratively building up data sets, using initially high (300 or more) and consistent valve counts and using subsampling to determine when the influence of either lake number or valve count plateaus. This technique is applicable to other types of microorganisms used in environmental assessments

Long-term trends in hypolimnetic volumes and dissolved oxygen concentrations in Boreal Shield lakes of south-central Ontario, Canada

Temperature–oxygen profiles, collected biweekly to monthly for ∼40 years, were used to calculate end-of-summer volume-weighted hypolimnetic oxygen (VWHO) concentrations in six small lakes located in south-central Ontario, Canada. Coherent decreases in thermocline depth and increases in hypolimnetic volume, mean hypolimnetic dissolved oxygen (DO) concentration, and VWHO were observed in five of the six study lakes. All lakes underwent an abrupt increase in VWHO and mean hypolimnetic DO after 2010. In four of the six study lakes, the highest hypolimnetic DO concentrations were observed in years where chlorophyll a concentrations were low, whereas at five of the six study lakes the highest hypolimnetic volumes were observed when dissolved organic carbon concentrations were relatively high. Warmer spring or winter air temperatures were associated with higher hypolimnetic DO concentrations at two sites, and longer ice-free periods were associated with smaller hypolimnetic volumes at two sites. These results suggest that the recent VWHO increases in the studied south-central Ontario lakes may be a function of multiple drivers that include changes in primary production, lake water transparency, and regional climatic factors.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

A morphological trait-based approach to environmental assessment models using diatoms

Diatom assemblages are excellent indicators for environmental monitoring. However, enumerating diatoms using fine-level taxonomy takes considerable effort, which must be undertaken by specialist taxonomists. One alternative is to enumerate assemblages using morphological traits. In this study, we compared the accuracy of models using 20 morphological traits with those using species assemblages to infer lake water pH, salinity, depth, and total phosphorus concentrations in four data sets, each comprising over 200 lakes. Assemblages aggregated by trait combinations were used to predict environmental variables via weighted averaging regressions, and richness of trait combinations was regressed against the environmental variables. Trait-based weighted averaging regressions showed slightly lower accuracy than species-level analyses and higher accuracy than analyses at the family and sometimes genus level. Richness of trait combinations showed relationships with pH, salinity, and lake depth that were marginally stronger than relationships using species richness. Although species-level analyses are the best approach when time and budgets allow, we suggest that trait combinations could provide an alternative method for water quality assessment programs, where funds do not allow the use of specialist taxonomists or where diatoms are being used as part of a multi-indicator analysis

Spatial distribution of surface-sediment diatom assemblages from 45 Tibetan Plateau lakes and the development of a salinity transfer function

The Tibetan Plateau (TP) is often referred to as the “Asian Water Tower”, as it plays a crucial role in supplying water for ∼1.9 billion people. Lakes in this arid mountain region have a wide salinity gradient and are sensitive to the complex interactions between climate and the water cycle, affecting aquatic ecosystems and species distributions. Here, we analyzed relationships between measured environmental variables and the spatial distribution of surface sediment diatom assemblages from 45 lakes located throughout the TP with the intention of developing a diatom-inference model for salinity. Diatom assemblage composition and diversity differed among lakes from the western (W), southern (S), northern (N), and southeastern (E) regions of the TP. The most common taxa observed in the lake set, Pantocsekiella ocellata, Nitzschia palea, and Staurosira venter, tended to have widespread distributions across the TP. In general, diatom diversity and richness tended to be highest in lakes with salinity concentrations between 0.1 and 10 g/L and were lowest in high salinity lakes (>20 g/L) of the N region. Canonical correspondence analysis (CCA) identified lake water salinity and maximum lake depth as explaining a statistically significant portion of diatom assemblage variation. Weighted-averaging (WA) was used to develop a diatom-based salinity inference model (R2jack = 0.71, RMSEPjack = 0.28) based on diatom optima from freshwater to meso-hyposaline lakes of the TP. Diatom-salinity reconstructions and changes in diatom community composition can potentially be used to track long-term patterns in climate and environmental conditions across the highly complex mountain landscape of the TP

Imaging use for low back pain by Ontario primary care clinicians: protocol for a mixed methods study – the Back ON study

Abstract Background At any one time, one in every five Canadians has low back pain (LBP), and LBP is one of the most common health problems in primary care. Guidelines recommend that imaging not be routinely performed in patients presenting with LBP without signs or symptoms indicating a potential pathological cause. Yet imaging rates remain high for many patients who present without such indications. Inappropriate imaging can lead to inappropriate treatments, results in worse health outcomes and causes harm from unnecessary radiation. There is a need to understand the extent of, and factors contributing to, inappropriate imaging for LBP, and to develop effective strategies that target modifiable barriers and facilitators. The primary study objectives are to determine: 1) The rate of, and factors associated with, inappropriate lumbar spine imaging (x-ray, CT scan and MRI) for people with non-specific LBP presenting to primary care clinicians in Ontario; 2) The barriers and facilitators to reduce inappropriate imaging for LBP in primary care settings. Methods The project will comprise an inception cohort study and a concurrent qualitative study. For the cohort study, we will recruit 175 primary care clinicians (50 each from physiotherapy and chiropractic; 75 from family medicine), and 3750 patients with a new episode of LBP who present to these clinicians. Clinicians will collect data in the clinic, and each participant will be tracked for 12 months using Ontario health administrative and self-reported data to measure diagnostic imaging use and other health outcomes. We will assess characteristics of the clinicians, patients and encounters to identify variables associated with inappropriate imaging. In the qualitative study we will conduct in-depth interviews with primary care clinicians and patients. Discussion This will be the first Canadian study to accurately document the extent of the overuse of imaging for LBP, and the first worldwide to include data from the main healthcare professions offering primary care for people with LBP. This study will provide robust information about rates of inappropriate imaging for LBP, along with factors associated with, and an understanding of, potential reasons for inappropriate imaging