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Covering 55% of Canada's total surface area and stretching from coast to coast to coast, the Canadian boreal zone is crucial to the nation's economic and ecological integrity. Although often viewed as relatively underdeveloped, it is vulnerable to numerous stressors such as mining, forestry, and anthropogenic climate change. Natural archives preserved in lake sediments can provide key insights by quantifying pre-disturbance conditions (pre-1850 CE) and the nature, magnitude, direction, and speed of environmental change induced by anthropogenic stressors over the past ~150 years. Here, we paired a review of paleolimnological literature of the Canadian boreal zone with analyses of published sediment core data to highlight the effects of climate change, catchment disturbances, and atmospheric deposition on boreal lakes. Specifically we conducted quantitative syntheses of two lake health indicators: elemental lead (Pb) and chlorophyll a. Segmented regressions and Mann--Kendall trend analysis revealed a generally increasing trend in elemental Pb across the boreal zone until ~1970 CE, followed by a generally decreasing trend to the present. Snapshot comparisons of sedimentary chlorophyll a from recent and pre-industrial sediments (i.e., top-bottom sediment core design) revealed that a majority of sites have increased over time, suggesting a general enhancement in lake primary production across the boreal zone. Collectively this body of work demonstrates that long-term sediment records offer a critical perspective on ecosystem change not accessible through routine monitoring programs. We advocate using modern datasets in tandem with paleolimnology to establish baseline conditions, measure ecosystem changes, and set meaningful management targets. Key words: paleolimnology, Taiga, metals, eutrophication, environmental monitoring, Introduction Stretching across the circumpolar north, the boreal zone is central to the economic and ecological integrity of the eight countries that host this ecosystem (Brandt 2009). Within the boreal [...]

Microplastics, i.e., plastic particles in the size range of planktonic organisms, have been found in the water columns and sediments of lakes and rivers globally. The number and mass of plastic particles drifting through a river can exceed those of living organisms such as zooplankton and fish larvae. In freshwater sediments, concentrations of microplastics reach the same magnitude as in the world's most contaminated marine sediments. Such particles are derived from a unique biogeochemical cycle that ultimately influences productivity, biodiversity, and ecosystem functioning. Furthermore, microplastics act as vectors of toxic substances to invertebrates, fishes, herpetofauna, and waterfowl. We contend that the concentration of this distinct particle component is an ecologically significant parameter of inland waterbodies because of its ubiquity, environmental persistence, and interactions with key ecological processes. No environmental field survey that has searched for microplastics has yet failed to detect their presence. Standardized limnological protocols are needed to compare spatio-temporal variation in the concentration of microplastics within and across watersheds. Data obtained from such protocols would facilitate environmental monitoring and inform policy for managing plastic waste; furthermore, they would enable more accurate modeling of contaminant cycling and the development of a global plastic budget that identifies sources, distribution and circulation pathways, reservoir size, and retention times. Key words: microplastics, freshwater ecosystems, food webs, limnology, contaminants, monitoring, plastic budget, biogeochemical cycles. Des microplastiques - des particules de plastique de la taille d'organismes planctoniques - ont ete trouves dans les colonnes d'eau et les sedimentsdes lacs et desrivieresdansle monde entier. Le nombre et la masse desparticules plastiquesderivant dans une riviere peuvent depasser ceux des organismes vivants tels que le zooplancton et les larves de poisson. Dans les sediments d'eau douce, les concentrations de microplastiques atteignent la meme ampleur que dans les sediments marins les plus contamines au monde. Ces particules proviennent d'un cyclebiogeochimiqueuniquequi, ultimement, influence la productivite, la biodiversite et le fonctionne-ment des ecosystemes. En outre, les microplastiques agissent comme des vecteurs de substances toxiques pour les invertebres, les pois-sons, l'herpetofaune et les oiseaux aquatiques. Les auteurs soutiennent que la concentration de ce composant particulaire distinct constitue un parametre ecologquement significatif des masses d'eau interieures en raison de son ubiquite, de sa persistance dans l'en-vironnement et de ses interactions avec des processus ecologiques cles. Aucune etude environnementale de terrain qui a recherche des microplastiques n'a encore manque de detecter leur presence. Des protocoles limnologiques normalises sont necessaires pour comparer les variations spatio-temporelles de la concentration de microplastiques dans et entre les bassins versants. Les donnees obtenues grace a de tels protocoles faciliteraient la surveillance environnementale et eclaireraient les politiques de gestion des dechets plastiques; par ail-leurs, elles permettraient une modelisation plus precise du cycle des contaminants et l'elaboration d'un bilan plastique mondial qui identifie les sources, les voies de distribution et de circulation, la taille des reservoirs et les temps de retention. [Traduit par la Redaction] Mots-cles : microplastiques, ecosystemes d'eau douce, reseaux alimentaires, limnologie, contaminants, surveillance, bilan plastique, cycles biogeochimiques., Introduction Plastics are engineered from long repeating chains of carbon molecules derived from oil and natural gas to produce a final product with desirable properties such as strength, rigidity or [...]

Little is known about the current state of freshwater biodiversity in Canada, one of the countries with the greatest amount of surface waters in the world. To address this knowledge gap, we compiled a list of all available assessments of conservation status for freshwater species (over 3000 taxa) and further evaluated the overall status of six distinct taxonomic groups, focusing on organisms reliant on fresh waters (i.e., aquatic plants, invertebrates (with a focus on freshwater mussels), fishes, herpetofauna (reptiles and amphibians), birds, and mammals). Overall, 11.7% of all freshwater species of plants and animals assessed were found to be 'at risk' (i.e., listed as 'Threatened', 'Endangered', or 'Extirpated') and 17.9% identified as 'Special Concern'. We found that 37.9% of species lacked sufficient data to enable their status to be assessed. Data gaps in Canada's assessment of its freshwater species were most prevalent in invertebrates (excluding freshwater mussels). Given the alarming state of freshwater biodiversity in Canada, we conclude by providing recommendations that focus on evaluating temporal trends and informing conservation actions. Les connaissances sur l'etat actuel de la biodiversite des especes d'eau douce au Canada, un des pays disposant de la plus grande quantite d'eau de surface au monde, sont limitees. Pour examiner cette lacune, nous avons compile une liste de toutes les evaluations disponibles du statut de conservation d'especes d'eau douce (plus de 3000 taxons) et evalue en outre le statut global de six groupes taxonomiques distincts, en mettant l'accent sur les organismes dependant des eaux douces (c.-a-d., les plantes aquatiques, les invertebres (plus particulierement les mulettes), les poissons, l'herpetofaune (reptiles et amphibiens), les oiseaux et les mammiferes). Globalement, 11,7 % de toutes les especes d'eau douce de plantes et d'animaux evaluees sont << en peril >> (c.-a-d., designees << menacees >>, << en voie de disparition >> ou << disparue au pays >>) et 17,9 % ont un statut de conservation << preoccupant >>. Nous constatons que les donnees disponibles sont insuffisantes pour permettre l'evaluation du statut de 37,9 % des especes. Le groupe des invertebres (a l'exception des mulettes) est celui pour lequel la prevalence des cas de manque de donnees pour l'evaluation d'especes d'eau douce au Canada est la plus grande. Au vu de l'etat alarmant de la biodiversite des especes d'eau douce au Canada, nous concluons en formulant des recommandations qui mettent l'accent sur l'evaluation des tendances dans le temps et la production de donnees pour eclairer les mesures de conservation. [Traduit par la Redaction], 1.0. Introduction Despite occupying less than 1% of the Earth's surface, the freshwater biome is home to 12% of all described species, including as much as one third of all [...]

Diatoms are key components of freshwater ecosystems and are regularly used for paleolimnological reconstructions, in which defining species optima and tolerances is fundamental for interpreting assemblage shifts in a sediment record. Here, we examined responses of diatoms across three major environmental gradients—dissolved inorganic carbon (range: 0.1–230.5 mg · L−1), total phosphorus (range: 3–326 μg · L−1), and maximum lake depth (range: 0.9–55.0 m)—taken from 158 lakes from across Canada. The lakes were sampled as part of the LakePulse Network, which conducted a standardized sampling of lakes spanning 12 Canadian ecozones. Hierarchical logistic regression was used to model the species responses of 37 common taxa, and species optima and tolerances were calculated with weighted average modeling. The most common response detected was the symmetrical unimodal model, suggesting we likely captured the full environmental ranges for many species, although skewed unimodal responses were also common. Indicator species analyses identified taxa with high predictive values and fidelities to particular ecozones, with high‐nutrient‐adapted taxa such as Stephanodiscus spp. and Cyclotella meneghiniana characteristic of the agriculturally productive Prairie region. The Prairies stood out in the dataset as the region with the most unique flora from the local contribution to beta diversity analysis. Overall, the autecological data provided by our study will allow for improved interpretations of paleolimnological records and other biomonitoring efforts, addressing management concerns and contributing to a better understanding of our changing environment. [ABSTRACT FROM AUTHOR]

Horizon scanning is a systematic approach increasingly used to explore emerging trends, issues, opportunities, and threats in conservation. We present the results from one such exercise aimed at identifying emerging issues that could have important scientific, social, technological, and managerial implications for the conservation of inland waters in Canada in the proximate future. We recognized six opportunities and nine challenges, for which we provide research implications and policy options, such that scientists, policy makers, and the Canadian society as a whole can prepare for a potential growth in each of the topic areas we identified. The issues spanned a broad range of topics, from recognizing the opportunities and challenges of community-enabled science and the need to consider the legal rights of nature, to the likely increase of pharmaceuticals in wastewater due to an aging population. These issues represent a first baseline that could help decision makers identify and prioritize efforts while simultaneously stimulate new research avenues. We hope our horizon scan will pave the way for similar exercises related to the conservation of biodiversity in Canada. L'analyse prospective est une approche systematique de plus en plus utilisee pour explorer les nouvelles tendances, questions, occasions et menaces dans le domaine de la conservation. Nous presentons les resultats d'un de ces exercices visant a cerner les questions emergentes qui pourraient etre importantes des points de vue scientifique, social, technologique et de la gestion relativement a la conservation des eaux interieures au Canada, pour l'avenir rapproche. Nous relevons six occasions a saisir et neuf defis, dont nous abordons les repercussions sur la recherche et les possibilites d'action qu'ils presentent, afin que les scientifiques, les decideurs et l'ensemble de la societe canadienne puissent se preparer en vue d'une croissance potentielle dans chacun des domaines cernes. Ces questions couvrent un vaste eventail de sujets allant de la reconnaissance des occasions et defis de la science facilitee par la collectivite et la necessite de prendre en compte les droits de la nature en vertu de la loi, a l'augmentation probable des produits pharmaceutiques dans les eaux usees en raison du vieillissement de la population. Ces questions representent un premier etat de reference qui pourrait aider les decideurs a cerner et prioriser les efforts tout en stimulant de nouvelles avenues de recherche. Nous esperons que cette analyse prospective ouvrira la voie a des exercices semblables concernant la conservation de la biodiversite au Canada. [Traduit par la Redaction], Introduction Rivers, lakes, springs, and other inland waters (i.e., all surface waters contained within lands; FAO 2008) are often classified among the most threatened ecosystems on the planet (Dudgeon et [...]

Crustacean zooplankton occupy a key position as primary consumers within lake food webs, acting as early indicators of wider ecosystem shifts that can cascade to higher trophic levels. Their communities can be assessed via water column net hauls or via sediment samples containing preserved subfossil remnants from various time periods; the latter probably integrate multiple years of data, habitats within lakes, and seasonal patterns. The degree to which such samples do or do not correspond has never been assessed across a wide variety of lake types and gradients.As part of a larger sampling of over 600 lakes across lake‐rich Canada, 85 lakes were selected along a gradient of human impact, according to contemporary catchment land use, to analyse cladoceran zooplankton assemblage relatedness among snapshot water column, contemporary and pre‐industrial sediment samples.We used a combination of ordinations and matrix correlations (RV coefficients), along with partial redundancy analyses, to determine the degree to which the different sample types were comparable and whether they responded similarly to >30 environmental variables. We also compared conclusions obtained using the full cladoceran assemblages versus pelagic‐only taxa and whether our results varied according to degree of human impact.Overall, while all sample types were correlated, congruence was highest between contemporary and pre‐industrial sediment sample types. This result could arise from the under‐representation of littoral taxa in water column samples relative to those from the sediment. In high impacted catchments, however, we observed greater similarity between water column and contemporary sediment samples, as water quality stressors potentially structure assemblages in parallel directions over time. In these modern‐day sample types and among measured variables, we identified lake depth and pH as the most important structuring variables across Canada.In this first study comparing cladoceran assemblages in water column, contemporary and pre‐industrial sediments across many lakes, we conclude that water column and sediment samples respond similarly to environmental drivers but should not be considered entirely analogous or redundant. [ABSTRACT FROM AUTHOR]

River flow regulation, fragmentation, and changes in water quality caused by dams have varying effects on aquatic biodiversity and ecosystem functions, but are not clearly resolved in boreal ecosystems. We adopted a multiscale approach to quantify fish community trajectories over 20 years using a network of sites spread across four reservoirs in two hydroelectricity complexes in northern Quebec, where other anthropogenic factors have been negligible. Across three spatial scales, we found little evidence of directional temporal trends in diversity relative to reference sites. Using beta-diversity analyses, we also detected a high degree of stability in fish composition over time and space at the complex and reservoir scales. However, changes in species assemblage following impoundment were detected at the scale of the sampling station. At this scale, we found that some species consistently benefited (coregonids and pikes) from impoundment, whereas others were detrimentally affected (suckers and one salmonid). Overall, we conclude that examining different scales is key when trying to understand the impacts of humans on biodiversity and in formulating management recommendations. La regulation du debit des rivieres, la fragmentation et les variations de la qualite de l'eau causees par les barrages ont des effets variables sur la biodiversite aquatique et les fonctions des ecosystemes, cependant, la comprehension de ces processus dans les ecosystemes boreaux est limitee. Nous avons adopte une approche a multi-echelles pour quantifier les trajectoires de communautes de poissons sur une periode de 20 ans en utilisant un reseau de sites repartis dans quatre reservoirs et deux complexes hydroelectriques dans le nord du Quebec, ou les effets d'autres facteurs anthropiques ont ete negligeables. Nous avons trouve peu d'indices de tendances temporelles directionnelles de la diversite par rapport a des sites de reference. En utilisant des analyses de la diversite beta, nous avons en outre detecte un degre eleve de stabilite de la composition de poissons dans le temps et l'espace a l'echelle du complexe et du reservoir, et ce aux trois echelles spatiales. Des variations dans l'assemblage des especes de poissons apres l'endiguement ont toutefois ete decelees a l'echelle de la station d'echantillonnage. A cette echelle, nous avons constate que l'endiguement s'avere avantageux pour certaines especes (coregonides et brochets), mais nefaste pour d'autres especes (meuniers et un salmonide). Globalement, nous concluons que l'examen a differentes echelles revet une importance cle pour la comprehension des impacts des humains sur la biodiversite et pour la formulation de recommandations de gestion. [Traduit par la Redaction], Introduction In response to increased demand for energy, many large hydroelectric dams are currently in operation or are being constructed (Grill et al. 2015; Winemiller et al. 2016). Dams such [...]

North temperate and boreal lakes are affected by a complex suite of anthropogenic stressors, yet little is known about how these ecosystems are faring across the most lake‐rich nation, Canada. The NSERC Canadian Lake Pulse Network is the first large‐scale national survey of its kind, with the aim of assessing the health of Canadian lakes, determined by the deviation of key variables from baseline pre‐industrial conditions (pre‐1880 CE).We examined midge remains (chironomids and Chaoborus) from modern and pre‐industrial sediment intervals in 67 lakes, spanning a range of sizes, ecozones, and degrees of catchment land‐use change. A marked northwest/southeast divide was evident in the modern chironomid assemblages, which was partially associated with water quality, physiographical and climatic variables, with a small portion of the variance explained by geography alone.Between the pre‐industrial and modern sediment intervals, taxa typically found in warmer waters increased across the country (p < 0.001); this pattern also was evident in the littoral assemblages (p = 0.01), providing additional support for the influence of warming.Turnover in chironomid assemblages varied across trophic classes. Mesotrophic lakes showed increases in macrophyte‐associated taxa, whereas eutrophic lakes showed declines in littoral taxa, perhaps reflecting increased turbidity, and the increase of low‐oxygen‐tolerant profundal taxa in eutrophic lakes with high human impacts.Overall, the distribution and dynamics of chironomid assemblages across Canadian lakes appear to be strongly linked to changes in climate and deep‐water oxygen conditions. [ABSTRACT FROM AUTHOR]

Declines in freshwater quality resulting from anthropogenic nutrient input remain a persistent issue worldwide. Yet, we still have a limited understanding of the magnitude and scale at which most lakes have been affected by human activities, namely Land Use/Land Cover (LULC) alterations. In response, the NSERC Canadian Lake Pulse Network has compiled the first nationwide systematic database of lake quality metrics by surveying 664 lakes across 12 ecozones over 3 years. To assess the influence of catchment development on water quality and its spatial variation, we built generally additive models and multivariate regressions to quantify the association between watershed LULC and lake temperature, Secchi depth, as well as chlorophyll-a, limiting nutrient, and ion concentrations. We found that agricultural and urban land use explained the greatest proportion of variation in water quality among LULC categories (R2 = 0.20–0.29). Overall, our study highlights that drivers of water quality are similar across regions; however, baseline conditions vary, so freshwater ecosystem management strategies must consider their geographic context to better predict where water quality thresholds will be surpassed. [ABSTRACT FROM AUTHOR]

Analyses of sedimentary DNA (sedDNA) have increased exponentially over the last decade and hold great potential to study the effects of anthropogenic stressors on lake biota over time.Herein, we synthesise the literature that has applied a sedDNA approach to track historical changes in lake biodiversity in response to anthropogenic impacts, with an emphasis on the past c. 200 years.We identified the following research themes that are of particular relevance: (1) eutrophication and climate change as key drivers of limnetic communities; (2) increasing homogenisation of limnetic communities across large spatial scales; and (3) the dynamics and effects of invasive species as traced in lake sediment archives.Altogether, this review highlights the potential of sedDNA to draw a more comprehensive picture of the response of lake biota to anthropogenic stressors, opening up new avenues in the field of paleoecology by unrevealing a hidden historical biodiversity, building new paleo‐indicators, and reflecting either taxonomic or functional attributes.Broadly, sedDNA analyses provide new perspectives that can inform ecosystem management, conservation, and restoration by offering an approach to measure ecological integrity and vulnerability, as well as ecosystem functioning. [ABSTRACT FROM AUTHOR]

The lakes surrounding the iron ore mining region of Schefferville, Quebec, Canada, sit within a landscape of historical disturbances, two of which have been relatively well documented over time: metal contamination and nutrient loading. Based on the analysis of sediment cores, we used cladoceran zooplankton subfossil assemblages from two lakes located in Schefferville to track both alpha and beta diversity over the last 100+ years. We showed that high metal concentrations were correlated with decreased cladoceran diversity, and that the site that experienced both direct wastewater input and atmospheric metal loading (Lake Dauriat) had the greatest declines in cladoceran richness. In both lakes, turnover in cladoceran assemblages was highest in the mining period. During the period of mine closures and improvement of wastewater treatment, some decreases in metal enrichment in the sediments and increases in cladoceran richness were observed in Lake Dauriat. Overall, a combined use of species richness and beta diversity metrics showed alpha and beta diversity are not always congruent, and that there are various ways to interpret scenarios of temporal beta diversity in northern freshwater systems. Les lacs entourant la region miniere ferrifere de Schefferville (Quebec, Canada) se trouvent dans un paysage marque par des perturbations passees, dont deux sont relativement bien documentees dans le temps, a savoir la contamination par les metaux et l'apport de nutriments. A la lumiere de l'analyse de carottes de sediments, nous avons utilise des assemblages de cladoceres zooplanctoniques subfossiles provenant de deux lacs situes a Schefferville pour caracteriser les diversites alpha et beta au cours des 100 dernieres annees et plus. Nous demontrons que de fortes concentrations de metaux sont correlees a une diversite de cladoceres reduite et que le site ayant recu des apports directs d'eaux usees et des apports atmospheriques de metaux (lac Dauriat) presente les plus fortes baisses de richesse des cladoceres. Dans les deux lacs, le renouvellement des assemblages de cladoceres etait a son plus fort durant la periode d'exploitation miniere. Durant la periode des fermetures de mines et de l'amelioration du traitement des eaux usees, certaines baisses de l'enrichissement en metaux dans les sediments et augmentations de la richesse des cladoceres ont ete observees dans le lac Dauriat. Dans l'ensemble, l'utilisation combinee de mesures de la richesse specifique et de la diversite beta a permis de demontrer que les diversites alpha et beta ne concordent pas toujours et qu'il y a differentes manieres d'interpreter les scenarios de diversite beta dans le temps dans les systemes d'eau douce nordiques. [Traduit par la Redaction], Introduction Perturbation of freshwater systems is of broad concern because of their importance in providing ecosystem services (Limburg 2009), their role as biodiversity hotspots (Strayer and Dudgeon 2010), and the [...]