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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 [...]

Ruth-Roy Lake (Killarney Provincial Park, Ontario, Canada) is an ultra-oligotrophic, naturally acidic waterbody. Lakes in Killarney Provincial Park were impacted by long-range transportation of contaminants from copper-nickel smelting operations in nearby Sudbury, but recent lake monitoring indicates that Ruth-Roy Lake has been less acidic than inferred pre- industrial pH conditions. We assessed the effects of pH change, reduced sulphur emissions, and drivers of reduced acidity using biological and geochemical paleolimnological techniques. Ruth-Roy Lake experienced notable biological and chemical change over the past ~150 years. All examined proxies supported that Ruth-Roy Lake was naturally acidic but further acidified as early as ca. 1920s, with the strongest acidification signal apparent in ca. 1940s. Biological recovery in diatom and cladoceran assemblages, however, is modest. We highlight the importance of understanding reference conditions to assess ecosystem recovery and climate-mediated change in clear acidic lakes located in industrial landscapes. Key words: acidification, smelting, monitoring, paleoecotoxicology, Introduction Sudbury (Ontario, Canada) is one of the world's largest copper-nickel metal smelter centres, with base metal ores discovered in the region in the late 19th century. Since the copper [...]

Since the 1950s, the widespread application of road salt for winter road maintenance and safety in cold regions has led to increased conductivity levels in many freshwater systems. Salting practices have adversely affected freshwater biota; however, the magnitude of ecological impacts may vary by species and ecosystem. Here, we examine diatom assemblage changes during the past ~200 years from the sedimentary records of five impacted lakes (measured specific conductance values of 149-350 [micro]S * [cm.sup.-1]) and a reference lake (18 [micro]S * [cm.sup.-1]) located in the Muskoka River Watershed, south-central Ontario, Canada. Diatom compositional changes in the road-salt-impacted sites were consistent with increasing conductivity and increased diatom-inferred (Dl)-conductivity was evident during the latter half of the 20th century in the impacted lakes, concurrent with known road-salt application. The strongest predictor of DI-conductivity changes among the six lakes was the kilometre equivalents of roads within the watershed (i.e., kilometres of road x number of lanes). Similar to changes observed in a previous study focusing on cladoceran assemblages, we conclude that even modest applications of road salt can affect diatom assemblages in softwater lakes. Depuis les annees 1950, l'epandage repandu de sel de voirie pour l'entretien hivernal et la surete des routes en regions froides s'est traduit en des degres de conductivite accrus dans de nombreux systemes d'eau douce. Si les pratiques d'epandage de sel ont eu des effets deleteres sur le biote d'eau douce, l'ampleur des impacts ecologiques pourrait varier d'une espece et d'un ecosysteme a l'autre. Nous examinons les modifications d'assemblages de diatomees au cours des ~200 dernieres annees a partir de registres sedimentaires de cinq lacs degrades (valeurs de conductance specifique mesurees de 149-350 [micro]S * [cm.sup.-1]) et d'un lac de reference (18 [micro]S * [cm.sup.-1]) situes dans le bassin versant de la riviere Muskoka (centre-sud de l'Ontario, Canada). Les changements de la composition de diatomees dans les sites ayant subi les impacts du sel de voirie concordent avec une conductivite croissante, et une augmentation de la conductivite inferee a partir des diatomees (conductivite ID) est evidente durant la deuxieme moitie du 20e siecle dans les lacs degrades, coincidant avec l'epandage connu de sel de voirie. Le predicteur de changements de la conductivite ID le plus fort pour les six lacs est le nombre d'equivalents kilometres de route dans le bassin versant (c.-a-d. kilometres de route multiplies par le nombre de voies). Nous concluons que, a l'instar des changements observes dans une etude anterieure portant sur des assemblages de cladoceres, meme des epandages modestes de sel de voirie peuvent avoir une incidence sur les assemblages de diatomees dans les lacs d'eau douce. [Traduit par la Redaction], Introduction Winter road de-icing has contributed to increases in conductivity and chloride ([Cl.sup.-]) concentrations in many freshwater systems across North America and Europe (Dugan et al. 2017). Since the onset [...]

Meromictic lakes provide a physically stable environment in which proxies for potentially harmful cyanobacteria are exceptionally well-preserved in the sediments. In Sunfish Lake, a meromictic lake that has recently become the focus of citizen concern due to the apparent rise in cyanobacteria blooms, we used a multi-proxy paleolimnological approach pairing novel spectral (i.e., VNIRS) and molecular (i.e., qPCR) assessment tools to explore long-term cyanobacteria trends. We hypothesized that climate change over the past 50 years altered the Sunfish Lake environment to favour cyanobacteria dominance, resulting in an increased incidence of bloom events. Spectral and genetic results aligned to reveal an unprecedented abundance of cyanobacteria in modern times and coincided with warmer and wetter climatic conditions in the region. Our findings offer evidence for climate-driven shifts in cyanobacteria abundance and suggest that a shift towards warmer and wetter conditions supports the rise of cyanobacteria in lakes. Les lacs meromictiques offrent un milieu stable sur le plan physique dans lequel des caracteristiques temoignant de la presence de cyanobacteries potentiellement nocives sont exceptionnellement bien preservees dans les sediments. Pour le lac Sunfish, un lac meromictique qui suscite depuis peu l'inquietude de citoyens en raison de la hausse apparente de proliferations de cyanobacteries, nous avons utilise une approche paleolimnologique basee sur plusieurs variables substitutives qui jumele de nouveaux outils devaluation spectrale (c.-a-d. VNIRS) et moleculaire (c.-a-d. qPCR) afin d'explorer les tendances a long terme des cyanobacteries. Nous avons postule que les changements climatiques au cours des 50 dernieres annees ont modifie le milieu du lac Sunfish de maniere a favoriser une domination des cyanobacteries qui se traduit par une incidence accrue de proliferations. Les resultats spectraux et genetiques temoignent tous deux d'une abondance sans precedent de cyanobacteries au cours des dernieres decennies coincidant avec des conditions climatiques plus chaudes et humides dans la region. Nos constatations soutiennent l'interpretation de variations induites par le climat de l'abondance de cyanobacteries et indiqueraient que le passage vers des conditions plus chaudes et humides appuie l'augmentation de cyanobacteries dans les lacs. [Traduit par la Redaction], Introduction Climate change has fundamentally reshaped ecosystems on a global scale, with freshwater lakes being particularly vulnerable due to their predisposition to incorporate atmospheric and terrestrial responses (Adrian et al. [...]

Anthropogenic waterways and canal systems have been part of the cultural and natural landscape for thousands for years. As of the late 20th century, more than 63 000 km of canals exist worldwide as transport routes for navigation, many with barriers (e.g., locks, dams) that fragment the system and decrease connectivity. Fragmentation alone can have negative implications for freshwater biodiversity; by isolating populations and communities, other human-mediated disturbances associated with canals like poor water quality and invasive species can exacerbate these negative effects. As such, the capacity of these interconnected freshwater systems to support biodiversity is continuously degrading at a global level. One critical, highly complex issue that unites canals worldwide is the challenge of governing these systems in a holistic, unified way to both protect biodiversity and preserve historical elements. Managing historic canals involves multiple objectives across many agencies and stakeholders, often with different or conflicting objectives. Here, we use the Rideau Canal, a UNESCO World Heritage Site and National Historic Site of Canada, as a case study to demonstrate the importance of considering canals as social-ecological systems for effective and efficient governance. Historic canals are integrated systems of both humans (social) and the environment (ecological), linked by mutual feedbacks and coevolution, and must be managed as such to achieve conservation goals while maintaining commemorative integrity. We discuss the history of the Rideau Canal and its current governance, biodiversity in the waterway, different threats and issues (user conflicts, aquatic pollution, shoreline development, water management, species at risk, and invasive species), and conclude by outlining ways to address the challenges of managing it as a coupled social-ecological system. We present different research needs and opportunities that would enable better management, though above all, we propose a shift from the current governance structure--which at best can be considered 'patchwork'--to a coordinated, multi-scalar and multi-stakeholder governance regime such that the Rideau Canal can be maintained for its historical integrity without compromising biodiversity conservation. Given that canals are now pervasive worldwide, this article is not only topical to the Rideau Canal, but also to other waterways in Canada and beyond. Key words: social-ecological system, adaptive governance, resilience, biodiversity conservation, aquatic connectivity. Les voies navigables et les systemes de canaux anthropiques font partie du paysage culturel et naturel depuis des milliers d'annees. a la fin du 20 (e) siecle, plus de 63 000 km de canaux existent dans le monde comme voies de transport pour la navigation, dont beaucoup comportent des barrieres (par exemple, des ecluses, des barrages) qui fragmentent le systeme et reduisent la connectivite. La fragmentation a elle seule peut avoir des repercussions negatives sur la biodiversite des eaux douces; en isolant les populations et les communautes, d'autres perturbations d'origine humaine associees aux canaux, comme la mauvaise qualite de l'eau et la presence d'especes envahissantes, peuvent exacerber ces effets negatifs. Ainsi, la capacite de ces systemes d'eau douce interconnectes a soutenir la biodiversite se degrade continuellement a l'echelle mondiale. Un probleme crucial et tres complexe qui unit les canaux a travers le monde est le defi de gerer ces systemes de maniere holistique et unifiee afin de proteger la biodiversite et de preserver les elements historiques. La gestion des canaux historiques implique des objectifs multiples entre de nombreuses agences et parties prenantes, qui ont souvent des objectifs differents ou contradictoires. Les auteurs utilisent ici le canal Rideau, site du patrimoine mondial de l'UNESCO et site historique national du Canada, comme etude de cas pour demontrer l'importance de considerer les canaux comme des systemes socioecologiques pour une gouvernance efficace et efficiente. Les canaux historiques sont des systemes integres a la fois de l'humain (social) et de l'environnement (ecologique), lies par des retroactions mutuelles et une coevolution, et ils doivent etre geres comme tels pour atteindre les objectifs de conservation tout en maintenant leur integrite commemorative. Les auteurs discutent de l'histoire du canal Rideau et de sa gouvernance actuelle, de la biodiversite de la voie navigable, des differentes menaces et preoccupations (conflits entre utilisateurs, pollution aquatique, amenagement des rives, gestion de l'eau, especes en peril et especes envahissantes), et ils concluent en decrivant des moyens de relever les defis de sa gestion en tant que systeme socioecologique couple. Ils presentent differents besoins et possibilites de recherche qui permettraient une meilleure gestion, mais surtout, ils proposent de passer de la structure de gouvernance actuelle--qui, au mieux, peut etre consideree comme une << mosaique >>--a un regime de gouvernance coordonne, multiscalaire, et multiacteurs, de sorte que le canal Rideau puisse etre maintenu dans son integrite historique sans compromettre la conservation de la biodiversite. Puisque les canaux sont desormais omnipresents dans le monde entier, cet article n'est pas seulement d'actualite pour le canal Rideau, mais aussi pour d'autres voies navigables au Canada et ailleurs dans le monde. [Traduit par la Redaction] Mots-cles : systeme socioecologique, gouvernance adaptative, resilience, conservation de la biodiversite, connectivite aquatique., Introduction For thousands of years, humans have modified natural waterways (e.g., lakes, rivers) and created others where they did not exist. The first canals constructed were done so by Mesopotamians [...]

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 [...]

Arctic freshwater ecosystems are on the "frontline" of climate change, but due to a lack of direct long‐term monitoring data, indirect approaches, such as algal‐based paleolimnology, must be used to reconstruct past limnological conditions. Our understanding of the responses of small‐ to mid‐sized Arctic lakes to climate warming has increased over the last ~30 years. However, until recently, little was known about even the basic limnological conditions of Canada's "Northern Great Lakes," such as Lake Hazen, Great Bear Lake, and Great Slave Lake. In this summary, we show that a continuum of algal changes, observable in the sedimentary archives of shallow ponds to very large Arctic lakes, signals the crossing of key aquatic thresholds linked to changing ice covers and thermal regimes, declining wind speeds, and other climate‐related variables. With recent accelerated warming, even the largest and most resilient Arctic waterbodies are now fundamentally different than they were just a few decades ago. These changes will undoubtedly cascade throughout the food web leading to important changes for local Indigenous populations as well as the global community. [ABSTRACT FROM AUTHOR]

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]