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Abstract Northern regions are warming faster than the rest of the globe. It is difficult to predict ecosystem responses to warming because the thermal sensitivity of their biophysical components varies. Here, we present an analysis of the authors’ expert judgment regarding the sensitivity of six ecosystem components – permafrost, peatlands, lakes, snowpack, vegetation, and endothermic vertebrates – across northern landscapes ranging from boreal to polar biomes. We identified 28 discontinuous component states across a 3700 km latitudinal gradient in northeastern North America and quantified sensitivity as the transition time from an initial to a contrasting state following a theoretical step change increase in mean annual air temperature of 5 °C. We infer that multiple interconnected state shifts are likely to occur within a narrow subarctic latitudinal band at timescales of 10 to more than 100 years, and response times decrease with latitude. Response times differ between components and across latitudes, which is likely to impair the integrity of ecosystems.

Diatoms are reliable environmental bioindicators, but their application in coastal environments remains limited. Substrate has been put forward in the literature as an important variable in determining diatom habitat preferences. This study focuses on benthic diatom assemblages and their relationship with substrate specificity in a subarctic tidal environment, which could be relevant for environmental monitoring and management. A variety of substrates were sampled and physicochemical variables measured in various areas of the Bay of Sept-Îles region (northern Gulf of Saint-Lawrence, Canada). We recorded 606 species at 14 sites from 11 substrate types to determine the associations between diatoms and their habitats. Our results suggest that the variability of assemblages in the bay is the result of a combination of the identified variables (temperature, salinity, and total dissolved solids), explaining 26.5% of the variation, and other unmeasured variables (e.g., nutrients, wave action, and currents). Substrate was not identified as a significant variable in the statistical analyses. However, some common species in the surveyed assemblages appeared to show preferences for the substrates they colonized.

This pilot study presents surface sediment diatom assemblages in four alpine lakes in the Zelengora Mountains. The four lakes are distributed across an alpine treeline, spanning temperate mixed forest and treeless alpine tundra zones, thus offering an excellent opportunity to study the interaction of physicochemical properties and biotic communities in different alpine lake settings. A total of 52 taxa from 28 genera were identified, with only one taxon (Staurosirella neopinnata) present in every lake. In the Orlovačko, Donje Bare and Crno lakes, the diatom assemblages were mainly comprised of benthic and tychoplanktonic species, as opposed to the Kotlaničko Lake where the planktonic Lindavia radiosa was the most abundant species. Our results identified water turbidity, macrophytes and pH to be the prevailing environmental factors which influence the diatom assemblage composition in the studied lakes. The results of this study also represent a starting point in establishing biomonitoring programmes for the sustainable management of these alpine aquatic ecosystems in a rapidly changing environment.

The Bécancour River in southern Quebec (Canada) has evolved under the influence of the long asbestos mining history of the Thetford Mines region (1877–2011 Common Era; CE). This river originates at the outflow of Lake Bécancour, flows through the old mining sites, and then widens to successively form Stater Pond, Trout Lake, Lake William, and Lake Joseph (25 km from the closest mine). Our objective was to assess asbestos fiber contamination in dated sediment cores retrieved at these sites by means of transmission electron microscopy. Chrysotile was the most abundant form of asbestos identified in the samples. Asbestiform actinolite and tremolite were also found. Our results revealed that precolonial sediments deposited at 4 out of the 5 study sites naturally contained asbestos fibers (up to 3.5 wt%), with mass accumulation rates historically reaching up to 1.0 mg cm−2 yr−1. However, fiber concentrations were greatly enhanced in the anthropogenic horizon of all sediment cores. The highest concentrations (up to 6.9 wt%) were found in layers from Stater Pond and Trout Lake deposited during the maximum of regional mining activities (1945‒1980 CE). Likewise, reconstructed mass accumulation rates indicated that asbestos fiber influx peaked (up to 38.6 mg cm−2 yr−1) during this epoch in all water bodies located downstream from Thetford Mines at magnitudes consistent with their proximity to the mining sites. They decreased after 1980 EC (≤ 24.4 mg cm−2 yr−1) following the decline of regional mining activities and improvement of air quality. Modern sediments of all study sites (including upstream Lake Bécancour) were nevertheless still highly enriched in asbestos fibers (up to 4.4 wt%), which can be attributed to intensive mining waste erosion in the lake catchments. Our study highlights that asbestos fiber contamination is important and widespread in the Bécancour River basin, which raises human and ecosystem health concerns.

Climate fluctuations and landscape evolution, with their associated impacts on northern coastal ecosystems, likely influenced human populations of Nunatsiavut who have inhabited the region for nearly 7000 years. As part of an interdisciplinary research initiative within the Nain Archipelago on the subarctic coast of Labrador, this project sought to reconstruct the postglacial palaeoclimatic and palaeoenvironmental variability of Dog Island and document its impacts on the evolution of lakes located in the vicinity of significant archaeological sites. To address these questions, we analysed physical, geochemical, and biological indicators preserved in sediment cores of two lakes. Results from Oakes Bay West Lake revealed gradual acidification since ca. 4900 cal. yr BP, coherent with terrestrial vegetation development and/or neoglacial cooling, interrupted by periods of milder climatic conditions (ca. 4900–3640 cal. yr BP and ca. 1520 cal. yr BP—present) that favoured large sediment inputs. Evilik Lake revealed the classic sequence of isolation of the basin in three major phases in response to glacio-isostatic rebound. These complementary results allowed for the development of a local palaeoenvironmental framework that contributes to a better understanding of how landscape evolution and climate have influenced human societies through site availability and proximity to marine resources, and how, in turn, they impacted their immediate environment through activities, such as wood harvesting and its associated effects on nutrients and lake sediment inputs.