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Understanding how animals respond to large-scale environmental changes is difficult to achieve because monitoring data are rarely available for more than the past few decades, if at all. Here, we demonstrate how a variety of palaeoecological proxies (e.g. isotopes, geochemistry and DNA) from an Andean Condor ( Vultur gryphus ) guano deposit from Argentina can be used to explore breeding site fidelity and the impacts of environmental changes on avian behaviour. We found that condors used the nesting site since at least approximately 2200 years ago, with an approximately 1000-year nesting frequency slowdown from ca 1650 to 650 years before the present (yr BP). We provide evidence that the nesting slowdown coincided with a period of increased volcanic activity in the nearby Southern Volcanic Zone, which resulted in decreased availability of carrion and deterred scavenging birds. After returning to the nest site ca 650 yr BP, condor diet shifted from the carrion of native species and beached marine animals to the carrion of livestock (e.g. sheep and cattle) and exotic herbivores (e.g. red deer and European hare) introduced by European settlers. Currently, Andean Condors have elevated lead concentrations in their guano compared to the past, which is associated with human persecution linked to the shift in diet.

Increases in oil sands mining operations in the Athabasca oil sands region have resulted in increased concentrations of polycyclic aromatic compounds (PACs) and heavy metals in aquatic systems located near surface mining operations. In the present study, sediment cores were collected from 3 lakes with varying proximity to surface mining operations to determine the differences in PAC concentrations. Sediment cores were separated into 2 sections-current mining (top; 2000-2017) and premining (bottom; pre-1945)-and extracts were prepared for in vitro screening using a well-established chicken embryonic hepatocyte (CEH) assay. Concentrations and composition of PACs varied between sites, with the highest ∑PACs in Saline Lake, 5 km from an active oil sands mine site. The proportion of alkylated PACs was greater than that of parent PACs in the top sediment sections compared with the bottom. Ethoxyresorufin-O-deethylase activity in CEH permitted the ranking of lake sites/core sections based on an aryl hydrocarbon receptor-mediated end point; mean median effect concentration values were lowest for the top cores from Saline Lake and another near-mining operations lake, referred to as WF1. A ToxChip polymerase chain reaction (PCR) array was used to evaluate gene expression changes across 43 target genes associated with numerous toxicological pathways following exposure to top and bottom sediment core extracts. The 2 study sites with the greatest ∑PAC concentrations (Saline Lake and WF1) had the highest gene expression alterations on the ToxChip PCR array (19 [top] and 17 [bottom]/43), compared with a reference site (13 [top] and 7 [bottom]/43). The avian in vitro bioassay was useful for identifying the toxicity of complex PAC extracts associated with variably contaminated sediment cores, supporting its potential use for hotspot identification and complex mixture screening. EnvironToxicol Chem 2021;40:1883-1893. © 2021 SETAC.

Seabirds in the Canadian Arctic congregate in large colonies, producing oases of biological productivity and diversity in coastal regions. Here, we examined sterols, stanols, and stable isotopes (δ15N and δ13C) in three 14C-dated pond sediment cores near a large seabird colony and archaeological site on Devon Island (Nunavut, Canada), showing historical occupation by the seabirds and an ancient human (Thule or Norse) settlement over an ∼1100 yr time period. Coprostanol in the sediment records captures the presence of humans at ca. 1150 CE, followed by their abandonment of the site by ca. 1300 CE. Increased seabird presence at this site after ca.1200 CE is indicated by increases in δ15N and cholesterol/sitosterol. Seabird population expansion is observed after ca. 1600 CE in δ15N and cholesterol/sitosterol profiles, coinciding with European whaling activities that expanded in the seventeenth through nineteenth centuries. Our study provides insights into human and seabird occupation in the High Arctic to inform archaeological and conservation efforts.

International audience; Recent estimates indicate that ∼70% of the world’s seabird populations have declined since the 1950s due to human activities. However, for almost all bird populations, there is insufficient long-term monitoring to understand baseline (i.e., preindustrial) conditions, which are required to distinguish natural versus anthropogenically driven changes. Here, we address this lack of long-term monitoring data with multiproxy paleolimnological approaches to examine the long-term population dynamics of a major colony of Leach’s Storm-petrel (Hydrobates leucorhous) on Grand Colombier Island in the St. Pierre and Miquelon archipelago—an overseas French territory in the northwest Atlantic Ocean. By reconstructing the last ∼5,800 y of storm-petrel dynamics, we demonstrate that this colony underwent substantial natural fluctuations until the start of the 19th century, when population cycles were disrupted, coinciding with the establishment and expansion of a European settlement. Our paleoenvironmental data, coupled with on-the-ground population surveys, indicate that the current colony is only ∼16% of the potential carrying capacity, reinforcing concerning trends of globally declining seabird populations. As seabirds are sentinel species of marine ecosystem health, such declines provide a call to action for global conservation. In response, we emphasize the need for enlarged protected areas and the rehabilitation of disturbed islands to protect ecologically critical seabird populations. Furthermore, long-term data, such as those provided by paleoecological approaches, are required to better understand shifting baselines in conservation to truly recognize current rates of ecological loss.

The discovery of two undisturbed caves in Jamaica with 14C and 210Pb dating indicating that the oldest layers of guano were ca. 200 years old in the first cave (81 cm long core), and as much as 4300 years old in the second cave (129 cm long core) provides exciting possibilities to examine past ecological communities. We analyzed genetic and pollen profiles in these ancient bat guano deposits and revealed DNA sequences most similar to arthropods, mainly insects such as caddisflies (Trichoptera), butterflies (Lepidoptera) and mayflies (Ephemeroptera), suggesting a potential source for past dietary data. Palynological analysis failed to recover well-preserved pollen grains and spores older than ca. 200 years, however in layers preserving pollen, angiosperms were the most abundant plants observed, with a regular occurrence of the potato (Solanaceae) and pepper families (Piperaceae), which are frequently bat-dispersed. In general, changes in frequency of particular plant taxa appear to reflect changes of vegetation and land use in the cave vicinity; however, some changes could be linked to hurricanes, leading to forest canopy damage and promoting the growth of light-demanding species such as guarumo (Cecropia). Higher amounts of mangrove (Rhizophora) pollen have also been recorded in the periods of heavy hurricane activities. Our data highlight the value of bat guano deposits in caves as a resource for the analysis of past ecological systems and stress the conservation values of these deposits.

Korosi JB, Thienpont JR, Eickmeyer DC, Kimpe LE, Blais JM. 2020. A paleolimnological approach for interpreting aquatic effects monitoring at the Diavik Diamond Mine (Lac de Gras, Northwest Territor...

Seabird population size is intimately linked to the physical, chemical, and biological processes of the oceans. Yet, the overall effects of long-term changes in ocean dynamics on seabird colonies are difficult to quantify. Here, we used dated lake sediments to reconstruct ~10,000-years of seabird dynamics in the Northwest Atlantic to determine the influences of Holocene-scale climatic oscillations on colony size. On Baccalieu Island (Newfoundland and Labrador, Canada)-where the world's largest colony of Leach's storm-petrel (Hydrobates leucorhous Vieillot 1818) currently breeds-our data track seabird colony growth in response to warming during the Holocene Thermal Maximum (ca. 9000 to 6000 BP). From ca. 5200 BP to the onset of the Little Ice Age (ca. 550 BP), changes in colony size were correlated to variations in the North Atlantic Oscillation (NAO). By contrasting the seabird trends from Baccalieu Island to millennial-scale changes of storm-petrel populations from Grand Colombier Island (an island in the Northwest Atlantic that is subjected a to different ocean climate), we infer that changes in NAO influenced the ocean circulation, which translated into, among many things, changes in pycnocline depth across the Northwest Atlantic basin where the storm-petrels feed. We hypothesize that the depth of the pycnocline is likely a strong bottom-up control on surface-feeding storm-petrels through its influence on prey accessibility. Since the Little Ice Age (LIA), the effects of ocean dynamics on seabird colony size have been altered by anthropogenic impacts. Subsequently, the colony on Baccalieu Island grew at an unprecedented rate to become the world's largest resulting from favorable conditions linked to climate warming, increased vegetation (thereby nesting habitat), and attraction of recruits from other colonies that are now in decline. We show that although ocean dynamics were an important driver of seabird colony dynamics, its recent influence has been modified by human interference.

Previous paleolimnological investigations have examined the effects of gold mining operations, local land-use changes, and regional climate warming on the aquatic biota from shallow lakes in Yellowknife, Northwest Territories, Canada. However, the long-term impacts of these multiple environmental stressors on the biota of deeper lakes that support large-bodied fish species have not been investigated. In this study, we examined multiple sedimentary proxies from two deep lakes around Yellowknife to assess the long-term effects of metalloid contamination, development of the city, and recent warming over the past ~ 200 years. The sedimentary metalloid profiles tracked the influence of mining operations and local land-use changes in the Yellowknife area and there were some similarities in the diatom responses to multiple stressors across the two lakes. However, the increases in sedimentary metalloid concentrations, eutrophic diatom taxa, and whole-lake primary production were more pronounced at Grace Lake relative to Alexie, likely because Grace is located nearer to the gold mines, as well as local city development. The overall lake primary production and the relative abundance of the planktonic diatom Discostella stelligera increased at both sites suggesting that some of the biological changes may be influenced by changes in thermal stratification, as has been documented in a wide spectrum of lakes across the Northern Hemisphere. Furthermore, the diatom assemblage changes in these deep lakes differed from those observed from shallow lakes in the region, suggesting that site-specific limnological characteristics will influence the biological responses to multiple environmental stressors through time.

Marked increases in ring-billed gulls and double-crested cormorants in the Laurentian Great Lakes during the last century have garnered attention over their ecological impacts, sparking debates about management strategies. However, monitoring data are generally sparse and of short duration for these colonies, hampering the ability to place recent changes within long-term context. Sediment records from ponds immediately surrounded by colonies on nesting islands can be used to track past bird populations, as they release wastes with geochemical signals that can be tracked using traditional paleolimnological methods, such as diatoms and stable isotopes of nitrogen (δ15N). Here, we provide new information about waterbird nesting histories on islands in eastern Lake Ontario that are of interest to wildlife managers. In all bird-impacted ponds, eutrophic diatom assemblages and elevated sediment chlorophyll-a coincided with high signatures of δ15N in the recent sediments, signifying bird influence. An absence of significant bird impacts in the oldest portion of one sediment core indicates that the current cormorant colony size (>2000 birds) is unprecedented over the ~150-year record. Diatoms and sediment chlorophyll-a also responded to even a small, short-duration cormorant nesting event on an actively managed reference island. Collating our findings with those from four previously studied sediment cores from nearby islands, we show that cormorants are unlikely to have occupied eastern Lake Ontario in their current numbers within the past ~150 years. However, ring-billed gulls have likely used several islands in the area for most of the 20th century (and perhaps earlier) until present.

Significance The paucity of monitoring data for seabird populations at suitable temporal and spatial scales challenges the development of realistic and effective conservation policies. We employ newly developed paleoenvironmental techniques at 10 key subarctic seaduck colonies to reconstruct broadscale population changes at decadal timescales through the 20th century. We show that harvesting practices in southwestern Greenland and northeastern Canada were unsustainable, timed with the advent of widespread use of shotguns and outboard motors for hunting across the North. Our historical population reconstructions, corroborated with two independent proxies (sterols and stable nitrogen isotopes), reaffirms that hunting restrictions were necessary to prevent the collapse of this subspecies., Where available, census data on seabirds often do not extend beyond a few years or decades, challenging our ability to identify drivers of population change and to develop conservation policies. Here, we reconstruct long-term population dynamics of northern common eiders (Somateria mollissima borealis). We analyzed sterols together with stable nitrogen isotopes in dated pond sediment cores to show that eiders underwent broadscale population declines over the 20th century at Canadian subarctic breeding sites. Likely, a rapidly growing Greenland population, combined with relocation of Inuit to larger Arctic communities and associated increases in the availability of firearms and motors during the early to mid-20th century, generated more efficient hunting practices, which in turn reduced the number of adult eiders breeding at Canadian nesting islands. Our paleolimnological approach highlights that current and local monitoring windows for many sensitive seabird species may be inadequate for making key conservation decisions.

Despite the economic benefits of the oil and gas industry in Northern Alberta, significant concerns exist regarding the impacts of increased oil production on the environment and human health. Several studies have highlighted increases in the concentrations of polycyclic aromatic compounds (PACs) and other hydrocarbons in the atmosphere, water, soil and sediments, plants, wildlife and fish in the Athabasca Oil Sands Region (AOSR) as a result of oil sands industrial activity. Sediment cores can provide information on the temporal trends of contaminants to the environment and provide important baseline information when monitoring data are absent. Here we combined analytical chemistry and a mammalian cell-based bioassay in dated lake sediment cores to assess paleotoxicity in freshwater systems in the AOSR. Sediment intervals were radiometrically dated and subsequently analysed for PACs. PAC extracts from select dated intervals were used in cell-based bioassays to evaluate their endocrine disrupting properties. We demonstrated spatial and temporal variability in the PAC composition of sediment cores around the AOSR with some of the highest concentrations of PACs detected near oil sands industrial activity north of Fort McMurray (AB) in La Saline Natural Area. Recent sediment had positive enrichment factors across most PAC analytes at this site with heavier pyrogenic compounds such as benz(a)anthracene/chrysene and benzofluoranthene/benzopyrene dominating. Our study is the first to link chemical analysis of sediment cores with biological effect assessments of endocrine activity showing feasibility of extending the usefulness of sediment cores in monitoring programs interested in complex mixture assessments. While we observed no spatial or temporal differences in ERα mediated signaling, AhR CALUX results mirrored those of the chemical analysis, demonstrating the utility of coupling biological effects assessments to historical reconstructions of contaminant inputs to the natural environment.

We examined polycyclic aromatic compounds (PACs) and petroleum biomarkers (steranes, hopanes, and terpanes) in radiometrically-dated lake sediment cores from the Athabasca oil sands region (AOSR) and the Peace-Athabasca Delta (PAD) region in Alberta (Canada) to determine whether contributions from petroleum hydrocarbons have changed over time. Two floodplain lakes in the PAD (PAD 30, PAD 31) recorded increased flux of alkylated PACs and increased petrogenic (petroleum-derived) hydrocarbons after ∼1980, coincident with a decline of sediment organic carbon content and a rise of bulk sedimentation rate, likely due to increased Athabasca River flow. A large expansion of upstream oilsands mining, upgrading, and refining may also have contributed to the observed shift to more petrogenic hydrocarbons to sediments since the 1980s. Alkylated PAC flux increased in the floodplain lake analyzed within the AOSR (Saline Lake) since the 1970s–1980s, coincident with a sharp rise in sediment organic carbon content and increased contributions of petrogenic hydrocarbons. These changes identify increased supply of petrogenic PACs occurred as Athabasca River floodwaters waned, and may implicate aerial contributions of petrogenic hydrocarbons from oilsands activity. PACs and petroleum biomarkers (steranes, hopanes, and terpanes) in sediment cores from Saline Lake, PAD 30 and PAD 31 revealed a predominance of petrogenic hydrocarbons in these lakes. In contrast, we recorded minimal petrogenic hydrocarbons in the reference lakes outside the surface minable area of the AOSR and PAD (Mariana Lake and BM11), though we noted slight increases in petrogenic contributions to modern (2010–2016) sediments. We show how a combined analysis of PACs and petroleum biomarkers in sediments is useful to quantify petrogenic contributions to lakes with added confidence and highlight the potential for petroleum biomarkers in lake sediment cores as a novel and effective method to track petroleum hydrocarbons in lake sediment.

Precious metal mining activities have left complex environmental legacies in lakes around the world, including some sites in climatically sensitive regions of the Canadian sub-Arctic. Here, we examined the long-term impacts of past regional gold mining activities on sub-Arctic lakes near Con Mine (Yellowknife, Northwest Territories) based on sediment core analysis (paleolimnology). In addition to receiving metal(loid)s from roaster stack emissions, the study lakes were also influenced by salt-rich mine drainage from Con Mine tailings. Water samples from these lakes had some of the highest concentrations for salinity-related variables (e.g. Ca2+, Cl−, Na+) and metal(loid)s (e.g. As, Cu, Ni, Sb) in the Yellowknife area. Furthermore, the presence of halophilic diatom (Bacillariophyceae) taxa (Achnanthes thermalis and Navicula incertata) in the recent sediments of Keg and Peg lakes suggest that the extreme saline conditions are strongly influencing the present biota, more than 10 years after the cessation of gold mining activities at Con Mine. The sedimentary metal(loid) profiles (e.g. As, Cu, Ni) of Kam Lake tracked the influence of regional gold mining activities, particularly those at Con Mine, while the algal assemblages recorded the biological responses to salinization and metal(loid) pollution (e.g. marked decreases in diatom species richness, Hill’s N2 diversity, and chrysophyte cyst:diatom valve ratio). At Kam Lake, the algal assemblage changes in the post-mining era were indicative of climate-mediated changes to lake thermal properties (e.g. rise in planktonic diatoms), nutrient enrichment related to urbanization (e.g. increase in eutrophic Stephanodisucs taxa), and/or a combination of both stressors. The lack of biological recovery (i.e. return to pre-mining assemblages) is consistent with investigations of mine-impacted lakes in temperate regions where elevated contaminant levels and emerging stressors (e.g. climate warming, land-use changes) are influencing lake recovery.

Following spills into water, petroleum oils can spread widely and produce surface slicks. Resulting slicks may impede volatilization and possibly increase chemical persistence in water. While the influence of oil films on chemical air-water exchange has been examined through theoretical and laboratory studies, field studies have not been conducted to assess the relevance of these effects following actual oil spill events. Here we evaluated the effect of diluted bitumen (dilbit) experimentally spilled in limnocorrals installed in a boreal lake on the volatilization of sulfur hexafluoride (SF6), a non-reactive volatile tracer gas. Dilbit spills were monitored over 70 days and SF6 was introduced twice (after 7 and 48 days) to evaluate the influence of spilled dilbit on the loss of SF6 from water. Volatilization rate constants of SF6 (kVOL) significantly decreased by up to 80% with increasing total dilbit spill cover. Using a theoretical equation, decreases in kVOL were largely explained by a reduction in open water area where chemical exchange across the air-water interface occurs. Apparent effects of the slick on SF6 mass transfer were estimated to be smaller by comparison (20%).To account for this reduction in volatilization, oil spill fate models should include a correction to consider the impact of spill cover on the air-water exchange of organic chemicals.

We examined the historical deposition of polycyclic aromatic compounds (PACs) recorded in radiometrically-dated lake sediment cores from a small, conventional oil and gas operation in the southern Northwest Territories (Cameron Hills), and placed these results in the context of previously published work from three other important regions of western Canada: (1) the Athabasca oil sands region in Alberta; (2) Cold Lake, Alberta; and (3) the Mackenzie Delta, NT. Sediment PAC records from the Cameron Hills showed no clear changes in either source or concentrations coincident with the timing of development in these regions. Changes were small in comparison to the clear increases in both parent and alkyl-substituted PACs in response to industrial development from the Athabasca region surface mining of oil sands, where parent PAC diagnostic ratios indicated a shift from pyrogenic sources (primarily wood and coal burning) in pre-development sediments to more petrogenically-sourced PACs in modern sediments. Cores near in-situ oil sand extraction operations showed only modest increases in PAC deposition. This work directly compares the history and trajectory of contamination in lake ecosystems in areas of western Canada impacted by the most common types of hydrocarbon extraction activities, and provides a context for assessing the environmental impacts of oil and gas development in the future.

Polyaromatic compounds (PACs) are by-products of combustion and are the major pollutants from the oil and gas industry. However, the mechanism of PACs induced toxicity still remains elusive. The aim of this study was to elucidate the effects of a typical mixture of PACs found in oil sand extract (OSE) on the respiratory, hepatic and nervous systems in humans using in vitro cell culture models followed by non-targeted metabolomics analysis. OSE collected from Alberta, Canada was fractionated into PAC and alkane fractions, and their effects after 24 h exposure on the cell viability measured by MTT assay in three human cell lines (A549, HepG2, and SK-N-SH) were studied. The PAC fractions showed significant dose-dependent cytotoxicity. A549 cells showed the highest sensitivity to OSE extracts, followed by SK-N-SH and HepG2. In contrast, the alkane fractions showed no effects on cell viability. The three human cell lines were further exposed with the PACs at 10% and 20% lethal concentration for 24 h. Metabolomics analysis of the cell extracts indicated that PACs treatments showed different disruptions on possible metabolic pathways on the three cell lines. PACs altered the sex steroid hormone metabolism and regulated the levels of leukotrienes metabolites in all three cell types. The amino acids L-cysteine, L-glutamine, L-tyrosine that are known to cause respiratory effects were significantly up-regulated in A549 cells. The PACs treated HepG2 cells showed down-regulation in metabolites responsible for the inflammatory mediation. Treatment of the differentiated SK-N-SH cells showed up-regulated metabolites involved with butanoate, fatty acid, and pyrimidine metabolism. Leukotriene metabolites were found to be significantly increased in all PACs treated cells. In conclusion, our results showed that PACs in OSE can alter the metabolism of the human lung, liver and neuronal cells and may induce toxicity in multiple target organs.

Most future growth in the Alberta bituminous sands will be based on thermal in-situ recovery technologies. To date, however, most attention on the environmental effects of bitumen recovery has focused on surface mining in the Athabasca region. Recent uncontrolled bitumen flow-to-surface incidents (FTS; appearance at the surface of bitumen emulsions from deep subsurface recovery zones) reported at the Cold Lake heavy oil fields highlight the need to better understand the potential role of in-situ extraction as a source of contaminants to landscapes and surface waters. We analyzed sediment cores from a lake located ∼2 km away from a recent bitumen FTS incident to provide a long-term perspective on the delivery of metals, polycyclic aromatic compounds (PACs), and polychlorinated biphenyls (PCBs) to surface freshwaters, and to assess whether the onset of local in-situ bitumen extraction can be linked to contaminant increases in nearby lakes. An increase in alkyl PACs coincided with the onset and expansion of commercial in-situ bitumen extraction, and multiple lines of evidence indicate a petrogenic source for recent alkyl PAC enrichment. However, no coincident increase in vanadium (enriched in bitumen) occurred that would suggest the source of petrogenic PAC enrichment is direct input of bituminous particles. Our results show that, similar to surface mining in the Athabasca region, activities associated with in-situ extraction can increase the burden of petrogenic PACs in nearby lakes, but many questions still remain regarding the exact sources and pathways of PACs into the environment. Given that more than 80% of Alberta's bitumen reserves can only be accessed using in-situ technologies, we recommend that this be made a research priority.

Seabirds are major vertebrates in the coastal ecosystems of the Canadian High Arctic, where they transport substantial amounts of marine-derived nutrients and pollutants from oceans to land by depositing guano and stomach oils to their nesting area, which often includes nearby freshwater ponds. Here we present novel indicators for evaluating the impact of seabirds on freshwater ecosystems. The ratio of cholesterol/(cholesterol + sitosterol) in pond sediments showed significant enrichment near a nesting colony of northern fulmars (Fulmarus glacialis) and was significantly correlated with ornithogenic enrichment of sediment as determined by sedimentary δ(15)N. The sterol ratio was also correlated with several bioaccumulative persistent organic pollutants (POPs), suggesting its usefulness in tracking biovector enrichment of contaminants. Human-derived epicoprostanol was also analyzed in the sediments, and its relationship with an abandoned, prehistoric camp was recorded, suggesting its potential as a tracer of prehistoric human activities in the Arctic. Sterols and stanols preserved in sediments appear to be useful geochemical tools that will inform our understanding of migratory species and the presence of prehistoric human populations in the Arctic, and possibly other animal populations.

Human activities can greatly affect the chemical and biological composition of High Arctic lakes that otherwise receive only sparse inputs from their watersheds and airsheds. This paper reports a study of three High Arctic waterbodies in which wastewater from an airport was released over the span of several decades. Using sediment cores from these waterbodies, we reconstructed the history of wastewater inputs using a multiproxy approach consisting of sterols, stanols, metals, and stable isotopes of carbon and nitrogen. This multi-proxy approach showed good concordance between δ15N, coprostanol (a stanol specific to human faecal sources), cholesterol, and cholestanol, which tracked the known history of human wastewater deposition to this High Arctic environment. Concentrations of plant derived sterols, such as campesterol and sitosterol, increased at the time of wastewater input, presumably due to increased plant growth stimulated by wastewater nutrients. Metal(loid)s normalized to titanium showed that copper and lead tracked the input of wastewater into one pond (R-12), while arsenic, cadmium, chromium, nickel, and zinc increased more than 15 years after the onset of wastewater input. These results demonstrated the ability of sterols and stanols to reconstruct the historical presence of humans in High Arctic locations within the last 80 years. They provided compelling evidence that these paleolimnological approaches may be useful to track the occupation of Arctic peoples beyond the last century.

Ore processing techniques used in Yellowknife's largest mining operation, Giant Mine, is responsible for the atmospheric release of approximately 20,000 t of particulate arsenic trioxide and other heavy metal(loids). This rapid deposition of heavy metal(loids) may have caused ecological disturbances to aquatic food webs. Here we use 210Pb and 137Cs dated lake sediment cores from 20 lakes within a 40 km radius of Yellowknife to examine the spatial-temporal distribution of arsenic, antimony and lead. Further, we model the toxicity of the sediment to aquatic biota pre-, during, and post-mining using palaeotoxicity modelling, enrichment factor assessment, and comparisons to national sediment quality guidelines. We found that metal(loid) profiles in sediment peaked during the height of mining operations. These peak metal(loid) concentrations were highest in lakes near the mine's roaster stack, and decreased with distance from the historic mine. Palaeotoxicity modelling of lake sediment archives indicate that there is no significant difference in the mean predicted toxicity of pre- and post-mining samples (p = 0.14), however mining activities in the region significantly increased the predicted toxicity of sediments to aquatic organisms during mining operations (p

We examined the accumulation of polycyclic aromatic hydrocarbons (PAHs), alkyl PAHs, and toxic metals in soils by the roots of Echinacea purpurea (L.) Moench, in a 20-week greenhouse study and a 2-year field study. In the greenhouse study, inoculation by arbuscular mycorrhizal fungus (AMF), Rhizoglomus intraradices (N.C. Schenck & G.S. Sm.). increased the first order accumulation rates (k1) for PAHs by 10-fold, though had no effect on the bioaccumulation rates of toxic metals. In the greenhouse study, PAHs concentrations in soil increased over time with AMF inoculation, suggesting AMF promote 'solvent depletion' in soils by enhancing absorption of minerals and carbon by roots, concentrating the more hydrophobic PAHs in the residual soil. Under field conditions, contaminant concentrations in soils remained unchanged over the 2-year duration of the study. Despite this, all contaminants in E. purpurea roots increased significantly, as a result of a long term extraction of contaminants by plants from soil and a reduction in soil volume as a result of plant growth. First order accumulation rates by roots were inversely correlated to log Kow for the PAHs and alkyl PAHs, indicating that accumulation is inversely related to the compound's hydrophobicity. This study is the first to our knowledge to assess the accumulation of alkyl PAHs by roots, with implications for soil bioremediation by plants because alkyl PAHs are a major source of petrogenic contamination in soils.

We performed accumulation-elimination experiments of polycyclic aromatic compounds (PACs) in wood frog tadpoles (Lithobates sylvaticus) using river sediment from Canada’s Athabasca oil sands region. The PACs in wood frog tadpoles were ∼2x higher on average when the animals were in direct contact with PAC-contaminated sediment than when they were separated from the sediment with a screen and exposed only to aqueous PACs. These results suggest that sediment exposure/ingestion contributes as much to PAC accumulation in tadpoles as exposure via aqueous pathways. Alkyl-substituted PAC concentrations in exposed tadpoles exceeded those of the unsubstituted (parent) PACs by about 10 × . Bioaccumulation factors ranged between 0.01 and 4.93, with parent PACs having higher bioaccumulation factors than alkylated PACs. Wood frog tadpoles efficiently eliminated and metabolized most parent and alkyl-substituted PACs, though some compounds (e.g., C4-naphthalenes) had higher bioaccumulation potential and may serve as effective markers of exposure. Here we present a comprehensive analysis of the toxicokinetics and bioaccumulation of PACs (52 analytes) in amphibian larvae, and highlight the importance of sediment exposure when considering the bioaccumulation and potential biological impact of PACs in benthic and epibenthic organisms.

Arctic freshwater ponds are typically pristine and oligotrophic, however seabird biovectors can markedly alter water quality via enrichment with marine-derived nutrients and bioaccumulated metals. These ornithogenic inputs can be the dominant factor structuring aquatic biota and the surrounding island flora. Here, we measured a suite of limnological water chemistry variables and sediment geochemistry from 21 freshwater ponds influenced by Common Eiders (Somateria mollissima) in Hudson Strait, near the northern communities of Cape Dorset (Nunavut) and Ivujivik (Quebec). Nest counts and sedimentary δ15N values were used as proxies of bird abundance. Nutrient-rich guano from the nesting eiders visibly promoted the growth of catchment vegetation. Elevated metal (Al, Cd, Zn), metalloid (Se), and nutrient concentrations (N, P) in the water of eider-affected sites were recorded (Sign test; p = 0.004), but the proximity of many sites to the coast meant that variables related to ocean spray (conductivity, Na+, Mg2+, Cl−, Sr) confounded the effects of birds on pond water chemistry. In contrast, sediment geochemistry appeared to more clearly characterize sites according to the level of eider activity in their catchments by tracking Pb, Cd, N, and P sedimentary concentrations (Sign test; p = 0.02). These results have direct implications for reconstructing historical eider population trends using sediment archives, which is necessary to inform effective conservation management strategies.

Niven Lake was the first wastewater disposal site for the City of Yellowknife (Northwest Territories, Canada), receiving domestic sewage for more than 30 years. Here, we used a high-resolution sediment core to track past sewage inputs to Niven Lake by comparing changes in sedimentary sterols and three diagnostic ratios for human fecal contamination, as well as biological assemblages and overall lake production, with the known history of sewage inputs to the lake from 1948 to 1981. Coprostanol, often considered the best indicator of human fecal contamination, increased by ~8% between depths of 7.5 cm and 5 cm (~1950 to 1981) and was more reliable in tracking sewage contamination than diagnostic sterol ratios. Muted responses in subfossil diatom and chironomid assemblages were noted during the time of sewage inputs, and similar responses have been reported in other eutrophic Arctic sites, as well as in many macrophyte-dominated shallow lakes in general. More marked shifts in diatoms and chironomids occurred a decade after the end of sewage inputs, in the 1990s, a time that closely aligned with the warmest years on record for Yellowknife. This post–sewage era response was indicative of anoxia and possibly of positive feedback from internal phosphorus loading. The response may have been facilitated by recent climate warming, resulting in a lagging recovery from eutrophication. Changes in the diatoms and chironomids of Niven Lake were also indicative of metal pollution, suggesting that the lake has experienced the compounding effects of arsenic contamination from nearby gold mining.

The synthetic polycyclic musks HHCB (Galaxolide ® ) and AHTN (Tonalide ® ) were monitored in fathead minnows (FHMs) caged for a month at various locations in the North Saskatchewan River (NSR), upstream and downstream of the Gold Bar wastewater treatment plant that serves the city of Edmonton, AB, Canada. In addition, the distribution of these musk compounds in the river was predicted using the fugacity-based Quantitative Water Air Sediment Interface (QWASI) model. In FHMs caged 0.15 km downstream of the wastewater outfall, mean concentrations of HHCB and AHTN were 7.4 and 0.4 μg g −1 wet weight, respectively. These are among the highest reported concentrations of these musk compounds in fish exposed to treated wastewater. The musk concentrations in FHMs were significantly lower further downstream of the outfall. High bioconcentration factors (BCFs) in FHMs that exceeded 10 4 higher than estimated concentrations in water indicated that there were low rates of biotransformation of the musks in the fish. In the FHMs caged at the site closest to the wastewater outfall, HHCB concentrations in FHMs were comparable to the body burdens that have been reported to moderate expression of vitellogenin in female rainbow trout, indicating that fish in the NSR downstream of the wastewater outfall may be at risk of anti-estrogenic effects. The QWASI model applied to six individual river sections of the NSR predicted that the largest fluxes of HHCB and AHTN would be for downstream transport in water, which explains why FHMs accumulated elevated concentrations of the musks at the furthest downstream site, 9.9 km from the wastewater discharge.

Many animal populations are under stress and declining. For numerous marine bird species, only recent or sparse monitoring data are available, lacking the appropriate temporal perspective needed to consider natural, long-term population dynamics when developing conservation strategies. Here, we use a combination of established palaeoenvironmental approaches to examine the centennial-scale dynamics of the world's largest colony (representing approx. 50% of the global population) of the declining and vulnerable Leach's Storm-petrel (Hydrobates leucorhous). By reconstructing the last approximately 1700 years of the colony's population trends, we corroborate recent surveys indicating rapid declines since the 1980s. More surprisingly, however, was that the colony size was smaller and has changed strikingly in the past, even prior to the introduction of human stressors. Our results challenge notions that very large colonies are generally stable in the absence of anthropogenic pressures and speak to an increasingly pressing need to better understand inter-colony movement and recruitment when inferring range- and species-wide trends. While the recently documented decline in storm-petrels clearly warrants conservation concern, we show that colony size was consistently much lower in the past and changed markedly in the absence of major anthropogenic activity. In response, we emphasize the need for enlarged protected area networks to maintain natural population cycles, coupled with continued research to identify the driver(s) of the current global seabird decline.

Bats are excellent ecological indicators because they are long-lived, globally distributed, and show predictable responses to environmental stressors. Unaltered bat guano deposits, although rare, can serve as environmental archives to reveal changes in dietary patterns over millennial time scales. We inferred changes in agricultural and industrial practices using a continuous 4300-year-old bat guano deposit from Jamaica. Cadmium, mercury, lead, and zinc increased during the Industrial Revolution, (which began in ca. 1760), a period characterized by elevated emissions of metals to the atmosphere. Beginning in the early 20th century, decreases in 206Pb/207Pb isotopes tracked the history of leaded gasoline use. Metal concentrations in the bat guano deposit exceeded those recorded in two nearby lake sediment cores from Jamaica. Carbon, nitrogen, and sulfur stable isotope profiles in bat guano tracked the agricultural history of Jamaica, specifically the introduction of nitrogen fertilizers, sugarcane, and possibly fungicides. Bat populations are under stress globally, and such intact guano deposits provide potentially critical information on long-term changes in their food source and exposure to metals.

Paleolimnology uses sedimentary biomarkers as proxies to reconstruct long-term changes in environmental conditions from lake sediment cores. This work describes an untargeted metabolomics-based approach and uniquely applies it to the field of paleolimnology to identify novel sediment biomarkers to track long-term patterns in treeline dynamics. We identified new potential biomarkers across the Canadian northern Arctic, non-alpine, treeline using high-resolution accurate mass spectrometry, and pattern recognition analysis. This method was applied to 120 sediment core extracts from 14 boreal, 25 forest-tundra, and 21 tundra lakes to assess long-term fluctuations in treeline position. High resolution accurate mass spectrometry resolved many compounds from complex mixtures with low mass accuracy errors. This generated a large dataset that required metabolomics styled statistical analyses to identify potential biomarkers. In total, 29 potential biomarkers discriminated between boreal and tundra lakes. Tetrapyrrole-type phorbides and squalene derivatives dominated in boreal regions, while biohopane-type lipids were in the tundra regions. Tetrapyrroles were in both surface and subsurface sediments of boreal lakes indicating these compounds can survive long-term burial in sediments. At the ecozone level, tetrapyrroles were more abundant in boreal Taiga Shield, and Taiga Plains. Boreal plant extracts belonging to Pinaceae and Ericaceae also contained tetrapyrroles. Squalene derivatives demonstrated long-term preservation, but wider distribution than tetrapyrroles. Hopanoids were present in tundra and forest-tundra lake regions, specifically the Low Arctic and Taiga Shield, and were absent in all boreal lake sediments. Herein, we describe a method that can systematically identify new paleolimnological biomarkers. Novel biomarkers would facilitate multi-proxy paleolimnological studies and potentially lead to more accurate paleoenvironmental reconstructions.

Sediment records are widely used to infer impact of atmospheric metal deposition in alpine lakes, however, the legacy effect and catchment erosion of historical pollutants could potentially affect metal influx into lakes. Here, we collect data (including six trace metals and three lithogenic elements) from well-dated sediment cores of seven alpine lakes in southeast Tibet, which is adjacent to southwest China. This area has a documented history of preindustrial pollution. Metals such as cadmium (Cd), zinc (Zn) and arsenic (As) are found at relatively low concentrations until a clear increase is observed after 1950s across lakes. This result is consistent with accelerating atmospheric metal deposition due to socio-economic development in the region. We observe no synchronous trend across lakes in the changes of lead (Pb), copper (Cu) and silver (Ag), which show no significant increase after ∼1950 over the last two centuries in most of the study lakes. The historical trends of 206Pb/207Pb ratio reflect an important source of anthropogenic Pb associated with preindustrial mining and smelting in this study region, suggesting a substantial impact of legacy contamination from ancient mines. Furthermore, the temporal variations in these six anthropogenic metals are largely accounted for by terrigenous elements (e.g. aluminum (Al) and titanium (Ti)) in most of the study lakes, and to a lesser degree by sediment grain sizes and organic matter content, suggesting a significant role of catchment erosion in modulating sediment metal signals. In all, this study highlights the legacy effect of historical pollutants may have enhanced the forcing of catchment erosion in modulating the sediment signals of anthropogenic deposition in southeast Tibet.

Dissolved organic carbon (DOC) is known to affect the Hg cycle in aquatic environments due to its overriding influence on complexation, photochemical, and microbial processes, but its role as a mediating factor in the bioaccumulation of Hg in aquatic biota has remained enigmatic. Here, we examined 26 tundra lakes in Canada's western Arctic that span a large gradient of DOC concentrations to show that total Hg (HgT) and methyl mercury (MeHg) accumulation by aquatic invertebrates is defined by a threshold response to Hg-DOC binding. Our results showed that DOC promotes HgT and MeHg bioaccumulation in tundra lakes having low DOC (8.6 - 8.8 mg C L(-1); DOC threshold concentration, TC) whereas DOC inhibits HgT and MeHg bioaccumulation in lakes having high DOC (DOC TC), consistent with bioaccumulation results in a companion paper (this issue) using a microbial bioreporter. Chemical equilibrium modeling showed that Hg bioaccumulation factors were elevated when Hg was associated mainly to fulvic acids, but became dramatically reduced when DOC was8.5 mg C L(-1), at which point Hg was associated primarily with strong binding sites on larger, less bioaccessible humic acids. This study demonstrates that the biological uptake of Hg in lakes is determined by binding thresholds on DOC, a water quality variable predicted to change markedly with future environmental change.

The extraction of bitumen from the Alberta oil sands using in-situ technologies is expanding at a rapid rate; however, investigations into the environmental impacts of oil sands development have focused on surface mining in the Athabasca region. We measured polycyclic aromatic hydrocarbons (PAH) in soils, spruce needles, and lake sediment cores in the Cold Lake oil sands region to provide a historical and spatial perspective on PAH contamination related to in-situ extraction activities. A pronounced increase in PAH concentrations was recorded in one of two study lakes (Hilda Lake) corresponding to the onset of commercial bitumen production in ∼1985. Distance from extraction rigs was not an important predictor of PAH concentrations in soils, although two samples located near installations were elevated in alkyl PAHs. Evidence of localized PAH contamination in Hilda Lake and two soil samples suggests that continued environmental monitoring is justified to assess PAH contamination as development intensifies.

[1] Forty-nine hydrothermal sulfide-sulfate rock samples from the Endeavour Segment of the Juan de Fuca Ridge, northeastern Pacific Ocean, were dated by measuring the decay of 226Ra (half-life of 1600 years) in hydrothermal barite to provide a history of hydrothermal venting at the site over the past 6000 years. This dating method is effective for samples ranging in age from ∼200 to 20,000 years old and effectively bridges an age gap between shorter- and longer-lived U-series dating techniques for hydrothermal deposits. Results show that hydrothermal venting at the active High Rise, Sasquatch, and Main Endeavour fields began at least 850, 1450, and 2300 years ago, respectively. Barite ages of other inactive deposits on the axial valley floor are between ∼1200 and ∼2200 years old, indicating past widespread hydrothermal venting outside of the currently active vent fields. Samples from the half-graben on the eastern slope of the axial valley range in age from ∼1700 to ∼2925 years, and a single sample from outside the axial valley, near the westernmost valley fault scarp is ∼5850 ± 205 years old. The spatial relationship between hydrothermal venting and normal faulting suggests a temporal relationship, with progressive younging of sulfide deposits from the edges of the axial valley toward the center of the rift. These relationships are consistent with the inward migration of normal faulting toward the center of the valley over time and a minimum age of onset of hydrothermal activity in this region of 5850 years.

Seabirds that congregate in large numbers during the breeding season concentrate marine-derived nutrients to their terrestrial nesting sites, and these nutrients disperse and enhance production in nearby terrestrial, freshwater and marine ecosystems. In the Canadian Arctic, large seabird colonies (>100,000 breeding pairs) nest on cliff faces that drain directly in the ocean, ultimately returning the nutrients back to the marine environment from which they were derived. However, strong winds blowing up cliff faces could transport nutrients up in elevation and onto surrounding terrestrial and aquatic environments. Here, we assess the degree to which seabird nutrients and metals have been delivered to coastal lakes near Hudson Strait (Nunavut, Canada) over the past century. Three lakes located at a higher elevation and increasing distance from a thick-billed murre (Uria lomvia) colony (~400,000 breeding pairs) were sampled for surface water chemistry. In addition, algal assemblages, nitrogen isotopes, and metal/metalloids were analyzed in four dated sediment cores. Elevated nutrients and major ions, as well as an enriched δ15N signature in the sediment cores, were measured in the lake 1km from the seabird colony. In contrast, similar oligotrophic and benthic diatom assemblages were identified in all three lakes, suggesting that diatoms were not influenced by enhanced nutrient inputs in this Arctic environment. Chemical tracers (e.g., total mercury) and algal assemblages in the lake near the colony suggest climate warming since ~1950 was the most likely driver of limnological changes, but this effect was muted in the more distant lakes. These pronounced changes in the seabird-impacted lake suggest that, with warming air temperatures and diminished lake ice cover, longer growing seasons may allow for aquatic organisms to more fully exploit the seabird nutrient subsidies.

Based on an analysis of sediment cores from Baptiste Lake (Alberta, Canada), we quantified century-scale trends in cyanobacteria and cyanotoxins, and identified possible drivers of toxigenic cyanobacteria. We measured concentrations of microcystins and pigments preserved in the sediment as proxies of toxigenic cyanobacteria and phytoplankton communities, respectively, while fossil diatom assemblages were used to infer past nutrient concentrations. Microcystins were detected in older sediments (ca. 1800s), pre-dating any significant alteration to the watershed. This demonstrates that toxigenic cyanobacteria may not be a recent phenomenon in eutrophic ecosystems. The dominant variants of microcystin throughout the sediment core were microcystin-LA and microcystin-LR. Other congeners including -LY, -7dmLR, -WR, -LF, -YR, and -LW (-RR was not detected) were mainly found in the upper layers of sediment (post 1980s). Starting in the 1990s, concentrations of microcystins both in the water column and in the sediment record increased in parallel. Total sediment microcystins were strongly correlated with historical nitrogen and phosphorus concentrations inferred from diatom assemblages ( r = 0.80–0.81, p n = 22); both nutrients increased over the past two decades coincident with the intensification of agriculture. Microcystins also tracked the rise in cyanobacterial pigments present throughout the core. In contrast, we found no relationship between climate-related variables and sediment microcystin concentrations, although such relationships were detected over the monitoring record with respect to water column concentrations. Overall, the rise in sediment microcystins was much greater than the rise in sediment cyanobacteria and diatom inferred nutrient concentrations. Furthermore, we demonstrate that the reconstruction of the microcystin sediment record can provide important insight for the development of realistic lake management goals. Applying this analytical approach to different lakes and regions of the world, where both natural and anthropogenic gradients vary, has the potential to markedly improve our understanding of long-term drivers of cyanotoxin production.

We examined dated sediment cores from 14 thermokarst affected lakes in the Mackenzie Delta uplands, NT, Arctic Canada, using a case-control analysis to determine how retrogressive thaw slump development from degrading permafrost affected the delivery of mercury (Hg) and organic carbon (OC) to lakes. We show that sediments from the lakes with retrogressive thaw slump development on their shorelines (slump-affected lakes) had higher sedimentation rates and lower total Hg (THg), methyl mercury (MeHg), and lower organic carbon concentrations compared to lakes where thaw slumps were absent (reference lakes). There was no difference in focus-corrected Hg flux to sediments between reference lakes and slump-affected lakes, indicating that the lower sediment Hg concentration in slump-affected lakes was due to dilution by rapid inorganic sedimentation in the slump-affected lakes. Sedimentation rates were inversely correlated with THg concentrations in sediments among the 14 lakes considered, and explained 68% of the variance in THg concentration in surface sediment, further supporting the dilution hypothesis. We observed higher S2 (algal-derived carbon) and particulate organic carbon (POC) concentrations in sediment profiles from reference lakes than in slump lakes, likely because of dilution by inorganic siliciclastic matter in cores from slump-affected lakes. We conclude that retrogressive thaw slump development increases inorganic sedimentation in lakes, and decreases concentrations of organic carbon and associated Hg and MeHg in sediments.

This study investigated the potential of Northern shrimp ( Pandelus borealis Kreyer) by-products as a source of omega-3 polyunsaturated fatty acids (ω-3 PUFAs). The by-products (heads, shell and tail) of processing accounted for approximately 50–60% of the catch. Supercritical CO 2 extraction (SFE) of the by-products at 35 MPa and 40 °C generated a deep red oil, rich in ω-3 PUFAs, specifically 7.8 ± 0.06% eicosapentaenoic acid (EPA) and 8.0 ± 0.07 % docosahexaenoic acid (DHA).

At Cape Vera, Devon Island (Nunavut, Canada), a colony of northern fulmars ( Fulmarus glacialis ) concentrates and releases contaminants through their guano to the environment. We determined whether persistent organic pollutants (POPs) from seabirds were transferred to coastal food webs. Snow buntings ( Plectrophenax nivalis ) were the most contaminated species, with ∑PCB and ∑DDT (mean: 168, 106 ng/g ww) concentrations surpassing environmental guidelines for protecting wildlife. When examined collectively, PCB congeners and DDT in jewel lichen ( Xanthoria elegans ) were lower in samples taken farther from the seabird colony, and increased with increasing δ 15 N values. However, only concentrations of p’p-DDE:∑DDT and PCB-95 were significantly correlated inversely with distance from the seabird cliffs. Linkages between marine-derived POPs and their concentrations in terrestrial mammals were less clear. Our study provides novel contaminant data for these species and supports biovector transport as a source of organic contaminants to certain components of the terrestrial food web.

With the expansion of urban centres in the mid-twentieth century and the post-1970 decrease in pesticides, populations of double-crested cormorants ( Phalacrocorax auritus ) and ring-billed gulls ( Larus delawarensis ) around Lake Ontario (Canada and USA) have rapidly rebounded, possibly to unprecedented numbers. Along with the use of traditional palaeolimnological methods (e.g. stable isotopes, biological proxies), we now have the capacity to develop specific markers for directly tracking the presence of waterbirds on nesting islands. Here, we apply the use of lipophilic sterols and stanols from both plant and animal-faecal origins as a reliable technique, independent of traditional isotopic methods, for pinpointing waterbird arrival and population growth over decadal timescales. Sterol and stanol concentrations measured in the guano samples of waterbird species were highly variable within a species and between the three species of waterbirds examined. However, cholesterol was the dominant sterol in guano, and phytosterols were also high in ring-billed gull guano. This variability highlights a specialist piscivorous diet for cormorants compared to a generalist, omnivorous diet for gulls, which may now often include grain and invertebrates from agricultural fields. A ratio that includes cholesterol and sitosterol plus their aerobically reduced products (cholestanol, stigmastanol) best explained the present range of bird abundance across the islands and was significantly correlated to sedimentary δ 15 N. Overall, we demonstrate the use of sterols and stanols as a direct means for tracking the spatial and temporal presence of waterbirds on islands across Lake Ontario, and probably elsewhere.

Seabirds are an important link between their marine feeding areas and their terrestrial breeding environments, transporting both marine-derived nutrients and contaminants and then depositing them on land in their guano. In this study, the impact of a large northern fulmar (Fulmarus glacialis) colony on the water chemistry of 26 nearby ponds spanning a gradient of seabird influence was investigated at Cape Vera, Devon Island, in the Canadian High Arctic. The presence of the fulmar colony has led to nutrient and trace element enrichment in the ponds, as evidenced by the close association among As, Cd, Co, Cu, Li, Mn, Mo, Ni, Sb, and Sr and the ornithogenic gradient. The ponds most affected by the fulmar colony were characterized by increased primary production, high organic carbon concentrations, and elevated pH — condi- tions favorable for the in situ removal of metals from the water column. Despite this, the highest trace element concentra- tions were observed in the seabird-influenced ponds, suggesting that these elements have undergone biotransport. Resume´ : Les oiseaux marins constituent un lien important entre leurs sites marins d'alimentation et leurs environnements terrestres de reproduction, car ils transportent ala fois des nutriments et des contaminants d'origine marine et les deposent sur terre dans leur guano. Nous evaluons, dans notre etude, l'impact d'une grande colonie de fulmars boreaux (Fulmarus glacialis) sur la chimie de l'eau de 26 etangs adjacents formant un gradient d'influence des oiseaux marins au cap Vera, ole Devon, dans le haut-arctique canadien. La presence de la colonie de fulmars boreaux provoque un enrichissement des etangs en nutriments et en elements en trace, comme le demontre l'association etroite entre As, Cd, Co, Cu, Li, Mn, Mo, Ni, Sb et Sr et le gradient ornithogene. Les etangs les plus affectes par la colonie de fulmars boreaux se caracterisent par une production primaire accrue, de fortes concentrations de carbone organique et un pH eleve ´ — des conditions favorables au retrait in situ des metaux de la colonne d'eau. Malgrecela, les concentrations les plus elevees de metaux en trace s'ob- servent dans les etangs influences par les oiseaux marins, ce qui laisse croire que ces elements subissent un transport biol- ogique. (Traduit par la Redaction)

Giant Mine, located in the city of Yellowknife (Northwest Territories, Canada), is a dramatic example of subarctic legacy contamination from mining activities, with remediation costs projected to exceed $1 billion. Operational between 1948 and 2004, gold extraction at Giant Mine released large quantities of arsenic and metals from the roasting of arsenopyrite ore. We examined the long-term ecological effects of roaster emissions on Pocket Lake, a small lake at the edge of the Giant Mine lease boundary, using a spectrum of palaeoenvironmental approaches. A dated sedimentary profile tracked striking increases (approx. 1700%) in arsenic concentrations coeval with the initiation of Giant Mine operations. Large increases in mercury, antimony and lead also occurred. Synchronous changes in biological indicator assemblages from multiple aquatic trophic levels, in both benthic and pelagic habitats, indicate dramatic ecological responses to extreme metal(loid) contamination. At the peak of contamination, all Cladocera, a keystone group of primary consumers, as well as all planktonic diatoms, were functionally lost from the sediment record. No biological recovery has been inferred, despite the fact that the bulk of metal(loid) emissions occurred more than 50 years ago, and the cessation of all ore-roasting activities in Yellowknife in 1999.