This study investigated methylmercury (MeHg) concentrations in Arctic benthic invertebrates from two shelf sites in the Canadian Beaufort Sea. Carbon, nitrogen, and sulfur stable isotopes and fatty acids were measured to examine diet influences on MeHg concentrations in 476 individuals from 53 taxa of benthic invertebrates representing three different feeding guilds. Taxonomic identifications were based on DNA-barcoding and traditional taxonomy. MeHg concentrations ranged from 3 to 421 ng/g dry weight and increased over three trophic levels (δ15N range = 4.4–14.2‰). Organic matter sources had small but significant influences on MeHg bioaccumulation in the benthic food web. Carbon stable isotope ratios (δ13C, range = −25.5 to −19.8‰) were positively correlated with MeHg concentrations, suggesting greater reliance on benthic carbon contributed to higher concentrations. Sulfur stable isotopes were unrelated to MeHg concentrations. Fatty acids suggested feeding on diatoms versus dinoflagellates, and reliance on benthic resources influenced MeHg concentrations. Higher MeHg concentrations were observed at the site closer to the Mackenzie River mouth than the Cape Bathurst site. This study generated the most taxonomically rich dataset of MeHg concentrations in invertebrates from the Arctic marine benthos to date and provides a basis for future research on food web MeHg dynamics in the Canadian Beaufort Sea.

Molluscan predators are rarely preserved in Late Pleistocene and Holocene marine sediments from the Canadian High Arctic. Predator-prey interactions in molluscan assemblages recorded as round holes in shells, recognized as the trace fossil Oichnus, are even less well known for Quaternary molluscan assemblages from the High Arctic. Because these biological interactions recorded in molluscan shells are an essential source of information for palaeoecological and environmental reconstructions, this study aims to identify Oichnus ichnospecies in bivalve shells to unveil the possible gastropod predators that were not recorded in Quaternary sediments from the Canadian High Arctic, particularly on Axel Heiberg Island (AHI). The whole assemblage consisted of a total of 3586 shells, where drilling frequency was 0.013 and prey effectiveness was 0.58. Boreholes were observed mainly in Astarte borealis, Hiatella arctica and Mya truncata (96% of the total assemblage) with a low drilling frequency. Those borings showed two different designs identified as Oichnus simplex and O. paraboloides, which could be produced by predatory gastropods belonging to the Naticidae and Muricidae families. The higher number of O. paraboloides observed in different prey species indicates that naticid gastropods produced a greater number of boreholes than muricid gastropods. These boreholes are preferentially located on the central area of A. borealis valves in the Late Quaternary bivalve shell assemblages from AHI. These findings provide evidence of predator-prey interactions, and therefore palaeoecological evidence that help us to understand the trophic structure of Late Quaternary benthic communities of the Canadian High Arctic.. Bivalves, drill holes, muricid, naticid, Quaternary, Axel Heiberg Island.

Long-term studies provide an effective way to assess the ecological impacts of decades-long environmental change in Arctic coastal benthic environments, but are rarely undertaken in the Canadian Arctic. In light of this, historical datasets can be compared with modern samples to examine temporal differences in benthic community structure. Frobisher Bay, Nunavut, provides a unique opportunity to use a historical census to examine the impacts that long-term environmental changes have had on the marine benthos. Between 1967 and 1976, and in 2016, infaunal samples were collected in inner Frobisher Bay and were compared to determine how the molluscan assemblages have changed between the two time periods. Molluscan assemblages in two regions of inner Frobisher Bay (Iqaluit and Cairn Island) were examined to minimize sampling discrepancies between the two time periods. A long-term increase in mean annual air temperature and a decline in the length of the ice cover season were observed. Both regions exhibited some change in sediment composition and quality as well as in molluscan assemblage between the two time periods, and species diversity indices also indicated some change between these time periods. Both the 1967–1976 and 2016 molluscan datasets provide a baseline for future long-term studies in a changing Arctic.

The Canadian Geographer / Le Géographe canadienVolume 63, Issue 3 p. e25-e26 Book Reviews / Comptes rendus de livres Natural Hazards: Explanation and Integration, Second Edition by Burrell E. Montz, Graham A. Tobin, and Ronald R. Hagelman III, ed., The Guilford Press, New York, 2017, 445 pp., paper $78.00 (ISBN 978-1462529179). Alec E. Aitken, Alec E. Aitken University of SaskatchewanSearch for more papers by this author Alec E. Aitken, Alec E. Aitken University of SaskatchewanSearch for more papers by this author First published: 27 August 2019 https://doi.org/10.1111/cag.12566Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume63, Issue3Special Section: Place-based policy in practice and Syrian refugee resettlement: The role of local immigration partnerships in three Ontario second-tier citiesFall / automne 2019Pages e25-e26 RelatedInformation

Seabed sediment composition is an important component of benthic habitat and there are many approaches for producing maps that convey sediment information to marine managers. Random Forest is a popular statistical method for thematic seabed sediment mapping using both categorical and quantitative supervised modelling approaches. This study compares the performance and qualities of these Random Forest approaches to predict the distribution of fine-grained sediments from grab samples as one component of a multi-model map of sediment classes in Frobisher Bay, Nunavut, Canada. The second component predicts the presence of coarse substrates from underwater video. Spatial and non-spatial cross-validations were conducted to evaluate the performance of categorical and quantitative Random Forest models and maps were compared to determine differences in predictions. While both approaches seemed highly accurate, the non-spatial cross-validation suggested greater accuracy using the categorical approach. Using a spatial cross-validation, there was little difference between approaches-both showed poor extrapolative performance. Spatial cross-validation methods also suggested evidence of overfitting in the coarse sediment model caused by the spatial dependence of transect samples. The quantitative modelling approach was able to predict rare and unsampled sediment classes but the flexibility of probabilistic predictions from the categorical approach allowed for tuning to maximize extrapolative performance. Results demonstrate that the apparent accuracies of these models failed to convey important differences between map predictions and that spatially explicit evaluation strategies may be necessary for evaluating extrapolative performance. Differentiating extrapolative from interpolative prediction can aid in selecting appropriate modelling methods.

Species distribution models are commonly used in the marine environment as management tools. The high cost of collecting marine data for modelling makes them finite, especially in remote locations. Underwater image datasets from multiple surveys were leveraged to model the presence–absence and abundance of Arctic soft-shell clam (Mya spp.) to support the management of a local small-scale fishery in Qikiqtarjuaq, Nunavut, Canada. These models were combined to predict Mya abundance, conditional on presence throughout the study area. Results suggested that water depth was the primary environmental factor limiting Mya habitat suitability, yet seabed topography and substrate characteristics influence their abundance within suitable habitat. Ten-fold cross-validation and spatial leave-one-out cross-validation (LOO CV) were used to assess the accuracy of combined predictions and to test whether this was inflated by the spatial autocorrelation of transect sample data. Results demonstrated that four different measures of predictive accuracy were substantially inflated due to spatial autocorrelation, and the spatial LOO CV results were therefore adopted as the best estimates of performance.

The first known ampeliscid (Amphipoda: Ampeliscidae) bed for the Canadian Arctic was reported in 2013 from the Canadian Beaufort Shelf (CBS), but species patterns were not examined. This study examines their distributions relative to differences in life strategies and environmental variables. The intent is to build a better understanding of this highly productive system in comparison with ampeliscid beds in the neighboring Bering and Chukchi Seas which are important resources for higher trophic level consumers. Data from 412 samples collected to 1000 m depth over 2002–2009 indicate that there are at least eight ampeliscid species on the CBS. Five occur elsewhere in polar and temperate latitudes and three may be new to science or are species complexes. All are limited to bottom temperatures < 0.41 °C. Congeners do not distribute coherently (Similarity Profiles analysis, p < 0.05). Resource-demanding Ampelisca macrocephala (max. 8467 ind. m −2 ) dominates Byblis spp. and Haploops laevis on the shelf enriched by wind-driven upwelling but dominance switches with depth to Haploops tubicola , Haploops sibirica and Haploops sp. Obligate suspension feeding with adaptations for fine particle capture enables deep living while abundance dominants supplement their diets with deposit feeding and predation. The ampeliscids may facilitate other amphipods by providing attachment sites on their tubes. Polychaetes may facilitate the ampeliscids by bringing buried resources to the surface. Given that the CBS is undergoing substantial environmental change, we recommend the CBS ampeliscids for monitoring its environmental regime to complement ongoing monitoring in other polar and temperate ampeliscid beds.

Macrofaunal biomass on the Canadian Beaufort Shelf (CBS) was mapped for major taxa and all showed increased biomass under the upwelling region on the eastern shelf. Stations having elevated biomass were defined as those in the top three of five biomass groups defined by the Jenks criterion of natural breaks, determined as biomass ≥143.2g shell-free wet wt (ww) m−2. Elevated macrofaunal biomass was estimated to cover 4550km2 of the CBS, spreading west from Cape Bathurst. Maximum macrofaunal biomass found was 1016.0±332.2gwwm−2, of which up to 307.3±51.2gwwm−2 was due to ampeliscid amphipods of the genera Ampelisca, Byblis and Haploops. Since ampeliscids form beds where pelagic–benthic coupling is high, we use the area of elevated ampeliscid biomass (2550km2) to indicate the area of strongest upwelling effect on the benthos. Low macrofaunal biomass (<50gwwm2) was observed on the shelf close to the Mackenzie River inflow and on the continental slope in the Beaufort Sea and Amundsen Gulf. Mackenzie Trough, also where upwelling occurs, had an observed maximal biomass of 364.8±101.8gwwm−2 at its head but this was due to the polychaete Maldane sarsi and the brittle star Ophiocten sericeum rather than ampeliscid amphipods. We suggest that the ampeliscid bed under the Cape Bathurst upwelling region could be a resource for summer visiting Pacific gray whales (Eschrichtius robustus), which intensively forage on ampeliscid beds elsewhere.

Maktak, Coronation and North Pangnirtung Fjords are situated on Cumberland Peninsula, Baffin Island, Canada, having a common freshwater source from the Penny Ice Cap. Bottom photographs were examined to identify epifaunal trails and shallow endobenthic burrow openings exposed on the seafloor surface. These were compared to biogenic sedimentary structures revealed through x-radiograph images and direct observations of Lehigh gravity core samples. Intermediate- and deep-tier structures characterize the ichnofabrics of the glaciomarine sediments. Extensive bioturbation by the shallow-tier and epibenthic tracemakers, most notably ophiuroid echinoderms (brittlestars) and other organisms, has destroyed much of the primary sedimentary fabric (i.e. lamination) resulting in homogenous silty clay sediments. The dominant deep-tier structure consisting of an open, three-dimensional boxwork burrow system is the most pervasive biogenic structure observed within the core samples. Interestingly, although proximal–distal trends in benthic macrofaunal composition are evident in the bottom photographs, ichnofabrics remain relatively constant along the length of the fjords. Environmental factors influencing the biological community in these modern high latitude fjords differ from conditions described in Paleozoic and Cenozoic fjord environments. An increasing number of recent studies are expanding significantly on the fjord ichnology database, and provide the basis for the revision of the currently proposed fjord trace-fossil model, accommodating the complexity and diversity of fjord settings.

Canada's Arctic environment is rich in hydrocarbon resources. As international attention turns to the Arctic to meet global energy demands there is increased recognition of the need to advance upstream impact assessment and decision-making to plan for energy development. There have been several applications of strategic environmental assessment (SEA) over the past decade in the international offshore energy sector; however, SEA remains underdeveloped offshore in comparison to project-based environmental impact assessment and unchartered territory in Canada's Arctic. This paper examines stakeholder perceptions of the opportunities and risks of advancing SEA for offshore energy planning and development in Canada's Beaufort Sea. Results indicate a number of perceived opportunities for SEA, including improved regulatory efficiency, better regional baselines and planning practices, an opportunity to assess cumulative effects, more meaningful project-based assessment, and greater certainty for industry stakeholders. At the same time there are a number of perceived risks, including foregoing anticipated development opportunities, the loss of flexibility in decision making, adding another layer of bureaucracy, and the added uncertainties of a novel approach. The implications of these findings for advancing SEA in the offshore energy sector are discussed.

Throughout northernCanada, live‐collected, pre‐bomb, deposit‐feeding marine molluscs from calcareous sediments yield greater apparent radiocarbon ages than do suspension feeders. We explore the size of this effect in a set of 57 paired datings of deposit feeders, mainlyPortlandia arctica, and suspension feeders, mainlyHiatella arcticaandMya truncata, collected from both calcareous and non‐calcareousHolocene sediments. Deposit feeders from calcareous sediments are older than their suspension‐feeding counterparts by as much as 2240±13014Cyears. This is attributed to the uptake of ‘old’ bicarbonate derived from calcareous bedrock. The age discrepancy between suspension and deposit feeders in calcareous terrain is non‐systematic in space and time, thereby invalidating the application of a correction. In contrast, the age comparisons are concordant at sites located on thePrecambrian Shield. In terrestrial environments underlain by carbonate, previous acceptance of dates on deposit feeders led to erroneous interpretations of deglaciation and relative sea‐level history, in both theNorthAmerican and theEurasianArctic. This has prompted several researchers to exclude deposit feeders from their lateQuaternary reconstructions. The same chronological problem of deposit‐feeding molluscs now needs to be more widely acknowledged by the marine community.

Variation in macrofaunal composition in relation to sediment and water variables was analysed in nine regions of the western Canadian Arctic on the Beaufort Shelf and in Amundsen Gulf. We hypothesized that benthic community composition was distinctive (1) in a recurrent polynya in Amundsen Gulf and (2) in upwelling regions (Cape Bathurst and Mackenzie Canyon) and (3) changed in a linear gradient across the Beaufort Shelf. Analysis was based on 497 taxa >0.4 mm from 134 samples at 52 stations sampled over 2002-4 in 11-1000 m water depth. Abundance ranged from 490.7 m(-2) in eastern Amundsen Gulf to 17,950 m(-2) off Cape Bathurst. (1) Community composition in Amundsen Gulf was not significantly different from the Beaufort Shelf at similar depth, indicating a lack of benthic effect of the polynya in Amundsen Gulf. (2) The Mackenzie Canyon macrofauna, although abundant and diverse, were similarly indistinct from the shelf community at similar depth. However, there was a 10-fold increase in inshore abundance in the upwelling region of Cape Bathurst due to large numbers of the amphipod Ampelisca macrocephala and the polychaete Barantolla americana, species that were not abundant elsewhere. (3) In the inshore fast ice and flaw lead regions of the Beaufort Shelf, under the influence of ice scour, storm effects, coastal erosion and the Mackenzie River, the macrofauna were dominated by the bivalve Portlandia arctica and the polychaete Micronephthys minuta. Offshore, where these influences were less and upwelling of deep Atlantic water occurred, the polychaete Maldane sarsi dominated. Faunal distribution across the Beaufort Shelf correlated with depth, water and sediment changes but was not significantly linear. Crown Copyright (C) 2007 Published by Elsevier B.V. All rights reserved.

Coastal regions within Auyuittuq National Park Reserve (ANPR) are sensitive to mass movement processes and threatened by flooding in response to sea level rise. These processes pose a risk to culturally significant archaeological sites within ANPR. Sites at risk of disturbance need to be identified and protected to conserve valuable archaeological resources. Since the costs of identifying and monitoring sites at risk in remote areas are substantial, modern technologies such as Geographic Information Systems (GIS) can be used to create a more rapid and cost-effective means to monitor coastal environments and manage coastal resources. This study examines the application of GIS technology to assess the risk of disturbance of 44 coastal archaeological sites by mass movement and marine flooding within ANPR. Data on surficial materials and slope angles are combined in an overlay analysis to assess terrain sensitivity to mass movement. The output from this analysis is a coarse regional assessment of mass movement potential as it relates to the strength of materials on slopes. The overall risk of disturbance for archaeological sites within ANPR is assessed by combining the risk of mass movement and the risk of marine flooding. Twenty-eight sites within ANPR are identified as being at considerable risk to disturbance: these sites are located largely on glaciomarine sediments at moderate or high slope angles and are at substantial risk to flooding (less than two metres above sea level).

This study describes patterns of abundance, diversity, and assemblages of benthic macrofauna within the Canadian Arctic Archipelago. A review of data reports and the published literature yielded 219 stations and 947 taxa from 7 sources in various regions of the Canadian Arctic Archipelago (i.e. Beaufort Sea and Mackenzie Shelf, Victoria Island, Hudson and James Bays, Frobisher Bay, Ungava Bay, and Southern Davis Strait). In general, we observed that eastern regions of the Canadian Arctic Archipelago showed greater values of species richness (or a diversity) than the western and central regions, whereas no specific patterns were observed for Shannon-Wiener's diversity (H') and Pielou's evenness (J') indices. The Beaufort Sea and Mackenzie Shelf region exhibited high values of taxonomic distinctness (Delta(+)), whereas Hudson Bay showed low values. However, the Hudson Bay region showed high values of turnover (beta(W)) diversity. A non-metric multi-dimensional scaling plot of similarity (Bray-Curtis index) and analysis of similarity revealed that species composition differed among regions, even those located in close proximity to one another. These investigations were conducted at different levels of taxonomic resolution (Species, Order, Class and Phyla) and the results demonstrated that most patterns were maintained up to the Order and Class level. A relatively small number of taxa, mainly annelids, were responsible for most of the dissimilarity among regions. Bottom salinity and temperature were the most important environmental variables (among depth of site, bottom temperature, salinity, physical and chemical sediment characteristics) for determining these assemblage patterns. Multiple regression analyses also demonstrated that variance in species richness and diversity (H') was best explained by variance in salinity (55 and 43% respectively). The analysis of a time series from Frobisher Bay revealed that the temporal (mo/yr-scale) variability of assemblages was of the same order as the spatial (km-scale) variability among sites.

Slope instability has been an on-going problem along the South Saskatchewan River within the city of Saskatoon, and has adversely affected private property, bridge foundations, and municipal roads and services. Wooded declivities were present prior to urban de velopment, but changes in drainage patterns associated with construction of an urban park about 30 years ago have resulted in pronounced gullying. Morphometric measurements of two gullies conducted from 1994 to 2000 showed that their headwalls have retreated approximately 7 and 19 m, respectively, with accompanying widening and deepening of the features. The process of retreat is driven largely by the seasonal precipitation regime; it mainly occurs after heavy summer rainstorms, although freeze–thaw activity during snowmelt and subsurface flow are also implicated. Retreat is further controlled by the inherent strength of the root mat that binds the surface soils until the undercut trees finally collapse. Surface runoff through the gullies recently has been redirected through a storm sewer that is designed to mitigate the erosion problem.

This study examines neontological and palaeontological data pertaining to arctic marine molluscs with the goal of reconstructing the palaeoecology of Late Quaternary ca. 12-1 ka BP glaciomarine environments in the Canadian Arctic Archipelago. A total of 26 taxa that represent 15 bivalves and 11 gastropods were recorded in shell collections recovered from Prince of Wales, Somerset, Devon, Axel Heiberg and Ellesmere islands. In spite of taphonomic bias, the observed fossil faunas bear strong similarities to modern benthic molluscan faunas inhabiting high latitude continental shelf environments, reflecting the high preservation potential of molluscan taxa in Quaternary marine sediments. The dominance of an arctic-boreal fauna represented by Hiatella arctica, Mya truncata and Astarte borealis is the product of natural ecological conditions in high arctic glaciomarine environments. Environmental factors controlling the distribution and species composition of the Late Quaternary molluscan assemblages from this region are discussed.

Temporal and spatial variations of the species composition of Late Quaternary macrofossil assemblages in the vicinity of Prince of Wales Island, central Canadian Arctic are examined in this study. A total of 2247 specimens representing 15 taxa (9 bivalves, 6 gastropods) were recovered at 32 sites. The dominant species are the bivalves Hiatella arctica, Mya truncata and Astarte borealis that together represent 91% of the total macrofossils represented in the collections. Taphonomic analysis (i.e. ratio of opposite valves; size range; shell abrasion and overgrowth; resistance to breakage) and comparison of the species composition of Holocene macrofaunal assemblages with modern counterparts and their habitats indicate that the subfossil faunas most commonly represent para-autochthonous assemblages which inhabited glaciomarine or nearshore marine environments. As observed previously by other authors, changes in faunal composition through time from survivor or pioneer groups (Hiatella arctica, Mya truncata, Portlandia arctica, Macoma calcarea) to more diverse faunas (e.g. Astarte borealis, Clinocardium ciliatum, Serripes groenlandicus) are noted. The succession of faunas in the study area is interpreted as the result of oceanographic changes after deglaciation due to increased summer insolation and warming of surface waters in the early Holocene.