Magdalen Islands Research Articles

Production and fluxes of inorganic carbon and alkalinity in a subarctic subterranean estuary

In this study, we focus on the biogeochemical processes that produce both dissolved inorganic carbon (DIC) and total alkalinity (TA) along a subarctic subterranean estuary (STE) located in the Gulf of St. Lawrence (Magdalen Island, Qc, Canada) in order to evaluate the DIC and TA fluxes as well as the buffering capacity of the exported groundwater to coastal waters. DIC and TA do not behave conservatively during mixing along the groundwater flow path and this implies the occurrence of internal redox reactions that control both their production and consumption. In addition, we show that the origin and composition of the organic carbon within the system alter the carbonate parameters by generating low pH conditions (5.9 - 7.2) and contributing to non-carbonate alkalinity (NCA) that accounts for more than 30% of TA. Whereas iron cycling plays a key role in the production of DIC in the fresh and low-salinity groundwaters, the precipitation of sulfide minerals neutralize the acidity produced by the metabolically produced CO2, in the saline groundwater where sulfate is available. The STE pCO2, computed from the DIC-pHNBS pair ranged from a few ppm to 16000 ppm that results in a CO2 evasion rate of up to 310 mol m−2d−1 to the atmosphere. Based on Darcy flow and the mean concentrations of DIC and carbonate alkalinity (Ac = TA - NCA) in the discharge zone, fluxes derived from submarine groundwater discharge were estimated at 1.43 and 0.70 mol m−2d−1 for DIC and Ac, respectively. Despite a major part of the metabolic CO2 being lost along the groundwater flow path, the SGD-derived DIC flux was still greater than the Ac flux, implying that groundwater discharge reduces the buffering capacity of the receiving coastal waters. This site-specific scale study demonstrates the importance of diagenetic reactions and organic matter remineralization processes on carbonate system parameters in STE. Our results highlight that subarctic STEs could be hot spots of CO2 evasion and a source of acidification to coastal waters that should be considered in carbon budgets.

An ensemble-based approach for pumping optimization in an island aquifer considering parameter, observation and climate uncertainty

Abstract. In coastal zones, a major objective of groundwater management is often to determine sustainable pumping rates which avoid well salinization. Understanding how model and climate uncertainties affect optimal management solutions is essential for providing groundwater managers with information about salinization risk and is facilitated by the use of optimization under uncertainty (OUU) methods. However, guidelines are missing for the widespread implementation of OUU in real-world coastal aquifers and for the incorporation of climate uncertainty into OUU approaches. An ensemble-based OUU approach was developed considering parameter, observation and climate uncertainty and was implemented in a real-world island aquifer in the Magdalen Islands (Quebec, Canada). A sharp-interface seawater intrusion model was developed using MODFLOW-SWI2 and a prior parameter ensemble was generated containing multiple equally plausible realizations. Ensemble-based history matching was conducted using an iterative ensemble smoother which yielded a posterior parameter ensemble conveying both parameter and observation uncertainty. Sea level and recharge ensembles were generated for the year 2050 and were then used to generate a predictive parameter ensemble conveying parameter, observation and climate uncertainty. Multi-objective OUU was then conducted, aiming to both maximize pumping rates and minimize the probability of well salinization. As a result, the optimal trade-off between pumping and the probability of salinization was quantified considering parameter, historical observation and future climate uncertainty simultaneously. The multi-objective, ensemble-based OUU led to optimal pumping rates that were very different from a previous deterministic OUU and close to the current and projected water demand for risk-averse stances. Incorporating climate uncertainty into the OUU was also critical since it reduced the maximum allowable pumping rates for users with a risk-averse stance. The workflow used tools adapted to very high-dimensional, nonlinear models and optimization problems to facilitate its implementation in a wide range of real-world settings.

Pumping Optimization Under Uncertainty in an Island Freshwater Lens Using a Sharp‐Interface Seawater Intrusion Model

AbstractPumping optimization under uncertainty is a powerful approach for the management of groundwater resources, and its implementation would be valuable in island aquifers where freshwater lenses are affected by seawater intrusion. Sharp‐interface numerical models are especially well suited for the task as they offer fast simulation times, but to date they have not been used because of a lack of guidelines and due to the specific challenges associated with this approach. This study presents a methodology for pumping optimization under uncertainty for island freshwater lenses using a sharp‐interface model (MODFLOW‐SWI2) and demonstrates it for a real case (Magdalen Islands, Quebec, Canada). The total pumping in a well field was maximized while avoiding well salinization due to upconing. To do so, the sharp interface simulated below the pumping wells was corrected successively for cell‐to‐well upconing and for dispersion. Pumping optimization under uncertainty was then conducted using PESTPP‐OPT, considering parameter and observation uncertainty, and was repeated for 23 reliability levels to illustrate a large range of risk‐averse, tolerant and neutral stances. The maximum pumping was obtained as a function of risk of well salinization. This approach enabled quantification of the tradeoffs between pumping and risk, allocation of pumping amongst wells, and an examination of the ability of the well field to meet the water demand while maintaining an acceptable level of risk. Ultimately, this framework allows groundwater managers to select the final pumping scenario themselves, depending on their attitude toward risk.

Temperature dependence of rock salt thermal conductivity: Implications for geothermal exploration

Rock salt has high thermal conductivity (>6 W m−1 K−1 at 20 °C) compared to most overlying and adjacent sedimentary rocks, resulting in a thermal blanket effect and a favorable play for low enthalpy geothermal resources. However, the effect of temperature on rock salt thermal conductivity is greater than most other rocks. The result can be a reduction in this contrast between rock types, which has implications for geothermal exploration. The temperature dependence of rock salt thermal conductivity was shown to be a critical factor in our geothermal potential assessment of the Magdalen Islands (Canada). We evaluated the subsurface temperature of this archipelago using numerical simulations of conductive heat transfer, specifying a bulk thermal conductivity of rocks that varies with temperature and porosity, and the latter varying with pressure. A steep geothermal gradient, locally exceeding 40 °C km−1, was found in layers overlying shallow salt domes at depths of ∼1 km but not over a deeper dome due to low thermal conductivity contrasts. This finding highlights the effect of temperature on rock salt thermal conductivity, which should be considered when assessing the geothermal potential of salt domes, intrusions or diapirs, to avoid overestimating the subsurface temperature.

Tourism Adaptation to Coastal Risks: A Socio-Spatial Analysis of the Magdalen Islands in Québec, Canada

Coastal tourism is one of the most important segments of the tourism industry but is facing major impacts of climate change. In light of these impacts, the infrastructure enabling coastal tourism activities needs to be adapted. It is through the production of a space framework inspired by the work of Henri Lefebvre that we will reveal how a tourism space is socially constructing its own adaptation process. Using a case study methodology, we will examine the case of the Magdalen Island Archipelago in Québec, Canada, and pinpoint the subcase of La Grave. The case study will show how tourism is adding value to land dynamics to justify major adaptation work on the shore in order to protect the capital accumulation capacities of the tourism space. These justifications are buttressed by discourses of heritage and economic impacts to validate proceeding with a form of spatial reordering that privileges certain spaces while potentially leaving out others.

A framework for parameter estimation using sharp-interface seawater intrusion models

Sharp-interface seawater intrusion models present shorter run times than variable density codes, which makes them practical for regional, decision-support groundwater modeling. Although parameter estimation and uncertainty analyses are essential steps for model-based decision making, their implementation in seawater intrusion models has remained limited. Few guidelines are available and it is unclear which observations should be used, what processing they require and what weighting strategy should be used. A framework has been developed for parameter estimation using a regional sharp-interface decision-support model applied to a real-world example in the Magdalen Islands (Quebec, Canada). This framework included the assimilation of head observations collected from shallow wells, deep open wells and pumping wells, as well as freshwater-seawater interface observations derived from deep open wells, TDEM (time-domain electromagnetic) and ERT (electrical resistivity tomography) geophysical surveys. A model was developed using MODFLOW-SWI2 in which fast model run times allowed the estimation of numerous parameters, including a heterogeneous hydraulic conductivity field with pilot points. Following parameter estimation with PEST, the uncertainty of several model forecasts, i.e. the volume of freshwater and the interface elevation near municipal pumping wells, was examined with the first-order second moment (FOSM) approach and a data worth analysis was carried out. While the observations presented a low signal-to-noise ratio, parameter estimation was effective to reduce the uncertainty of model forecasts. Interface observations, and particularly geophysical observations, were most useful to reduce predictive uncertainties. Head and interface observations from deep open wells were biased and could not be suitably reproduced by the model. The framework developed here is relatively straightforward and could be implemented more systematically. The study also provides recommendations to guide future data collection strategies in coastal aquifers.

Foraging habitat of North Atlantic right whales has declined in the Gulf of St. Lawrence, Canada, and may be insufficient for successful reproduction

Climate-induced changes in calanoid copepod (Calanusspp.) availability in traditional feeding areas might explain why a large proportion of the North Atlantic right whaleEubalaena glacialispopulation has fed in the Gulf of St. Lawrence (Canada) in recent years. However, little is known about the distribution of copepods in the gulf, and whether their abundance is sufficient to energetically sustain right whales. We used a mechanistic modelling approach to predict areas within the gulf that have foraging potential for adult female right whales, based on the annual energetic needs of resting, pregnant and lactating females, and their theoretical prey density requirements. We identified suitable foraging areas for right whales by coupling a foraging bioenergetics model with a 12 yr data set (2006-2017) describing the abundance and 3-dimensional distribution of late-stageCalanusspp. in the gulf. Prey densities in the southern gulf (from Shediac Valley to the Magdalen Islands) supported all 3 reproductive states in most (≥6) years. However, foraging habitat became progressively sparse in the southern gulf over time, with noticeably less suitable habitat available after 2014. Few other potentially suitable foraging areas were identified elsewhere in the gulf. Overall, the availability of foraging habitat in the gulf varied considerably between years, and was higher for resting females than for pregnant and lactating females. Our findings are consistent with the recent low calving rates, and indicate that prey biomass in the Gulf of St. Lawrence may be insufficient in most years to support successful reproduction of North Atlantic right whales.

Improving delivery of care in rural emergency departments: a qualitative pilot study mobilizing health professionals, decision-makers and citizens in Baie-Saint-Paul and the Magdalen Islands, Qu\xe9bec, Canada

BackgroundEmergency departments (EDs) in rural and remote areas face challenges in delivering accessible, high quality and efficient services. The objective of this pilot study was to test the feasibility and relevance of the selected approach and to explore challenges and solutions to improve delivery of care in selected EDs.MethodsWe conducted an exploratory multiple case study in two rural EDs in Québec, Canada. A survey filled out by the head nurse for each ED provided a descriptive statistical portrait. Semi-structured interviews were conducted with ED health professionals, decision-makers and citizens (n = 68) and analyzed inductively and thematically.ResultsThe two EDs differed with regards to number of annual visits, inter-facility transfers and wait time. Stakeholders stressed the influence of context on ED challenges and solutions, related to: 1) governance and management (e.g. lack of representation, poor efficiency, ill-adapted standards); 2) health services organization (e.g. limited access to primary healthcare and long-term care, challenges with transfers); 3) resources (e.g. lack of infrastructure, limited access to specialists, difficult staff recruitment/retention); 4) and professional practice (e.g. isolation, large scope, maintaining competencies with low case volumes, need for continuing education, teamwork and protocols). There was a general agreement between stakeholder groups.ConclusionsOur findings show the feasibility and relevance of mobilizing stakeholders to identify context-specific challenges and solutions. It confirms the importance of undertaking a larger study to improve the delivery of care in rural EDs.

The Upper Visean Magdalen Islands Basalts of Eastern Quebec, Canada: A Complex Assemblage of Contrasting Mafic Rock Types Erupted in Peak Stages of Transtensional Basin Development above a Mantle Plume

A thick succession of mafic upper Asbian volcanic rocks is exposed as cap rocks in the Magdalen Islands of eastern Quebec. This succession records peak stages of a Late Devonian to Early Carboniferous magmatic system that regionally developed from transtensional tectonics above a mantle plume. In the upper part of the succession, tholeiitic basalts with enriched mid-oceanic ridge basalt (E-MORB) affinities are tightly interbedded with highly alkaline basalts with ocean island affinities, whereas the lower part is composed of moderately alkaline basalts and pyroclastic deposits that are interpreted as the products of mixing between these two compositionally distinct melts. Based on trace-element contents and geological constraints, the tholeiitic basalts were produced by decompressional melting in depleted uppermost asthenospheric mantle material enriched over the average (E-MORB-type source) at the top of the plume, whereas the highly alkaline basalts were produced subsequently when decompressional melting reached down into the enriched mantle (ocean island basalt–type source). These two primary melts may have been thermally stratified below the lithosphere before being tapped by transtensional structures to feed a thick magmatic underplating that regionally developed at the base of the crust, where magma mixing may have occurred. Interbedding of the two contrasting melts in the upper part of the succession implies that, although the two primary mantle sources were still being tapped into, magma mixing was by then no longer occurring. Above a small gap, the uppermost flow is a fluorine-rich tholeiitic basalt with arc affinities that suggest partial melting of the regional subcontinental lithospheric mantle source, which was previously enriched by nearly continuous subduction below eastern Canada in early to middle Paleozoic times. The latter setting seemingly corresponds to the local waning of the magmatic system in uppermost Asbian times, possibly because of the westward migration of the overridden plume toward New Brunswick, where alkaline volcanism from a sublithospheric source resumed in Brigantian times.

Local egg production and larval losses to advection contribute to interannual and long-term variability of American lobster (Homarus americanus) settlement intensity

American lobster (Homarus americanus) egg production and settlement intensity were examined over a 19-year period (1995–2013) in the Gulf of St. Lawrence at the Magdalen Islands (MI), where the population is spatially isolated during the benthic phase. Settlement and hatch dates by year were back-calculated from observed young-of-the-year size structure and juvenile and larval growth models. Drift of locally released larvae, from stage I to the end of stage III, was simulated using an ocean circulation model. Settlement intensity was related positively to egg production and negatively to drift distance. There was a strong positive trend in settlement intensity explained largely by increasing egg production, as well as by declining larval duration and drift distance. In the last years of the study, settlement intensity may have been limited by nursery saturation. The results suggest that demographic connectivity through larval drift is highly dynamic in time and that it declined during our study period. The demographic dependence of the MI lobster population on other populations in the Gulf of St. Lawrence is probably low.

Identification of native and non-native grass shrimps Palaemon spp. (Decapoda: Palaemonidae) by citizen science monitoring programs in Atlantic Canada

Grass shrimp collected by the Community Aquatic Monitoring Program (CAMP) in estuaries of the southern Gulf of St. Lawrence, Canada were previously assumed to be the native Palaemon vulgarisSay, 1818. Taxonomic identification of grass shrimps from CAMP estuaries revealed most individuals were P. vulgaris, but several from the Souris River and Trout River estuaries in Prince Edward Island (PEI) belong to the European species P. adspersusRathke, 1837. We provide the first documented presence of P. adspersus in PEI estuaries, extending its known range in Atlantic Canada from coastal Newfoundland and the Magdalen Islands. Boat traffic was probably responsible for the introduction of P. adspersus. The results highlight the importance of community-based monitoring in coastal ecology.

Aromas from Quebec. VI. Morella pensylvanica from the Magdalen Islands: a (-)-α-bisabolol-rich oil featuring a new bisabolane ether

Aerial parts of northern bayberry (Morella pensylvanica (Mirbel) Kartesz) from the Magdalen Islands were submitted to steam distillation to evaluate both yield and composition of essential oil and hydrosol. It yielded 0.15% (m/m) of a pleasantly scented essential oil featuring a different composition than that reported in Connecticut. This oil appeared to be rich in (-)-α-bisabolol, β-caryophyllene, linalyl acetate, geraniol and γ-terpinene. It also contained a new α-bisabolol derivative that was identified as 2,2,6-trimethyl-6-(4-methylcyclohex-3-en-1-yl)tetrahydro-2H-pyran, and named Magdalen ether. The hydrosol contained 160 mg/L of aromatic compounds among which α-bisabolol, linalool, α-terpineol and α-bisabolol oxide B, and a few minor phenolic compounds. The oil was tested for its cytotoxicity in vitro on WS-1 human fibroblasts and was shown to be four times less cytotoxic than the generally recognized as safe α-bisabolol, but did not show anti-inflammatory properties through inhibition of nitrous oxide production by murine macrophages.

Relative sea-level changes and glacio-isostatic adjustment on the Magdalen Islands archipelago (Atlantic Canada) from MIS 5 to the late Holocene

The Magdalen Islands (Québec, Canada) in the centre of the Gulf of St. Lawrence are located in a strategic position for providing an overview of the relative sea-level (RSL) history of the Maritime Provinces of eastern Canada. Although data are available for the coastal terrestrial areas of the Maritimes, data from the Gulf are very scarce and both the RSL and glacio-isostatic adjustment (GIA) models extrapolate for this central region. This study provides new stratigraphic and chronological data from four outcrops and two coring sites on the Magdalen Islands. In addition to the five samples used mainly for age control purposes, nine new luminescence ages are presented. With these new data added to the available literature, a new RSL curve is reconstructed for the LGM to the late Holocene period and a partial curve is proposed for the interval between the late MIS 4 to the MIS 3. Data also indicate a few insights for the MIS 5 period. Results reveal that for the LGM to the late Holocene, the curve corresponds to the J-shaped curve scenario recognized in the literature. The RSL changes during this period are the result of glacio-isostatic rebound, migration and collapse of the peripheral forebulge, and eustatic sea-level changes. For the LGM to the early Holocene, glacio-isostatic depression curves displaying a few local differences are also proposed. For the late Holocene, the data constrain the curve between two types of indicators, i.e. marine and terrestrial, and indicate that the RSL has risen at least 3 m during the last two millennia. Sediments dated to the MIS 5 and the interval between the late MIS 4 and the MIS 3 illustrate that the GIA following the LGM also occurred for the MIS 5 interglacial and the MIS 3 interstadial. Finally, recent GIA models are discussed in light of the results of this paper.

Nitrogen transformations along a shallow subterranean estuary

Abstract. The transformations of chemical constituents in subterranean estuaries (STEs) control the delivery of nutrient loads from coastal aquifers to the ocean. It is important to determine the processes and sources that alter nutrient concentrations at a local scale in order to estimate accurate regional and global nutrient fluxes via submarine groundwater discharge (SGD), particularly in boreal environments, where data are still very scarce. Here, the biogeochemical transformations of nitrogen (N) species were examined within the STE of a boreal microtidal sandy beach located in the Magdalen Islands (Quebec, Canada). This study revealed the vertical and horizontal distribution of nitrate (NO3−), nitrite (NO2−), ammonia (NH4+), dissolved organic nitrogen (DON) and total dissolved nitrogen (TDN) measured in beach groundwater during four spring seasons (June 2011, 2012, 2013 and 2015) when aquifer recharge was maximal after snowmelt. Inland groundwater supplied high concentrations of NOx and DON to the STE, whereas inputs from seawater infiltration were very limited. Non-conservative behaviour was observed along the groundwater flow path, leading to low NOx and high NH4+ concentrations in the discharge zone. The long transit time of groundwater within the beach (∼ 166 days), coupled with oxygen-depleted conditions and high carbon concentrations, created a favourable environment for N transformations such as heterotrophic and autotrophic denitrification and ammonium production. Biogeochemical pathways led to a shift in nitrogen species along the flow path from NOx-rich to NOx-poor groundwater. An estimate of SGD fluxes of N was determined to account for biogeochemical transformations within the STE based on a N-species inventory and Darcy's flow. Fresh inland groundwater delivered 37 mol NOx yr−1 per metre of shoreline and 63 mol DON m−1 yr−1 to the STE, and NH4+ input was negligible. Near the discharge zone, the potential export of N species was estimated around 140, 1.5 and 33 mol yr−1 per metre of shoreline for NH4+, NOx and DON respectively. In contrast to the fresh inland groundwater, the N load of beach groundwater near the discharge zone was dominated by NH4+ and DON. Our study shows the importance of tidal sands in the biogeochemical transformation of the terrestrial N pool. This local export of bioavailable N probably supports benthic production and higher trophic levels leading to its rapid transformation in surface sediments and coastal waters.

Wind drives microbial eukaryote communities in a temperate closed lagoon

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 78:187-200 (2017) - DOI: https://doi.org/10.3354/ame01814 Wind drives microbial eukaryote communities in a temperate closed lagoon Bérangère Péquin1, Vani Mohit1, Timothée Poisot2, Réjean Tremblay3, Connie Lovejoy1,* 1Département de Biologie, Québec-Océan, Institut de Biologie Intégrative et des Systèmes (IBIS), 1045 avenue de la Médecine, Université Laval, Québec G1V 0A6, Canada 2Québec Centre for Biodiversity Sciences and Département de Sciences Biologiques Université de Montréal, 90 Avenue Vincent d’Indy, Montréal, Québec H2V 2S9, Canada 3Institut des Sciences de la Mer (ISMER), Université du Québec à Rimouski, 310 Allée des Ursulines, Rimouski, Québec G5L 3A1, Canada *Corresponding author: connie.lovejoy@bio.ulaval.ca ABSTRACT: Phylogenetically diverse pico- (cells <2 µm diameter) and nanoplanktonic (2–20 µm) microbial eukaryotes are ubiquitous in coastal ecosystems; however, there is little understanding of the intrinsic (biological) and extrinsic (abiotic) factors that influence species composition in these communities. We investigated the microbial eukaryotes in the Havre-aux-Maisons Lagoon (Magdalen Islands, Gulf of St. Lawrence), which lacks riverine inputs and has little exchange with the surrounding gulf. We hypothesized that intrinsic successional processes and nutrient drawdown in the lagoon would lead to a decrease in average cell size over the summer. Samples for nutrients, cell concentrations from flow cytometry (FCM), and taxonomic identity using high throughput amplicon sequencing of the V4 region of the 18S rRNA gene were collected on 10 occasions between June and October 2009 and analysed in the context of physical and climatological data. Ratios of pico- to nanophytoplankton indicated no decline in average cell size over the summer, with picophytoplankton concentrations more variable. The microbial eukaryotic communities formed 3 major clusters based on phylogeny and UniFrac analysis. Taxonomically, dinoflagellates were dominant in the largest cluster, while picophytoplankton and nanoflagellates dominated the 2 other clusters. The concentrations of eukaryotic picophytoplankton increased in early summer, but decreased following periods with lower average wind speeds and increased following higher average winds. During periods with lower average wind speeds, dinoflagellates dominated. The clear impact of wind was consistent with climatological events indirectly influencing biotic interactions and picophytoplankton species composition. KEY WORDS: Dinoflagellates · Coastal processes · Microbial community selection · 18S rRNA gene Full text in pdf format Supplementary material PreviousCite this article as: Péquin B, Mohit V, Poisot T, Tremblay R, Lovejoy C (2017) Wind drives microbial eukaryote communities in a temperate closed lagoon. Aquat Microb Ecol 78:187-200. https://doi.org/10.3354/ame01814 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 78, No. 3. Online publication date: March 10, 2017 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2017 Inter-Research.

Reconstructing late Holocene relative sea‐level changes at the Magdalen Islands (Gulf of St. Lawrence, Canada) using multi‐proxy analyses

ABSTRACTProxy records of late Holocene relative sea‐level changes are important for our understanding of mechanisms that drive contemporary sea‐level trends. In the Gulf of Saint Lawrence (eastern Canada), the Magdalen Islands currently experience higher than global average rates of relative sea‐level rise. This article presents original reconstruction data of sea‐level changes from the Magdalen Islands over the past few millennia collected from a variety of coastal deposits and proxy records including salt‐marsh foraminifera, testate amoebae and plant macrofossils. Reconstructed late Holocene relative sea‐level trends are between 1.3 and 2.0 mm a−1 for the past 2000 years. When combined with contemporaneous trends in tide‐gauge data from Cap‐aux‐Meules (Magdalen Islands), multi‐proxy data show acceleration in the rate of relative sea‐level rise to over 4 mm a−1 during the 20th century. This signal corresponds to similar inflexions also registered in salt marshes and tide‐gauge data along the east coast of North America.

Glomeromycetes from the Magdalen Islands archipelago: analyzing diversity and meta-community structure in a sand-dune ecosystem

This report presents the first survey and analysis of the arbuscular mycorrhizal fungi community associated with Ammophila breviligulata Fernald (American beachgrass), of the Magdalen Islands archipelago, Quebec. Of the 36 selected harvesting sites, a total of 180 sand samples were collected from the rhizosphere of American beachgrass. Analyses were performed on the original sand samples and root and sand trap cultures. Of the 34 spore-morphotypes found, 31 belonged to glomoid spore species. Of the field sand samples, 72% contained the spores of Glomeromycetes and subsequent trap cultures increased this percentage to 84%. Of the 34 species, 29 were found sporulating in indigenous sand samples at harvest time, and only five additional species were recovered from root and sand trap pot culturing. Among the more generalist species were Rhizoglomus irregulare and G. sp4, which were found in 19 sites, Rhizoglomus aggregatum and Corymbiglomus tortuosum (found in 17 sites), Funneliformis mosseae and G. sp3 (found in 15 sites). This meta-community of Glomeromycetes is shown to have significant nestedness, indicating that fungal taxa that are more frequent in the whole archipelago are also more abundant locally. Some species pairs are shown to display significant negative associations in their patterns of co-occurrence. The relevance of these results for arbuscular mycorrhizal fungal community assembly and dynamics is discussed.

Chronology and stratigraphy of the Magdalen Islands archipelago from the last glaciation to the early Holocene: new insights into the glacial and sea‐level history of eastern Canada

The Magdalen Islands (Québec, Canada) are a key location for unravelling the glacial and sea‐level history of the Maritime Provinces of eastern Canada. Although many sedimentary sequences have been described in the literature, absolute ages are lacking, impeding an accurate interpretation of the deposits and the establishment of a precise chronological framework. This study provides a detailed description of 21 stratigraphical sequences located throughout the archipelago, as well as the first comprehensive luminescence chronology from the Last Glacial Maximum (LGM) to c. 10 ka. In addition to the five samples collected for age control purposes, 34 luminescence samples were taken from 17 different sites in glacial, periglacial and coastal deposits. The stratigraphical and chronological data reveal that the islands were at the crossroads of two icecaps during the LGM; the southern islands were glaciated by the Escuminac icecap located in the western Gulf of St. Lawrence whereas the northern archipelago was glaciated at the end of the LGM by an ice flow from Newfoundland. The glacial deposit covering the northern Magdalen Islands was associated with the Newfoundland icecap; here it is named the Grande‐Entrée till and is dated to c. 20 ka. OSL ages between c. 23 and 17 ka acquired from cryopediment and coastal deposits on the southern islands indicate that this part of the archipelago was deglaciated shortly after the LGM and was affected by a high sea level and periglacial processes. Around 15 ka, the entire archipelago was deglaciated and partially submerged until c. 10 ka. This data set is the first major contribution to a detailed chronology of the Magdalen Islands and constitutes the first step towards interpreting the glacial and sea‐level history of the central area of the Gulf of St. Lawrence; this new understanding will provide input to regional marine and glacial modelling.

HERPESVIRUSES INCLUDING NOVEL GAMMAHERPESVIRUSES ARE WIDESPREAD AMONG PHOCID SEAL SPECIES IN CANADA.

Little is known about herpesviruses in Canadian pinnipeds. We measured prevalence of antibodies to herpesviruses in the sera from Canadian phocid seals by an indirect enzyme-linked immunosorbent assay. Wild harbor seals (Phoca vitulina) and captive harbor seals were positive for antibodies to Phocid herpesvirus 1 (PhoHV-1) at prevalences of 91% and 100%, respectively. Sera from wild hooded seals (Cystophora cristata), harp seals (Pagophilus groenlandica), and grey seals (Halichoerus grypus) were positive for antibodies to PhoHV-1 antigenically related herpesvirus antigens at 73%, 79%, and 96%, respectively. We isolated new herpesviruses in cell culture from two hunter-harvested ringed seals (Pusa hispida) in poor body condition from Ulukhaktok, Northwest Territories, Canada; one lethargic hooded seal from the St. Lawrence Estuary, Québec, Canada; and one captive, asymptomatic harp seal from the Magdalen Islands, Québec. Partial sequencing of the herpesvirus DNA polymerase gene revealed that all four virus isolates were closely related to PhoHV-2, a member of the Gammaherpesvirinae subfamily, with nucleotide similarity ranging between 92.8% and 95.3%. The new seal herpesviruses were genetically related to other known pinniped herpesviruses, such as PhoHV-1, Otariid herpesvirus 3, Hawaiian monk (Monachus schauinslandi) seal herpesvirus, and Phocid herpesvirus 5 with 47-48%, 55%, 77%, and 70-77% nucleotide similarities, respectively. The harp seal herpesvirus and both ringed seal herpesviruses were almost identical to each other, whereas the hooded seal herpesvirus was genetically different from the three others (92.8% nucleotide similarity), indicating detection of at least two novel seal herpesviruses. These findings are the first isolation, partial genome sequencing, and identification of seal gammaherpesviruses in three species of Canadian phocid seals; two species of which were suspected of exposure to one or more antigenically related herpesviruses based on serologic analyses.

Salt-marsh sea-level indicators and transfer function development for the Magdalen Islands in the Gulf of St. Lawrence, Canada

Abstract Late Holocene salt-marsh sediments allow the reconstruction of pre-industrial relative sea-level changes. Typically, reconstructions are derived by quantifying a relationship between contemporary proxies and elevation which is then applied to down-core fossil assemblages via a transfer function. Common sea-level indicating proxies are salt-marsh foraminifera and diatoms, however, testate amoebae represent an alternative complementary proxy. With current sea-level research increasingly invoking (multi-)decadal timescale processes such as ocean current strength or wind stress to explain relative sea-level changes, there is a need for increased vertical precision in reconstructions. This paper presents new surface assemblages of salt-marsh foraminifera and testate amoebae with respect to elevation from two coastal locations in the Magdalen Islands in the Gulf of St. Lawrence, eastern Canada. We analyse the suitability of each proxy for reconstructing sea level using multivariate statistics, ordination and regression modelling. Testate amoebae are found in greater abundance and diversity than foraminifera and their assemblage variations can be better accounted for by changes in elevation. The contemporary training sets from the Magdalen Islands were able to predict marsh-surface elevations (viz. sea level) to precisions of ± 0.08 m and ± 0.12 m for testate amoebae and foraminifera respectively. There were no benefits from combining the two proxies into a unified training set. It was possible to improve the performance of the foraminifera-based transfer function by incorporating a second dataset from Newfoundland which served to increase the range of the sampled environment and improve the correlation coefficient between sample elevations and model predictions. In accordance with existing literature, we find transfer function performance to be better at locations with smaller tidal ranges.