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  • OPEN ACCESS
    A paleolimnological archive of metal sequestration and release in the Cumberland Basin Marshes, Atlantic Canada
    FACETS • Vol. 2 • pp. 440 - 460
    We used a paleolimnological approach at Long Lake, Nova Scotia, to construct a 10 500-year record of metal deposition in lakebed sediments and elucidate the influence of both natural and anthropogenic environmental changes. Aquatic sediment concentrations of mercury (Hg), arsenic (As), and chromium (Cr) in Long Lake fluctuated substantially and, during some periods, exceeded guidelines for the protection of aquatic life. Increases in lead (Pb), Hg, Cr, trace metals, and nitrogen stable isotopes (δ15N) were broadly coincident with a period of widespread drying from ca. 8000 to 4000 cal BP and were likely a consequence of regional fires. From ca. 4000 cal BP until 1700 AD, metal levels in general were low due to decreased erosion, increased precipitation, and reduced fire activity. Water level lowering and forced sediment aggradation (tiding) in the 1800s led to increases in minerogenic Pb and Cr, though fossil fuel combustion also likely contributed to total Pb concentrations. Stratigraphic proxies indicated increased inorganic sedimentation rates, and reduced autochthonous productivity were coincident with lower Hg and As concentrations in the Long Lake sediment. Our data indicate that natural phenomena (fire) can result in sediment contaminant exceedances, that most metals have multiple sources, and that both human-induced disturbance and emissions have contributed to Pb contamination in the last 200 years. In addition, wetter and generally cooler climate appeared to favour lower concentrations of contaminants in lake sediments. Although wetland sediments in the Cumberland Basin Marshes are not heavily polluted with metals, the development of constructed wetlands and the disruption of aquatic sediments have the potential to concentrate, mobilize, and increase the bioavailability of metals.
  • OPEN ACCESS
    Variation in isotopic niche, digestive tract morphology, and mercury concentrations in two sympatric waterfowl species wintering in Atlantic Canada
    FACETS • Vol. 5 • No. 1 • pp. 393 - 408
    Sympatric communities of organisms may exploit different ecological niches to avoid intra- and interspecific competition. We examined the isotopic niches of American black ducks (Anas rubripes) and mallards (A. platyrhynchos) wintering in coastal and urban areas of Atlantic Canada and compared isotopic niche with digestive tract morphologies and blood mercury (Hg) concentrations. Isotopic niche width (for δ13C and δ15N) varied between the three groups of ducks studied, with coastally foraging black ducks exhibiting the widest isotopic niche, followed by coastal mallards, while urban feeding black ducks had a narrow isotopic niche. These niche differences had physical and chemical consequences: coastal black ducks had longer digestive tracts, a larger range in gizzard sizes, and higher and more variable Hg concentrations than urban black ducks and coastal mallards. This plasticity in ecological niche may reduce competition among and within species, and subsequently explain why winter numbers of black ducks and mallards have increased in Atlantic Canada.
  • OPEN ACCESS
    Host traits and lifetime fitness costs of being parasitized in red-breasted mergansers
    FACETS • Vol. 6 • pp. 2155 - 2176
    The addition of eggs to a nest by a conspecific is known for approximately 250 bird species. Understanding the evolution of conspecific brood parasitism (CBP) requires assessment of fitness consequences to the egg recipient (host). We addressed host traits and the effects of CBP on future reproduction (i.e., annual survival) and hatching success of hosts by following the nesting of 206 red-breasted mergansers (Mergus serrator) for a colony in which an average of 41% of nests was parasitized annually. Each host was tracked for ≥2 seasons and up to seven seasons. The proportion of a host’s nesting attempts that was parasitized averaged 43% and varied considerably across individuals (range 0%–100%). Probability of parasitism, however, was not repeatable across a host’s nests. Rather, rates of CBP throughout a host’s lifetime increased with earlier dates of nest initiation. CBP had no effect on annual survival of a host. Hatching success throughout a host’s lifetime declined with a greater number of foreign eggs added to the individual’s nests. This study revealed that there may be measurable costs of CBP to lifetime reproductive success in red-breasted mergansers, although our observations suggest that costs to hosts are limited to the most heavily parasitized clutches.
  • OPEN ACCESS
    Dynamic vegetation cover and decline in common eider breeding numbers in Nova Scotia, Canada
    FACETS • Vol. 8 • pp. 1 - 12
    The American common eider (Somateria mollissima dresseri) is a colonially nesting sea duck breeding on islands in the coastal regions of Atlantic Canada. Declines in colony size have been pronounced in some parts of its range, notably in Nova Scotia, and may be attributable to a variety of interconnected factors including changes in habitat conditions. Using surveys collected two decades apart, we compared nesting habitat types, availability, and use by breeding eiders on 16 islands that supported >1600 eider nests in 1992–1993, but 830 nests in 2013. While general patterns of eider nesting habitat use remained consistent (e.g., nesting preferences exhibited for Low Shrubland and Grassland habitats, and avoidance of forest or beach habitats), overall vegetation cover declined, but relative habitat changes were inconsistent across islands. Three of the islands with the greatest change in vegetation had cormorant (Phalacrocorax spp.) colonies in 2013 that were not there in the earlier years. We suggest that changes in vegetation, in some cases facilitated by cormorant colony formation, influenced susceptibility of nesting females to predators, and these interconnected factors may be contributing to local population declines.
  • OPEN ACCESS
    Spatiotemporal patterns of low and highly pathogenic avian influenza virus prevalence in murres in Canada from 2007 to 2022—a case study for wildlife viral monitoring
    FACETS • Vol. 9 • pp. 1 - 13
    Migratory seabirds move across ocean basins and are one of the primary reservoirs of low pathogenic avian influenza virus (LPAIV). This includes the millions of thick-billed murres (Uria lomvia) and common murres (Uria aalge) that are distributed across northern hemisphere oceans. In response to increasingly frequent detections of highly pathogenic avian influenza virus (HPAIV) in Europe in 2020–2021, avian influenza virus (AIV) monitoring in wildlife has increased. We compiled data from murres tested for AIV in Canada between 2007 and 2022 to quantify spatiotemporal variation in the prevalence of LPAIV and HPAIV in these birds. No HPAIV was detected in murres prior to 2022, but HPAIV was present in 46% of both live/harvested and found dead murres in the northwestern Atlantic in 2022 with prevalence peaking at 63% among live birds in the summer. In the eastern Canadian Arctic, HPAIV prevalence in 2022 was <1% while LPAIV prevalence was 21%, which was significantly higher than previous sampling years. Power analyses suggest approximately 100 samples from breeding murres should be collected annually per colony or region to detect moderate changes in HPAIV prevalence. These analyses inform robust monitoring of viruses in wildlife, with implications for conservation, harvest management, and public health.