Arctic seabirds and shrinking sea ice: egg analyses reveal the importance of ice-derived resources

In the Arctic, sea-ice plays a central role in the functioning of marine food webs and its rapid shrinking has large effects on the biota. It is thus crucial to assess the importance of sea-ice and ice-derived resources to Arctic marine species. Here, we used a multi-biomarker approach combining Highly Branched Isoprenoids (HBIs) with δ13C and δ15N to evaluate how much Arctic seabirds rely on sea-ice derived resources during the pre-laying period, and if changes in sea-ice extent and duration affect their investment in reproduction. Eg

Variable sea-ice conditions influence trophic dynamics in an Arctic community of marine top predators

Sea-ice coverage is a key abiotic driver of annual environmental conditions in Arctic marine ecosystems and could be a major factor affecting seabird trophic dynamics. Using stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in eggs of thick-billed murres (Uria lomvia), northern fulmars (Fulmarus glacialis), glaucous gulls (Larus hyperboreus), and black-legged kittiwakes (Rissa tridactyla), we investigated the trophic ecology of prebreeding seabirds nesting at Prince Leopold Island, Nunavut, and its relationship with sea-ice conditions. The seabird community of Prince Leopold Island had a broader isotopic niche during lower sea-ice conditions, thus having a more divergent diet, while the opposite was observed during years with more extensive sea-ice conditions. Species' trophic position was influenced by sea ice; in years of lower sea-ice concentration, gulls and kittiwakes foraged at higher trophic levels while the opposite was observed for murres and fulmars. For murres and fulmars over a longer time series, there was no evidence of the effect of sea-ice concentration on species' isotopic niche. Results suggest a high degree of adaptation in populations of high Arctic species that cope with harsh and unpredictable conditions. Such different responses of the community isotopic niche also show that the effect of variable sea-ice conditions, despite being subtle at the species level, might have large

Declining trends of polychlorinated dibenzo-p-dioxins, dibenzofurans and non-ortho PCBs in Canadian Arctic seabirds

Polychorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (PCBs) such as the non-ortho PCBs (nPCBs) persist in the environment despite international measures to ban their emissions. We determined congener patterns and temporal trends for PCDDs, PCDFs, nPCBs as well as their toxic equivalents (TEQs) in eggs of thick-billed murres (Uria lomvia) and northern fulmars (Fulmarus glacialis) sampled from Prince Leopold Island in the Canadian Arctic between 1975 and 2014. The dominant PCDD congeners were 1,2,3,7,8-PnCDD, 2,3,7,8-TCDD and 1,2,3,6,7,8-HxCDD, and the dominant PCDF congener was 2,3,4,7,8-PnCDF. The nPCB profile was dominated by PCB-126. The TEQ profile in the murre eggs was dominated by nPCB-TEQ whereas in the fulmar eggs, the PCDF-TEQ contribution to ΣTEQ was slightly greater than that of nPCB-TEQ. Concentrations of ΣPCDD, ΣPCDF, ΣnPCB and ΣTEQ declined between 1975 and 2014 in both murre and fulmar eggs. Based on TEQ thresholds in the literature for other species, and taking into account the trend towards declining TEQ levels, it is unlikely that current levels of PCDDs, PCDFs or nPCBs are affecting the reproductive success of thick-billed murres or northern fulmars in the Canadian Arctic

Declining Trends of Polychlorinated Naphthalenes in Seabird Eggs from the Canadian Arctic, 1975-2014

There are relatively few studies of polychlorinated naphthalenes (PCNs) for biota in polar regions and even fewer reports of temporal trends. We determined concentrations of PCNs in eggs of thick-billed murres (Uria lomvia) collected from the Canadian high Arctic between 1975 and 2014 and calculated their associated toxic equivalents (TEQs). Concentrations of Σ67PCN decreased significantly in the murre eggs between 1975 and 2014 at an average annual rate of -14.9 pg g-1 wet weight. Although the penta- and tetra-CNs (predominantly CN-52/60 and CN-42) dominated the PCN profile, the hexa-CNs (mainly CN-66/67) accounted for the majority of the Σ67TEQ-PCN, concentrations of which also decreased significantly between 1975 to 2014. On average, Σ67TEQ-PCN in the murre eggs accounted for only 1.9% of the total toxicity calculated for dioxin-like compounds measured in the murre eggs. As such, the TEQ-PCN concentrations calculated for the murre eggs in this study are several orders of magnitude lower than TEQ levels associated with reproductive effects in birds. This is the first published study of temporal trends of PCNs in Canadian Arctic biota

Nitrogen and sulfur isotopes predict variation in mercury levels in Arctic seabird prey

Mercury (Hg) biotransformation and biomagnification are processes that affect Hg burdens in wildlife. To interpret variation in Hg in seabird eggs, used as Hg bioindicators in the Arctic, it is important to understand how Hg biomagnifies through the food web. We evaluated the use of δ34S, along with other commonly used stable isotope signatures (δ15N and δ13C), for the determination of possible sources of Hg in an Arctic food web (56 individuals of 15 species of fish and invertebrates). Hg correlated with δ34S (R2 = 0.72). When the combined effects of δ34S and δ15N were considered in mixed-effects models, both δ34S and δ15N together described Hg patterns in Arctic food webs better than either isotope alone. Our results demonstrate the usefulness of δ34S to account for variation in Hg among marine animals and to study the possible underlying effects that MeHg production may have on Hg pathways in Arctic ecosystems

Variation in organochlorine and mercury levels in first and replacement eggs of a single-egg clutch breeder, the thick-billed murre, at a breeding colony in the Canadian Arctic

Contaminant concentrations may vary among sequentially-laid eggs in multi-egg clutches, and this variation has implications for the interpretation of contaminant concentrations in monitoring programs. The thick-billed murre (Uria lomvia) is a key species for monitoring contaminants in the Canadian Arctic and lays only a single egg per year. Therefore, the potential issue of intra-clutch variation in contaminant concentrations is avoided. However, if the egg is removed or lost early in the incubation stage, the adult female murre will relay. In this study, we examined contaminant concentrations and patterns in first-laid and replacement eggs of thick-billed murres breeding in northern Hudson Bay in order to determine whether or not these eggs could be sampled interchangeably. Concentrations of the major legacy organochlorines (e.g. PCBs, DDT, chlordanes) were generally higher, and total mercury concentrations lower, in the replacement eggs compared with the first-laid eggs. The organochlorine profile was comprised primarily of ΣDDT and Σ70PCB, and Σ70PCB was comprised primarily of hexa-hepta PCBs in both first-laid and replacement eggs. As both concentrations and organochlorine patterns showed differences between first-laid and replacement eggs, we recommend that randomly selected first-laid eggs of thick-billed murres be consistently sampled for contaminant monitoring in the Canadian Arctic

Temporal trends of legacy organochlorines in eggs of Canadian Arctic seabirds monitored over four decades

We compared temporal trends of legacy organochlorine pesticides and PCBs in eggs of five seabird species breeding at Prince Leopold Island in the Canadian high Arctic. Concentrations of most of the major organochlorine groups/compounds have either declined (e.g. Σ35PCB, ΣDDT, ΣCBz, ΣCHL, octachlorostyrene) or shown no consistent directional change (e.g. heptachlor epoxide) since 1975 in eggs of thick-billed murres (Uria lomvia), northern fulmars (Fulmarus glacialis) and black-legged kittiwakes (Rissa tridactyla). Aside from β-HCH, which increased in most species, the major organochlorine compounds either declined or showed no trend between 1993 and 2013 in eggs of five seabird species (thick-billed murre, northern fulmar, black-legged kittiwake, black guillemot Cepphus grylle, glaucous gull Larus hyperboreus). Most of the declines occurred during the 1970s to 1990s followed by little change during the 2000s. Glaucous gull eggs had the highest concentrations of almost all organochlorines in the five years compared (1993, 1998, 2003/04, 2008, 2013), and murre eggs generally had among the lowest concentrations. The primary organochlorines found in eggs of all five species were Σ35PCB, ΣDDT (mainly p,p′-DDE), ΣCBz (mainly hexachlorobenzene) and ΣCHL (mainly oxychlordane) although proportions varied by species and year. The major PCB congeners found in eggs of all five species were CB-153, -138, -118 and -180. The penta-, hexa- and heptachlorobiphenyl homologs comprised the largest proportion of Σ35PCB in all five species. Although levels of most legacy organochlorines have declined since 1975, the potential for climate change to alter chemical transport pathways as well as exposure pathways in the biotic environment could affect temporal trends. Therefore, it is important to continue to monitor these legacy contaminants in order to determine how these changes will affect the temporal trends observed to date

Trace element concentrations and gastrointestinal parasites of Arctic terns breeding in the Canadian High Arctic

Baseline data on trace element concentrations are lacking for many species of Arctic marine birds. We measured essential and non-essential element concentrations in Arctic tern (Sterna paradisaea) liver tissue and brain tissue (mercury only) from Canada's High Arctic, and recorded the presence/absence of gastrointestinal parasites during four different phases of the breeding season. Arctic terns from northern Canada had similar trace element concentrations to other seabird species feeding at the same trophic level in the same region. Concentrations of bismuth, selenium, lead and mercury in Arctic terns were high compared to published threshold values for birds. Selenium and mercury concentrations were also higher in Arctic terns from northern Canada than bird species sampled in other Arctic areas. Selenium, mercury and arsenic concentrations varied across the time periods examined, suggesting potential regional differences in the exposure of biota to these elements. For unknown reasons, selenium concentrations were significantly higher in birds with gastrointestinal parasites as compared to those without parasites, while bismuth concentrations were higher in Arctic terns not infected with gastrointestinal parasites

Mercury and marine birds in Arctic Canada: Effects, current trends, and why we should be paying closer attention

Mercury (Hg) is a naturally occurring trace element that is also a by-product of anthropogenic activities and, in its methylated form, it is a neurotoxin that can have adverse effects on wildlife. The toxicity of Hg for humans, wildlife, and ecosystem health merits monitoring of its concentrations by various sampling means. Marine birds are widely used as indicators of ecosystem health, including biomonitoring of Hg in the Arctic. Since the mid-1970s, Hg concentrations in marine birds have been monitored across the Canadian North. Current Hg burdens in most northern marine bird species are below levels associated with health concerns, but several species have concentrations that are at or near levels associated with impaired reproduction. Arctic marine birds in Canada may be particularly at risk from increasing Hg levels associated with changing climatic conditions and long-term Hg deposition patterns. Research on marine birds should, therefore, continue to focus on spatial and temporal patterns of Hg contamination, assessing levels and biological effects in species that are experiencing high concentrations, and among species that are widely harvested due to the possible implications for human health