Integrated Assessment of Ocean Acidification Risks to Pteropods in the Northern High Latitudes: Regional Comparison of Exposure, Sensitivity and Adaptive Capacity

Exposure to the impact of ocean acidification (OA) is increasing in high-latitudinal productive habitats. Pelagic calcifying snails (pteropods), a significant component of the diet of economically important fish, are found in high abundance in these regions. Pteropods have thin shells that readily dissolve at low aragonite saturation state (Ωar), making them susceptible to OA. Here, we conducted a first integrated risk assessment for pteropods in the Eastern Pacific subpolar gyre, the Gulf of Alaska (GoA), Bering Sea, and Amundsen Gulf. We determined the risk for pteropod populations by integrating measures of OA exposure, biological sensitivity, and resilience. Exposure was based on physical-chemical hydrographic observations and regional biogeochemical model outputs, delineating seasonal and decadal changes in carbonate chemistry conditions. Biological sensitivity was based on pteropod morphometrics and shell-building processes, including shell dissolution, density and thickness. Resilience and adaptive capacity were based on species diversity and spatial connectivity, derived from the particle tracking modeling. Extensive shell dissolution was found in the central and western part of the subpolar gyre, parts of the Bering Sea, and Amundsen Gulf. We identified two distinct morphotypes: L. helicina helicina and L. helicina pacifica, with high-spired and flatter shells, respectively. Despite the presence of different morphotypes, genetic analyses based on mitochondrial haplotypes identified a single species, without differentiation between the morphological forms, coinciding with evidence of widespread spatial connectivity. We found that shell morphometric characteristics depends on omega saturation state (Ωar); under Ωar decline, pteropods build flatter and thicker shells, which is indicative of a certain level of phenotypic plasticity. An integrated risk evaluation based on multiple approaches assumes a high risk for pteropod population persistence with intensification of OA in the high latitude eastern North Pacific because of their known vulnerability, along with limited evidence of species diversity despite their connectivity and our current lack of sufficient knowledge of their adaptive capacity. Such a comprehensive understanding would permit improved prediction of ecosystem change relevant to effective fisheries resource management, as well as a more robust foundation for monitoring ecosystem health and investigating OA impacts in high-latitudinal habitats.

Ringed Seal Diet and Body Condition in the Amundsen Gulf region, Eastern Beaufort Sea

Diet from stomach contents and body condition from morphometric measurements were obtained for 169 (108 stomachs analysed) ringed seals (Pusa hispida) for the Amundsen Gulf region in the western Canadian Arctic from 2015 to 2018. Sampling was from subsistence-harvested seals from the three communities of Paulatuk (spring, summer, and autumn), Sachs Harbour (summer), and Ulukhaktok (winter), Northwest Territories. Stomach contents were separated through sieves and by hand, and taxa identified to the lowest taxonomic level possible and weighed. Stomachs were fullest (by weight and prey count) in the autumn, which suggests that foraging was most intense and successful at that time. A total of 93 prey taxa, including 17 fish and 76 invertebrate species were identified. Several fish and invertebrate species were regularly found together, the most common being Arctic cod (Boreogadus saida), sand lance (Ammodytes hexapterus), capelin (Mallotus villosus), and hyperiid amphipods (Themisto spp.). Condition measurements inferred from blubber thickness, although showing considerable variation among sites and years, had a seasonal relationship with maximal depth during the autumn and winter. Overall, the diet of ringed seals in Amundsen Gulf was broadly similar to those reported from other areas while also indicating some degree of regional specificity. When compared to the diet of ringed seals in the same area in the 1980s, the results presented here were more diverse, with new or increased numbers of subarctic species (e.g., saffron cod, Eleginus gracilis) found in the samples. This finding is a likely consequence of climate warming, as increasing numbers of subarctic species move north with warming ocean temperatures in the Arctic.

Bowhead whales overwinter in the Amundsen Gulf and Eastern Beaufort Sea

The bowhead whale is the only baleen whale endemic to the Arctic and is well adapted to this environment. Bowheads live near the polar ice edge for much of the year and although sea ice dynamics are not the only driver of their annual migratory movements, it likely plays a key role. Given the intrinsic variability of open water and ice, one might expect bowhead migratory plasticity to be high and linked to this proximate environmental factor. Here, through a network of underwater passive acoustic recorders, we document the first known occurrence of bowheads overwintering in what is normally their summer foraging grounds in the Amundsen Gulf and eastern Beaufort Sea. The underlying question is whether this is the leading edge of a phenological shift in a species' migratory behaviour in an environment undergoing dramatic shifts due to climate change.

Biological Impact of Ocean Acidification in the Canadian Arctic: Widespread Severe Pteropod Shell Dissolution in Amundsen Gulf

Increasing atmospheric CO2, cold water temperatures, respiration, and freshwater inputs all contribute to enhanced acidification in Arctic waters. However, ecosystem effects of ocean acidification (derived from anthropogenic and/or natural sources) in the Arctic Ocean are highly uncertain. Zooplankton samples and oceanographic data were collected in August 2012–2014 and again in August 2017 to investigate the pelagic sea snail, Limacina helicina, a biological indicator of the presence and potential impact of acidified waters in the Canadian Beaufort Sea. Between 2012 and 2014 L. helicina abundance ranged from <1 to 1942 Ind. m–2, with highest abundances occurring at stations on the Canadian Beaufort Shelf in 2012. The majority of individuals (66%) were located between 25 and 100 m depth, corresponding to upper halocline water of Pacific origin. In both 2014 and 2017, >85% of L. helicina assessed (n = 134) from the Amundsen Gulf region displayed shell dissolution and advanced levels of dissolution occurred at all stations. The severity of dissolution was not significantly different between 2014 and 2017 despite the presence of larger individuals that are less prone to dissolution, and higher food availability that can provide some physiological benefits in 2014. Corrosive water conditions were not widespread in the Amundsen Gulf at the time of sampling in 2017, and aragonite undersaturation (Ωar < 1) occurred primarily at depths >150 m. The majority of dissolution was observed on the first whorl of the shells strongly indicating that damage was initiated during the larval stage of growth in May or early June when sea ice is still present. Evidence of shell modification was present in 2014, likely supported by abundant food availability in 2014 relative to 2017. The proportion of damaged L. helicina collected from coastal embayments and offshore stations is higher than in other Arctic and temperate locations indicating that exposure to corrosive waters is spatially widespread in the Amundsen Gulf region, and periods of exposure are extreme enough to impact the majority of the population.

Inuit observations of a Tunicata bloom unusual for the Amundsen Gulf, western Canadian Arctic

Inuit are at the forefront of ecosystem change in the Arctic, yet their observations and interpretations are rarely reported in the literature. Climate change impacts are rapidly unfolding in the Arctic and there is a need for monitoring and reporting unique observations. In this short communication, we draw upon observations and experiential knowledge from western Canadian Inuit (Inuvialuit) harvesters combined with a scientific assessment to describe and interpret an unusual account of gelatinous organisms at high densities during summer 2019 in eastern Amundsen Gulf, near Ulukhaktok, Northwest Territories. The gelatinous organisms were identified as primarily appendicularian larvaceans (Oikopleura spp., pelagic tunicates) and their gelatinous “houses”. The organisms were observed within 3–5 km of the marine coast, from ∼1–2 m below the surface and to depths of ∼30 m with an underwater camera. Pelagic tunicates have rarely been documented in the eastern Amundsen Gulf and, to our knowledge, this was the first time these organisms had been noted by the people of Ulukhaktok. The pelagic tunicates clogged subsistence fishing nets and Inuvialuit harvesters were concerned about negative impacts to marine mammals and fishes, which they depend on for food security. These interpretations highlight major knowledge gaps for appendicularians in the Arctic. Video Inuit Ukiuktaktumi nunamingni tautukpaktut nunaktik aalangnujuhianik, taimaa tautukpaktait ilihimaliktait titiraqtauyuitut titiqani. Nunam aallangujuhia tautuktauyuq kayumikhipluni Ukiuktaktun nunanni, taimatun munariyauyukhak titiraqhimayukhat aallangujuhiit. Uvani tittiqaniInuit tautukpaktait ilihimaliktait titiraqhimayut Inuvialuit anguniaqtiinnit attauttimut iliblugit qablunaat tittiratainnutilituritiarumaplugitumayuutigut tamainnut auyanani 2019mi, tahamani Admundson Gulfmi Ulukhaktuum haniani North west Territoriesmi. Tahapkuat uumayut hauniittut imangmi attauttimiitpaktut. Uumayut tahapkuat tautuktauvaktut pingahunikluunniin tallimanitulluunniin kilometresmik ungahiktilanganik tariukmitalvattauk atauhikmikluunniin, malguknikluunniin metresnik ititigiyumi. Ilaani ititqiyami 30 metresmi takunnaqpaktun ajiliurunmun. Tahapkuninga tautuyuittugaluat taja kihimi tautukpaliktait. Ulukhaktuunmiutat taja tautukpaliktait. Tahapkuat uumayut nuvaktut inmate kuvyanut himiutkpiaqpaktut, kuvyallu iqaluguikhutik. Inuit iqalukhiuktullu anguniaqtullu ihumaalugiliktait anguyamingnik niqiqaramik. Tahapkuat ilituriliktavut ilihimatttaingitnaptigit nunaptingni ukiuktaktumi ilitturrinahuaqqaqhaluavut.

Characterization of epibenthic community structure in the Beaufort Sea area

The Canadian Arctic is facing new issues with increased marine traffic, exploration and exploitation of resources. Knowledge of the environment is needed to address these issues. Fisheries and Oceans Canada conducted a survey during summers 2012 to 2014 in the Canadian Beaufort Sea and the Amundsen Gulf. The “BREA-MFP” Beaufort Regional Environmental Assessment-Marine Fish Project” objective was to improve knowledge of the composition of fish communities and their habitats in offshore waters of the Beaufort Sea and the Amundsen Gulf. As an important part of the fish habitat and diet, the epibenthos was sampled to characterize and improve the knowledge of epibenthic community structure (diversity and abundance) in these areas. The benthos is ideal as an ecological indicator index because organisms are sessile, highly diverse, and long-lived. Moreover, environmental factors such as organic matter content, benthic Chla, and sediment grain size are known to influence the benthic community composition. Collected data are used to establish baselines for epibenthic diversity, abundances, and community compositions, and for comparisons among regions (Beaufort Sea, Amundsen Gulf) and gradients (nearshore-offshore depth, East-West). Furthermore, the study highlighted new occurrences of species for the area indicating additional studies are needed to assess benthic biodiversity in this area.

Characterization of epibenthic community structure in the Beaufort Sea area

The Canadian Arctic is facing new issues with increased marine traffic, exploration and exploitation of resources. Knowledge of the environment is needed to address these issues. Fisheries and Oceans Canada conducted a survey during summers 2012 to 2014 in the Canadian Beaufort Sea and the Amundsen Gulf. The “BREA-MFP” Beaufort Regional Environmental Assessment-Marine Fish Project” objective was to improve knowledge of the composition of fish communities and their habitats in offshore waters of the Beaufort Sea and the Amundsen Gulf. As an important part of the fish habitat and diet, the epibenthos was sampled to characterize and improve the knowledge of epibenthic community structure (diversity and abundance) in these areas. The benthos is ideal as an ecological indicator index because organisms are sessile, highly diverse, and long-lived. Moreover, environmental factors such as organic matter content, benthic Chla, and sediment grain size are known to influence the benthic community composition. Collected data are used to establish baselines for epibenthic diversity, abundances, and community compositions, and for comparisons among regions (Beaufort Sea, Amundsen Gulf) and gradients (nearshore-offshore depth, East-West). Furthermore, the study highlighted new occurrences of species for the area indicating additional studies are needed to assess benthic biodiversity in this area.

Observations of Beachcast Bowhead Whales (Balaena mysticetus) in the Southeastern Beaufort Sea and Amundsen Gulf, 1987–2016

Each spring, most Bowhead Whales (Balaena mysticetus) of the Bering-Chukchi-Beaufort (BCB) population migrate to the Canadian Beaufort Sea and Amundsen Gulf for summer feeding. Occasionally, Inuvialuit hunters and others observe beachcast (stranded) or adrift Bowhead Whale carcasses. From 1987 to 2016, 26 such occurrences were recorded. Most (65%) were found by Inuvialuit hunters travelling on the land, with the majority (54%) reported during 2000–2006. Bowhead Whale carcasses were found widely distributed throughout the region, with twice as many in Amundsen Gulf (65%) compared with the southeastern Beaufort Sea (35%). It was possible to measure or estimate standard length for 17 of 26 specimens, and all were either provisional ‘subadults’ (7–9.5 m; n = 10; 59%) or provisional ‘mature adults’ (13–16 m; n = 7; 41%). The cause(s) of mortality was not determined for any of the specimens. Whales in the ‘subadult’ group were likely 1–4 years old, while the ‘mature adult’ group were likely mostly mature animals (~25 y), including some potentially very old (>100 y). There was evidence or direct observation of Polar Bears (Ursus maritimus) and/or Grizzly Bears (U. arctos) scavenging at 60% of the carcasses for which presence or absence of bears or bear sign (scats and/or tracks) was reported. It is important to continue to record incidental observations of beachcast Bowhead Whales, as this may enable stranding rates to be evaluated.