Pacific salmon in the Canadian Arctic highlight a range-expansion pathway for sub-Arctic fishes.

Rapid climate change is altering Arctic ecosystems at unprecedented rates. These changes in the physical environment may open new corridors for species range expansions, with substantial implications for subsistence-dependent communities and sensitive ecosystems. Over the past 20 years, rising incidental harvest of Pacific salmon by subsistence fishers has been monitored across a widening range spanning multiple land claim jurisdictions in Arctic Canada. In this study, we connect Indigenous and scientific knowledges to explore potential oceanographic mechanisms facilitating this ongoing northward expansion of Pacific salmon into the western Canadian Arctic. A regression analysis was used to reveal and characterize a two-part mechanism related to thermal and sea-ice conditions in the Chukchi and Beaufort seas that explains nearly all of the variation in the relative abundance of salmon observed within this region. The results indicate that warmer late-spring temperatures in a Chukchi Sea watch-zone and persistent, suitable summer thermal conditions in a Beaufort Sea watch-zone together create a range-expansion corridor and are associated with higher salmon occurrences in subsistence harvests. Furthermore, there is a body of knowledge to suggest that these conditions, and consequently the presence and abundance of Pacific salmon, will become more persistent in the coming decades. Our collaborative approach positions us to document, explore, and explain mechanisms driving changes in fish biodiversity that have the potential to, or are already affecting, Indigenous rights-holders in a rapidly warming Arctic.

Borealization of nearshore fishes on an interior Arctic shelf over multiple decades.

Borealization is a type of community reorganization where Arctic specialists are replaced by species with more boreal distributions in response to climatic warming. The process of borealization is often exemplified by the northward range expansions and subsequent proliferation of boreal species on the Pacific and Atlantic inflow Arctic shelves (i.e., Bering/Chukchi and Barents seas, respectively). But the circumpolar nearshore distribution of Arctic-boreal fishes that predates recent warming suggests borealization is possible beyond inflow shelves. To examine this question, we revisited two nearshore lagoons in the eastern Alaska Beaufort Sea (Kaktovik and Jago lagoons, Arctic National Wildlife Refuge, Alaska, USA), a High Arctic interior shelf. We compared summer fish species assemblage, catch rate, and size distribution among three periods that spanned a 30-year record (baseline conditions, 1988-1991; moderate sea ice decline, 2003-2005; rapid sea ice decline, 2017-2019). Fish assemblages differed among periods in both lagoons, consistent with borealization. Among Arctic specialists, a clear decline in fourhorn sculpin (Myoxocephalus quadricornis, Kanayuq in Iñupiaq) occurred in both lagoons with 86%-90% lower catch rates compared with the baseline period. Among the Arctic-boreal species, a dramatic 18- to 19-fold increase in saffron cod (Eleginus gracilis, Uugaq) occurred in both lagoons. Fish size (length) distributions demonstrated increases in the proportion of larger fish for most species examined, consistent with increasing survival and addition of age-classes. These field data illustrate borealization of an Arctic nearshore fish community during a period of rapid warming. Our results agree with predictions that Arctic-boreal fishes (e.g., saffron cod) are well positioned to exploit the changing Arctic ecosystem. Another Arctic-boreal species, Dolly Varden (Salvelinus malma, Iqalukpik), appear to have already responded to warming by shifting from Arctic nearshore to shelf waters. More broadly, our findings suggest that areas of borealization could be widespread in the circumpolar nearshore.

Diet energy density estimated from isotopes in predator hair associated with survival, habitat, and population dynamics.

Sea ice loss is fundamentally altering the Arctic marine environment. Yet there is a paucity of data on the adaptability of food webs to ecosystem change, including predator-prey interactions. Polar bears (Ursus maritimus) are an important subsistence resource for Indigenous people and an apex predator that relies entirely on the under-ice food web to meet its energy needs. In this study, we assessed whether polar bears maintained dietary energy density by prey switching in response to spatiotemporal variation in prey availability. We compared the macronutrient composition of diets inferred from stable carbon and nitrogen isotopes in polar bear guard hair (primarily representing summer/fall diet) during periods when bears had low and high survival (2004-2016), between bears that summered on land versus pack ice, and between bears occupying different regions of the Alaskan and Canadian Beaufort Sea. Polar bears consumed diets with lower energy density during periods of low survival, suggesting that concurrent increased dietary proportions of beluga whales (Delphinapterus leucas) did not offset reduced proportions of ringed seals (Pusa hispida). Diets with the lowest energy density and proportions from ringed seal blubber were consumed by bears in the western Beaufort Sea (Alaska) during a period when polar bear abundance declined. Intake required to meet energy requirements of an average free-ranging adult female polar bear was 2.1 kg/day on diets consumed during years with high survival but rose to 3.0 kg/day when survival was low. Although bears that summered onshore in the Alaskan Beaufort Sea had higher-fat diets than bears that summered on the pack ice, access to the remains of subsistence-harvested bowhead whales (Balaena mysticetus) contributed little to improving diet energy density. Because most bears in this region remain with the sea ice year round, prey switching and consumption of whale carcasses onshore appear insufficient to augment diets when availability of their primary prey, ringed seals, is reduced. Our results show that a strong predator-prey relationship between polar bears and ringed seals continues in the Beaufort Sea. The method of estimating dietary blubber using predator hair, demonstrated here, provides a new metric to monitor predator-prey relationships that affect individual health and population demographics.

Antarcticibacterium arcticum sp. nov., a bacterium isolated from marine sediment of the Canadian Beaufort Sea.

A Gram-stain-negative, aerobic, yellow-pigmented, flexirubin-negative, rod-shaped and non-motile bacterial strain, PAMC 28998T, was isolated from a surface sediment sample collected from the Canadian Beaufort Sea. Strain PAMC 28998T grew at 4-37 °C (optimum, 25 °C), at pH 7.0-9.0 (optimum, pH 7.5) and in the presence of 1.0-10.0 % (w/v) NaCl. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain PAMC 28998T belongs to the genus Antarcticibacterium showing the highest sequence similarity (96.8 %) with Antarcticibacterium flavum JB01H24T. The average nucleotide identity and genome-to-genome distance values between PAMC 28998T and the most closely related species (A. flavum JB01H24T) were 74.1 and 18.5 %, respectively, indicating that strain PAMC 28998T is clearly distinguished from A. flavum. The genomic DNA G+C content calculated from genome sequences was 39.8 %. The major fatty acids (>10 %) were iso-C15 : 0 (19.5 %), anteiso-C15 : 0 (18.0 %), iso-C16 : 0 (11.6 %) and summed feature 3 (C16:1 ω6c and/or C16:1 ω7c; 11.4 %). The major polar lipids were phosphatidylethanolamine, aminoglycolipid, two unidentified aminolipids, three unidentified phospholipids and four unidentified lipids. The major respiratory quinone was MK-6. Based on the phylogenetic, genomic and phenotypic data presented here, strain PAMC 28998T is considered to represent a novel species of the genus Antarcticibacterium, for which the name Antarcticibacterium arcticum sp. nov. is proposed with the strain PAMC 28998T (=KCCM 43316 T=JCM 33514T).

Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity.

The effects of declining Arctic sea ice on local ecosystem productivity are not well understood but have been shown to vary inter-specifically, spatially, and temporally. Because marine mammals occupy upper trophic levels in Arctic food webs, they may be useful indicators for understanding variation in ecosystem productivity. Polar bears (Ursus maritimus) are apex predators that primarily consume benthic and pelagic-feeding ice-associated seals. As such, their productivity integrates sea ice conditions and the ecosystem supporting them. Declining sea ice availability has been linked to negative population effects for polar bears but does not fully explain observed population changes. We examined relationships between spring foraging success of polar bears and sea ice conditions, prey productivity, and general patterns of ecosystem productivity in the Beaufort and Chukchi Seas (CSs). Fasting status (≥7 days) was estimated using serum urea and creatinine levels of 1,448 samples collected from 1,177 adult and subadult bears across three subpopulations. Fasting increased in the Beaufort Sea between 1983-1999 and 2000-2016 and was related to an index of ringed seal body condition. This change was concurrent with declines in body condition of polar bears and observed changes in the diet, condition and/or reproduction of four other vertebrate consumers within the food chain. In contrast, fasting declined in CS polar bears between periods and was less common than in the two Beaufort Sea subpopulations consistent with studies demonstrating higher primary productivity and maintenance or improved body condition in polar bears, ringed seals, and bearded seals despite recent sea ice loss in this region. Consistency between regional and temporal variation in spring polar bear fasting and food web productivity suggests that polar bears may be a useful indicator species. Furthermore, our results suggest that spatial and temporal ecological variation is important in affecting upper trophic-level productivity in these marine ecosystems.

Increased Arctic sea ice drift alters adult female polar bear movements and energetics.

Recent reductions in thickness and extent have increased drift rates of Arctic sea ice. Increased ice drift could significantly affect the movements and the energy balance of polar bears (Ursus maritimus) which forage, nearly exclusively, on this substrate. We used radio-tracking and ice drift data to quantify the influence of increased drift on bear movements, and we modeled the consequences for energy demands of adult females in the Beaufort and Chukchi seas during two periods with different sea ice characteristics. Westward and northward drift of the sea ice used by polar bears in both regions increased between 1987-1998 and 1999-2013. To remain within their home ranges, polar bears responded to the higher westward ice drift with greater eastward movements, while their movements north in the spring and south in fall were frequently aided by ice motion. To compensate for more rapid westward ice drift in recent years, polar bears covered greater daily distances either by increasing their time spent active (7.6%-9.6%) or by increasing their travel speed (8.5%-8.9%). This increased their calculated annual energy expenditure by 1.8%-3.6% (depending on region and reproductive status), a cost that could be met by capturing an additional 1-3 seals/year. Polar bears selected similar habitats in both periods, indicating that faster drift did not alter habitat preferences. Compounding reduced foraging opportunities that result from habitat loss; changes in ice drift, and associated activity increases, likely exacerbate the physiological stress experienced by polar bears in a warming Arctic.

Decadal shifts in autumn migration timing by Pacific Arctic beluga whales are related to delayed annual sea ice formation.

Migrations are often influenced by seasonal environmental gradients that are increasingly being altered by climate change. The consequences of rapid changes in Arctic sea ice have the potential to affect migrations of a number of marine species whose timing is temporally matched to seasonal sea ice cover. This topic has not been investigated for Pacific Arctic beluga whales (Delphinapterus leucas) that follow matrilineally maintained autumn migrations in the waters around Alaska and Russia. For the sympatric Eastern Chukchi Sea ('Chukchi') and Eastern Beaufort Sea ('Beaufort') beluga populations, we examined changes in autumn migration timing as related to delayed regional sea ice freeze-up since the 1990s, using two independent data sources (satellite telemetry data and passive acoustics) for both populations. We compared dates of migration between 'early' (1993-2002) and 'late' (2004-2012) tagging periods. During the late tagging period, Chukchi belugas had significantly delayed migrations (by 2 to >4 weeks, depending on location) from the Beaufort and Chukchi seas. Spatial analyses also revealed that departure from Beaufort Sea foraging regions by Chukchi whales was postponed in the late period. Chukchi beluga autumn migration timing occurred significantly later as regional sea ice freeze-up timing became later in the Beaufort, Chukchi, and Bering seas. In contrast, Beaufort belugas did not shift migration timing between periods, nor was migration timing related to freeze-up timing, other than for southward migration at the Bering Strait. Passive acoustic data from 2008 to 2014 provided independent and supplementary support for delayed migration from the Beaufort Sea (4 day yr-1 ) by Chukchi belugas. Here, we report the first phenological study examining beluga whale migrations within the context of their rapidly transforming Pacific Arctic ecosystem, suggesting flexible responses that may enable their persistence yet also complicate predictions of how belugas may fare in the future.

Distribution of mercury in modern bottom sediments of the Beaufort Sea in relation to the processes of early diagenesis: Microbiological aspect.

This study investigated the contents of total mercury (THg), trace metals, and CH4 and determined the signature microbes involved in various biogeochemical processes in the sediment of the Canadian Beaufort Sea. The THg ranged between 32 and 63 µg/kg and the trace metals such as Fe, Al, Mn, and Zn were significant in distributions. The pH, SO42-, Fe2+, and redox proxy metals were crucial factors in the spatial and vertical heterogeneity of geochemical distributions. CH4 was detected only at the mud volcano site. Microbial analyses identified Clostridium, Desulfosporosinus, Desulfofustis, and Desulftiglans as the predominant Hg methylators and sulfate reducers; Nitrosopumilus and Hyphomicrobium as the major nitrifiers and denitrifiers; Methanosarcina and Methanosaeta as keystone methanogens; and Methyloceanibacter and Methyloprofundus as signature methanotrophs. Altogether, this study expands the current understanding of the microbiological and geochemical features and could be helpful in predicting ecosystem functions in the Canadian Beaufort Sea.

Microplastics in beluga whale (Delphinapterus leucas) prey: An exploratory assessment of trophic transfer in the Beaufort Sea.

Microplastics (MPs, <5 mm in length) have been identified as emerging contaminants in marine environments, with ingestion by a variety of biota being of increasing concern. Few studies exist on MP ingestion in Arctic fish, and there are currently no such data from the Beaufort Sea. We investigated MP abundance in five ecologically valuable species from three sampling sites in the Eastern Beaufort Sea to evaluate possible trophic-level pathways of MPs from prey to beluga whales. Polymer analysis confirmed that 21% of fish gastrointestinal tracts (n = 116) contained microplastic particles. Fish that contained MPs had a mean abundance of 1.42 ±â€¯0.44 particles per individual and an overall mean abundance of 0.37 ±â€¯0.16 particles. No plastic particles >5 mm were found, and 78% of the particles observed were fibers. Based on energetic needs, we estimate that individual beluga may ingest between 3800 and 145,000 microplastics annually through trophic transfer, with uncertain health implications.

Alexandrium on the Alaskan Beaufort Sea shelf: Impact of upwelling in a warming Arctic.

The harmful algal genus Alexandrium has characteristically been found in temperate and subtropical regions; however recent evidence suggests global warming may be expanding its range into high latitude waters. Alexandrium cysts have previously been documented in the Chukchi Sea and we hypothesize that Alexandrium may be expanding further into the Arctic due to distribution by the Beaufort shelfbreak jet. Here we document the presence of Alexandrium catenella along the Alaskan Beaufort Sea shelf, marking an expansion of its known range. The observations of A. catenella were made using three different methods: FlowCAM imaging, 18S eukaryotic sequencing, and real-time quantitative PCR. Four occupations of a shelf/slope transect spanned the evolution of a strong wind-driven upwelling event over a 5-day period. A nearby mooring provided the physical context for the event, revealing that enhanced easterly winds reversed the Beaufort shelfbreak jet to the west and induced upwelling of colder, denser water onto the outer shelf. A. catenella sequences dominated the surface phytoplankton community at the onset of the upwelling event. This signal vanished during and after the event, likely due to a combination of alongstream advection, cross-stream advection, and wind mixing. These results suggest contrasting physical processes that are both subject to global warming amplification, delivery of warm waters via the Beaufort shelfbreak jet and upwelling, may control the proliferation of this potential harmful alga into the Arctic.

Estimation of chromophoric dissolved organic matter and its controlling factors in Beaufort Sea using mixture density network and Sentinel-3 data.

With the warming of the high-latitude regional climate, melting of permafrost, and acceleration of hydrological cycles, the Arctic Ocean (AO) has undergone a series of rapid changes in the past decades. As a dominant optical component of the AO, the variations in chromophoric dissolved organic matter (CDOM) concentration affect the physiological state marine organisms. In this study, machine learning retrieval model based on in situ data and mixture density network (MDN) was developed. Compared to other models, MDN model performed better on test data (R2 = 0.83, and root mean squared error = 0.22 m-1) and was applied to Sentinel-3 OLCI data. Afterward, the spatiotemporal distribution of CDOM during the ice-free (June-September) from 2016 to 2020 in the Beaufort Sea was obtained. CDOM concentration generally exhibited an upward trend. The maximum monthly average CDOM concentration appeared in June and gradually decreased thereafter, reaching its lowest value in September of each year. The maximum value appeared in June 2020 (0.91 m-1), and the minimum value was observed in September 2017 (0.81 m-1). The CDOM concentration nearshore was higher than that in other areas; and gradually decreased from offshore to the open sea. CDOM was highly correlated with salinity (R2 = 0.49) and discharge (R2 = 0.53), and the tight correlation between salinity and CDOM further suggested that terrestrial inputs were the main source of CDOM in the Beaufort Sea. However, sea level pressure contributed to the spatial variations in CDOM. When southerly wind prevailed and wind direction was aligned with the CDOM diffusion direction, the wind accelerated the diffusion of CDOM into the open sea. Meanwhile, seawater was diluted by the sea ice melting, resulting in decrease in CDOM concentration. Herein, this paper proposed a robust and near real-time method for CDOM monitoring and influence factor analysis, which would promote the understanding of AO CDOM budgets.

Complete mitochondrial genome of the marine polychaete, Nereis zonata (Phyllodocida, Nereididae) isolated from the Beaufort Sea.

Here, we present the first whole mitogenome sequence of the marine polychaete, Nereis zonata, isolated from the Beaufort Sea. The mitochondrial genome of N. zonata is 15,757 bp in length and consists of 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes, and a non-coding region that is typical of polychaetes. GC content of the N. zonata mitogenome is 37.2%. A maximum-likelihood gene tree based on the N. zonata mitogenome combined with previously published annelid mitogenome data revealed that N. zonata is clustered with Cheilonereis cyclurus, which form a sister group to Nereis sp.

Anthropogenic particles (including microfibers and microplastics) in marine sediments of the Canadian Arctic.

We report the first Canadian Arctic-wide study of anthropogenic particles (APs, >125 µm), including microfibers (synthetic, semi-synthetic and anthropogenically modified cellulose) and microplastics, in marine sediments from 14 sites. Samples from across the Canadian Arctic were collected between 2014 and 2017 from onboard the CCGS Amundsen. Samples were processed using density separation with calcium chloride (CaCl2). APs >125 µm were identified and a subset (22%) were characterized using Raman spectroscopy. Following blank-correction, microfiber numbers were corrected using Raman data in a novel approach to subtract possible "natural" cellulose microfibers with no anthropogenic signal via Raman spectroscopy, to estimate the proportion of cellulose microfibers that are of confirmed anthropogenic origin. Of all microfibers examined by Raman spectroscopy, 51% were anthropogenic cellulose, 11% were synthetic polymers, and 7% were extruded fibers emitting a dye signal. The remaining 31% of microfibers were identified as cellulosic but could not be confirmed as anthropogenic and thus were excluded from the final concentrations. Concentrations of confirmed APs in sediments ranged from 0.6 to 4.7 particles g-1 dry weight (dw). Microfibers comprised 82% of all APs, followed by fragments at 15%. Total microfiber concentrations ranged from 0.4 to 3.2 microfibers g-1 dw, while microplastic (fragments, foams, films and spheres) concentrations ranged from 0 to 1.6 microplastics g-1 dw. These concentrations may exceed those recorded in urban areas near point sources of plastic pollution, and indicate that the Canadian Arctic is a sink for APs, including anthropogenic cellulose fibers. Overall, we provide an important benchmark of AP contamination in Canadian Arctic marine sediments against which to measure temporal trends, including the effects of source reduction strategies and climate change, both of which will likely alter patterns of accumulation of anthropogenic particles.

Microplastics in beluga whales (Delphinapterus leucas) from the Eastern Beaufort Sea.

Microplastics (MPs, particles <5 mm) represent an emerging global environmental concern, having been detected in multiple aquatic species. However, very little is known about the presence of MPs in higher trophic level species, including cetaceans. We worked with community based monitors and Inuvialuit hunters from Tuktoyaktuk (Northwest Territories, Canada) to sample seven beluga whales (Delphinapterus leucas) in 2017 and 2018. Microplastics were detected in the gastrointestinal tracts in every whale. We estimate that each whale contained 18 to 147 MPs in their GI tract (average of 97 ±â€¯42 per individual). FTIR-spectroscopy revealed over eight plastic polymer types, with nearly half being polyester. Fibres made up 49% of MPs. The diversity of MP shapes and polymeric identities in beluga points to a complex source scenario, and ultimately raises questions regarding the significance and long-term exposure of this pollutant in this ecologically and culturally valuable species.

Characterization of sediment contaminants in Arctic lagoons and estuaries.

Baseline characterizations of estuarine sediments in Chukchi and Beaufort Seas, were conducted. Concentrations of 194 organic and elemental chemicals were analyzed in sediment and fish, plus stable isotopes of carbon and nitrogen. The estuaries are shallow embayments, with little shoreline relief. The water columns were turbid, high salinity, and not stratified. Concentrations of arsenic and nickel were elevated throughout the region. Arsenic in fish tissue was elevated. Concentrations of PAHs were relatively high for pristine locations, but did not include petroleum hydrocarbons. Characteristics of PAHs indicate large contributions of terrestrial organic matter. With the exception of Peard Bay, all the estuaries reflected the strong influence of terrestrial plant input with low δo/oo values for carbon and nitrogen. Chlorinated pesticides and PCBs were uniformly low, but detectable in fish tissue. PCB and cyclodiene concentrations were half that seen in southeast Bristol Bay. Hexachlorobenzene was detected in all fish samples.

Spatial and temporal variability in ringed seal (Pusa hispida) stable isotopes in the Beaufort Sea.

Arctic ecosystem dynamics are shifting in response to warming temperatures and sea ice loss. Such ecosystems may be monitored by examining the diet of upper trophic level species, which varies with prey availability. To assess interannual variation in the Beaufort Sea ecosystem, we examined spatial and temporal trends in ringed seal (Pusa hispida) δ13C and δ15N in claw growth layers grown from 1964 to 2011. Stable isotopes were correlated with climate indices, environmental conditions, seal population productivity, and geographic location. Sex and age did not influence stable isotopes. Enriched 13C was linked to cyclonic circulation regimes, seal productivity, and westward sampling locations. Higher δ15N was linked to lower sea surface temperatures, a higher percentage of pups in the subsistence harvest, and sample locations that were eastward and further from shore. From the 1960s to 2000s, ringed seal niche width expanded, suggesting a diversification of diet due to expansion of prey and/or seal space use. Overall, trends in ringed seal stable isotopes indicate changes within the Beaufort Sea ecosystem affected by water temperatures and circulation regimes. We suggest that continued monitoring of upper trophic level species will yield insights into changing ecosystem structure with climate change.

The seasonal energetic landscape of an apex marine carnivore, the polar bear.

Divergent movement strategies have enabled wildlife populations to adapt to environmental change. In recent decades, the Southern Beaufort Sea subpopulation of polar bears (Ursus maritimus) has developed a divergent movement strategy in response to diminishing sea ice where the majority of the subpopulation (73-85%) stays on the sea ice in summer and the remaining bears move to land. Although declines in sea ice are generally considered a challenge to energy balance in polar bears residing in some regions of the Arctic, little quantitative data exists concerning the seasonal energy expenditures of this apex marine carnivore. We used GPS satellite collars with tri-axial accelerometers and conductivity sensors to measure the location, behavior, and energy expenditure of five adult female polar bears in the southern Beaufort Sea across seasons of sea ice breakup and minimum extent. Using a Bayesian mixed-effects model, we found that energy expenditure was influenced by month, ocean depth, and habitat type (sea ice or land). Total energy expenditure from May through September ranged from 37.7 to 47.2 mJ/kg for individual bears. Bears that moved to land expended 7% more energy on average from May through September than bears that remained on the receding sea ice. In August, when bears were moving from the sea ice to land or moving north with the receding pack ice, bears that moved to land spent 7% more time swimming and expended 22% more energy. This means the immediate cost of moving to land exceeded the cost of remaining on the receding summer pack ice. These findings suggest a physiological reason why the majority of the Southern Beaufort Sea subpopulation continues to inhabit a diminishing summer ice platform. However, bears that moved to land spent 29% more time in preferred hunting habitats over the continental shelf than bears that remained on the sea ice. Bears on land also had access to subsistence-harvested bowhead whale carcasses. Hence, our findings indicate there may be a greater overall energetic benefit to move to land in this region, which suggests that the use of the diminishing summer sea ice may be functioning as an ecological trap.

Effects of offshore oil exploration and development in the Alaskan Beaufort Sea: A three-decade record for sediment metals.

Impacts from oil exploration, development, and production in the Beaufort Sea, Alaska, USA are assessed using concentrations of metals in sediments collected during 2014 to 2015, combined with a large data set for 1985 to 2006. Concentrations of 7 (1980s) or 17 (1999-2015) metals in 423 surface sediments from 134 stations, plus 563 samples from 30 cores were highly variable, primarily as a function of sediment granulometry with naturally greater metals concentrations in fine-grained, Al-rich sediment. Metals versus Al correlation plots were used to normalize metals concentrations and identify values significantly above background. Barium, Cr, Cu, Hg, and Pb concentrations were above background, but variable, within 250 m of some offshore sites where drilling occurred between 1981 and 2001; these areas totaled <6 km2 of 11 000 km2 in the total lease area. Random and fixed sampling along the coastal Beaufort Sea from 1985 to 2015 yielded 40 positive anomalies for metals in surface sediments (∼0.8% of 5082 data points). About 85% of the anomalies were from developed areas. Half the anomalies were for the 5 metals found enhanced near drilling sites. No metals concentrations, except As, exceeded accepted sediment quality criteria. Interannual shifts in metals values for surface sediments at inner shelf sites were common and linked to storm-induced transitions in granulometry; however, metal-to-Al ratios were uniform during these shifts. Sediment cores generally recorded centuries of background values, except for As, Fe, and Mn. These 3 metals were naturally enriched in sediments from deeper water (>100 m) via diagenetic remobilization at sediment depths of 5 to 15 cm, upward diffusion, and precipitation in surface oxic layers. Minimal evidence for anthropogenic inputs of metals, except near some exploratory drilling sites, is consistent with extraction of most oil from land or barrier islands in the Alaskan Arctic and restricted offshore activity to date. Integr Environ Assess Manag 2019;15:209-223. © 2018 SETAC.

Strong Seasonality in Arctic Estuarine Microbial Food Webs.

Microbial communities in the coastal Arctic Ocean experience extreme variability in organic matter and inorganic nutrients driven by seasonal shifts in sea ice extent and freshwater inputs. Lagoons border more than half of the Beaufort Sea coast and provide important habitats for migratory fish and seabirds; yet, little is known about the planktonic food webs supporting these higher trophic levels. To investigate seasonal changes in bacterial and protistan planktonic communities, amplicon sequences of 16S and 18S rRNA genes were generated from samples collected during periods of ice-cover (April), ice break-up (June), and open water (August) from shallow lagoons along the eastern Alaska Beaufort Sea coast from 2011 through 2013. Protist communities shifted from heterotrophic to photosynthetic taxa (mainly diatoms) during the winter-spring transition, and then back to a heterotroph-dominated summer community that included dinoflagellates and mixotrophic picophytoplankton such as Micromonas and Bathycoccus. Planktonic parasites belonging to Syndiniales were abundant under ice in winter at a time when allochthonous carbon inputs were low. Bacterial communities shifted from coastal marine taxa (Oceanospirillaceae, Alteromonadales) to estuarine taxa (Polaromonas, Bacteroidetes) during the winter-spring transition, and then to oligotrophic marine taxa (SAR86, SAR92) in summer. Chemolithoautotrophic taxa were abundant under ice, including iron-oxidizing Zetaproteobacteria. These results suggest that wintertime Arctic bacterial communities capitalize on the unique biogeochemical gradients that develop below ice near shore, potentially using chemoautotrophic metabolisms at a time when carbon inputs to the system are low. Co-occurrence networks constructed for each season showed that under-ice networks were dominated by relationships between parasitic protists and other microbial taxa, while spring networks were by far the largest and dominated by bacteria-bacteria co-occurrences. Summer networks were the smallest and least connected, suggesting a more detritus-based food web less reliant on interactions among microbial taxa. Eukaryotic and bacterial community compositions were significantly related to trends in concentrations of stable isotopes of particulate organic carbon and nitrogen, among other physiochemical variables such as dissolved oxygen, salinity, and temperature. This suggests the importance of sea ice cover and terrestrial carbon subsidies in contributing to seasonal trends in microbial communities in the coastal Beaufort Sea.

Synthesis of mycosporine-like amino acids by a size-fractionated marine phytoplankton community of the arctic beaufort sea.

During the RV-ARAON cruise, a comparative study on the biosynthesis of mycosporine-like amino acids (MAAs) was conducted for the size-fractionated phytoplankton of the Beaufort Sea (Arctic). The MAAs contents in the micro-phytoplankton community (>20 µm size) is considerably higher than that observed in the nano- (20-2 µm size) and pico-phytoplankton (<2 µm size) communities. The micro-phytoplankton of the Mackenzie Shelf had a relatively higher Chlorophyll a (Chl a) concentration. Considering the total phytoplankton community, the MAAs concentration as well as net production of individual MAAs (such as shinorine and palythine) were higher at the Mackenzie Shelf rather than at the sites located beyond the Beaufort Sea; precisely, the highest net production rates of shinorine and palythine were 0.211 (±0.02) ng C L-1 d-1 and 0.136 (±0.001) ng C L-1 d-1 respectively (No other MAAs were detected). The micro-phytoplankton used around 0.5% of the total carbon uptake for the synthesis of MAAs. Compared to the smaller phytoplankton community, the micro-phytoplankton utilized more of their energy for the biosynthesis of MAAs; on the other hand, nano- and pico-phytoplankton focused on cellular activity and had poor biosynthesis of MAAs. This clearly indicates the phytoplankton size-dependent variation in the biosynthesis of MAA in the natural phytoplankton community. This study revealed the environmental adaptation of the various sizes of phytoplankton community as well as their physiological response in the Arctic Beaufort Sea.