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1. Changes in gray whale phenology and distribution related to prey variability and ocean biophysics in the northern Bering and eastern Chukchi seas

   https://doi.org/10.1371/journal.pone.0265934  

   Moore, Sue E.; Clarke, Janet T.; Okkonen, Stephen R.; Grebmeier, Jacqueline M.; Berchok, Catherine L.; Stafford, Kathleen M. (April 2022, PLOS ONE)

   Ummenhofer, Caroline (Ed.)

   Changes in gray whale ( Eschrichtius robustus ) phenology and distribution are related to observed and hypothesized prey availability, bottom water temperature, salinity, sea ice persistence, integrated water column and sediment chlorophyll a , and patterns of wind-driven biophysical forcing in the northern Bering and eastern Chukchi seas. This portion of the Pacific Arctic includes four Distributed Biological Observatory (DBO) sampling regions. In the Bering Strait area, passive acoustic data showed marked declines in gray whale calling activity coincident with unprecedented wintertime sea ice loss there in 2017–2019, although some whales were seen there during DBO cruises in those years. In the northern Bering Sea, sightings during DBO cruises show changes in gray whale distribution coincident with a shrinking field of infaunal amphipods, with a significant decrease in prey abundance (r = -0.314, p<0.05) observed in the DBO 2 region over the 2010–2019 period. In the eastern Chukchi Sea, sightings during broad scale aerial surveys show that gray whale distribution is associated with localized areas of high infaunal crustacean abundance. Although infaunal crustacean prey abundance was unchanged in DBO regions 3, 4 and 5, a mid-decade shift in gray whale distribution corresponded to both: (i) a localized increase in infaunal prey abundance in DBO regions 4 and 5, and (ii) a correlation of whale relative abundance with wind patterns that can influence epi-benthic and pelagic prey availability. Specifically, in the northeastern Chukchi Sea, increased sighting rates (whales/km) associated with an ~110 km (60 nm) offshore shift in distribution was positively correlated with large scale and local wind patterns conducive to increased availability of krill. In the southern Chukchi Sea, gray whale distribution clustered in all years near an amphipod-krill ‘hotspot’ associated with a 50-60m deep trough. We discuss potential impacts of observed and inferred prey shifts on gray whale nutrition in the context of an ongoing unusual gray whale mortality event. To conclude, we use the conceptual Arctic Marine Pulses (AMP) model to frame hypotheses that may guide future research on whales in the Pacific Arctic marine ecosystem. 

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2. Spatiotemporal transitions in Pseudo-nitzschia species assemblages and domoic acid along the Alaska coast

   https://doi.org/10.1371/journal.pone.0282794  

   Hubbard, Katherine A.; Villac, Maria Célia; Chadwick, Christina; DeSmidt, Alexandra A.; Flewelling, Leanne; Granholm, April; Joseph, Molly; Wood, Taylor; Fachon, Evangeline; Brosnahan, Michael L.; et al (March 2023, PLOS ONE)

   Cooper, Lee W (Ed.)

   The toxic diatom genus Pseudo-nitzschia is distributed from equatorial to polar regions and is comprised of >57 species, some capable of producing the neurotoxin domoic acid (DA). In the Pacific Arctic Region spanning the Bering, Chukchi, and Beaufort seas, DA is recognized as an emerging human and ecosystem health threat, yet little is known about the composition and distribution of Pseudo-nitzschia species in these waters. This investigation characterized Pseudo-nitzschia assemblages in samples collected in 2018 during summer (August) and fall (October-November) surveys as part of the Distributed Biological Observatory and Arctic Observing Network, encompassing a broad geographic range (57.8° to 73.0°N, -138.9° to -169.9°W) and spanning temperature (-1.79 to 11.7°C) and salinity (22.9 to 32.9) gradients associated with distinct water masses. Species were identified using a genus-specific Automated Ribosomal Intergenic Spacer Analysis (ARISA). Seventeen amplicons were observed; seven corresponded to temperate, sub-polar, or polar Pseudo-nitzschia species based on parallel sequencing efforts ( P . arctica , P . delicatissima , P . granii , P . obtusa , P . pungens , and two genotypes of P . seriata ), and one represented Fragilariopsis oceanica . During summer, particulate DA (pDA; 4.0 to 130.0 ng L -1 ) was observed in the Bering Strait and Chukchi Sea where P . obtusa was prevalent. In fall, pDA (3.3 to 111.8 ng L -1 ) occurred along the Beaufort Sea shelf coincident with one P . seriata genotype, and south of the Bering Strait in association with the other P . seriata genotype. Taxa were correlated with latitude, longitude, temperature, salinity, pDA, and/or chlorophyll a , and each had a distinct distribution pattern. The observation of DA in association with different species, seasons, geographic regions, and water masses underscores the significant risk of Amnesic Shellfish Poisoning (ASP) and DA-poisoning in Alaska waters. 

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3. Trends in benthic macrofaunal populations, seasonal sea ice persistence, and bottom water temperatures in the Bering Strait region

   https://doi.org/10.5670/oceanog.2018.224  

   Grebmeier, Jacqueline M.; Frey, Karen E.; Cooper, Lee W.; Kedra, K. (January 2018, Oceanography)

   Recent declines in sea ice extent and warming seawater temperatures in the Arctic have the potential to impact regional and pan-Arctic marine ecosystems. To investigate marine biological response to these key drivers and other environmental factors, we undertook a robust trend analysis of benthic macrofaunal populations and environmental drivers in the Bering Strait region. Our focus was on the waters of the northern Bering and southern Chukchi Seas, which are shallow (<100 m) and seasonally productive, with strong pelagic-benthic coupling between water column derived organic matter and the seafloor. Studies indicate that both in situ production and advection of upstream phytodetritus support persistent biologically productive regions, termed hotspots, in the greater Bering Strait region. The benthic marine ecosystem is dominated by macroinvertebrates (e.g., clams, polychaetes, and amphipods) that in turn serve as food resources for diving mammals and seabirds, thus allowing for changes to cascade strongly through the food web from prey to predator. During our study, the persistence of seasonal sea ice significantly declined; trend analyses indicate both earlier sea ice breakup and later fall freeze-up in recent years. When combined with warming seawater temperatures in the region, these changes have ramifications for water column processes that influence benthic faunal biomass and composition, which can transfer to upper trophic level predators. We studied these changes by evaluating time series sites in three benthic biomass hotspots starting in 1998 (Southeast Chukchi Sea region), 1999 (Chirikov Basin region), and 2000 (St. Lawrence Island Polynya region). We present these data within a broader evaluation of benthic biomass results from prior cruises dating as early as the 1970s. The current study focuses on the period 1998–2015 at sites occupied annually each July using CCGS Sir Wilfrid Laurier. Since 2010, these time series sites have become part of the international Distributed Biological Observatory (DBO), a network of standard time series stations and transect lines in the Pacific Arctic that is used for evaluating changes within the biological system. We found that these regions have experienced northward shifts in high benthic biomass and changes in dominant macrofaunal composition that are coincident with recent reduced sea ice cover and variable warming of seasonal water column temperatures. Hydrographic changes can influence chlorophyll a inventories in surface sediments and total organic carbon content, both of which are indicators of food supply to the benthos. In addition, sediment grain size reflects variable current flow that in turn influences faunal composition. Time series studies are essential for evaluating whether this region is transitioning or even reaching a “tipping point” that could shift the benthic-dominated system to a pelagic one, with large-scale ramifications for ecosystem structure in this highly productive Pacific Arctic ecosystem. 

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4. Discrete O2/Ar (Oxygen/Argon) and oxygen isotope data collected on a research cruise on the vessel Ocean Starr, Bering, Chukchi, and Beaufort Seas, Arctic Ocean, 2019.

   https://doi.org/10.18739/A20R9M539  

   Cynar, Haley; Juranek, Laurie; Mordy, Calvin; Strausz, David; Bell, Shaun (January 2021, NSF Arctic Data Center)

   Data were collected on Cruise identifier (ID) OS1901_L1 between August 1, 2019 and August 24, 2019 from either the surface uncontaminated seawater supply of research vessel (R/V) Ocean Starr or from Niskin-style water sample bottles attached to a conductivity-temperature-depth package maintained by the National Oceanic and Atmospheric Administration (NOAA) Pacific Marine Environmental Laboratory. Data were collected periodically over the cruise track which departed from Dutch Harbor, Alaska (AK) and sampled waters of the Bering and Chukchi Sea, ending in Nome, AK. This was a part of the Arctic Integrated Ecosystem Survey (Arctic IES) program. The objective of Arctic IES is to understand how reductions in Arctic sea ice and the associated changes in the physical environment influence the flow of energy through the ecosystems of the Chukchi and Beaufort seas. Two research expeditions in the Beaufort and Chukchi seas during late summer and early fall 2017 and 2019 were designed to address this objective. This survey takes measurements of the: 1) physical environment (temperature, salinity, nutrients); 2) seasonal composition, distribution and production of phytoplankton (plants); 3) distribution and standing stocks of zooplankton (bird, whale, and fish food); 4) assemblages, distributions, abundances, size, diet, and fitness of larval, early juvenile, and adult fishes; and 5) distribution and relative abundances of seabirds and marine mammals. The measurements here contribute to characterizing both the chemical environment and the rate of net biological oxygen production. 

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5. Sipunculan fauna of the northern Bering and Chukchi Seas

   Kędra, M. (January 2018, Proceedings of the 2nd International Symposium on the Biology of the Sipuncula. Smithsonian Contributions to the Marine Sciences, Smithsonian Institution Scholarly Press, Washington DC 42: 159-167; 0.5479/si.1943-667X.42)

   Sipuncula is a species-poor phylum yet sipunculans can play a considerable role in the high latitudes marine ecosystems where they often occur in very high numbers and biomass. Sipunculan studies and associated publications have been mainly concentrated in the Atlantic sector of the Arctic, with only two publications found in the Pacific sector (Murina 1977, 1985), both only published in Russian. This article presents a synopsis of the composition and distribution of sipunculans in the waters of the northern Bering and Chukchi Seas in the Pacific Arctic region, based on our own samples and published data. 

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