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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. Prevalence of pelagic diatoms and harmful algae in tellinid bivalve diets during record low sea ice in the Pacific Arctic determined by DNA metabarcoding

   https://doi.org/10.3389/fmars.2025.1480327  

   Koch, Chelsea W; Sonsthagen, Sarah A; Cooper, Lee W; Grebmeier, Jacqueline M; Riddle-Berntsen, Ann E; Cornman, Robert S (February 2025, Frontiers in Marine Science)

   Understanding changes at the base of the marine food web in the rapidly transforming Arctic is essential for predicting and evaluating ecosystem dynamics. The northern Bering Sea experienced record low sea ice in 2018, followed by the second lowest in 2019, highlighting the urgency of the issue for this region. In this study, we investigated the diet of the clamMacoma calcareain the Pacific Arctic using DNA metabarcoding, employing 18S and rbcL markers to identify dietary components. Our findings revealed a strong dependence on pelagic diatoms, particularlyChaetocerossp., with a near absence of ice algae in the clam diet. This pattern reflects the lack of lipid-rich ice algal production during these low sea ice events. Additionally, our analysis detected algae capable of producing harmful toxins, notablyAlexandriumdinoflagellates, in the clam diet, underscoring the need for increased monitoring due to potential ecosystem and human health risks. This study demonstrates the utility of DNA metabarcoding in unraveling the complex dynamics of Arctic marine food webs and pelagic-benthic coupling, providing a glimpse of future conditions in a rapidly changing environment. 

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3. The Distributed Biological Observatory: A Change Detection Array in the Pacific Arctic

   https://doi.org/10.1016/j.dsr2.2019.05.005  

   Grebmeier, Jacqueline M.; Moore, Sue E.; Cooper, L. W.; Frey, K. E. (January 2019, Deepsea research)

   The Distributed Biological Observatory (DBO) is a change detection array for select ecosystem variables along eight sampling transects in the Pacific Arctic Region (PAR). The overall objective of the DBO is to provide for the detection and consistent monitoring of the biophysical responses to major reductions in seasonal sea ice and concomitant increases in seawater temperatures observed across the region. A key uncertainty is how the PAR marine ecosystem is responding to these shifts in the timing of spring sea-ice retreat and/or delays in fall sea-ice formation. Variations in upper ocean hydrography, stratification, light penetration, planktonic production, pelagic-benthic coupling, and sediment carbon cycling are all influenced by sea ice and temperature changes. Observations of reduced sea ice extent/duration and seawater warming are linked to shifts in species composition and abundance, as well as northward range expansions in some upper trophic predators (e.g. humpback whales and commercially harvested fish), generally with negative impacts on ice-dependent species such as ice-associated seals and walruses. Some distributional shifts may be driven by changes in lower trophic level productivity that directly cascade into upper trophic levels. This special issue is a result of the international effort by participating scientists to implement a coordinated DBO that will meet these needs to understand the ecosystem responses to changing sea ice and thermal regimes. The key geographical focus is on the biologically productive waters in the PAR that are influenced by the inflow of North Pacific water through Bering Strait. Papers in this volume are based upon selected biological measurements at multiple trophic levels, together with appropriate hydrographic surveys and satellite observations. The DBO is developing into a significant national and international change detection resource for the identification and consistent monitoring of marine biophysical responses to climate change, with ongoing plans to expand into a pan-Arctic biological observing network. 

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4. The Distributed Biological Observatory: A change detection array in the Pacific Arctic – An introduction

   https://doi.org/10.1016/j.dsr2.2019.05.005  

   Grebmeier, Jacqueline M.; Moore, Sue E.; Cooper, Lee W.; Frey, Karen E. (January 2019, Deepsea research)

   The Distributed Biological Observatory (DBO) is a change detection array for select ecosystem variables along eight sampling transects in the Pacific Arctic Region (PAR). The overall objective of the DBO is to provide for the detection and consistent monitoring of the biophysical responses to major reductions in seasonal sea ice and concomitant increases in seawater temperatures observed across the region. A key uncertainty is how the PAR marine ecosystem is responding to these shifts in the timing of spring sea-ice retreat and/or delays in fall sea-ice formation. Variations in upper ocean hydrography, stratification, light penetration, planktonic production, pelagic-benthic coupling, and sediment carbon cycling are all influenced by sea ice and temperature changes. Observations of reduced sea ice extent/duration and seawater warming are linked to shifts in species composition and abundance, as well as northward range expansions in some upper trophic predators (e.g. humpback whales and commercially harvested fish), generally with negative impacts on ice-dependent species such as ice-associated seals and walruses. Some distributional shifts may be driven by changes in lower trophic level productivity that directly cascade into upper trophic levels. This special issue is a result of the international effort by participating scientists to implement a coordinated DBO that will meet these needs to understand the ecosystem responses to changing sea ice and thermal regimes. The key geographical focus is on the biologically productive waters in the PAR that are influenced by the inflow of North Pacific water through Bering Strait. Papers in this volume are based upon selected biological measurements at multiple trophic levels, together with appropriate hydrographic surveys and satellite observations. The DBO is developing into a significant national and international change detection resource for the identification and consistent monitoring of marine biophysical responses to climate change, with ongoing plans to expand into a pan-Arctic biological observing network. 

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5. A Chlorophyll Biomass Time-Series for the Distributed Biological Observatory in the Context of Seasonal Sea Ice Declines in the Pacific Arctic Region

   https://doi.org/10.3390/geosciences12080307  

   Cooper, Lee W.; Grebmeier, Jacqueline M. (August 2022, Geosciences)

   Declines in seasonal sea ice in polar regions have stimulated projections of how primary production has shifted in response to greater light penetration over a longer open water season. Despite the limitations of remotely sensed observations in an often cloudy environment, remote sensing data provide strong indications that surface chlorophyll biomass has increased (since 2000) as sea ice has declined in the Pacific Arctic region. We present here shipboard measurements of chlorophyll-a that have been made annually in July since 2000 from the Distributed Biological Observatory (DBO) stations in the Bering Strait region. This time series as well as shipboard observations made in other months since the late 1980s implicate complexities that intrude on a simple expectation that, as open water periods increase, the production and biomass of phytoplankton will increase predictably. These shipboard observations indicate that there have not been sharp increases in chlorophyll-a, for either maxima observed in the water column or integrated over the whole water column, at the DBO stations over a time-series extending for as long as 20 years coinciding with seasonal sea ice declines. On the other hand, biomass may be increasing in other months: we provide a shipboard confirmation of a fall bloom in October as wind mixing introduced nutrients back into the upper water column. The productive DBO stations may be at a high enough production already that additional enhancements in chlorophyll-a biomass should not be expected, but our time-series record does not exclude the possibility that additional enhanced production may be present in other areas outside the DBO station grid. These findings may also reflect limitations imposed by nutrient cycling and water column structure. The increasing freshwater component of waters flowing through the Bering Strait is likely associated with increased stratification that limits the potential change in biological production associated with decreases in seasonal sea ice persistence. 

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