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Synthesis of Arctic Research (SOAR) in Marine Ecosystems of the Pacific Arctic

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Fig. 2. Schematic marine food web for the Pacific Arctic region.
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Preface
Synthesis of Arctic Research (SOAR) in marine ecosystems of the Pacific
Arctic
1. Introduction
The Pacific Arctic marine ecosystem extends from the northern
Bering Sea, across the Chukchi Sea to the East Siberian and Beaufort
seas (Fig. 1). The northern Bering, Chukchi and East Siberian seas
are comprised of broad–shallow continental shelves, while the
Beaufort Sea has a narrow shelf and steep slope culminating in
the deep Canadian Basin. Sea ice covers this region for 5–7 months
of the year, typically reaching maximum and minimum areal
extent in March and September, respectively. The narrow
(85 km) and shallow (50 m) Bering Strait is the only gateway for
Pacific water to enter the Arctic. Transport is primarily northward
and comprised of three water masses, the Alaska Coastal Water
(ACW), Bering Shelf Water (BSW) and Anadyr Water (AW).
Bering Strait inflow peaks in summer, providing a strong pulse of
comparatively fresh water, heat, nutrients and plankton to the
Chukchi–Beaufort marine ecosystem. The striking seasonality of
both sea-ice cover and transport provides foundational biophysical
conditions for ecosystem dynamics, extending from primary pro-
duction (ice algae and phytoplankton) to lower trophic (zooplank-
ton, benthic invertebrates and fishes) and upper trophic (marine
birds and mammals) animals including humans.
The Pacific Arctic marine food web is comprised of compara-
tively short linkages leading from primary production to humans
(Fig. 2). However, the simple linkages typical of arctic ecosystem
schematic diagrams belie the biophysical complexity underlying
these systems. Specifically, the influences of dynamic ocean pro-
cesses such as upwelling, lateral transport and eddies are not
depicted and so the ecosystem can appear static rather than typi-
fied by extremes in intra and inter-annual variability.
Fortunately, the dynamic nature of arctic marine ecosystems is
becoming better known. In just the past 5 years, there have been
numerous publications describing responses of arctic marine
ecosystems to recent extreme physical changes. Of the many books
and journal articles, three volumes stand out as especially relevant
to this special issue: Wassmann (2011), which focused on impact
of rapid climate changes on marine ecosystems primarily in the
Atlantic arctic region; Kulkarni et al. (2012), which summarized
results of research conducted during the International Polar Year
in the Canadian Arctic region; and Grebmeier and Maslowski
(2014), which reviewed status and trends of the Pacific Arctic mar-
ine ecosystem. Articles in each of these volumes provide context
for this issue, from the ‘discovery’ of winter production by bacteri-
oplankton and protists (e.g., Darnis et al., 2012) to projections of
novel biogeochemical cycling schemes anticipated with the loss
of sea ice (e.g., Wassmann, 2011). As in recent-past volumes, the
synthesis of information provided here contributes to an expand-
ing body of knowledge and an improved understanding of the sta-
tus and trajectories of arctic marine ecosystems.
The initiation of the Synthesis of Arctic Research (SOAR) project
coincided with the recognition that biophysical changes in the
Pacific Arctic region were so extreme, compared to the recent past,
that they acquired the moniker ‘new normal’ (Jeffries et al., 2013).
Consequently, describing the biophysical properties of the ‘new’
Pacific Arctic marine ecosystem was foundational to the SOAR
effort and the focus of five papers in this issue. Examining biolog-
ical responses to the new biophysical forcing then became the task
of researchers focused on the study of lower trophic level (LTL)
communities and upper trophic level (UTL) species. Two papers
provide integrated results from direct sampling of benthic and fish
communities, while three papers report on changes in LTL species
occurrence inferred by shifts in the diets of seals and marine birds.
Six papers focus on UTL species, with four presenting information
on seasonal occurrence in hotspot or core-use habitats, and two
describing variability in marine mammal body condition in the
context of decadal-scale environmental variability. Together, these
papers provide a synthetic context to focus hypotheses underpin-
ning the next-decade of research in the Pacific Arctic marine
ecosystem.
2. Biophysics of the Pacific Arctic marine ecosystem
The Pacific Arctic marine ecosystem is comprised of inflow
shelves (northern Bering and Chukchi seas) coupled to interior
shelves (East Siberian and Beaufort seas), with the contrasting
biophysics of these domains summarized in Carmack et al.
(2006). Circulation on both inflow and interior shelves is linked
to pan-arctic teleconnection mechanisms (e.g., Arctic Oscillation),
with interior shelves also strongly influenced by the seasonal
outflow of relatively warm fresh water from arctic rivers.
Evaluating ecosystem status and trends in the Pacific Arctic was
the focus of a recent book, with 10 (of 12) chapters devoted to
observations and modeling of the atmosphere, ocean physics and
chemistry (Grebmeier and Maslowski, 2014). The papers in this
issue add to that body of knowledge, especially with regard to bio-
logical responses to biophysical drivers, and in this way contribute
to a more holistic understanding of the Pacific Arctic marine
ecosystem.
http://dx.doi.org/10.1016/j.pocean.2015.05.017
0079-6611/Published by Elsevier Ltd.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Progress in Oceanography xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Progress in Oceanography
journal homepage: www.elsevier.com/locate/pocean
2.1. Physical observations and open-water projections in the ‘new
normal’ Pacific Arctic
Recent observations (2003–2013) of environmental changes in
the Pacific Arctic support the contention that a ‘new normal’ cli-
mate is emerging (Fig. 3;Jeffries et al., 2013; Wood et al., this
issue). The iconic indicator of this change is the dramatic summer-
time loss of sea ice (50% by area, 75% by volume), which in some
years (e.g., 2012) has resulted in nearly ice-free conditions in the
region. Specifically, satellite data from 1979 to 2012 reveal local-
ized changes in sea ice occurrence of up to 1.64 days/year in
the Canada Basin and 1.24 days/year in the Beaufort Sea, which
accelerated to 6.57 days/year (Canada Basin) and 12.84 days/
year (Beaufort Sea) during the 2000–2012 period (Frey et al., this
issue). Multiyear sea ice has almost entirely disappeared, with
inter-annual variability in ice concentration largely driven by wind
forcing in the Beaufort Sea. In the Canada Basin, differences in
annual sea ice are primarily thermally driven, while sea-ice extent
is influenced by both winds and heat on the Bering Sea shelf.
The summer atmospheric patterns influence ocean circulation,
freshwater pathways and the movement and melting of sea ice.
During the last decade, the intensification of the Beaufort High
(Ogi and Wallace, 2012) resulted in anomalous summer winds.
These anomalous winds together with the loss of multi-year ice
were the primary factors that transformed the Chukchi and north-
ern Beaufort seas into an open water environment (Wood et al.,
this issue). In particular, the eastern Beaufort Sea appears to be
particularly susceptible to anomalous winds through their effect
on the advection of warm, fresh water from the Mackenzie River
plume. In addition, transport anomalies in the Bering Strait are
determined by competing large-scale atmospheric patterns, the
Beaufort High and Aleutian Low (Danielson et al., 2014). Notably,
changes in Bering Strait flow through can impact the world climate
far beyond the Bering Strait and Arctic region (e.g., Hu et al., 2015).
Frey et al. (this issue, Fig. 13) investigate the influence of the
Pacific Decadal Oscillation (PDO) and the Arctic Oscillation (AO)
on the persistence of sea ice in summer and winter. They found sig-
nificant negative correlations between sea ice on the southeastern
Bering Sea shelf and the PDO in winter, as well as significant pos-
itive correlations between the AO and sea-ice cover just south of St.
Lawrence Island. Significant positive correlations between the PDO
and sea ice in the Canada Basin-Canadian Archipelago were found
in summer, as well as between the AO and sea ice in the Chukchi–
Beaufort seas. This novel investigation of teleconnections between
the PDO, the AO and sea-ice cover provides a critical step in under-
standing how global and regional climate patterns influence the
physics of the Pacific Arctic region.
The unprecedented loss of sea ice has resulted in a tremendous
increase in open-water susceptible to rapid solar heating, with
additional heat and fresh water provided by a 50% increase in
Pacific Water inflow at Bering Strait from 2001 to 2011
(Woodgate et al., 2012; Wood et al., this issue). The influence of
increased heat stored in the Chukchi and Beaufort seas is not well
understood. Suggestions that heat released to the atmosphere in
late autumn and winter drives aspects of mid-latitude weather
remain speculative, largely due to the short time record available
(Wood et al., this issue). Freshening of the Arctic Ocean has been
occurring at least since the 1990s (e.g., Giles et al., 2012). Several
explanations have been proposed including increased sea-ice melt,
fresher Pacific Water flowing through Bering Strait, changes in the
120°
140°
160°
180°160°E140°
65°
60°
55°
0
200 400 km
Siberia
Alaska
Canada
Siberian Coastal
Current
Atlantic
Water
Beaufort
Gyre
Alaska
Coastal
Water
Anadyr
Water
Bering
Shelf
Water
Arctic Ocean
September
March
Beaufort Sea
East
Siberian Sea
Chukchi Sea
Wrangel
Island
St. Lawrence
Island
Bering Sea
Bering Strait
75°N
70°
100°W
Fig. 1. Pacific Arctic regional map depicting maximum (March) and minimum (September) sea ice extent (see Frey et al., this issue; Fig. 1) and major currents (see Wood
et al., this issue; Fig. 13).
2Preface / Progress in Oceanography xxx (2015) xxx–xxx
Bowhead
whale Arctic/Saffron
Cod
Seabirds
Phytoplankton
Polar bear
Zooplankton
Killer whale
Walrus
Seal
Ice algae
Human
Beluga
whale
Gray
whale
Epibenthos
Benthos
Algae mat
Fig. 2. Schematic marine food web for the Pacific Arctic region.
Fig. 3. Highlights of recent biophysical changes in the Pacific Arctic marine ecosystem.
Preface / Progress in Oceanography xxx (2015) xxx–xxx 3
magnitude of river discharge and the mean strengthening of the
Beaufort High. In recent years, relatively strong easterly winds have
been common due to the Arctic-wide pattern of circulation around
an intensified Beaufort High. Under these conditions fresh and
warm water fromthe Mackenzie River plume can be laterally trans-
ported far out into the Beaufort Sea (Wood et al., this issue, Fig. 17).
Wang and Overland (this issue) used twelve coupled climate
models to produce composite projections of the duration of open
water in the Chukchi and Beaufort seas, at decadal intervals from
2010 to 2050, and in 2090. For waters north of the 70°N, open-wa-
ter duration shifts from 3 to 4 months in 2010 to a projected
5 months by 2040. Projected open-water duration is about
1 month longer along the same latitudes in the Chukchi Sea com-
pared with the Beaufort Sea, with uncertainty of about ±1 month
estimated from the range of model results. All models projected
open-water duration to expand quickly over the next three dec-
ades, which will impact regional economic access and potentially
alter ecosystems. Yet the Pacific Arctic region will remain covered
with thin first-year ice from January through May into the second
half of the century, due to seasonal lack of sunlight.
2.2. Changes in primary production and ocean acidification
The dramatic loss of sea-ice extent and volume has resulted in a
concomitant increase light penetration in the upper ocean across
the Arctic. Given the thinning and areal reduction of sea ice, a fun-
damental question arises: have these changes fostered an increase
in marine primary production? Specifically, is the Pacific Arctic
region more productive than it was three decades ago? In the
Atlantic arctic, Leu et al. (2011) measured primary production
by both ice algae and phytoplankton in contrasting years
(2007–2008) of sea-ice cover in a Svalbard fjord, and concluded
that earlier ice break up corresponded with earlier onset of a
phytoplankton bloom. Similarly, Tremblay et al. (2012) report
increased primary production for 2007–2008 associated with
extreme sea-ice retreats and increased upwelling at stations
located south and east of Banks Island in the southeastern
Beaufort Sea. But, can conclusions drawn from measurements so
restricted in space and time be extrapolated to larger arctic
regions? Using satellite imagery, Arrigo and van Dijken (this
issue) investigated changes in sea ice at both regional and basin
scales from 1998 to 2012 and estimated how these changes have
impacted rates of net primary production (NPP) by phytoplankton.
They report that annual NPP increased 30% during this period, with
the largest increases on the interior shelves (including the East
Siberian and Beaufort) and smaller increases on inflow shelves
(including the Chukchi). Outflow shelves either exhibited no
change in annual NPP, or a significant decline, perhaps indicating
that nutrients had been consumed further upstream. Increased
annual NPP was often, but not always, associated with reduced
sea-ice extent and resultant longer phytoplankton growing season.
Human activities have increased the atmospheric CO
2
concen-
tration by about 40% since the beginning of the industrial age
and it is estimated that the ocean has absorbed more than 25% of
the total anthropogenic emissions (Mathis et al., this issue). The
oceanic uptake of CO
2
triggers a series of chemical reactions in
the surface ocean that reduces pH and results in ocean acidification
(OA). In short, OA makes seawater corrosive to calcium carbonate
minerals, which many marine organisms rely on for body struc-
tures. High-latitude oceans have naturally low carbonate concen-
trations, so are considered to be more vulnerable to the impacts
of OA because additional carbonate loss represents a much greater
proportional change to the system. In a novel study, Mathis et al.
provide a risk assessment of OA impacts to commercial and tradi-
tional fisheries focused on shellfish, salmon and finfish. The resul-
tant index suggests that while the northern Bering Sea is at
medium risk from OA impacts to fisheries, Pacific Arctic waters
north of the Seward Peninsula are currently at low risk, due largely
to a lack of dependence on these food sources.
3. Lower trophic level communities: signals from direct and
indirect sampling
The predominant conceptual model framing how marine
ecosystems in the Pacific Arctic respond to reduced sea ice is based
on changes anticipated from a shift in pelagic–benthic coupling
Benthic Dominated Pelagic Dominated
Past Future
Ice algae
Phytoplankton
Phytoplankton
Ice algae
Benthos
Walrus
Gray whale,
Bearded seal
Demersal fish
Zoo-
plankton
Benthos
Pelagic fish
Bowhead
whale
Seabirds
Gray whale
Diving ducks
Zoo-
plankton
Fig. 4. Generalized conceptual model depicting the influence of sea ice on pelagic–benthic coupling on Pacific Arctic continental shelves.
4Preface / Progress in Oceanography xxx (2015) xxx–xxx
(Fig. 4). On the broad shelves that comprise much of the Pacific
Arctic marine ecosystem, new primary production from sea-ice
algae and phytoplankton blooms falls to the sea floor to support
rich benthic communities (Grebmeier, 2012). As sea ice thins and
retreats earlier in the season, it is anticipated that earlier and larger
phytoplankton blooms will switch from a benthic-dominated to a
pelagic-dominated marine ecosystem. This shift will cascade
through the system, supporting novel communities of secondary
and tertiary consumers (zooplankton and forage fishes) and upper
trophic level marine birds and mammals. Indeed, Grebmeier et al.
(2006) suggested that this type of ecosystem shift is already under-
way in the marine communities of the northern Bering Sea. The
Pacific Arctic is often described as a benthic-dominated marine
ecosystem, one that does not support a large biomass or species
diversity of fishes. A description of conditions that have fostered
existing benthic hotspots offers a solid foundation for assessing
future changes, while an accounting of the existing communities
of marine fishes across a spectrum of habitats provides a starting
point upon which to build a long-term record.
3.1. Benthic hotspots and marine fishes across a spectrum of habitats
A record of extant conditions is key to interpreting marine
ecosystem responses to the new biophysical forcing now evident
in the Pacific Arctic. Such a record exists for four benthic ‘hotspot’
communities in the northern Bering and Chukchi seas (Grebmeier
et al., this issue), but not for marine fishes. Long-term sampling of
benthic macrofaunal communities indicates that the benthic hot-
spots have maintained consistently high biomass for up to four
decades, due to reoccurrence of seasonally reliable moderate-to-
high water column production coupled with significant export of
carbon from overlying waters to the sea floor. Upper trophic level
benthivores target prey aggregations in each of the hotspots.
Overall, bottom-up forcing by hydrography and food supply to
the benthos influences persistence and composition of benthic
prey, which in turn influences the upper trophic level species com-
position and seasonal occurrence. When consistently sampled in
tandem, these benthos–benthivore connections can facilitate use
of UTL species as sentinels of shifts in prey composition and
abundance (Moore et al., 2014).
Since the 2000s, there have been a host of Arctic marine fish sur-
veys in the western Beaufort and Chukchi seas, precipitated by both
scientific interest in the impacts of climate change and commercial
interest in oil and gas development (Logerwell et al., this issue).
Results from these surveys provide a novel opportunity to compare
Arctic fish communities across a spectrum of habitats, ranging from
lagoons and beaches to benthic and pelagic continental shelf
waters. A synthesis of data from these surveys revealed more sim-
ilarities than differences in habitat use between the two seas. For
example, nearshore habitat is used by all age classes of forage fishes
and is also a nursery area for other species in both the Chukchi and
western Beaufort seas. Notably, some commercial species may be
expanding their range north to these waters, including chinook sal-
mon (Oncorhynchus tshawytscha), walleye pollock (Gadus
chalcogrammus) and flatfishes (Pleuronectidae). In addition, a syn-
thesis of information on relative abundance and age of arctic cod
(Boreogadus saida) and saffron cod (Eleginus gracilis), both key prey
species in Arctic food webs, supported the development of life his-
tory and distribution models that will inform future research on
trophic dynamics in the Pacific Arctic sector.
3.2. Inferences of marine ecosystem shifts from seals, seabirds and sea
ducks
Additional information regarding the impact of ‘new normal’
biophysical conditions on lower trophic level species can be
inferred from shifts in the diet and body condition of marine mam-
mals and birds. Crawford et al. (this issue) compared the diet and
condition of ringed seals (Pusa hispida) and bearded seals
(Erignathus barbatus) harvested in the Alaskan Bering and
Chukchi seas during historical (1975–1984) and recent (2003–
2012) periods. They found the proportion of fish in the diet of both
species increased in the recent reduced-ice period compared to the
historical period. In addition, ringed seals grew faster, had thicker
blubber and matured 2 years earlier. Bearded seals had thicker
blubber in the recent period, but did not manifest the other
changes reported for the ringed seals. Although a number of the
comparisons were not statistically significant, taken together these
observations suggest greater fish availability in the Alaskan
Bering–Chukchi marine ecosystem supporting good body condi-
tion in the seals.
As in the seal paper, Divoky et al. (this issue) parsed a long-term
data set into recent (2003–2012) and historical (1975–1984) peri-
ods to compare oceanographic conditions, nestling diet and fledg-
ing success at a black guillemot (Cepphus grylle mandtii) breeding
colony in the western Beaufort Sea. From 15 July to 1 September,
sea ice retreated an average of 1.8 km per day to an average dis-
tance of 95.8 km from the colony during the historical period,
while in the recent period ice retreat averaged 9.8 km per day to
an average distance of 506.9 km. Sea surface temperature near
the colony increased by 2.9 °C between the two periods. While
Arctic cod comprised over 95% of the prey provided to nestlings
in the historical period, this proportion decreased to <5% of the
nestling diet during most years in the recent period, when demer-
sal sculpin (Cottidae) comprised the majority of the diet. The shift
away from Arctic cod was associated with a five-fold increase in
the rate of nestling starvation and reductions in nestling growth
and fledging mass. Conversely, annual adult survival during the
nonbreeding season (September–May), showed no significant dif-
ference between the two periods, suggesting no change in the
availability of Arctic cod or other prey to black guillemots in their
Bering Sea wintering area.
In contrast to a reliance on pelagic prey, Lovvorn et al. (this
issue) investigated potential climate-related limits to benthic feed-
ing by sea ducks along their migration corridor in the northeastern
Chukchi Sea. King eiders (Somateria spectabilis) primarily eat clams
(bivalves) during migration and recent sampling has shown that
dense clam assemblages occur only in specific locations along the
migration corridor. Sea ice can prevent eiders from reaching these
prime feeding sites, with satellite data for April–May (2001–2013)
showing that access can vary from 0% to 100%. In a warming and
increasingly variable climate, access to benthic feeding sites may
be further eroded by the effects of winds on unconsolidated ice.
These results underscore the importance of maintaining a range
of benthic feeding areas throughout the migration corridor to
ensure prey availability to the eiders each year.
4. Upper trophic level species: marine birds and mammals as
ecosystem sentinels
As top predators, marine birds and mammals must adapt to
changes in their habitats resulting from physical forcing and
thereby can serve as sentinels to ecosystem shifts (Moore et al.,
2014; Moore and Gulland, 2014). Responses of upper trophic level
(UTL) species to altered habitats can be categorized as extrinsic,
including shifts in range, migratory timing (phenology), or regions
of high abundance (hotspots); or intrinsic, including changes in
diet, body condition and chemical composition (Fig. 5).
Responses are inter-related such that a shift in range, phenology
or use of hotspots will be reflected in changes in diet, body condi-
tion and chemistry. It is this connection that allows us to detect
ecosystem reorganization by tracking changes in the ecology and
Preface / Progress in Oceanography xxx (2015) xxx–xxx 5
physiology of UTL species. Although there have been no coordi-
nated long-term studies of UTL species in the Pacific Arctic, a syn-
thesis of information from visual surveys, satellite tagging of
individuals and year-round acoustic detections provides an ecolog-
ical foundation that can provide a baseline to inform future
investigations.
4.1. Seasonal occurrence, hotspot habitats and acoustic ecology
Kuletz et al. (this issue) depict spatial patterns of relative abun-
dance of seabirds and marine mammals in summer and fall,
derived from 6 years of visual surveys in the eastern Chukchi and
western Beaufort seas. Using statistical spatial analysis tools, hot-
spots for seabirds, walrus, and gray whales were identified in the
Chukchi Sea, while hotspots for bowhead whales and seals were
described near Barrow Canyon and along the Beaufort Sea shelf
and slope. Hotspots for belugas occurred in both the Chukchi and
Beaufort seas. In summer, three hotspots were shared by both sea-
birds and marine mammals in the Chukchi Sea: waters offshore
Wainwright, south of Hanna Shoal, and at the mouth of Barrow
Canyon. Only the Barrow Canyon hotspot was occupied through
the fall. Shared hotspots were characterized by strong fronts
caused by upwelling and currents, which can serve to aggregate
prey. Using a different approach, Citta et al. (this issue) provide
detailed analysis of the seasonal movements and habitat use by a
single species throughout 1 year. Locations from 54 bowhead
whales (Balaena mysticetus), obtained by satellite telemetry from
2006 to 2012, were used to identify a total of six core-use areas
in the Beaufort (3), Chukchi (1) and northern Bering (2) seas.
Taken together, the timing of use (phenology) and physical charac-
teristics (oceanography, sea ice, and winds) associated with each
area, describe a seasonal circuit by the whales through areas
thought to support elevated prey densities.
Passive acoustic sampling has become a common year-round
tool to detect calling marine mammals in arctic seas (Moore
et al., 2006; Stafford et al., 2012). Since 2007, there has been an
especially strong sampling effort associated with oil and gas explo-
ration in the northeast Chukchi and western Beaufort seas (e.g.,
Hannay et al., 2013;http://www.afsc.noaa.gov/nmml/cetacean/
chaoz.php). These recorder deployments augment a long-standing
acoustic study in the central Beaufort Sea (Blackwell et al., 2007)
and more recent deployments in the Bering Strait region (K.
Stafford, pers. comm.). Heretofore, researchers conducted each of
these studies independent of one another. Clark et al. (this issue)
presents a novel synthesis of the combined output from six
research efforts using four types of recorders and a variety of
sub-sampling and analysis schemes to describe an ‘acoustic year’
in the life of the bowhead whale. Detections of bowhead calls from
20 sites extending over 2300 km from the northern Bering Sea to
the southeast Beaufort Sea were combined over a 14-month period
(2009–2010) to describe whale occurrence across their range. The
spatial and temporal variability in sound levels within the fre-
quency band of bowhead whales was also quantified. The lowest
underwater sound levels occurred from late November until May
in the Chukchi Sea. During winter 2009–2010, singing bowhead
whales elevated broadband sound levels for roughly 38 days in
the northern Bering Sea, followed by a second month-long period
of elevated sound levels due to singing by bearded seals. High-
wind events also resulted in 2–5 day periods of elevated sound
levels, evident on multiple recorders hundreds of miles apart.
Although there were few seismic surveys during the 14-month
period, air gun sounds were detected in the Chukchi Sea in late
summer 2009, roughly 700 km away from the seismic survey
underway in the eastern Beaufort Sea.
In a second paper describing the acoustic ecology of marine
mammals in the Pacific Arctic, MacIntyre et al. (this issue)
investigated bearded seal calling activity in relation to variability
in sea-ice cover. Acoustic data were analyzed from 9 recording
locations extending from the Bering to the western Beaufort Sea.
Bearded seals were vocally active nearly year-round in the
Beaufort and Chukchi seas, with peak activity occurring during
the springtime mating season. Conversely, bearded seal calling
Fig. 5. Marine birds and mammals are upper trophic level (UTL) species that reflect ecosystem alterations by changes in habitat use (extrinsic) and body condition (intrinsic).
Tracking both extrinsic and intrinsic responses in UTL species can reveal fundamental changes in marine ecosystems (modified from Moore et al., 2014).
6Preface / Progress in Oceanography xxx (2015) xxx–xxx
activity lasted only about 5 months in the Bering Sea, again with a
mating-season peak in the spring. In all areas, calling activity was
positively correlated with sea-ice cover (p< 0.01). These results
suggest that losses in sea ice may negatively impact bearded seals,
both by loss of haul-out habitat and by altering the phenology of
calling for bearded seals in the Pacific Arctic sector.
4.2. Diet and body condition
For bowhead whales, changes associated with the new biophys-
ical conditions in the Pacific Arctic may be a ‘good bump’ in a long
road. Bowhead whales can live for a century or more, with a few
whales estimated to have lived over 200 years (George et al.,
1999). The Bering–Chukchi–Beaufort (BCB) population is still
recovering in number from roughly 170 years of commercial whal-
ing, which ended around 1920, so responses by this species to
recent changes in the marine ecosystem must be interpreted in
that context. George et al. (this issue) examined the relationship
between body condition of BCB bowhead whales and inter-annual
variability in summertime environmental conditions (seasonal
sea-ice cover and wind stress) for whales harvested by Alaskan
hunters from 1989 to 2011. During this period, there was a signif-
icant increase in axillary girth (fatness) associated with the reduc-
tion in sea ice and shifts in wind stress to patterns associated with
upwelling along the slope and shelf of the Beaufort Sea.
Specifically, strong positive correlations were described between
whale girth and late-summer open water fraction in the Beaufort
Sea, and with open water and upwelling-favorable winds in areas
of the Mackenzie Delta and waters west of Banks Island.
Whether due to increased secondary productivity associated with
upwelling, or due to a longer feeding period associated with
reduced ice cover, the improved body condition of whales in the
BCB bowhead population suggest they are finding increased access
to prey in the ‘new normal’ Pacific Arctic.
The utility of looking to UTL species as ecosystem sentinels is
further explored in Harwood et al. (this issue), where body condi-
tion of five predators, monitored from harvests in the Beaufort Sea
over the past 2–4 decades, indicate that all have been affected by
biophysical changes in the marine ecosystem. Improved body con-
dition is described for Arctic char (Salvelinus alpinus) and sub-adult
bowhead whales, primarily associated with the extent and persis-
tence of sea ice. Conversely, three species, which likely feed pri-
marily on arctic cod (ringed seal, beluga and black guillemot
chicks), showed declines in condition, growth and/or production
during the same period. Although the proximate causes of these
contrasting changes are unknown, they are likely mediated by an
upward trend in secondary productivity accompanied by a down-
trend in the availability of forage fish, especially Arctic cod, a key
species in arctic food webs. Notably, the reported decline in body
condition for ringed seals contrast with that reported in
Crawford et al. (this issue), but this may be due to differences in
prey availability in sub-regions of the Pacific Arctic where the har-
vested seals were feeding; i.e., the eastern Beaufort Sea (Harwood
et al.) and the Bering–Chukchi (Crawford et al.). Similar contrasts
in size and body condition for polar bears (Ursus maritimus) were
recently described for animals from the Chukchi Sea (good) and
the Beaufort Sea (poor) populations (Rode et al., 2013). Indeed,
Harwood et al. (this issue) advocate the inclusion of multiple UTL
species in the sampling design of future marine ecosystem
research programs, at ecologically relevant spatial and temporal
scales.
5. Biophysics and marine ecology of the Pacific Arctic region
The biophysics and marine ecology of the Pacific Arctic region is
a study in contrasts, resulting from differing processes that occur
over the broad and shallow inflow shelves of the northern Bering
and Chukchi seas, compared to the narrow interior shelf, steep
slope and deep basin of the Beaufort Sea. Carmack and
Wassmann (2006) provide a pan-Arctic overview on the role of
shelves in guiding oceanographic processes, and promote ‘shelf
geography’ as a unifying concept with regard to linking physical
processes to food webs. Using this concept, Carmack and
Wassmann (2006) identified the Pacific Arctic region as one of four
contiguous domains comprising the pan-Arctic; the other three are
the seasonal ice zone domain, the pan-Arctic marginal (shelf-break
and slope) domain and the riverine coastal domain. As described in
Wood et al. (this issue), hydrography in the Pacific Arctic region is
defined by Pacific waters entering the Chukchi through Bering
Strait, warming as they are advected through the Chukchi Sea
and circulating at depths <200 m within the Beaufort gyre of the
Canada Basin. The entrapment of this inflow within the gyre
increases the volume of fresh water and intensifies stratification
with the warmer–saltier Atlantic water below.
The role of sea ice in regulating pelagic–benthic coupling (see
Fig. 4) is the foundational model regarding the structure of food
webs on the broad in-flow shelves. Indeed, the biophysics and ecol-
ogy of benthic communities in the Pacific Arctic is fully described
in Grebmeier et al. (this issue). However, nutrients and expatriate
zooplankton from the northern Bering Sea are also advected in
Pacific water across the wide Chukchi shelf and into the Beaufort
Sea (Nelson et al., 2014), and the role of this transport is often
ignored in conceptual models of the marine ecosystems. Clearly,
advected prey are important to UTL species – one example being
the consumption of Pacific species of euphausiids by bowhead
whales at Barrow and as far east as Kaktovik, Alaska in the eastern
Beaufort Sea (Lowry et al., 2004). A new conceptual model is
required to capture the complex interconnectivity between the
role of pelagic–benthic coupling and that of the strongly seasonal
transport of heat, nutrients and prey into the region.
5.1. Ecosystem conceptual models and visualization tools: the ‘Arctic
Marine Pulse’ model
The sea-ice driven pelagic–benthic coupling model has served
the science community well for nearly three decades (Grebmeier,
2012, and references therein). While the pelagic–benthic model
serves as a strong framework for depicting processes on the shal-
low shelf habitat of the northern Bering and Chukchi seas, it does
not depict the interactive processes occurring along the narrow
interior shelf, slope and deep basin of the Beaufort Sea. Carmack
and Wassmann (2006) advocate for the development of ‘‘an ecol-
ogy of advection’’ to advance ecosystem models that can support
inter-comparisons of existing and future arctic food webs.
Grebmeier et al. (2015) provide a comprehensive conceptual
model linking advective processes in the Chukchi and Beaufort.
The input function for this model is the advection north of Pacific
Water (comprised of AW, BSW, ACW; see Fig. 1). The three path-
ways for this inflow cross the Chukchi Sea, then enter the
Beaufort Sea primarily at canyons with further advective processes,
including eddy shedding, along the slope. Freshwater inflow from
the Yukon and Mackenzie rivers is depicted, as is nearshore out-
flow of Siberian Coastal Water (SCW) along the Russian north
coast. This conceptual advective model is an essential tool to frame
our understanding of the Pacific Arctic marine ecosystem, but
remains a comparatively static representation of very dynamic
processes.
The ‘krill trap’ model, developed during a study of bowhead
whales feeding on euphausiids transported to local waters near
Barrow, provides a starting point to animate an advective model
for a portion of the Pacific Arctic region (Ashjian et al., 2010).
Physical drivers of this local-area model invoke wind forcing,
Preface / Progress in Oceanography xxx (2015) xxx–xxx 7
shelf-break topography and current structure along Barrow
Canyon to explain the retention of krill along a front on the west-
ern Beaufort shelf (Okkonen et al., 2011). This dynamic model
essentially ‘‘rocks back and forth’’ between two states: upwelling
of prey and nutrients onto the narrow shelf induced by easterly
winds, and prey retention induced by relaxed or southerly winds.
This model focuses on only the western Beaufort Sea, however,
and requires expansion to serve the full Pacific Arctic region.
Here we propose an Arctic Marine Pulses (AMP) conceptual
model for the Pacific sector, which aims to both animate the
Grebmeier et al. (2015) advection model and link it to the pela-
gic–benthic coupling model (Fig. 6). In this way, the zooplankton
and forage fish predicted by the pelagic–benthic model with the
loss of sea ice are advected across the Chukchi and into the
Beaufort Sea by the advective model. The AMP model employs
the contiguous domain concept, described in Carmack and
Wassmann (2006), to join physical habitats by the integration of
common features such as the seasonal cycles of inflow at Bering
Strait, sea-ice advance and retreat, and riverine export.
Specifically, the AMP model connects four contiguous domains
(Fig. 7):
(i) Pacific Arctic domain – this is the ‘focal region’, comprised of
a broad–shallow inflow system (Chukchi) connecting to
Fig. 6. Components of the Arctic Marine Pulses (AMP) conceptual model – linking pelagic–benthic coupling and advective models to derive a seasonal model for the Pacific
Arctic framed by contiguous domains.
Fig. 7. Arctic Marine Pulses (AMP) conceptual model depicting seasonal biophysical ‘pulses’ across a latitudinal gradient linking four contiguous domains: (i) summertime
peak-inflow of Pacific Water initiates advective processes in the Pacific Arctic domain; (ii) variability in the annual cycle of the seasonal ice zone domain influences pelagic–
benthic coupling on continental shelves of the northern Bering and Chukchi seas and shelf-basin exchange in the Beaufort sea; (iii) advection and upwelling dominate
processes along the Beaufort Sea shelf-break and slope in the Pacific marginal domain, while (iv) the riverine and coastal domain is influenced by summertime outflow of
warm-fresh water from the Yukon and Mackenzie rivers.
8Preface / Progress in Oceanography xxx (2015) xxx–xxx
inner-shelf-slope-basin system (Beaufort); the strong sum-
mer-pulse of comparatively fresh water, heat, nutrients and
plankton through Bering Strait initiates the AMP model, as
it does the advection model in Grebmeier et al. (2015);
(ii) Seasonal ice zone domain – seasonal ice retreat serves to link
the AMP model to the pelagic–benthic coupling model.
Timing and pace of sea-ice retreat across the Chukchi Sea
drives pulses of organic material either to the benthos, or
toward the pelagic system; sea-ice retreat beyond the nar-
row Beaufort shelf in late summer allows the system to
respond to winds that can induce pulses of upwelling of
nutrients and prey onto the shelf;
(iii) Pacific marginal domain – the Beaufort Sea shelf break and
slope is a transport pathway for nutrients and prey advected
across the Chukchi Sea; this marginal domain also provides
links to the deep basin where stores of nutrients and prey
can be upwelled by wind forcing after the sea-ice retreats;
Herald and Barrow canyons are focal points of shelf-basin
exchange (i.e., secondary pulse-points) although local winds
can reverse flow;
(iv) Riverine coastal domain – the Yukon and Mackenzie river
outflows provide seasonal pulses of warm and fresh
water to the northern Bering and Beaufort seas, respectively.
In the Beaufort, the Mackenzie outflow can trap nutrients
and prey. The Mackenzie outflow has increased dramatically
over the past decade (Wood et al., this issue) and,
with increased seasonal run-off, the Sagavanirktok
and Colville rivers may have greater influence now than in
the past.
The AMP conceptual model could be enhanced by the applica-
tion of visualization tools to provide the capability to see a season
unfold. The ability to track water mass characteristics and to move
nutrients, prey and UTL species through the Pacific Arctic in space
and time would provide a foundation for insight and aid in the
development of dynamic ecosystem models. Although not quanti-
tative, a step in this regard was taken during the production of a
short animated film called ‘Arctic Currents: a year in the life of a
bowhead whale’ (http://www.uaf.edu/museum/exhibits/digital-
media/arctic-currents/). The film depicts the movements of
individual whales equipped with satellite tags, in tandem with
the seasonal advection of krill through Bering Strait, across the
Chukchi Sea and along the Beaufort Sea slope. What is not por-
trayed are the pelagic–benthic ‘pulses’ of nutrients so important
to the development of benthic ‘hotspots’ and the prey of
benthivores such as eiders, walruses, bearded seals and gray
whales. Currently, visualization tools are most commonly applied
to satellite-derived data, which can only provide information on
the ‘skin’ of the ocean. Visualizing biophysical pulses in three
dimensions, parameterized by measured values where available,
could move us in the direction of predictive model capability for
the Pacific Arctic marine ecosystem.
6. Outlook
The papers in this special issue provide a range of synthesis
approaches to capture the existing conditions in the Pacific
Arctic marine ecosystem. By design, the focus was on the state
of the ecosystem now, that is the biophysics of the ‘new normal’
Pacific Arctic – which has emerged during this century.
Collectively the papers cover all ecosystem topics, from atmo-
spherics, sea ice and shifting hydrography, to responses by LTL
and UTL species to the new and highly variable state of the
marine ecosystem. This compendium of papers serves as a step
toward a more holistic understanding of the Pacific Arctic marine
ecosystem.
The SOAR project is not the only effort focused on an integrated
synthesis of conditions in the Pacific Arctic. The seasonal and inter-
annual dynamics of the northeastern Chukchi Sea ecosystem was
the focus of intense study from 2008 to 2010, resulting in a special
volume of papers (Hopcroft and Day, 2013). A second special vol-
ume of papers describing results of sampling across the full
Chukchi Sea during the decade-long RUSALCA project is antici-
pated by the end of this year (K. Crane, pers. comm.).
Alternatively, the Pacific Marine Arctic Regional Synthesis
(PacMARS) project provided an extensive review and compilation
of extant data for the Pacific Arctic region, as well as detailed sug-
gestions for future research themes and focal areas (Grebmeier
et al., 2015).
All of these synthesis efforts point to the need for future
research focused on key areas and processes, including:
KEY areas – Spatial focus: Bering Strait, Hanna Shoal, Herald
Canyon, Barrow Canyon, Beaufort outer shelf and slope,
Siberian coast, Mackenzie delta and coast, the polynyas offshore
of St. Lawrence Island, Anadyr and Cape Bathurst.
KEY processes – Temporal focus: Seasonal sea ice, Bering Strait
transport, Advection of fresh water, heat, nutrients and prey
from the northern Bering Sea to the Beaufort Sea, Upwelling
and eddies along Beaufort slope, the Mackenzie Plume, Yukon
outflow and contributions of other rivers (e.g., Canning,
Sagavanirktok, Colville) to the Beaufort coastal system.
Visualization tools applied to an integrated model, such as the
AMP, would greatly aid the development of dynamic ecosystem
models connecting atmosphere–ocean physics with biological
responses. Because they must respond to ecosystem variability to
survive, upper trophic level species, including marine fishes, birds
and mammals should be included in these models. They not only
act as sentinels to ecosystem variability, but also provide a funda-
mental link to humans – as essential food and cultural keystones
for those that live in the Arctic and as icons of the Arctic region
for those that do not.
Personal communications
K. Stafford, Applied Physics Laboratory, University of
Washington, Seattle, WA, USA. Email: stafford@apl.washington.
edu.
K. Crane, Ocean and Atmospheric Research, NOAA, Silver Spring,
MD, USA. Email: Kathy.Crane@noaa.gov.
Acknowledgements
The Synthesis of Arctic Research (SOAR) and was funded pri-
marily by the U.S. Department of the Interior, Bureau of Ocean
Energy Management (BOEM), Environmental Studies Program
through Interagency Agreement No. M11PG00034 with the U.S.
Department of Commerce, National Oceanic and Atmospheric
Administration (NOAA), Office of Oceanic and Atmospheric
Research (OAR), Pacific Marine Environmental Laboratory (PMEL).
The SOAR project brought together over 100 scientists and local
experts to produce a synthesis of data and observations presented
in the papers comprising this issue. While the BOEM Alaska Region
supported many of the studies upon which these papers depend,
the papers also represent contributions of data from research sup-
ported by NSF, ONR, USFWS, NSB, NPRB, ADF&G and others. The
Preface / Progress in Oceanography xxx (2015) xxx–xxx 9
SOAR project was enriched by the thoughtful and efficient work of
project coordinator Lisa Sheffield Guy (JISAO), while the figures in
this preface were significantly improved by the graphic arts talent
of Karen Birchfield (PMEL). We thank both Dr. Charles Monnett
(BOEM-retired) and Dr. Heather Crowley (BOEM) for their enthusi-
asm and management of the project. Finally, we sincerely thank all
of our academic, agency and arctic community colleagues who
contributed to this special issue; quite literally, we could not have
done it without you.
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Sue E. Moore
NOAA/Fisheries, 7600 Sand Point Way NE, Seattle, WA 98115, USA
Tel.: +1 206 526 6889.
E-mail address:Sue.Moore@noaa.gov
Phyllis J. Stabeno
NOAA/OAR, 7600 Sand Point Way NE, Seattle, WA 98115, USA
Available online xxxx
Preface / Progress in Oceanography xxx (2015) xxx–xxx 11
... Arctic region, to pelagic-dominated systems following the loss of sea ice and shifts in organic carbon sources (Kędra et al. 2015, Moore & Stabeno 2015. If and when these ecosystem shifts will occur is complex, owing to possible increases in suitable habitat for ice algae as first year ice becomes dominant or if there will be a mismatch in timing of production with life cycles of certain consumers that disrupts the food web , Leu et al. 2011, Dezutter et al. 2019, Nadaï et al. 2021). ...
... However, declining sea ice cover and persistence along with changes in the timing of the sea ice cycle are likely to disrupt this ecosystem structure (Grebmeier et al. 2006a, Leu et al. 2011, Kędra et al. 2015. Sea ice has declined overall in the Arctic with With the increasing open water season for the Pacific Arctic, there are a number of possible outcomes that will impact trophic stability and function as a result of changes in the timing, quality and quantity of the basal food source (Moore & Stabeno 2015). Lower trophic level consumers coordinate life cycles (i.e. ...
... Arctic is hypothesized to increase through pelagic trophic chains to the detriment of the benthic ones, which will have a large impact on the whole food web in terms of both quality and standing stock (Kędra et al. 2015, Moore & Stabeno 2015. The shift to a pelagicdominated food web, together with access to ice-free waters are likely to lead to population increases in foraging pelagic fish, along with water column feeding whales and seabirds (Moore & Huntington 2008, Kędra et al. 2015. ...
Thesis
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Our current understanding of ice algae as a carbon source at the base of the Arctic food web is limited because of difficulties unequivocally distinguishing sympagic (sea ice) from pelagic primary production once assimilated by consumers. For this study, I tested the utility of highly branched isoprenoids (HBI), which are unusual lipids produced by diatoms. This includes a biomarker found exclusively in Arctic sea ice termed the ice proxy with 25-carbon atoms (IP25) and two other HBIs with sea ice and pelagic sources. HBI measurements in the Pacific Arctic (the northern Bering and Chukchi seas) were sparse compared to the rest of the Arctic prior to this investigation. Analysis of surface sediments and cores collected across the continental shelf revealed a latitudinal gradient of increasing sympagic HBIs. Some of the highest concentrations of IP25 recorded in the Arctic were found in the Chukchi Sea. Fluxes of IP25 indicated year-round export of ice algal lipids in this region. Persistent diatom fluxes and rapid burial of sympagic carbon are likely a sustaining resource for infaunal communities throughout the year. As such, HBIs were measured in benthic primary consumers and indicated an elevated utilization of ice algae by surface and subsurface deposit feeders, while suspension feeders by contrast showed greater pelagic organic carbon utilization. Sympagic organic carbon signatures were largely influenced by the HBI content in local sediments. This led to the identification of two species with possible dependencies on ice algae. This method was extended to transient, higher trophic organisms by measurement of HBIs in Pacific walrus livers harvested during subsistence hunting activities. Relative HBI proportions were shown to relate to foraging location and revealed a higher reliance on sympagic organic carbon by female and juvenile Pacific walruses relative to males. This is likely due to a greater requirement for sea ice habitat by females and calves in the Bering and Chukchi seas. This study showed that HBI biomarkers can robustly track sea ice organic carbon contributions through the Pacific Arctic food web and should be considered alongside other trophic markers in future monitoring efforts in response to climate change.
... Alterations in benthic biomass and community composition have already been observed in response to environmental change in the Pacific-Arctic region (Goethel et al., 2019;Grebmeier, 2012;Stabeno et al., 2020;Waga et al., 2020), with likely impacts on carbon cycling (Jones et al., 2021). A decline in phytodetrital input to the seafloor has been predicted (Lee et al., 2013;Moore and Stabeno, 2015), and model results for the Chirikov Basin suggest this decline will result in a steady loss of deposit feeders followed by a decline in carnivorous polychaetes (Lovvorn et al., 2016). However, deposit-feeding polychaetes remained relatively constant under simulated declines of different magnitudes south of St. Lawrence Island, and carnivorous polychaetes declined slightly (Lovvorn et al., 2016). ...
... In addition to being a dynamic environment, Arctic shelves are also highly susceptible to climate change effects, which have already manifested in reduced sea-ice extent, species range shifts, and changes in pelagic primary productivity, OM deposition, and hydrography, all of which may have major and varying impacts on macro-to microorganisms van Dijken, 2011, 2015;Grebmeier, 2012a;Moore and Stabeno, 2015;Nelson et al., 2014). In this ecologically important region that is relatively unstudied with respect to benthic prokaryotes and experiencing rapid environmental change, we used 16S rRNA amplicon surveys of sediment samples to 1) assess vertical structure of prokaryotic communities in sediments of the Northern (N) Bering and Southeastern (SE) Chukchi Seas, 2) investigate environmental correlates of prokaryotic community structure in surface sediments (0-1 cm) on a broader spatial scale from the N Bering to the Northeast (NE) Chukchi Sea shelf, and 3) provide a contextual baseline for benthic prokaryotes in surface sediments across the North American Arctic from the N Bering to the Eastern (E) Beaufort Sea. ...
Article
Benthic bacteria and archaea can be considered biogeochemical engineers as they play a major role in organic matter (OM) degradation and nutrient cycling. As such, prokaryotic community structure, yielded from 16S rRNA amplicon sequencing, can reflect environmental conditions such as OM composition and quantity, nutrient availability, redox conditions, and natural/anthropogenic contaminants (e.g. petroleum hydrocarbons). To assess prokaryotic community structure, we sequenced marine sediments in the upper 10-cm layer on the northern Bering and southern Chukchi Sea shelves, a high-latitude region undergoing rapid environmental change. We then explored broader spatial patterns in community structure for surface sediments (upper 1cm), incorporating samples from the Northeast Chukchi and Beaufort Seas in relation to environmental variables. Three assemblages were characterized at distinct depth horizons in the upper 10-cm sediment layer from the Northern Bering and Southern Chukchi benthos. One assemblage was exclusively found in sediments at greater than 1 cm sediment depth and contained a relatively higher proportion of anaerobic taxa (e.g. Anaerolineaceae, Desulfobulbaceae, and Desulfosarcinaceae). Overall, community distribution in the upper 10-cm reflected sediment grain size, OM quantity and composition, and possibly the influence of bioturbation. Two assemblages were characterized in surface sediments (upper 1 cm) across the broader Northern Bering and Chukchi Sea study area. A relatively high abundance of anaerobic taxa (e.g. SEEP-SRB4, Subgroup 23, and R76-B128) in one assemblage suggested comparatively suboxic sediments, and the other suggested allochthonous input of phytodetritus based on high abundance of diatom/particle associated microbes (e.g. Polaribacter, Dokdonia, and Ulvibacter), combined with high sediment chl-a concentration. This latter assemblage may reflect depositional areas influenced by hydrographic patterns. Prokaryotic community structure across the North American Arctic region highlights regional differences in environmental controls, with food-supply regimes influencing structure on the Bering-Chukchi inflow shelves, in contrast to the Beaufort interior shelves where nearshore heterogeneity (riverine input and terrigenous material) are major drivers of sediment prokaryote communities.
... Hundreds of species have already exhibited range shifts (Molinos et al., 2017;Pinsky et al., 2020;Poloczanska et al., 2013Poloczanska et al., , 2016 and future shifts are projected for more species (Cheung et al., 2013;Grebmeier et al., 2006;Molinos et al., 2015;Morley et al., 2018). An altered ecosystem in the Arctic may inevitably lead to winners and losers (Sigler et al., 2011;Fossheim et al., 2015;Bouchard et al., 2017;Moore and Stabeno, 2015;Kleisner et al., 2017). Restructuring of the ecosystem may benefit some species but will be detrimental to others. ...
Article
We used genetic techniques to identify gadids (cods) to species in the Pacific Arctic during a time of substantial physical change in the marine ecosystem between 2012 and 2019. The dominant fish species in the Chukchi Sea is Arctic Cod (Boreogadus saida); however, other gadids such as Saffron Cod (Eleginus gracilis), Pacific Cod (Gadus macrocephalus) and Walleye Pollock (Gadus chalcogrammus) have been observed. Two aims in this study were to evaluate the accuracy of at sea morphological identification (which can be difficult for juveniles) with genetic species identification and to document potential variation in species composition and distribution of gadids in the Pacific Arctic in response to changing environmental conditions. Microsatellite and mtDNA genetic results revealed that most B. saida collected in the Chukchi Sea in 2012 and 2013 were correctly identified at sea. Conversely, genetic results from samples collected in 2017 and 2019 revealed a large number of G. chalcogrammus and some G. macrocephalus and E. gracilis that were initially identified at sea as B. saida. The majority of misidentification occurred between B. saida and G. chalcogrammus. This study indicates a northward shift of G. chalcogrammus and B. saida during warmer conditions. In addition, juvenile Polar Cod (A. glacialis), which is not typically found in the Chukchi Sea and was not identified at sea, was genetically detected on 3 hauls on the northern Chukchi Shelf, outside of its documented distribution. Accurate species identification, especially during a time of changing marine landscapes, is not only important for survey abundance estimates but for downstream analyses as well. This emphasizes the value of implementing strategies for correct identification of the gadid species to better capture and monitor responses to varying and likely changing conditions. Our results provide strong evidence of distributional shifts and range expansions of gadid species in the Arctic, which may be the result of changing climactic conditions.
... Ringed seals are also a traditional resource for coastal Inuit people who continue to rely on ringed seals and other marine mammals for nutritional, cultural and spiritual purposes [14]. Ringed seals thus reflect ecosystem health as sentinels of environmental change [15,16], ultimately playing important roles in shifting ecological interactions and food web productivity in response to the loss of sea ice [17][18][19]. Understanding how changing snow and ice regimes are impacting these ice-obligate seals is relevant to the health of both Arctic marine ecosystems and coastal communities. ...
Article
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There has been significant sea ice loss associated with climate change in the Pacific Arctic, with unquantified impacts to the habitat of ice-obligate marine mammals such as ringed seals ( Pusa hispida ). Ringed seals maintain breathing holes and excavate subnivean lairs on sea ice to provide protection from weather and predators during birthing, nursing, and resting. However, there is limited baseline information on the snow and ice habitat, distribution, density, and configuration of ringed seal structures (breathing holes, simple haul-out lairs, and pup lairs) in Alaska. Here, we describe historic field records from two regions of the eastern Chukchi Sea (Kotzebue Sound and Ledyard Bay) collected during spring 1983 and 1984 to quantify baseline ringed seal breeding habitat and map the distribution of ringed seal structures using modern geospatial tools. Of 490 structures located on pre-established study grids by trained dogs, 29% were pup lairs (25% in Kotzebue Sound and 33% in Ledyard Bay). Grids in Ledyard Bay had greater overall density of seal structures than those in Kotzebue Sound (8.6 structures/km ² and 7.1 structures/km ² ), but structures were larger in Kotzebue Sound. Pup lairs were located in closer proximity to other structures and characterized by deeper snow and greater ice deformation than haul-out lairs or simple breathing holes. At pup lairs, snow depths averaged 74.9 cm (range 37–132 cm), with ice relief nearby averaging 76 cm (range 31–183 cm), and ice deformation 29.9% (range 5–80%). We compare our results to similar studies conducted in other geographic regions and discuss our findings in the context of recent declines in extent and duration of seasonal cover of landfast sea ice and snow deposition on sea ice. Ultimately, additional research is needed to understand the effects of recent environmental changes on ringed seals, but our study establishes a baseline upon which future research can measure pup habitat in northwest Alaska.
... Timing of melt-back in sea ice controls the seasonal transition from ice algae to phytoplankton as primary producers. An earlier melt-back could shift the ecosystem from a benthic-dominated to a pelagic-dominated regime (Grebmeier et al., 2006;Moore & Stabeno, 2015). Through brine rejection during ice production, the frequency, extent, and duration of polynyas influence the density of winter waters and the depth to which they ventilate the western Arctic (Itoh et al., 2012;Weingartner et al., 1998). ...
Article
A composite dataset of 27 moorings across the Chukchi Sea and Bering Strait in 2013-14, along with satellite sea ice concentration data, weather station data, and atmospheric reanalysis fields, are used to explore the relationship between the circulation, ice cover, and wind forcing. We find a clear relationship between northeasterly winds along the northwest coast of Alaska and reversed flow along the length of Barrow Canyon and at a mooring site ∼100 km upstream on the northeast shelf. Atlantic Water is frequently upwelled into the canyon during the fall and winter, but is only able to reach the head of Barrow Canyon after a series of long upwelling events. A pair of empirical orthogonal function (EOF) analyses of ice cover reveal the importance of inflow pathways on the pattern of freeze-up and melt-back, and shed light on the relative influence of sensible heat and wind forcing on polynya formation. An EOF analysis of 25 mooring velocity records reveals a dominant pattern of circulation with coherent flow across the shelf, and a secondary pattern of opposing flow between Barrow Canyon and Bering Strait. These are related to variations in the regional wind field.
... On the Pacific side, the ongoing Synthesis Of Arctic Research (SOAR) established a "new normal" for the present biophysical conditions in the Pacific Arctic Chukchi and Beaufort Seas (Moore and Stabeno 2015) and the US national Bering Sea project (2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014) has conducted a comparatively large Arctic shelf ecosystem investigation which provided current knowledge on the Bering Sea (Deep Sea Research II special issues in 2012 -2016). Such extensive efforts have not yet taken place in the northern Barents region, but through dedicated region-specific studies and by comparing systems across the Pan-Arctic domain, we aim to understand similarities and differences in physical drivers and ecosystem responses that will help us understand the heterogeneous Arctic marine region. ...
Article
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The scientific investigation of a rapidly changing northern environment leads to research questions of such intellectual, empirical and logistical complexity—and of such importance to the management of national resources and associated international obligations—that they can only be addressed properly through national and prioritized cooperation, with the highest scientific standards.
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Bearded seals are pan-Arctic ice-obligate phocids; for the threatened Beringia population, the majority of the population feeds in the summer in the Chukchi Sea, then migrates south to overwinter in the northern Bering Sea. Contemporary information on the impact of rapidly changing climatic conditions on bearded seal distribution is essential for effective management. To monitor for marine mammals, passive acoustic recorders were deployed throughout the eastern Chukchi and northern Bering seas (64° N to 72° N), sampling at a rate of 16 kHz on a duty cycle of either 80 or 85 min every five hours. Data from year-long deployments at nine sites over four years (2012–2016) were manually analyzed, totaling 13,275 days (∼75,000 h). Bearded seal calling activity was present at every site in every year. Calling activity increased from September through February and reached sustained and saturated levels from March through June, at which point calling ceased abruptly regardless of ice cover. The timing of calling and its abrupt cessation correspond with the known breeding season of bearded seals. However, the timing of the cessation of calling occurred earlier each year, corresponding with an earlier sea ice retreat. The sustained calling detected overwinter at all locations suggests that this is more than just a few animals that are remaining in the Chukchi Sea. Preceding this main pulse was a smaller peak in calling that progressed southward, corresponding with the fall migration of bearded seals to the Bering Sea. These results increase our knowledge on the year-round spatio-temporal distribution and migration patterns of this pagophilic species, and the relationship between calling activity and sea ice concentration.
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A regional ocean biogeochemical model for the Bering Sea is used to dynamically downscale three Earth System Models from the CMIP5 archive under the RCP 8.5 and RCP 4.5 scenarios. These continuous model runs, completed in conjunction with the Alaska Climate Integrated Modeling Project (ACLIM), span the 2006–2100 timeframe and project continued warming, freshening, and ocean acidification (OA) for the Bering Sea shelf region over the 21st Century, with larger magnitude changes in the RCP 8.5 scenario. The downscaled projections suggest that annual average surface seawater aragonite saturation state (Ωarag) for the Bering Sea shelf will decrease by 0.63–0.86 under RCP 8.5 and 0.18–0.43 under RCP 4.5 by 2100. Surface pH values decrease by 0.31–0.35 under RCP 8.5 and 0.07–0.13 under RCP 4.5. Seasonally, Ωarag < 1 conditions start to emerge for ∼2 months per year during winter between 2015-2030 under both climate change scenarios. Under RCP 8.5, the duration of these undersaturated conditions grows to ∼5 months per year by 2100, occurring from mid-October through mid-March. Under RCP 4.5, these conditions remain constrained to 2–3 months per year by 2100. In both scenarios, summer months maintain conditions of Ωarag > 1 due to primary productivity, though the maximum in Ωarag is greatly reduced under RCP 8.5. Spatially, the regions of greatest pH and Ωarag decline are the southeastern Bering Sea shelf and the outer shelf domain near the shelf break. Linear trends in carbonate variables between our downscaled simulations and the Earth System Model (ESM) output are comparable and indistinguishable compared to the model spread. However, bottom water trends differ somewhat between the ESM and our downscaled simulations, with the latter more consistently resolving the different shelf domains. The OA information provided by these downscaled simulations can help inform biological sensitivity experiments and longterm strategic planning for marine fisheries management.
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Domoic acid (DA) and saxitoxin (STX)‐producing algae are present in Alaskan seas, presenting exposure risks to marine mammals that may be increasing due to climate change. To investigate potential increases in exposure risks to four pagophilic ice seal species (Erignathus barbatus, bearded seals; Pusa hispida, ringed seals; Phoca largha, spotted seals; and Histriophoca fasciata, ribbon seals), this study analyzed samples from 998 seals harvested for subsistence purposes in western and northern Alaska during 2005–2019 for DA and STX. Both toxins were detected in bearded, ringed, and spotted seals, though no clinical signs of acute neurotoxicity were reported in harvested seals. Bearded seals had the highest prevalence of each toxin, followed by ringed seals. Bearded seal stomach content samples from the Bering Sea showed a significant increase in DA prevalence with time (logistic regression, p = .004). These findings are consistent with predicted northward expansion of DA‐producing algae. A comparison of paired samples taken from the stomachs and colons of 15 seals found that colon content consistently had higher concentrations of both toxins. Collectively, these results suggest that ice seals, particularly bearded seals (benthic foraging specialists), are suitable sentinels for monitoring HAB prevalence in the Pacific Arctic and subarctic.
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The annual migration of bowhead whales (Balaena mysticetus) past Barrow, Alaska, has provided subsistence hunting to Iñupiat for centuries. Bowheads recurrently feed on aggregations of zooplankton prey near Barrow in autumn. The mechanisms that form these aggregations, and the associations between whales and oceanography, were investigated using field sampling, retrospective analysis, and traditional knowledge interviews. Oceanographic and aerial surveys were conducted near Barrow during August and September in 2005 and 2006. Multiple water masses were observed, and close coupling between water mass type and biological characteristics was noted. Short-term variability in hydrography was associated with changes in wind speed and direction that profoundly affected plankton taxonomic composition. Aggregations of ca. 50-100 bowhead whales were observed in early September of both years at locations consistent with traditional knowledge. Retrospective analyses of records for 1984-2004 also showed that annual aggregations of whales near Barrow were associated with wind speed and direction. Euphausiids and copepods appear to be upwelled onto the Beaufort Sea shelf during E or SE winds. A favorable feeding environment is produced when these plankton are retained and concentrated on the shelf by the prevailing westward Beaufort Sea shelf currents that converge with the Alaska Coastal Current flowing to the northeast along the eastern edge of Barrow Canyon.
Chapter
Extreme reductions in sea ice extent and thickness in the Pacific Arctic Region (PAR) have become a hallmark of climate change over the past decade, but their impact on the marine ecosystem is poorly understood. As top predators, marine fishes, birds and mammals (collectively, upper trophic level species, or UTL) must adapt via biological responses to physical forcing and thereby become sentinels to ecosystem variability and reorganization. Although there have been no coordinated long-term studies of UTL species in the PAR, we provide a compilation of information for each taxa as an ecological foundation from which future investigations can benefit. Subsequently, we suggest a novel UTL-focused research framework focused on measurable responses of UTL species to environmental variability as one way to ascertain shifts in the PAR marine ecosystem. In the PAR, indigenous people rely on UTL species for subsistence and cultural foundation. As such, marine fishes, birds and mammals represent a fundamental link to local communities while simultaneously providing a nexus for science, policy, education and outreach for people living within and outside the PAR.
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Bearded seals (Erignathus barbatus) are widely distributed in the Arctic and sub-Arctic; the Beringia population is found throughout the Bering, Chukchi and Beaufort Seas (BCB). Bearded seals are highly vocal, using underwater calls to advertise their breeding condition and maintain aquatic territories. They are also closely associated with pack ice for reproductive activities, molting, and resting. Sea ice habitat for this species varies spatially and temporally throughout the year due to differences in underlying physical and oceanographic features across their range. To test the hypothesis that the vocal activity of bearded seals is related to variations in sea ice, passive acoustic data were collected from nine locations throughout the BCB from 2008–2011. Recording instruments sampled on varying duty cycles ranging from 20% to 100% of each hour, and recorded frequencies up to 8192 Hz. Spectrograms of acoustic data were analyzed manually to calculate the daily proportion of hours with bearded seal calls at each sampling location, and these call activity proportions were correlated with daily satellite-derived estimates of sea ice concentration. Bearded seals were vocally active nearly year-round in the Beaufort and Chukchi Seas with peak activity occurring from mid-March to late June during the mating season. The duration of call activity in the Bering Sea was shorter, lasting typically only five months, and peaked from mid-March to May at the northernmost recorders. In all areas, call activity was significantly correlated with higher sea ice concentrations (p < 0.01). These results suggest that losses in ice cover may negatively impact bearded seals, not just by loss of habitat but also by altering the behavioral ecology of the BCB population.
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Bowhead whales, Balaena mysticetus, in the Bering-Chukchi-Beaufort (BCB) population, experience a variable acoustic environment among the regions they inhabit throughout the year. A total of 41,698 hours of acoustic data were recorded from 1 August 2009 through 4 October 2010 at 20 sites spread along a 2300 km transect from the Bering Sea to the southeast Beaufort Sea. These data represent the combined output from six research teams using four recorder types. Recorders sampled areas in which bowheads occur and in which there are natural and anthropogenic sources producing varying amounts of underwater noise. We describe and quantify the occurrence of bowheads throughout their range in the Bering, Chukchi, and Beaufort seas over a 14-month period by aggregating our acoustic detections of bowhead whale sounds. We also describe the spatial-temporal variability in the bowhead acoustic environment using sound level measurements within a frequency band in which their sounds occur, by dividing a year into three, 4-month seasons (Summer-Fall 2009, August – November 2009: Winter 2009-2010, December 2009 – March 2010: and Spring-Summer 2010, April – July 2010) and their home range into five zones. Statistical analyses revealed no significant relationship between acoustic occurrence, distance offshore, and water depth during Summer-Fall 2009, but there was a significant relationship during Spring-Summer 2010. A continuous period with elevated broadband sound levels lasting ca. 38 days occurred in the Bering Sea during the Winter 2009-2010 season as a result of singing bowheads, while a second period of elevated levels lasting at least 30 days occurred during the early spring-summer season as a result of singing bearded seals. The lowest noise levels occurred in the Chukchi Sea from the latter part of November into May. In late summer 2009 very faint sounds from a seismic airgun survey approximately 700 km away in the eastern Beaufort Sea were detected on Chukchi recorders. Throughout the year, but most obviously during this same November into May period, clusters of intermittent, nearly synchronized, high-level events were evident on multiple recorders hundreds of miles apart. In some cases, these clusters occurred over 2-5 day periods and appear to be associated with high wind conditions.