WATER COLUMN AND BENTHIC LIFE
Water Column and Benthic Life
CHLOROPHYLL-A
Grebmeier et al. (2006b) show that the
northern Bering and Chukchi seas are shifting
away from tight coupling of pelagic-benthic
productivity, coinciding with lower benthic
prey populations, higher pelagic fish
populations, reduced sea ice, and increased air
and ocean temperatures. They state that “the
vulnerability of the ecosystem to
environmental change is thought to be high,
particularly as sea ice extent declines and
seawater warms.” Climate change may
potentially break this short link between
primary productivity and the benthos,
converting the area to a pelagic- rather than
benthic-oriented system (Grebmeier et al.
2006a; Grebmeier et al. 2006b).
Understanding the relationship between ice
cover and productivity is essential in
understanding Arctic marine ecology under
reduced ice thickness and extent (Stockwell
2008).
Description
Phytoplankton are microscopic plants, which
are the basic building block of the marine
food web. Chlorophyll is the green pigment
found in plant matter, including
phytoplankton and ice-algae.
Chlorophyll absorbs light in the blue and red
portions of the spectrum while reflecting
green light. Reflectance values collected by the
Aqua MODIS sensor measure chlorophyll-a
biomass as a proxy to indicate areas that tend
to be high in primary productivity at the
surface of the ocean.
A study in the nearshore Beaufort Sea
suggests that ice-algae provides about twothirds and phytoplankton provides about onethird of the spring primary production
(Horner and Schrader 1982). A second Arcticwide study found that ice algae makes up on
average 57% of the water column and sea ice
productivity (Gosselin et al. 1997). On the
map, areas of higher productivity are shown
in green, yellow, and brown. Bering Strait,
Norton Sound, Kotzebue Sound, and
MacKenzie Bay are the most productive
waters in the project area.
See related maps and descriptions of
Bathymetry, Ecoregions, Ocean Circulation,
Sea Ice Dynamics, Sea Surface Temperature,
Observed Climate Change, Net Primary
Productivity, Zooplankton, and Benthic
Biomass.
Data Compilation and Mapping
Methods
Variation in ice cover is the dominant factor
in the spatial pattern of primary production
from phytoplankton (Wang et al. 2005). In the
northern Bering and Chukchi seas,
chlorophyll-a and primary productivity are
tightly coupled with benthic biomass
(Grebmeier et al. 1988; Springer and McRoy
1993; Dunton et al. 2005; Grebmeier et al.
2006a). Chlorophyll-a and primary
productivity in the Beaufort Sea are less
closely linked, except around Barter Island
where both relatively high biomass and
chlorophyll-a are found (Dunton et al. 2005;
Grebmeier and Harvey 2005).
Data for all open water months (May to
October) were collected for five years, from
2004 to 2008. Chlorophyll-a measurements
were collected by the Aqua MODIS satellite
and served through the NASA Ocean Color
website as monthly 4-km raster grids
(Feldman and McClain 2009). Some southern
areas were ice-free for all six months, and
northern areas were ice-free for only one
month per year. Chlorophyll-a grids were
summed from May to October, indicating the
total available primary productivity over the
course of the ice-free season. Last, the five
years were averaged, for a final result
3-1
Arctic Marine Synthesis: Atlas of the Chukchi and Beaufort Seas
reflecting the average yearly mean
chlorophyll-a during ice-free months.
year, and those years are averaged as well, the
data gap of missing days tends to be
minimized. There were no concerning data
gaps in the remotely sensed information
presented in the map.
Data Quality
This map has a data quality rating of good
because it provides a complete geographic
picture of chlorophyll-a over the entire project
area at a consistent 4-km resolution. Primary
productivity within the sea ice and potential
changes in primary productivity caused by
climate change are known data gaps.
Summary and Synthesis
Areas of high productivity indicate important
biological hotspots for multiple trophic levels
in the marine ecosystem—these areas provide
the basic building blocks of the food web
which flow throughout the food chain.
Monitoring of chlorophyll-a through satellite
imagery should be continued. This
information provides a baseline from which
climate changes can be measured. Such longterm, consistent data at a good resolution with
complete geographic coverage are very rare
for the Arctic.
The data are limited in that production
throughout the water column and in the
bottom of the sea ice are not picked up by
satellite sensors. The data presented here uses
chlorophyll-a biomass as a proxy to indicate
areas that tend to be high in primary
productivity at the surface of the ocean. Few
studies have directly measured water column
productivity, which would permit regional and
seasonal differences to be derived;
productivity is highly sensitive to sea ice
dynamics, which are the result of regional
climate patterns (Stockwell 2008). These
patterns are constantly changing, such that
field studies that sample a small portion of the
project area for only one week or month per
year will never be able to capture the fully
dynamics of the system. This makes study of
remotely sensed information highly desirable
even with its known limitations.
Text Citations
Dunton, K.H., J.L. Goodall, S.V. Schonberg,
J.M. Grebmeier, and D.R. Maidment.
2005. Multi-decadal synthesis of
benthic-pelagic coupling in the
western Arctic: role of cross-shelf
advective processes. Deep Sea
Research Part II: Topical Studies in
Oceanography 52:3462-3477.
Gosselin, M., M. Levasseur, P. Wheeler, R.
Horner, and B. Booth. 1997. New
measurements of phytoplankton and
ice algal production in the Arctic
Ocean. Deep Sea Research Part II:
Topical Studies in Oceanography
44:1623-1644.
Taking into consideration the limitations
described above, remotely sensed chlorophylla data are of high quality. The data are
available daily, or in weekly, monthly,
seasonal, or annual averages, beginning in July
2002. No data areas existed in the original
data because of either cloud cover or sea ice
cover. It was assumed that ice-covered areas
had no chlorophyll production. For cloud
cover, although data may not be available for
a number of days because of cloud cover,
when the available data are averaged over a
month, and those months are averaged over a
Grebmeier, J.M., and H.R. Harvey. 2005. The
western Arctic shelf-basin interactions
(SBI) project: an overview. Deep Sea
Research Part II: Topical Studies in
Oceanography 52:3109-3115.
Grebmeier, J.M., C.P. McRoy, and H.M.
Feder. 1988. Pelagic-benthic coupling
on the shelf of the northern Bering
3-2
Water Column and Benthic Life
and Chukchi Seas. I: Food supply
source and benthic biomass. Marine
Ecology Progress Series 48:57-67.
Map Data Sources
Audubon Alaska. 2009. Average seasonal
mean chlorophyll-a, May–October,
2004–2008. GIS raster dataset (based
on Feldman and McClain 2009).
Grebmeier, J.M., L.W. Cooper, H.M. Feder,
and B.I. Sirenko. 2006a. Ecosystem
dynamics of the Pacific-influenced
northern Bering and Chukchi seas in
the Amerasian Arctic. Progress in
Oceanography 71:331-361.
Feldman, G.C., and C.R. McClain. 2009.
Ocean color web, aqua MODIS,
NASA Goddard Space Flight Center.
N. Kuring, S. Bailey, and W. April,
editors.
<http://oceancolor.gsfc.nasa.gov/>.
Accessed June 2009.
Grebmeier, J.M., J.E. Overland, S.E. Moore,
E.V. Farley, E.C. Carmack, L.W.
Cooper, K.E. Frey, J.H. Helle, F.A.
McLaughlin, and S.L. McNutt. 2006b.
A major ecosystem shift in the
northern Bering Sea. Science
311:1461-1464.
Horner, R., and G.C. Schrader. 1982. Relative
contributions of ice algae,
phytoplankton, and benthic
microalgae to primary production in
nearshore regions of the Beaufort Sea.
Arctic 35:485-503.
Springer, A.M., and C.P. McRoy. 1993. The
paradox of pelagic food webs in the
northern Bering Sea – III: patterns of
primary production. Continental Shelf
Research 13:575-599.
Stockwell, D. 2008. Phytoplankton (primary
productivity). In Arctic Ocean
synthesis: analysis of climate change
impacts in the Chukchi and Beaufort
seas with strategies for future research.
R. Hopcroft, B. Bluhm, and R.
Gradinger, editors. Institute of Marine
Sciences, University of Alaska
Fairbanks.
Wang, J., G.F. Cota, and J.C. Comiso. 2005.
Phytoplankton in the Beaufort and
Chukchi Seas: distribution, dynamics,
and environmental forcing. Deep Sea
Research Part II: Topical Studies in
Oceanography 52:3355-3368.
3-3
Arctic Marine Synthesis: Atlas of the Chukchi and Beaufort Seas
3-4
Water Column and Benthic Life
NET PRIMARY
PRODUCTIVITY
(Behrenfeld and Falkowski 1997). A
chlorophyll-based model, it estimates net
primary productivity by relating chlorophyll,
available light, temperature, and
photosynthetic efficiency (Oregon State
University 2009). The model used MODIS
chlorophyll-a and sea surface temperature
data, SeaWiFS Photosynthetically Active
Radiation data, and euphotic zone (1% light
level) depth based on a model by Morel and
Berthon (1989).
Description
The total amount of productivity in a region is
its gross primary productivity. Some of the
energy captured in photosynthesis goes to
growth, which is available energy to water
column grazers, and the other portion is used
up by the primary producers themselves. Net
primary productivity is the productivity
available to support consumers and the
benthos in the sea. It is the total growth of
phytoplankton, including reproduction. In the
Arctic, this productivity is primarily from
phytoplankton and ice-algae. This map is
similar to the preceding chlorophyll-a map,
which is a related method for estimating
primary productivity. Reflectance values
collected by the Aqua MODIS sensor
measure chlorophyll-a biomass as a proxy to
indicate areas that tend to be high in primary
productivity at the surface of the ocean.
Chlorophyll-a data were combined with other
information to model net primary
productivity throughout the euphotic zone
(the area with sufficient light for
photosynthesis). Net primary productivity is
highest in Norton Sound, Kotzebue Sound,
MacKenzie Bay, Bering Strait, and the
Chirikov and Hope basins.
Net primary productivity grids were summed
from May to October, indicating the total
available productivity over the course of the
ice-free season. This calculation was
performed for each of five years from 2003 to
2007. Those years were then averaged, for a
final result reflecting the average rate of net
primary production during the ice-free season.
Data Quality
This map has a data quality rating of good
because it provides a complete geographic
picture of net primary productivity over the
entire project area at a consistent 7.5-km
resolution. Primary productivity within the sea
ice and potential changes in primary
productivity caused by climate change are
known data gaps.
These data are limited in that production
throughout the water column and in the
bottom of the sea ice is not picked up by
satellite sensors. The data presented here use
chlorophyll-a as a surrogate for primary
productivity at the surface of the ocean. Few
studies have directly measured water column
productivity for use in deriving regional and
seasonal differences; productivity is highly
sensitive to sea ice dynamics, which are the
result of regional climate patterns (Stockwell
2008). Because these patterns are constantly
changing, field studies that sample a small
portion of the project area for only one week
or month per year will never be able to
See related maps and descriptions of
Bathymetry, Ecoregions, Ocean Circulation,
Sea Ice Dynamics, Sea Surface Temperature,
Observed Climate Change, Chlorophyll-a,
Zooplankton, and Benthic Biomass.
Data Compilation and Mapping
Methods
Data for all months from January 2003 to
December 2007 were collected from Oregon
State University’s Ocean Productivity website
(2009). The website data is based on the
Vertically Generalized Production Model
3-5
Arctic Marine Synthesis: Atlas of the Chukchi and Beaufort Seas
capture the full dynamics of the system.
Consequently, study of remotely sensed
information is highly desirable even with its
known limitations.
/ocean.productivity/index.php>.
Accessed April 2009.
Stockwell, D. 2008. Phytoplankton (primary
productivity). In Arctic Ocean
synthesis: analysis of climate change
impacts in the Chukchi and Beaufort
seas with strategies for future research.
R. Hopcroft, B. Bluhm, and R.
Gradinger (Eds.). Institute of Marine
Sciences, University of Alaska
Fairbanks.
Taking into consideration the limitations
described above, modeled net primary
productivity data are of good quality. The data
from Oregon State University (2009) was
available in monthly grids beginning in 2003.
There is an odd data gap in Long Strait,
between Wrangel Island and the northern
Chukotkan coast. Persistent sea ice cover
explains the lack of remotely sensed net
primary productivity in the Canada Basin, but
the same is not true for Long Strait. It is not
known why this area appears to have no
productivity.
Map Data Sources
Audubon Alaska. 2009. Mean yearly sum of
net primary productivity, 2003–2007.
GIS raster dataset (based on
Behrenfeld and Falkowski 1997;
Oregon State University 2009).
Summary and Synthesis
Behrenfeld, M.J., and P.G. Falkowski. 1997.
Photosynthetic rates derived from
satellite-based chlorophyll
concentration. Limnology and
Oceanography 42:1-20.
Areas of high productivity indicate important
biological hotspots for multiple trophic levels
in the marine ecosystem—these areas provide
the basic building blocks of the food web
which flow throughout the food chain.
Monitoring of chlorophyll-a through satellite
imagery and modeling of net primary
productivity should be continued. This
information provides a baseline from which
we can measure climate changes. Such longterm, consistent data at a good resolution with
complete geographic coverage are very rare in
the Arctic.
Oregon State University. 2009. Ocean
productivity. GIS datasets.
<http://www.science.oregonstate.edu
/ocean.productivity/index.php>.
Accessed April 2009.
Text Citations
Morel, A., and J.F. Berthon. 1989. Surface
pigments, algal biomass profiles, and
potential production of the euphotic
layer: relationships reinvestigated in
view of remote-sensing applications.
Limnology and Oceanography
34:1545-1562.
Oregon State University. 2009. Ocean
Productivity. GIS datasets.
<http://www.science.oregonstate.edu
3-6
Water Column and Benthic Life
ZOOPLANKTON
primary production, creating a pelagic-driven
system. Changes in temperature, circulation,
and ice cover due to climate change may alter
plankton dynamics in the Chukchi and
Beaufort seas; the effects of such changes,
which are not well understood, may have
significant implications for the ecology of the
Arctic marine system (Lane et al. 2008;
Hopcroft et al. in press).
Description
Zooplankton are a key component in marine
ecosystems. The seasonal success of
zooplankton communities affects related
species at higher trophic levels, such as fish,
seabirds, and whales (Hopcroft 2008). These
small planktonic animals vary in size from
microscopic to several feet long. The spatial
distribution of zooplankton communities in
the Chukchi Sea is strongly tied to water
masses and circulation patterns (Springer et al.
1989; Plourde et al. 2005; Hopcroft 2008).
Zooplankton is carried to the Chukchi Sea
through the Bering Strait, so that both
communities are Pacific-influenced; the
Beaufort Sea in contrast is primarily Arctic in
terms of species composition (Hopcroft
2008). In both areas Calanus and Pseudocalanus
species of copepods appear to dominate
zooplankton biomass and/or abundance
(Horner and Murphy 1985; Springer et al.
1989; Ashjian et al. 2003; Plourde et al. 2005;
Lane et al. 2008; Hopcroft et al. in press), and
less abundant euphausiids are also important
prey for whales, birds, and fish (Hopcroft
2008). Other important and less known
groups include chaetognaths, amphipods,
ctenophores, and cnidarians (Horner and
Murphy 1985; Hopcroft 2008). They are a
highly important string in the marine food
web, and yet little cohesive data exists on the
distribution and abundance of species, or
seasonal and annual variation.
See related maps and descriptions of
Ecoregions, Ocean Circulation, Observed
Climate Change, Chlorophyll-a, Net Primary
Productivity, Capelin, Pacific Herring, Saffrod
Cod, Pink Salmon, Chum Salmon, Kittlitz’s
Murrelet, Ivory Gull, Northern Fulmar, ShortTailed Shearwater, Bowhead Whale, Gray
Whale, Human Impact, and Predicted Climate
Change.
Data Compilation and Mapping
Methods
Zooplankton data were digitized from a
georeferenced TIFF image in NOAA’s Bering,
Chukchi, and Beaufort Seas Coastal and Ocean Zones
Strategic Assessment Data Atlas (1988).
Data Quality
This map has a data quality rating of poor
because it provides an incomplete geographic
picture of zooplankton distribution and
abundance. No data are available for large
portions of the project area, and those areas
for which data are available are mapped at a
low resolution. It is unclear why some areas
are lacking information altogether. The
information shown here is more than 20 years
old and does not have enough detail for useful
application in research or planning.
Areas of very high primary productivity, such
as Anadyr waters north of the Bering Strait,
produce more biomass than can be consumed
by zooplankton (Springer et al. 1989). This
excess biomass creates a benthic-driven
marine system, as excess nutrients fall to the
seafloor, feeding the benthos. This contrasts
with the southern Bering Sea, where
zooplankton consume a greater amount of the
These data should be critically examined and
updated. Current knowledge of zooplankton
is fragmented and incomplete (Hopcroft
2008). Although a large number of surveys
have collected data, such as those available on
the Arctic Ocean Diversity website, those
surveys did not use consistent methodologies
3-7
Arctic Marine Synthesis: Atlas of the Chukchi and Beaufort Seas
or provide comparable results. “It is essential
that we collect and collate detailed and
extensive baseline information on these
communities as our current knowledge is
fragmented and incomplete…we still lack
unbiased and comprehensive estimates of the
abundance, biomass, and composition of the
zooplankton in the Chukchi and Beaufort
seas, due to sampling inadequacies of the
past” (Hopcroft 2008).
Sea during summer 2004. Deep Sea
Research II.
Horner, R., and D. Murphy. 1985. Species
composition and abundance of
zooplankton in the nearshore
Beaufort Sea in winter-spring. Arctic
38:201-209.
Lane, P.V.Z, L. Llinas, S.L. Smith, and D.
Pilz. 2008. Zooplankton distribution
in the western Arctic during summer
2002: hydrographic habitats and
implications for food chain dynamics.
Journal of Marine Systems 70:97-133.
Summary and Synthesis
Hopcroft (2008) recommends establishing
long-term repeated measurements, annual,
year-round sampling at a series of fixed
locations and transects, and sampling in
Russian waters, as well as compiling and
consolidating existing data into a central
database. An understanding of the role of
zooplankton in Arctic marine food webs is
critical to comprehend ecosystem structure
and functioning, and how climate change is
affecting the region.
MarineBio. 2010. Zooplankton.
<http://marinebio.org/Oceans/Zoop
lankton.asp>. Accessed January 2010.
Plourde, S., R.G. Campbell, C.J. Ashjian, and
D A. Stockwell. 2005. Seasonal and
regional patterns in egg production of
Calanus glacialis/marshallae in the
Chukchi and Beaufort Seas during
spring and summer, 2002. Deep Sea
Research Part II: Topical Studies in
Oceanography 52:3411-3426.
Text Citations
Ashjian, C.J., R.G. Campbell, H.E. Welch, M.
Butler, and D. Van Keuren. 2003.
Annual cycle in abundance,
distribution, and size in relation to
hydrography of important copepod
species in the western Arctic Ocean.
Deep-Sea Research Part IOceanographic Research Papers
50:1235-1261.
Springer, A.M., C.P. McRoy, and K.R. Turco.
1989. The paradox of pelagic food
webs in the northern Bering Sea – II:
zooplankton communities.
Continental Shelf Research 9:359-386.
Map Data Sources
NOAA. 1988. Bering, Chukchi, and Beaufort
seas coastal and ocean zones strategic
assessment data atlas.
Hopcroft, R. 2008. Zooplankton. In Arctic
Ocean synthesis: analysis of climate
change impacts in the Chukchi and
Beaufort Seas with strategies for
future research. R. Hopcroft, B.
Bluhm, and R. Gradinger, editors.
Institute of Marine Sciences,
University of Alaska Fairbanks.
Hopcroft, R.R., K.N. Kosobokova, and A.I.
Pinchuk. In press. Zooplankton
community patterns in the Chukchi
3-8
Water Column and Benthic Life
BENTHIC BIOMASS
productivity, such as Anadyr waters north of
the Bering Strait, produce far more biomass
than is consumed by zooplankton (Springer et
al. 1989). This excess biomass falls to the
seafloor, becoming nutrients for the benthos
(Gagaev 2007; Bluhm et al. 2008). Epibenthos
sampling between the 1970s and 1990s reveals
increased abundance and biomass for the
Chukchi and northeastern Bering seas (Feder
et al. 2005; Feder et al. 2007). Range
expansions of warm-water Pacific species are
probably indicative of climate change (Gagaev
2007).
Description
Benthic organisms live on, in, or just above
the seafloor. The combined weight, or
biomass, of these organisms indicates
potential forage for benthic-feeding bird and
mammal species. Hotspots of benthic food
resources are shown in yellow, orange, and
red. The map indicates that the Bering Strait
region, including the Chirikov and Hope
basins, plus Hanna Shoal, Prudhoe Bay,
Stefansson Sound, and waters around Barter
Island are rich in benthic biomass, and are
potentially important foraging areas for
mammals and birds. Benthic organisms are
less affected by seasonal and annual
variability, so that high biomass sites indicate
areas that likely have persistently high
nutrients from the water column (Bluhm et al.
2008).
See related maps and descriptions of
Bathymetry, Ecoregions, Sea Ice Dynamics,
Sea Floor Substrate, Observed Climate
Change, Chlorophyll-a, Net Primary
Productivity, Opilio Crab, Spectacled Eider,
Steller’s Eider, King Eider, Common Eider,
Long-Tailed Duck, Pacific Walrus, Bearded
Seal, Gray Whale, Energy Development And
Protected Areas, and Predicted Climate
Change.
Sediment heterogeneity, type, and structure
(how well sorted, grain size, etc.), along with
temperature, salinity, and ice gouging, are
major regulating factors on benthic
community structure and diversity (Grebmeier
et al. 1989; Barber et al. 1994; Bluhm et al.
2008). The Chukchi Sea and Kotzebue Sound
epibenthos (organisms on or just above the
sea floor) are dominated in abundance by
echinoderms, crustaceans, polychaetes, and
bivalve mollusks (mainly Macoma calearea)
(Gagaev 2007; Bluhm et al. 2009), and in
biomass by echinoderms (mainly sea stars)
(Feder et al. 2005). Close to 1,200 species
have been identified in the Chukchi Sea,
dominated by amphipods, clams, and
polychaetes; the most important prey species
may be Macoma bivalves for walrus and
benthic amphipods for gray whales and
bearded seals (Bluhm et al. 2008).
Data Compilation and Mapping
Methods
Benthic biomass samples were interpolated
using the natural neighbor methodology
available in ESRI’s Spatial Analyst extension.
Other methods such as kriging, spline, and
inverse distance weighted did not appear to
represent the data as well as the natural
neighbor methodology. Sample locations are
denoted by a diamond so that the map reader
can see where data gaps exist.
Data Quality
This map has a data quality rating of fair. It
provides a partially complete geographic
picture of benthic biomass. Data across the
project area are variable—some portions of
the map are represented by reliable, highquality data and data for other portions are
outdated or are missing altogether. Sampling
locations are a collection of 50 years worth of
Differences between benthic systems in the
Chukchi Sea are attributed to water mass flow
patterns. Areas of very high primary
3-9
Arctic Marine Synthesis: Atlas of the Chukchi and Beaufort Seas
data, and large areas have not been sampled at
all. Although this map is a very informative
and important snapshot, mapping temporal or
seasonal change is not possible, and more
sampling should be done.
Sample locations are indicated on the map,
revealing large tracts of seafloor that have not
been sampled, including the Russian Chukchi
Sea and the Canada Basin. Although surveys
have taken place on the Beaufort Sea shelf,
those measurements were not made in
comparable units and could not be integrated
into our analysis.
Text Citations
Barber, W.E., R.L. Smith, and T.J.
Weingartner. 1994. Fisheries
oceanography of the northeast
Chukchi Sea—final report. MMS,
Alaska OCS Region, Anchorage,
Alaska.
Bluhm, B. K. Dunton, J. Grebmeier, and B.
Sirenko. 2008. Benthos. In Arctic
Ocean synthesis: analysis of climate
change impacts in the Chukchi and
Beaufort Seas with strategies for
future research. R. Hopcroft, B.
Bluhm, and R. Gradinger, editors.
Institute of Marine Sciences,
University of Alaska Fairbanks.
It is not yet known how climate change will
affect the Arctic marine system. Although it is
known that water temperatures are rising,
evidence about whether benthic biomass will
increase or decrease on the whole in a
warming climate is not conclusive at this
point. However, climate change is
hypothesized to weaken the short link
between primary productivity and the
benthos, converting the area to a pelagicrather than benthic-oriented system
(Grebmeier et al. 2006).
Bluhm, B., K. Iken, S.M. Hardy, B.I. Sirenko,
and B.A. Holladay. 2009. Community
structure of epibenthic megafauna in
the Chukchi Sea. Aquatic Biology
7:269-293.
Summary and Synthesis
Repeated benthic sampling should occur at
established points every one to three years
(Bluhm et al. 2008). Dunton et al. (2003)
suggest that sampling stations should be
placed 50 to 100 km apart for optimum
results; however, such a grid may not provide
enough resolution to understand ecological
processes and effects at the fine scale used in
project planning efforts. Areas of the highest
biomass, which are likely key foraging habitats
for birds and marine mammals, should be
priority areas for protections. Some such areas
include Chirikov Basin, Bering Strait, Hope
Basin, Long Strait, Hanna Shoal, Herald
Shoal, Peard Bay, Stefansson Sound, and
waters around Barter Island.
Dunton, K.H., J.M. Grebmeier, D.R.
Maidment, and S.V. Schonberg. 2003.
Benthic community structure and
biomass in the western Arctic: linkage
to biological and physical properties.
SBI I Final Report.
Feder, H.M., S.C. Jewett, and A. Blanchard.
2005. Southeastern Chukchi Sea
(Alaska) epibenthos. Polar Biology
28:402-421.
Feder, H.M., S.C. Jewett, and A.L. Blanchard.
2007. Southeastern Chukchi Sea
(Alaska) macrobenthos. Polar Biology
30:261-275.
Gagaev, S.Y. 2007. Unusual abundance of
macrobenthos and Pacific species
invasions into the Chukchi Sea.
Biologiya Morya 33:399-407.
Grebmeier, J.M., H.M. Feder, and C.P.
McRoy. 1989. Pelagic-benthic
3-10
Water Column and Benthic Life
coupling on the shelf of the northern
Bering and Chukchi seas – II: benthic
community structure. Marine
Ecology-Progress Series 51:253-269.
Grebmeier, J.M., J.E. Overland, S.E. Moore,
E.V. Farley, E.C. Carmack, L.W.
Cooper, K.E. Frey, J.H. Helle, F.A.
McLaughlin, and S.L. McNutt. 2006.
A major ecosystem shift in the
northern Bering Sea. Science
311:1461-1464.
Springer, A.M., C.P. McRoy, and K.R. Turco.
1989. The paradox of pelagic food
webs in the northern Bering Sea – II:
zooplankton communities.
Continental Shelf Research 9:359-386.
Map Data Sources
AOOS. 2009. 1 km topographic/bathymetric
map of Alaska. Raster dataset.
<http://ak.aoos.org/aoos/tools.html
>. Accessed February 2009.
Audubon Alaska. 2009. Bathymetric contour
lines. GIS feature class (based on
AOOS 2009).
Audubon Alaska. 2009. Benthic biomass. GIS
raster dataset (based on Grebmeier et
al. 2006; Shelf Basin Interaction 2008).
Grebmeier, J.M., L.W. Cooper, H.M. Feder,
and B.I. Sirenko. 2006. Ecosystem
dynamics of the Pacific-influenced
northern Bering and Chukchi seas in
the Amerasian Arctic. Progress in
Oceanography 71:331-361.
Shelf Basin Interaction (SBI). 2008. Benthic
samples. Microsoft Access database.
<http://www.eol.ucar.edu/projects/s
bi/all_data.shtml>. Accessed July
2008.
3-11
Arctic Marine Synthesis: Atlas of the Chukchi and Beaufort Seas
3-12
Water Column and Benthic Life
OPILIO (TANNER OR
SNOW) CRAB
to be of commercial size. Bluhm et al. (2009)
found the Opilio crab in high abundance at
sample locations throughout the American
and Russian Chukchi Sea.
Chionoecetes opilio
See related maps and descriptions of
Bathymetry, Sea Floor Substrate, Chlorophylla, Net Primary Productivity, Zooplankton,
Benthic Biomass, Spectacled Eider, Steller’s
Eider, King Eider, Common Eider, Capelin,
Pacific Herring, Saffron Cod, Pink Salmon,
Chum Salmon, Bearded Seal, and Gray Whale.
Description
Opilio crab, also known as snow crab or
tanner crab, is a key commercial species in
Alaskan waters, especially the Bering Sea.
Currently no commercial fishery exists in the
Chukchi or Beaufort seas, although a small
number of crabs of commercial size were
recently found in a survey north of Barrow
(NOAA and MMS 2008). Essential Fish
Habitat for adults and juveniles is defined as
bottom habitats to 100-m depth south of
Cape Lisburne, wherever there are substrates
consisting mainly of mud (North Pacific
Fishery Management Council [NPFMC]
2009). Those areas are outlined in yellow on
the map.
Data Compilation and Mapping
Methods
Data were digitized from three sources, each
showing Opilio crab present in its research
area. One source was NOAA’s Bering, Chukchi,
and Beaufort Seas Coastal and Ocean Zones Strategic
Assessment Data Atlas (1988), which indicated
that Opilio crabs were found only as far north
as the Bering Strait. Paul and Paul (1997)
indicated that these crabs were found in the
northwestern Chukchi Sea as well. Finally,
surveys by NOAA and MMS (2008) indicate
that Opilio crabs live north of Barrow in the
Beaufort Sea.
Opilio crabs mature between seven and nine
years of age (NPFMC 2009), and weigh one
to two pounds (Alaska Department of Fish
and Game [ADFG] 1994). Eggs incubate in
the female for a year before hatching during
April to June, often coinciding with the spring
plankton bloom (ADFG 2009). In the larval
stage they feed on plankton and are preyed
upon by pelagic fishes. Juveniles feed on
diatoms and detritus, and adults feed on
benthic organisms, including crustaceans,
bivalves, brittle stars, worms, and fish
(National Research Council [NRC] 1996).
Both juvenile and adults crabs are prey for
demersal fish, seals, and humans (ADFG
1994).
The map has a data quality rating of poor
because it provides an incomplete geographic
picture of Opilio crab distribution and
abundance. No data are available for large
portions of the project area, and the data for
those areas provide only rudimentary
estimates of abundance and size.
Data Quality
The Arctic Fishery Management Plan
(NPFMC 2009) indicates that biomass for this
species is estimated at 66,000 metric tons on
the Alaskan Chukchi Sea shelf and 30,000
metric tons in the surveyed portion of the
Beaufort Sea. Of the Beaufort Sea biomass,
approximately 6,500 metric tons are estimated
Areas not indicating the presence of this
species are likely due to no data rather than an
actual absence of Opilio crab. Data from
NOAA and MMS (2008) and Paul and Paul
(1997) indicate the species is present
throughout their research areas in high
abundance. Information on concentration
areas for larvae, juvenile, and adult crabs is
lacking.
3-13
Arctic Marine Synthesis: Atlas of the Chukchi and Beaufort Seas
Summary and Synthesis
Although the Arctic is closed to commercial
harvest, the Opilio crab, an important prey
species, could be targeted in the future.
Knowledge of its abundance, distribution,
concentration areas, and role in the ecosystem
is rudimentary and should be further studied.
Text Citations
ADFG. 1994. Tanner crabs. In Wildlife
notebook series. Public
Communication Section, ADFG,
Juneau, Alaska.
Bluhm, B., K. Iken, S.M. Hardy, B.I. Sirenko,
and B.A. Holladay. 2009. Community
structure of epibenthic megafauna in
the Chukchi Sea. Aquatic Biology
7:269-293.
Paul, J.M., and A.J. Paul. 1997. Reproductive
biology and distribution of the snow
crab from the northeastern Chukchi
Sea. American Fisheries Society
Symposium 19:287-294.
Audubon Alaska. 2009. Opilio crab. GIS
feature class (based on NOAA 1988;
Paul and Paul 1997; NOAA and MMS
2008).
National Marine Fisheries Service (NMFS).
2005. Final environmental impact
statement for essential fish habitat
identification and conservation in
Alaska. NOAA NMFS, Alaska
Region, Anchorage, Alaska.
NOAA and MMS. 2008. Cruise report for the
2008 Beaufort Sea Survey, July 27August 30, 2008.
NOAA. 1988. Bering, Chukchi, and Beaufort
seas coastal and ocean zones strategic
assessment data atlas.
Paul, J.M., and A.J. Paul. 1997. Reproductive
biology and distribution of the snow
crab from the northeastern Chukchi
Sea. American Fisheries Society
Symposium 19:287-294.
NOAA and MMS. 2008. Cruise report for the
2008 Beaufort Sea Survey, July 27August 30, 2008.
NPFMC. 2009. Fishery management plan for
fish resources of the Arctic
Management Area.
NRC. 1996. The Bering Sea ecosystem.
National Academy Press, Washington,
D.C.
Map Data Sources
AOOS. 2009. 1 km topographic/bathymetric
map of Alaska. Raster dataset.
<http://ak.aoos.org/aoos/tools.html
>. Accessed February 2009.
Audubon Alaska. 2009. Bathymetric contour
lines. GIS feature class (based on
AOOS 2009).
3-14