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RUSCALA
Benthic infaunal community structure in the Chukchi Sea
Boris Sirenko and Sergey Gagaev (Zoological Institute, Russian Academy of Sciences. St. Petersburg)
Jackie Grebmeier , Lee Cooper, and Arianne Balsom (University of Tennessee)
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Boris Sirenko and Arianne
Balsam by B. Bluhm
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The main goal of our scientific sampling team was to study the composition and distribution of benthic infaunal communities in the Chukchi Sea. In connection with this goal both Russian and US scientists undertook collaborative studies as follows. The main objectives of the Zoological Institution objectives were:
1. To
examine the composition, distribution and quantitative data (abundance and
wet weight abundance per square meter) of both the macro-and meiobenthos.
2. To
map Chukchi Sea benthic community distributions in both Russian and U.S. waters.
3. To
explore benthic community variations.
4. To
determine the influence of climate change on distributions of warm water fauna
in the Chukchi Sea.
5. To
analyze dominant species’ trophic structure interactions.
The main objectives of the
University of Tennessee, Knoxville were:
1. To
determine species composition, abundance and biomass (both wet weight and
carbon biomass), of infaunal marine benthic communities.
2. Measurement
of sediment chemistry parameters important to these benthic communities (sediment
chlorophyll a content, total organic
carbon content, sediment grain size, pigment content, and sedimentation rates
using 7Be and 137Cs as indicators of particle setting
rate).
3. Determination
of 18O stable oxygen isotope
composition in the overlying water column, indicative of water mass variation
and fresh water input.
4. Comparison
of RUSALCA 2004 marine community analyses with data collections undertaken
on previous Russian-U.S. cruises in this same region, particularly the BERPAC
sponsored cruises that involved Russian and U.S. scientists in 1988 (Academik Korolev), 1993 (Okean), and 1995 (R/VAlpha Helix).
Sampling equipment used:
1. Van
Veen benthic grab (0.1 m2)
2. Ocean
benthic grab (0.25 m2)
3. Small
rectangle dredge (entrance 22x70 cm, 1 cm mesh size)
4. Set
of 10.5 and 1 mm mesh washing sieves.
5. Net
of 100 μm mesh to collect qualitative meiobenthic samples.
6. Device
to collect quantitative meiobenthic samples (18.8 cm2).
The majority of samples (both
infauna and surface sediment samples) were obtained using the van Veen grab.
In total, 122 grab samples were taken at 17 stations. At 4 of these 17 stations,
3 van Veen replicates were collected for the Zoological Institute (deployments
#1-#3), 5 van Veen replicates were collected for the University of Tennessee
(deployments #4-#8), and additional grabs (#9-#10) were obtained, when requested,
for other members of the expedition studying surface sediment parameters.
Sediments from 8th and 9th grabs were used for studies of sediment parameters by the University
of Tennessee, in addition to other RUSALCA sampling teams’ studies of quantitative
meiobenthic distribution, microbiology, geology, epifaunal distribution, trophic
structure, and ichthyology. Finally, three additional stations (st. 22, 24
and 58B) were occupied for 3 grabs/station faunal collections for the Zoological
Institute.
In
order to examine the relationship between infaunal and epifaunal components
in the composition and distribution of benthic Chukchi Sea communities, collaborations
between RUSALCA participants are necessary.
Infaunal community analysis will be examined in comparison with epifaunal
samples collected using an otter trawl (in collaboration with Drs. D. Stein,
C. Mecklenburg and B. Sheiko), and a beam trawl (in collaboration with Dr.
B. Holladay). Data obtained from Remotely
Operated Video Operations (in cooperation with Drs. K. Crane, V. Gladysh,
B. Smirnov, V. Kaulio), and infaunal and epifaunal samples taxonomically sorted
for trophic structure analysis (in collaboration with Drs. K. Iken and B.
Bluhm) will also be used.
In
addition to the investigation of the macrobenthos during the expedition, meiobenthic
materials were also collected for analysis at the Zoological Institute: 15
quantitative samples at the all main stations and 16 qualitative samples at
8 stations.
Preliminary results
Several specimens of the Northern
Pacific crab (Telmessus cheiragonus)
were collected in the south-eastern Chukchi Sea at station 17.
These specimens are the third northernmost documentation of this species
in the Chukchi Sea; the most northern discovery of T.
cheiragonus was made in 1988 (Academic
Korolev, st. 66), near the entrance of Kotzebue Sound. The second northernmost
find occurred during 1990 in Kotzebue Sound by Feder et al. (in print). At RUSALCA station 17, the Pacific crab Oregonia gracilis and the bivalve Pododesmus macrochisma were also found,
and to our knowledge, for the first time in the Chukchi Sea. These three findings
of Pacific taxa in Arctic waters may testify to a continued warming trend
in the Chukchi Sea; mentioned previously by P.V. Ushakov (1952).
The
taxa at the two most southerly transect lines (st 11-15, 22-25) demonstrated
an infaunal community composition dominated by the bivalve Macoma calcarea in the south-central and south-eastern Chukchi Sea
(66º50’N to 68º20’N and 168º20’W to 173º00’W), which was also documented in
the beginning of the last century. Macrobenthic community wet weight biomass
in the south-central Chukchi Sea stations averaged 1000-2000g/m2,
exceeding 4000 g/m2 at st. 13. Soft bottom benthic communities
do not show these values of high biomass in temperate regions of the World
Ocean, but they have been reported in the Arctic Ocean. These large supplies
of bivalves may be attracting walruses, which feed on primarily on benthic
animals.
Such
protracted existence of high productive benthic communities of bivalves in
the south-central and south-eastern Chukchi Sea most likely results from currents
moving northwesterly from the Bering Strait, before veering to the northeast
in the Chukchi Sea. The settlement of infaunal larvae in other regions of
the Chukchi Sea is impeded by this water circulation pattern. These currents also entrain concentrated amounts
of food utilized by benthic communities, namely phytoplankton, zooplankton
and fecal pellet material. Organic materials synthesized by phytoplankton
in the southwestern Chukchi Sea are consumed by benthic animals inside the
boundary of the aforementioned Macoma
calcarea community. The northwesterly currents are likely phosphate-,
silicate-, nitrate- and phytoplankton-poor; benthic biomass in those regions
falls to a wet weight biomass range of 200-300 g/m2. However, sufficient
data is needed in the central and western Chukchi Sea in order to support
this hypothesis. In our opinion, one of the main tasks of future RUSALCA Chukchi
Sea expeditions must be a much more detailed hydrological and hydrobiological
investigation in both the central and western regions.
Taxa
using filtration feeding strategies dominated in eastern Chukchi Sea benthic
communities, communities exhibited low wet weight biomass (80-250 g/m2,st.
17 and 18); these results were similar to previous expeditions to the same
region.
The
northernmost transect line (st. 58B, 62B, 73B, 85B, 106 and 107) in Herald
Trough and its vicinity was dominated by polychaetes (Maldane sarsi, Nicomache lumbricalis,
Nephtys ciliata), brittle stars (Ophiura sarsi) and sipunculids (Golfingia
margaritacea) with a wet weight biomass ranging form from 102 to 343 g/m2.
An unexpectedly rich settlement of sedentary epifaunal organisms (soft corals,
sponges and bryozoans) encrusting both pebbles and manganese nodules was encountered
on st.62B. On this same transect line, the Remotely Operated Video filmed
a Cerianthid (Tube Anemone), which was the first known observation of this
taxonomic order in the Chukchi Sea .
Appendix
Bottom communities of the Chukchi Sea and their quantitative characters
Station |
Nm2 |
Bm2 |
Community |
|
11 |
306 |
1291.2 |
Yoldia hyperborea+Macoma calcarea+Leionucula
tenuis +(Ampelisca sp.) |
|
13 |
819 |
4231.7 |
M. calcarea |
|
15 |
167 |
1081.7 |
M. calcarea |
|
17 |
310 |
248.8 |
Cheliosoma
orientalis+Nephtys ciliata |
|
18 |
60 |
86.3 |
Polychaeta varia |
|
20 |
320 |
156.1 |
Ophiura
sarsi+Nephtys spp. |
|
22 |
640 |
260 |
M. calcarea+L. tenuis
|
|
23 |
1350 |
612.8 |
L. tenuis |
|
24 |
350 |
491.4 |
M. calcarea |
|
25 |
1150 |
934.6 |
M. calcarea+Y. hyperborea
|
|
27 |
680 |
12.2 |
Gammaridea+Polychaeta |
|
106 |
110 |
116.9 |
Maldane sarsi+O.sarsi |
|
85B |
340 |
231.4 |
M.
sarsi+Astarta borealis+Ct.crispatus |
|
73B |
550 |
380 |
M. sarsi |
|
62B |
510 |
343.1 |
Golfingia
margaritacea+Nicomache lumbricalis |
|
58B |
170 |
134.6 |
N.
ciliata+M. sarsi+Actiniaria |
|
107 |
300 |
102.5 |
N.
ciliata+M. Sarsi+G. margaritacea |