HR: 0800h
AN: OS51B-0564    [Abstracts]
TI: Benthic Community Composition and Seabed Characteristics of a Chukchi Sea Pockmark
AU: * MacDonald, I R
EM: imacdonald@falcon.tamucc.edu
AF: Texas A&M University-Corpus Christi, Physical and Life Sciences Dept., Corpus Christi, TX 78412 United States
AU: Bluhm, B
EM: bluhm@ims.uaf.edu
AF: University of Alaska Fairbanks, Institute of Marine Sciences, Fairbanks, AK 99775 United States
AU: Iken, K
EM: iken@ims.uaf.edu
AF: University of Alaska Fairbanks, Institute of Marine Sciences, Fairbanks, AK 99775 United States
AU: Gagaev, S
EM: gagaev@russacademysci.ru
AF: Russian Academy of Sciences, Zoological Institute, St. Petersburg, 99999 Russian Federation
AU: Robinson, S
EM: srobinson@kestrel.tamucc.edu
AF: Texas A&M University-Corpus Christi, Physical and Life Sciences Dept., Corpus Christi, TX 78412 United States
AB: Several dozen seafloor features were mapped by Larry Mayer and his colleagues using swath bathymetry during a 2003 cruise with the USCGC HEALY near the eastern edge of the Chukchi Plateau (Chukchi Sea 76.6N, 163.9W). These were sub-circular depressions ranging from approximately 250 to over 1000m in width, with depths of up to 50m below the surrounding seabed, and situated in water depths from 500 to 950m. The origin of these features was undetermined, but one possibility was that they were pockmarks formed as a result of gas or fluid expulsion processes. We report here on benthic sampling undertaken at one of these pockmarks on 18 July 2005, also from USCGC HEALY. This elongated feature had maximum water depth of approximately 940m, was 1200m in maximum width, and was depressed approximately 40m below the surrounding seabed. The ocean in the vicinity of the pockmark was heavily ice-covered, which tightly restricted the ship's mobility during sampling operations. We used an ROV to collect and photograph the benthic epifauna during a 6h transit that crossed from the outside of the pockmark to near the center over a distance of 900m. We used a down-looking digital camera to collect over 800 pictures of the benthos at altitudes of 2 to 3m above the seabed. We also collected three cores with a 25x25cm box corer. Our investigations did not provide any direct evidence for gas or fluid flux through the seabed of this feature. Neither did we see any secondary indications of methane flux such as authigenic carbonates or bacterial mats. The abundance and diversity of benthic epifauna at this station was the highest among 8 stations sampled using similar methods during a 30 day cruise. The ROV observed brittle stars, various types of anemones, shrimps, eel pouts, stalked crinoids, benthic ctenophore (likely new species), burrows and mounts, gooseneck barnacles, mysids. Holothurians (c.f. Peneagone sp.) were the single most abundant group and were often photographed in densities of over 50 individuals per square meter. Preliminary analysis of the box core samples: Polychaetes (e.g. Chaetozone setose, Aricidea sp., Ophelina sp., Progoniada sp., Proclea graffi, Protula globifera), Foraminifera, Nemertini, Coronata (Cnidaria tubes), Sipunculida (Golfingia), Bivalvia, Anthozoa.
UR: http://www.oceanexplorer.noaa.gov/explorations/05arctic
DE: 3004 Gas and hydrate systems
DE: 4207 Arctic and Antarctic oceanography (9310, 9315)
DE: 4219 Continental shelf and slope processes (3002)
DE: 4802 Anoxic environments (0404, 1803, 4834, 4902)
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005