ROBIN M. ROSS, Marine Science Institute, University of California, Santa Barbara, California 93106
KAREN S. BAKER, Marine Research Division, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093
Each year since 1993, the Palmer Long-Term Ecological Research (LTER) program has surveyed a mesoscale study region west of the Antarctic Peninsula with a standard grid that was set up at the initiation of the program (Waters and Smith 1992). During the 1997 cruise aboard the R/V Polar Duke ( PD 97-1), sampling occurred between 11 January and 13 February. The cruise plan (table) included standard cardinal transect lines (figure 1), high-density sampling within the foraging range of Adélie penguins nesting near Palmer Station (figure 2), periodic visits to the stations near Palmer, and spatial variance transects. Three of the five major cruise objectives for 1997 are common to all January cruises:
These nearshore stations are within 3.7 kilometers (km) of Palmer Station and sampled from zodiacs from November through March to document interannual variability in seasonal patterns (Baker et al., Antarctic Journal, in this issue). The fourth objective this year was to document spatial variance of multiple physical and biological parameters on both on/offshore and alongshore transects. The fifth objective was to initiate cooperative studies with the British Antarctic Survey (BAS) making a visit to Rothera Station (figure 1). In addition, the R/V Polar Duke participated in a broadcast of Live from Antarctica 2 from Palmer Station in late January. Questions from middle school students were answered real-time by those onboard through use of satellite communications. Finally, personnel aboard participated in an expendable bathythermograph study directed by Janet Sprintall of Scripps Institution of Oceanography during the southbound crossing.
Standard measurements at stations 20 km apart on cardinal transect lines included seabird community composition as well as the following water column characteristics:
Bioacoustic surveys and net tows for zooplankton and krill were centered on each station, and physiological condition determined for krill collected. Underway surface measurements between stations included
Sea ice was encountered only in the southern part of Grandidier Channel (inside north), the inner reaches of Crystal Sound (inside south), and Tickle Channel (TC) in northern Marguerite Bay. Only one bad weather day was logged, preventing sampling at the two outermost stations on the 500 cardinal transect line. Chlorophyll- a concentrations were an order of magnitude lower in the northern area of the Peninsula grid in comparison with January 1996. Further, there was less of an onshore-to-offshore biomass gradient and fewer phytoplankton communities dominated by Cryptomonads and Prymnesiophytes. In the southern area of the Peninsula grid, biomass was generally less than 1 milligram per cubic meter (mg m-3), although a large phytoplankton bloom was found within Marguerite Bay having surface chlorophyll values ranging from 10 to 30 mg m-3 and water-column-integrated-to-30-m values from 2 to 4 mg m-3 that were coincident with low pCO2 values. Diatoms and the Prymnesiophyte Phaeocystis sp. dominated the phytoplankton community. A mixture of salps and krill was found at many stations, and antarctic krill abundances were at average levels.
In addition to the mesoscale survey, intensive sampling was conducted within the foraging area of Adélie penguins whose reproductive success and foraging ecology were being studied simultaneously by investigators at Palmer Station. Surveys were conducted at Torgersen and Humble Islands in conjunction with zodiac tracking of Adélie penguins. The relative distributions of the predator (Adélie penguins) and prey (antarctic krill) were observed on 3.7- and 10-km picket-line transects (Smith et al. 1995) and on high-density grids (figure 2). Only seabird counts were performed on the picket lines farther than 10 km from Palmer Station. The 10-km 20-km high-density grid (figure 2), as described for January 1995 (Quetin et al. 1995), was repeated twice. These seabird censuses showed higher numbers of Adélie penguins foraging within 10 km of Palmer Station than in previous years and showed that most penguins were foraging relatively close (<20 km) to their rookeries where acoustic biomass (primarily antarctic krill) was higher than farther offshore.
Annual servicing of the two Palmer LTER program sediment trap moorings (Hugo Island and Palmer Basin) and replacement of two automatic weather stations (AWS Bonaparte and AWS Hugo) (figure 1) were carried out during cruise PD 96-12 in December 1996. In early January, however, the R/V Polar Duke visited Hugo Island to complete the AWS Hugo service and to survey the island bird population. During the day of exchange with BAS personnel at Rothera, LTER procedures were discussed (Smith et al. 1996) and demonstrated to those involved with the new British nearshore sampling program. In addition, the diets of Adélie penguins on Ginger Island were sampled. The R/V Polar Duke also paid the first official visit of the U.S. Antarctic Program to the Ukrainian station, Vernadsky Station.
This research cruise was a result of a productive team composed of Palmer LTER research team members with team leaders: Karen Carney with W.R. Fraser, Wendy Kozlowski with M. Vernet, Dave Menzies with R. Smith, and Luis Tupas with D. Karl. Special thanks go to Charleen Johnson and Janice Jones as well as to Antarctic Support Associates personnel and Captain Karl Sanden and his crew of the R/V Polar Duke . Our grateful appreciation is extended to all. This research was supported by National Science Foundation grant OPP 96-32763. This is Palmer LTER contribution number 148.
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Live from Antarctica 2. Passport to Knowledge, P.O. Box 1502, Summitt, NJ 07902-1502 ( http://quest.arc.nasa.gov/antarctica2 ).
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Smith, R.C., L.B. Quetin, J.L. Jones, D.W. Menzies, T.A. Newberger. 1996. Palmer LTER: Small boat design for water column sampling. Antarctic Journal of the U.S., 31(2), 167-169.
Smith, R.C., L.B. Quetin, R.M. Ross, J. Jones, W.R. Fraser, W.Z. Trivelpiece, L. Somervill, and D. Hardesty. 1995. Palmer LTER: Seabird picket-line sampling and zodiac tracking during the January 1995 cruise. Antarctic Journal of the U.S. , 30(5), 273-274.
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