KAREN S. BAKER, WENDY A. KOZLOWSKI, and MARIA VERNET, Marine Research Division, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093
JANICE L. JONES, LANGDON B. QUETIN, ROBIN M. ROSS, and RAYMOND C. SMITH, Institute for Computational Earth System Science and Marine Science Institute, University of California at Santa Barbara, Santa Barbara, California 93106
WILLIAM R. FRASER, Polar Oceans Research Group, Biology Department, Montana State University, Bozeman, Montana 59717
The Palmer Long-Term Ecological Research (LTER) Program (Smith et al. 1995) completed a sixth season of sampling at Palmer Station. The Palmer LTER sampling strategy combines seasonal time series data from the nearshore Palmer grid and seabird observations from nesting sites near Palmer Station with annual cruises that cover a regional grid along the western Antarctic Peninsula. The LTER January cruise ( PD 97-1) visited the Palmer Basin inshore stations four times to provide continuity in the seasonal record (Ross and Baker, Antarctic Journal , in this issue).
A summary of events for the 1996-1997 Palmer field season is given in tables 1 and 2; table 1 gives the weekly standard sampling plan, which varied somewhat, and table 2 gives the season's sampling overview. An additional activity late in the season was excavation of penguin rookery sediments for local paleo studies (S. Emslie). Significant dates include
In table 2, each line summarizes one cycle of standard sampling (from table 1). Initial event number, month begin, day begin, day end, and year are given in the first five columns. The sixth column summarizes the types of standard days included in this particular cycle, and a prime indicates a subset of that standard day. Acoustic transects, hydrographic and optical profiling, phytoplankton sampling, targeted krill tows for physiological condition, and instantaneous growth-rate experiments are given in the next columns followed by general comments.
Some changes in the sampling program were necessary from past seasons (Baker et al. 1996). With six LTER personnel for the 1996-1997 season (1/S016; 1/S032; 1/S028; 1/share; 2/S035) rather than 10 as in 1995-1996 (3/S016; 1.5/S032; 2.5/S028; 3/S035 ), the daily sampling week had to be reduced by
Further, only the sum of nitrite and nitrate were measured rather than the individual components. Nutrients taken on station at the start of the season were run concurrently with cruise samples when additional personnel were available. The hardware and software for high-performance liquid chromatography and nutrient analysis remained the same as last year. Equipment upgrades included addition of an anemometer for wind speed and a thermometer for air temperature on the zodiac Roze. Also this season, the satellite network link LES9 provided two blocks of approximately 5 hours of online time per day making possible FTP file transfer of data and real-time electronic communication. The data transfer served as both a method of data archive as well as the conduit enabling real-time data analysis at home institutions.
In addition to standard chlorophyll samples run in replicate for the greater than 0.45-micrometer (µm) phytoplankton at selected depths, the <20-µm fraction was sampled at the 50 percent light level [ranging from 2.5 meters (m) to 19 m]. Hydrographic profiles were also run as requested at station Janus (Karentz personal communication) and at the pier (Amos personal communication). Concurrent deployment with the stations' salinity-temperature-depth (STD) instrument will permit intercomparison studies.
During the 1996-1997 U.S. Antarctic Program season, there was no consolidated ice in September 1996. High winds throughout the month of October contributed to ice movement, and the last of the pack ice left on 29 October. Brash ice continued to appear sporadically through April, accompanied by high winds. This pattern differed from that of 1995-1996 (Baker et al. 1996) when the spring and summer were preceded by a heavy-ice winter, and pack ice did not begin to clear from the nearshore Palmer region until November 1995. Preliminary data show seasonal progression in selected parameters through the spring and summer (figure), providing an overview of the season. The 1996-1997 season showed average to low chlorophyll biomass with initial surface phyto-plankton blooms of 5-10 milligrams per cubic meter (mg m-3) in November at station B and in December at station E. Chlorophyll concentrations remained below 1-3 mg m-3 through January, followed by another short bloom reaching 5 mg m-3 occurring in February 1997 at station E. The nitrate-nitrite showed less pronounced bloom activity this season compared with last season.
Between 22 November and 21 March, 14 acoustic transects were run from stations A to E (figure, block C ), and 14 from F to J. Acoustic biomass in the spring and early summer was generally less than 100 grams per square meter (g m-2), whereas from mid-January to mid-February acoustic biomass was between 100 and 500 g m-2, decreasing to extremely low values in late February and early March. Length frequency distributions of antarctic krill collected with target tows indicated that age class 1 and 2 krill between 9 and 30 millimeters (mm) dominated the catch in the spring and early summer. Salps were abundant on the surface in late spring (mid- to late December) but did not exclude the krill. Some of the reproductive events associated with breeding chronology of Adélie penguins on Humble Island this season (Fraser et al. 1997) are noted by diamonds in the figure (block C ). The breeding success of these penguins was 1.47 chicks creched per pair, representing a small decrease relative to last year.
The LTER seasonal observations of the marine environment, the lower-trophic level abundance and distributions for the area, and the seabird observations at nesting sites near Palmer were recorded from October 1996 to March 1997. The sampling event log, participant list, and other project information for the season are available online ( / ).
Acknowledgement and thanks are given to members of the Palmer LTER research team and of Antarctic Support Associates. This research was supported by National Science Foundation grant OPP 96-32763 and is Palmer LTER contribution number 147.
Amos, T. 1997. Personal communication.
Baker, K.S., M. Vernet, W.A. Kozlowski, R.C. Smith, J.L. Jones, R.M. Ross, L.B. Quetin, and W.R. Fraser. 1996. Palmer LTER: Annual season October 1995 to March 1996. Antarctic Journal of the U.S. , 31(2), 160-162.
Fraser, W., D. Patterson, E. Holm, K. Carney, and J. Carlson. In press. Seabird research undertaken as part of the NMFS/AMLR ecosystem monitoring program at Palmer Station, 1996/97. In J. Martin (Ed.), AMLR 1996/97 field season report: Objectives, accomplishments and tentative conclusions . La Jolla, California: Southwest Fisheries Science Center.
Karentz, D. 1997. Personal communication.
Ross, R.M., and K.S. Baker. 1997. Palmer LTER: Annual January cruise for 1997 ( PD 97-1). Antarctic Journal of the U.S. , 32(5).
Smith, R.C., K.S. Baker, W.R. Fraser, E.E. Hofmann, D.M. Karl, J.M. Klinck, L.B. Quetin, B.B. Prézelin, R.M. Ross, W.Z. Trivelpiece, and M. Vernet. 1995. The Palmer LTER: A long-term ecological research program at Palmer Station, Antarctica. Oceanography , 8(3), 77-96.