ACCEPTED: Antarctic Journal 1996 REFERENCE AS: Vernet, M., and K. S. Baker, Palmer LTER: Annual January Cruise for 1996 (PD96-1), Antarct. J. U. S. 1996. Palmer LTER Contribution #106 Palmer LTER: Annual January Cruise for 1996 (PD96-1) Maria Vernet and Karen S. Baker Marine Research Division Scripps Institution of Oceanography University of California at San Diego San Diego, CA, 92122 The Palmer LTER (PAL) annual cruises provide physi- cal and biological data west of the Antarctic Peninsula. Sampling on PD96-1 from 08 January to 10 February 1996 aboard the R/V Polar Duke included cardinal transect lines, inshore stations, and periodic visits to the nearshore Palmer grid to provide temporal continuity to the Palmer station season sampling effort (Fig. 1). Standard measurements included optics, hydrography, microbial parameters, plant pigments, primary production, plant physiology, acoustic surveys, net tows for zoo- plankton, krill and fish, and krill physiological condi- tion (Table 1). In addition, higher density observations within the foraging area of Palmer Ade'lie penguins link this apex predator to the environment during critical periods of its life history. Surveys of seabird abundances (Fig. 2) were continued using picket line (PL) transects, high- density grids (HD) and observations from zodiacs. Also, a day was spent recording Ade'lie penguin's arriving and departing from Torgersen Island. A continuous underway carbon dioxide equilibrator system mapped variations in the air-to-sea gradients in carbon dioxide partial pres- sure. Two one-day experiments were conducted to investi- gate particle flux in ice covered regions in Marguerite Bay. Stations North (N, Fig.1) (Biscoe- Renaud/Lemaire/Grandidier) and South (S, Fig.1) (Biscoe- Levoisier/Crystal Sound) inshore of the coastal islands are in some years ice covered, are often highly produc- tive and are considered nursery grounds for larval fish and Antarctic krill. High density sampling (Quetin et al., in press) along with coincidental measurements of terrestrial sam- pling on Ade'lie penguin foraging durations were col- lected. Over time this sampling has been modified based upon results from previous cruises. Originally a 70 km x 70 km grid near Palmer was sampled twice in January 93. A smaller 50 km x 50 km grid within the previous 70 km grid was sampled once in January 94. Based upon these results, a 10 km x 20 km grid (HD1) within the 50 km x 50 km area was sampled three times in January 95 and twice in Janu- ary 96. During January 1996, the Bismarck Strait was sampled (HDB; Fig.2) in addition to acoustic transects on the south side of the Bismarck Strait and along the 200 km contour to the east of the Palmer Basin. Picket line seabird censuses, adopted during PD95-1 (Smith et al., in press), indicated again foraging range of Ade'lie penguins to be within 50 km of Palmer station. Acoustic biomass measurements were added to the last four 3.7 km picket line surveys to quantify the temporal link between the location of penguins and acoustic (primarily krill) biomass. A new radial picket line (PLR; Fig.2) was initiated to determine whether counting penguins in the direction of travel impacted a survey. The direction of travel from island breeding sites was determined using penguin tracking from zodiacs. Annual servicing of the two LTER program sediment trap moorings (Hugo Island and Palmer Basin) was con- ducted on PD95-10 the preceeding December. In addition, the Hugo Automatic Weather Station (AWS) was serviced. High seas prevented small boat landings on later visits to repair the water temperature probe. A visit to the British Antarctic Survey (BAS) Station at Rothera permit- ted discussion of a British nearshore sampling program scheduled to begin in 96/97. Ice-free open water was observed during most of the cruise. Ice was encountered in the southern part of Grandidier Strait (inshore North), in the southern part of Crystal Sound (inshore South), and in the southern part of Marguerite Bay. Bad weather days were used to sample nearshore so only one day (05 Feb) was lost due to stormy weather. The highest concentration of feeding penguins was found further from Torgersen Island as January pro- gressed, varying from within 3.7 km on 9 Jan, to within 10 km on 16 Jan, and to within 30 km on 25 Jan. Acoustic biomass was observed with higher concentrations nearshore, along the 200-m contour line, and in Palmer Basin. During January , the pattern of krill aggregations changed from layers to more defined swarms. Phytoplankton biomass was higher than in the three previous January cruises with a strong North-South component and large biomass accumulation in Palmer Basin and Marguerite Bay. A large diatom bloom near Palmer Station extended to 600.080 and the Lemaire Channel. Thanks are given to the Palmer LTER research team members, the Antarctic Support Associates as well as the Captain and crew of the R/V Polar Duke. This research was supported by National Science Foundation grant OPP90-11927 and is Palmer LTER Contribution No. xx. References L.Quetin, K.S.Baker, W.R.Fraser, D.Hardesty, J.Jones, R.Ross, R.C.Smith, L.Somervill, W.Trivelpiece, and M.Vernet. in press. Palmer LTER: Observations in foraging areas of Ade'lie penguins during the January 1995 cruise. Antarctic Journal of the United States. R.M.Ross, E.E.Hofmann, and L.B.Quetin (eds). in press. Foundations for Ecological Research West of the Antarctic Peninsula. AGU Antarctic Research Series. R.C.Smith, L.B.Quetin, R.M.Ross, J.Jones, W.R.Fraser, W.Z.Trivelpiece, L.Somerville, and D.Hardesty. in press. Palmer LTER: Seabird picket line sampling and zodiac tracking during the January 1995 cruise. Antarctic Jour- nal of the United States. Figure Legends Figure 1. The cardinal stations of the Palmer LTER regional grid (dots) off the Antarctic Peninsula are overlaid with large dots to indicate stations occupied during PD96-1. Labeled are Anvers Island (1), Adelaide Island (2), Torgersen Island (T), Palmer Station (o), Rothera Station (R), Hugo Automatic Weather Station (H; 64o957'S, 65o941'W), Northern Stations (N), Southern Sta- tions (S), and Marguerite Bay (M). The Hugo area sediment trap site is marked with a filled triangle. The 1000 m bathymetry line (dotted) is shown. Figure 2. Sampling area in the vicinity of Palmer Station on Anvers Island with the Neumeyer (N) and Gerlache Strait to the East. The Hugo Automatic Weather Station (H) location is given. The Palmer basin sediment trap site is marked with a filled triangle. Shown are the 3.7 km, 10 km, and 30 km picket lines (dashed lines), the radial picket line sampling (PLR) grid originating at station E (triangle), and the Bismark High Density grid (HDB). The LTER regional grid 600 line stations 040, 060, 080, 100, 120 are marked (filled squares). Table Legend Table 1. LTER 96Jan (PD96-1) Cruise Overview. Daily events summarized including LTER gridlines, LTER nearshore stations, High Density Grid (HD), Picket Lines (PL), zodiac operations and Automatic Weather Station (AWS). Event time use during cruise is summarized at the bottom of the table.