brcensus 93aug 25aug93-29sep93 At-sea seabird censuses to determine abundance and distribution in the Palmer LTER marine grid between the 600 and 200 lines during the 92-93 season. The files provide general spatial and environmental data associated with both stationary and moving transects, and specific data on the species encountered (including marine mammals), their abundance, distribution and behavior. crxxx93h.dat cruise number, event number, transect start time (GMT), transect start point on LTER grid, transect end point on LTER grid, ship speed (knots), sea state (Beaufort scale), marine habitat type, ice cover (octas), ice type, ice color, crxxx93t.dat cruise number, event number, time of observation (the minute the observation is made), taxa observed, number observed, linkages (feeding associations between species), behavior, notes, crxxx93s.dat cruise number, event number, station number, time (GMT), sea state, marine habitat type, ice cover (octas), ice type, ice color, time of observation (the minute the observation is made), taxa observed, linkages (feeding associations between species), behavior, notes, Stationary censuses, twice at each station; moving censuses, 1-3 between stations. Two types of transects are conducted, moving and stationary. During moving transects (the ship underway at 6 knots or more in open water; 3 knots or more in ice) between stations, seabirds are censused as they enter a 90 degree quadrant off the ship's starboard or port side bow. These censuses also start and end with a stern count of seabirds following the ship. The use of these quarters alternates, depending on what side offers better visibility, but both quarters are never used during the same census. Censuses are confined to seabirds within 300m of the ship and typically last 30 minutes each. In the second type of transect, an instantaneous census lasting 1 minute is made to document all seabirds around the ship when it stops to begin an oceanographic station. This census covers 360 degrees and includes all seabirds within 300m of the ship. After completing this census, another 15 minute census is done that is confined to birds that enter a 90 degree quadrant off the ship's starboard or port-side bow. All censuses also record marine mammals (seals within 300m of the ship an whales within 800m of the ship). The objectives of the LTER seabird component during the 92-93 season cruises were similar. These objectives included 1) determining the pelagic abundance and distribution of Adelie Penguins, 2) examining how the physical and biological characteristics of the marine environment influence these parameters and, 3) using these data to identify foraging areas that may be important to Adelie populations being studied as part of land-based work at Palmer Station. Secondary objectives included documenting the abundance and distribution of other seabirds and marine mammals within the LTER study area. The focus during the August-September cruise was winter ecology, hence, sampling over a large spatial scale. Seabird censuses were thus conducted along the LTER 600, 500, 400, 300 and 200 lines, which were also sampled by other LTER components at 20 km intervals. Ninety-three 30-minute transects and 50 station censuses, were completed during the August-September cruise. Although seabirds were widely distributed throughout the study area, the highest densities and greatest biomass occurred consistently at the shelf break along each of the LTER lines. The most productive line in terms of overall seabird abundance, biomass and species diversity was the 200 line. Except at the 200 line, Adelie Penguins were generally rare throughout the area; Snow Petrels and Antarctic Petrels were the dominant members of the seabird community in terms of both abundance and biomass. The most important variables accounting for variation in the distribution and abundance of seabirds appeared to be the location of the shelf break, the presence of deep bottom features on the shelf itself and sea ice characteristics, with older ice in general being associated with increasing biomass and species diversity. antarctica, adelie penguin, seabirds, biomass, foraging ecology, sea ice, winter ascii local DBASE online LTER ~lter/lterdata/93aug/brcensus/crjan93h.txt ~lter/lterdata/93aug/brcensus/crjan93s.txt ~lter/lterdata/93aug/brcensus/crjan93t.txt ~lter/lterdata/93aug/brcensus/craug93h.txt ~lter/lterdata/93aug/brcensus/craug93s.txt ~lter/lterdata/93aug/brcensus/craug93t.txt William R. Fraser Wayne Z. Trivelpiece William R. Fraser William R. Fraser Donna L. Patterson Nina Karnovsky Douglas Wallace William R. Fraser Donna L. Patterson Nina Karnovsky Douglas Wallace William R. Fraser 12 December 1996 Fraser, W.R. and D.G. Ainley. 1986. Ice edges and seabird occurrence in Antarctica. BioScience 36: 258-263. Ainley, D.G., W.R. Fraser, C.W. Sullivan, J.J. Torres, T.L. Hopkins and W.O. Smith. 1986. Antarctic mesopelagic micronekton: evidence from seabirds that pack ice affects community structure. Science 232: 847-849. Ainley, D.G., W.R. Fraser and K.L. Daly. 1988. Effects of pack ice on micronektonic communities in the Weddell Sea. In, Antarctic Ocean and Resources Variability, D. Sahrhage, ed., Springer-Verlag, Berlin, 140-146. Fraser, W.R., R.L. Pitman and D.G. Ainley. 1989. Seabird and fur seal responses to vertically migrating krill swarms in Antarctica. Polar Biology 10: 37-41. Ainley, D.G., W.R. Fraser, W.O. Smith, T.L. Hopkins and J.J. Torres. 1991. The structure of upper level pelagic food webs in the Antarctic: Effect of phytoplankton distribution. Journal of Marine Systems 2: 111-122. Ribic, C.A., D.G. Ainley and W.R. Fraser. 1991. Habitat selection by marine mammals in the marginal ice zone. Antarctic Science 3: 181-186. Ainley, D.G., C.A. Ribic and W.R. Fraser. 1992. Does prey preference affect habitat choice in Antarctic Seabirds? Marine Ecology Progress Series 90: 207-221. Fraser, W.R., W.Z. Trivelpiece, D.G. Ainley and S.G. Trivelpiece. 1992. Increases in Antarctic penguin populations: reduced competition with whales or a loss of sea ice due to global warming? Polar Biology 11: 525-531. Fraser, W.R., W.Z. Trivelpiece, B. Houston and D.L. Patterson. 1992. Palmer LTER: Seabird research undertaken during 1991-1992 at Palmer Station, Antarctic Peninsula, Antarctic Journal of the Unites States 27: 249-250. Fraser, W.R. and W.Z. Trivelpiece. 1996. Factors controlling the distribution of seabirds: Winter-Summer heterogeneity in the distribution of Adelie Penguin Populations. In, Foundations for Ecological Research West of the Antarctic Peninsula, E. Hofmann, R. Ross and L. Quetin, eds., AGU Antarctic Research Series, Washington, D.C. Key to acronyms and abreviatons used in pal-lter seabird databases. Palmer manual for censusing seabirds at sea. All data are initially recorded in field notebooks. Quality assurance is determined during two subsequent stages. The first is when data are moved from field notebooks to data sheets; the second is when data are moved from data sheets to databases.

Datafile Form V1.2 for describing a data file.