At-sea seabird censuses. Data on the species encountered (including marine mammals), their abundance, distribution and behavior. Data collected aboard cruises off the coast of the Western Antarctic Penninsula, 1993 - 2018.

• Main Authors: LTER, Palmer Station Antarctica, Fraser, William
• Format: Dataset
• Language: English
• Published: Environmental Data Initiative 2020
• Subjects: Antarctic; Antarctic Peninsula; Anvers; Anvers Island; Major Island; Palmer Station; Palmer-Station; The Antarctic; Antarc*; South Polar Skuas
• Online Access: https://dx.doi.org/10.6073/pasta/daa3753c4d20470b0ff1a0caa9dc19e2; https://portal.edirepository.org/nis/mapbrowse?packageid=knb-lter-pal.95.5

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 of the January cruise was the nearshore foraging habitat, which required sampling at smaller scales. All seabird censuses were thus conducted within approximately 100 kms of Palmer Station while traversing a sampling grid with stations at 10km intervals. The first two days (18-20 January) of this cruise were spent covering the selected grid as rapidly as possible resulting in 45 transects spaced at 45-60 minute intervals. There were no stops at the 10km stations during this Fast Grid phase. Upon completion of the Fast Grid, a force 12 gale suspended data collection for 24 hours. From January 22-25 the grid direction was reversed and the grid repeated. During this Slow Grid phase, 2-M net tows were done at 10km intervals and BOPS and 1-M and 2-M net tows every 20 km. All seabird censuses during the cruise were done using the procedures outlined in the previous paragraph. Seventy-two 30-minute transects and 15 station censuses were completed during the January cruise. Athough seabirds were widely distributed throughout the study area, the highest densities and greatest biomass occurred consistently within 2-5 km of Anvers Island and several major island groups to the south and west near the Antarctic Peninsula. Adelie Penguins were the dominant component of this seabird assemblage in terms of both abundance and biomass. South Polar Skuas ranked second and Black-browed Albatross third, with the latter becoming the dominant assemblage member at distances greater than 10km from land. Although South Polar Skuas had been expected to occur in more pelagic habitats, few were censused at distances greater than 10km from land. The presence of both skuas and penguins so close to land was unexpected. The most important variable accounting for variation in the distribution and abundance of seabirds appeared to be the location of the 200m contour, which throughout the study area occurred 2-5km from the adjoining land masses. Approximately 65% of the seabirds censused during this cruise (85% of the biomass) occurred in association with this contour.