The significance of the north water polynya to arctic top predators

Abstract

The North Water polynya (~76°N to 79°N and 70°W to 80°W) is known to be an important habitat for several species of marine mammals and sea birds. For millennia, it has provided the basis for subsistence hunting and human presence in the northernmost part of Baffin Bay. The abundance of air-breathing top predators also represents a potential source of nutrient cycling that maintains primary production. In this study, aerial surveys conducted in 2009 and 2010 were used for the first time to map the distribution and estimate the abundance of top predators during spring in the North Water. Belugas (Delphinapterus leucas) were not detected north of 77°20'N but were found along the coast of West Greenland and offshore in the middle of the North Water with an abundance estimated at 2245 (95 % CI 1811-2783). Narwhals (Monodon monoceros) were widely distributed on the eastern side of the North Water with an estimate of abundance of 7726 (3761-15 870). Walruses (Odobenus rosmarus) were found across the North Water over both shallow and deep (>500 m) water with an estimated abundance of 1499 (1077-2087). Bearded (Erignathus barbatus) and ringed seals (Phoca hispida) used the large floes of ice in the southeastern part of the North Water for hauling out. Most polar bears (Ursus maritimus) were detected in the southern part of the polynya. The abundances of bearded and ringed seals were 6016 (3322-10 893) and 9529 (5460-16 632), respectively, and that of polar bears was 60 (12-292). Three sea bird species were distributed along the Greenland coast (eiders, Somateria spp.), in leads and cracks close to the Greenland coast (little auks, Alle alle) or widely in open water (thick-billed guillemots, Uria lomvia).

Fig. 1

Transect lines and strata covered in the North Water during the surveys in May–June 2009 and 2010. Dotted lines Transects surveyed in 2009, thin solid lines 2010 transects, and thick solid lines transects surveyed in both years. Sea bird colonies are indicated for guillemots (red dots) and little auks (blue lines)

Fig. 2

Tagging of a walrus in the North Water in 2010 with satellite-linked time-depth-recorders for measurements of time spent at the surface available for detection by the visual aerial surveys

Fig. 3

Visible-band images from the MODIS instrument on NASA’s Aqua satellite showing open-water areas (black) in the North Water on May 23, 2009 (left) and on May 29, 2010 (right)

Fig. 4

Development of sea ice extent in a the North Water and b Baffin Bay based on satellite data during March–June for the years 1979–-2011 with all years shown as gray lines and 10 year averages shown in blue (1982–1991), green (1992–2001), and red (2002–2011). Dates of the surveys (May 19–30) are shown as vertical dotted lines

Fig. 5

Observations of whales, walruses, seals, and three sea birds during the aerial survey of the North Water in May–June 2009–2010