Fig 1.
The Chukchi Sea, showing (a) current locations; and (b) geographic strata and survey effort. Bathymetry data are from the International Bathymetric Chart of the Arctic Ocean www.ibcao.org.
Table 1.
Sampling effort by year, northeastern Chukchi Sea, 2008–2018.
Table 2.
Species of seabirds recorded during ship-based surveys in the northeastern Chukchi Sea, 2008–2018.
Fig 2.
Seasonal and interannual differences in sampling effort in the northeastern Chukchi Sea, 2008–2018.
Table 3.
Factor loading output from principal component analysis of 5 oceanographic variables calculated over survey transects within hexagon shaped grid cells.
Fig 3.
Temperature and salinity of water in bottom 10 m of water column, northeastern Chukchi Sea.
Early summer was 13 Aug–6 September and late summer was 7 September–2 October.
Fig 4.
Temperature and salinity of water in upper 10 m of water column, northeastern Chukchi Sea.
Early summer was 13 Aug–6 September and late summer was 7 September–2 October.
Fig 5.
Seabird species rarefaction curves from surveys conducted in the northeastern Chukchi Sea in early and late summer, 2008–2018.
Early summer (pink) was 13 August–6 September and late summer (aqua) was 7 September–2 October. Shading indicates 95% confidence intervals based on resampling transects without replacement.
Fig 6.
Species composition of seabird community in geographic strata of the northeastern Chukchi Sea, 2008–2018.
Fig 7.
Non-metric multidimensional scaling (nMDS) of the seabird community in the northeastern Chukchi Sea, 2008–2018.
Table 4.
PERMANOVA of species composition of the seabird community in the northeastern Chukchi Sea, 2008–2018.
Fig 8.
Distribution of 8 species of seabirds in the northeastern Chukchi Sea, early summer 2008–2018.
Values in cells are means of transects from surveys conducted during 13 August–6 September.
Fig 9.
Distribution of 8 species of seabirds in the northeastern Chukchi Sea, late summer 2008–2018.
Values in cells are means of transects from surveys conducted during 7 September–2 October.
Fig 10.
Effect of hydrography on seabird density, northeastern Chukchi Sea, 2008–2018.
Response curves are from the best-fitting generalized additive model. Solid lines represent the smooth function and 95% confidence limits for early summer (pink) and late summer (aqua). Gray shading indicates the 95% confidence intervals. Colored ticks indicate the distribution of observations.
Table 5.
Generalized additive models that best explained variation in abundance and distribution of seabirds in the northeastern Chukchi Sea, 2008–2018 (n = 256 hexagonal cells, 30-km from vertex to vertex).
Table 6.
Variables that best described the variation in distribution and abundance of 8 species of seabirds in the northeastern Chukchi Sea, 2008–2018.
P-values indicate statistical significance from generalized additive models (GAM). Dist. Shore is the distance to shore from the centroid of each cell in the sampling grid.
Fig 11.
Effect of distance to shore on seabird density, northeastern Chukchi Sea, 2008–2018.
Response curves are from the best-fitting generalized additive model. Solid lines represent the smooth function and 95% confidence limits for early summer(pink) and late summer(aqua). Gray shading indicates the 95% confidence intervals. Colored ticks indicate the distribution of observations.
Fig 12.
Effect of latitude on seabird density, northeastern Chukchi Sea, 2008–2018.
Response curves are from the best-fitting generalized additive model. Solid lines represent the smooth function and 95% confidence limits for early summer(pink) and late summer(aqua). Gray shading indicates the 95% confidence intervals. Colored ticks indicate the distribution of observations.