Fig 1.
The central Beaufort Sea region in Arctic Alaska, situated between the Ikpikpuk River and the Canning River, contains a diversity of aquatic habitat. The large Colville River, AK, USA (ca. watershed area 60,000 km2), located in the middle of the central Beaufort Sea coast, contains minor tributaries that drain from the Brooks Range (thin grey lines) and main tributaries (thick dark grey lines) that flow toward a large delta on the edge of the Beaufort Sea, near the community of Nuiqsut, AK. Fish were collected at three sites (black triangles) within the Colville River (site 1 = Itkillik, site 2 = Puviksuk, site 3 = Umiat). Data sources: USGS National Map Viewer (http://viewer.nationalmap.gov/viewer/), Natural Earth (http://www.naturalearthdata.com/), National Hydrography Dataset (https://www.usgs.gov/national-hydrography/national-hydrography-dataset).
Fig 2.
Cross-section of Arctic aquatic ecosystems. Circles with error bars represent the mean and standard deviation of the organism from each type of ecosystem (Dark blue = marine, light blue = estuarine, green = riverine, gold = lacustrine). Error bars on estuarine species and benthic particulate organic matter values represent the standard error. Circles without error bars represent a single sample. For comparison, data from outside the study area is shown: marine samples are from Admiralty Inlet in the Northwest Territories, CA; lagoon samples are from sites along the eastern Beaufort Sea coast, Alaska, USA; riverine samples are from the lower MacKenzie River, Yukon, CA, and Lacustrine samples are from Toolik Lake, Alaska, USA. Additional isotope sources: See S2, S3 Tables.
Fig 3.
The difference in δ15N and δ13Cˈ (muscle minus liver) for each Broad Whitefish (Coregonus nasus) sampled in the Colville River, AK, USA. Scatter plot shapes represent the collection site locations (Itkillik = circle, Puviksuk = triangle, Umiat = square) and the color represents the individual fish’s length (blue ≤ 40 cm, purple = 50 cm, red ≥ 60 cm). For both isotope ratios, positive values indicate a shift from foraging food sources from more enriched (e.g., marine gastropod) to a food source with more depleted values (e.g., lacustrine amphipod), while negative values indicate the opposite.
Fig 4.
The scatterplot shows stable isotopes δ18O versus δD along with the associated boxplot for each isotope measured in muscle of Broad Whitefish (Coregonus nasus) from the Colville River, AK, USA.
Boxplots show median values (horizontal black line), interquartile range (IQR) (box with blue outline), the maximum value within 1.5 times the IQR (vertical black line), and outside values are greater than 1.5 times the IQR (black dots).
Fig 5.
Cluster dendrogram (A) shows the individual Broad Whitefish (Coregonus nasus) from the Colville River, AK, USA, clusters (coded by color; purple = cluster 1, blue = cluster 2, turquoise = cluster 3, yellow = cluster 4), and height of the dendrogram. Cluster plot (B) shows each cluster (purple circle = cluster 1, blue triangle = cluster 2, turquoise square = cluster 3, yellow plus = cluster 4) overlaid across two principal components.
Fig 6.
Isotope values and hierarchal clustering groups.
Scatterplots (A, C, E) show stable isotopes δ18O, δ15N, and δD versus δ13Cˈ along with the associated cluster group (purple = cluster 1, blue = cluster 2, turquoise = cluster 3, yellow = cluster 4) of Broad Whitefish (Coregonus nasus) from the Colville River, AK, USA. Boxplots (B, D, F) show stable isotopes δ18O, δ15N, and δD by cluster group (purple = cluster 1, blue = cluster 2, turquoise = cluster 3, yellow = cluster 4) along with median (horizontal black line), interquartile range (IQR) (box with colored outline), and maximum value within 1.5 times the IQR (vertical colored line).
Fig 7.
Isotope values and life history group.
Boxplots (A, B, C, D) showing δ13Cˈ, δ15N, δ18O, and δD by Broad Whitefish (Coregonus nasus) life history group (anadromous (black), semi-anadromous (purple), nonanadromous (pink), along with median (horizontal black line), interquartile range (IQR) (box with colored outline), and maximum value within 1.5 times the IQR (vertical colored line).